Title: Balanced linked tuner turns ratio Post by: AMLOVER on September 14, 2024, 12:44:36 PM Hi to all,
I am preparing a linked balanced tuner for a 1/8 wave length 600 ohm ladder line feeding a resonant low band monobander dipole. I have calculated the resistive part of the impedance on the edge of my ladder line to around 118 ohm and the reactive part to about +615jx. As far my tuner space is limited and the antenna is monobander I am wondering if the turns ratio of the inductors is transforming the resistive part and the capacitor cares for the reactive part. If so I'll only need few turns for the big inductor. Let say 118 ohm:50 ohm =2.4 and sqr 2.4=1.55 which will be the turns ratio factor for multiplying the link's turns. Per example 5 turns for the link inductor and 1.55X5=8 turns for the big inductor. For safety I'll make 2024 turns which will save me lot of space in comparison with the 45 turns for a multiband tuner. Is this makes any sense or somewhere I miss something and I'll anyway need a 45 turns inductor? Greetings Stefano Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 14, 2024, 09:43:14 PM See Cebicks article:
http://www.antentop.org/w4rnl.001/link.html or see 4. Link Coupling https://www.dj0ip.de/antennamatchboxes/symmetricalmatchboxes/ Title: Re: Balanced linked tuner turns ratio Post by: W7TFO on September 15, 2024, 01:59:39 PM Taking into account some of us build with balanced output right from the finals, a balun isn't necessary in the circuit.
I usually copy the output section of the Raytheon AM BC transmitters. Yes, they were able to match 50Z all the way up to 600Z. 73DG Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 16, 2024, 01:25:29 AM Stefano, I hope this will help you. Image 1, circuit diagram. L is a modeled 75 meter dipole at 50 feet with an overall length of 125 feet, T1 is 1/8 wavelength of 600 ohm line. Image 2, impedance at the end of the 600 ohm line vs frequency. A is the link, C1 is the tuning capacitor to match the antenna from 3.5 to 4Mhz and G is the transmitter model. Image 3, SWR vs frequency vs C1, C1 was swept from 66p to 141p. Maximum SWR is 1.53:1 at 4 mhz, C1=66pf.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 16, 2024, 11:40:23 AM Wrote a short script in MATLAB to solve
for the link coupled transformer where the load is complex and the source is real. Like your case where the reactance is not tuned out. There is an exact solution but the values are not practical. If you resonate out the j615 ohm at at say 3.75 MHz, then the link coupled match is nice. The series C is 69 pF and the balanced side L is 6 uH and the 50 ohm side L is 1.35 uH. The coupling k value is reasonable and easy to set and measure. An exact match on the 50 ohms side requires a shunt C. The Q values are low and the response pretty broadband. The response is shown below, with schematic and S parameter response. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 16, 2024, 02:09:14 PM This is the equation being solved in the script.
I use T.J. Maresca paper in QST Oct 1959 to seed the MATLAB script with initial values. See his case equations for ParallelResonant Primary Untuned Secondary on page 30 of QST. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 16, 2024, 03:23:05 PM DMOD,
Very usefull info at the provided links, I spend time to learn more in deep. W7TFO, This is a succesfull technic but as far I use a narrow band (50100 Khz) I try to find out the right turns ratio in order to keep the inductor, if possible, as small as possible. Ka1bwo, Your calculation is almost as mine but I use a cap (C2) in parallel with the balance inductor and a link coil with reactance 50 ohm (per example 2.1225uH for 3750Khz) so there is no need for C1. With C2 in parallel with balanced inductor I would expect no reactance such as the X=450 Ohm in your scheme. Redrawing your scheme is how is my set up and follows in the attachment with some modifications. The perfect scenario is to cancell the +588jx or +615jx in my case with C2 and the 118 Ohm resistance to 50 Ohm with the ratio of the balanced inductor to the link coil. Could you please recalculate with the C2 in this place? In this case the balanced inductor will be not that big and the tuner will be of course usefull only for a narrow band. W4AMV, This is a very nice set up. I have never seen the parallel to the link coil 1.7nf cap. All schematics have it in series with the link in order to cancel if needed some of its reactance. Could you please explain me if the 69pf cap which cancells the +615jx at 3750Khz is in parallel with the load as it is drawn in the 2nd attachment (TUNER) as C2? or it should be in series with one of the ladder line legs? Greetings Stefano Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 16, 2024, 04:14:34 PM To clarify. I took your stated measured or calculated impedance at the end of the 600 ohm line to be 118 ohms series with j 615 ohms. That series Z is the R2 + jX2 value across the secondary link L2. The reflected Z is calculated via the equation I posted using the MATLAB script and the resulting reflected Z is in addition to the primary inductance on the low Z side, namely the 50 ohm side. I convert the series Z on the primary side to its parallel equivalent and hence the parallel C that you spoke of results. The result is the primary side is REAL and matched to 50 ohms.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 16, 2024, 04:23:13 PM Oh, the Z load you stated is a series Z. I assume that is the case. Correct me if wrong. So yes, the 69 pF is in series tuning out the j615 ohms at 3.75 MHz. Now the problem is just taking the 118 ohm and transferring it to 50 ohms at the desired frequency. If I desire to use no secondary tuning C and reflect the complex load to the primary, that is possible. However, the resulting component values are not nice. This is partially drive by the fact that the Q of your load is higher than desired.
Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 16, 2024, 05:49:16 PM Ka1bwo, Your calculation is almost as mine but I use a cap (C2) in parallel with the balance inductor and a link coil with reactance 50 ohm (per example 2.1225uH for 3750Khz) so there is no need for C1. With C2 in parallel with balanced inductor I would expect no reactance such as the X=450 Ohm in your scheme. Redrawing your scheme is how is my set up and follows in the attachment with some modifications. The perfect scenario is to cancell the +588jx or +615jx in my case with C2 and the 118 Ohm resistance to 50 Ohm with the ratio of the balanced inductor to the link coil. Could you please recalculate with the C2 in this place? In this case the balanced inductor will be not that big and the tuner will be of course usefull only for a narrow band. Stefano, here is the rev schematic and SWR chart. Your scheme will be more efficient due to less series resistance in the inductors. Link turns ratio = 7.538 Joe Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 16, 2024, 07:34:54 PM You can convert your series antenna Z to its parallel equivalent. This provides yet another solution. The basic configuration follows the link coupled topology from the QST paper discussed as resonant primary non resonate secondary, see figure. However, the author of this paper did not address the complex load. If you convert series to parallel then the 69 pF cap is in shunt with the balanced line and secondary winding and a new set of primary and secondary inductance values emerge. As well, the k factor can change as desired as you alter the matching bandwidth or Q of the source and load side of the link coupled network.
Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 16, 2024, 10:11:50 PM You can convert your series antenna Z to its parallel equivalent. This provides yet another solution. The basic configuration follows the link coupled topology from the QST paper discussed as resonant primary non resonate secondary, see figure. However, the author of this paper did not address the complex load. If you convert series to parallel then the 69 pF cap is in shunt with the balanced line and secondary winding and a new set of primary and secondary inductance values emerge. As well, the k factor can change as desired as you alter the matching bandwidth or Q of the source and load side of the link coupled network. W4AMV MATCHING SOLUTION: Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 17, 2024, 07:48:43 AM You can convert your series antenna Z to its parallel equivalent. This provides yet another solution. The basic configuration follows the link coupled topology from the QST paper discussed as resonant primary non resonate secondary, see figure. However, the author of this paper did not address the complex load. If you convert series to parallel then the 69 pF cap is in shunt with the balanced line and secondary winding and a new set of primary and secondary inductance values emerge. As well, the k factor can change as desired as you alter the matching bandwidth or Q of the source and load side of the link coupled network. W4AMV MATCHING SOLUTION: Joe, Could you please try once more with the attached scheme which is the usual 'balanced link coupled tuner'? Greetings Stefano Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 17, 2024, 10:46:05 AM This follows the QST paper guideline, parallel resonant primary, series resonate secondary. The solution is not unique. You can vary the Q on wither side of the network despite the give antenna complex Z. So you can vary the coupling coefficient, k, of the link coupled coils. The only mod from the paper is tuning out the reactance of the antenna. Another solution is obtained by converting the antenna Z from its series to parallel equivalent. Then proceed again with the link coupled equations. I encourage you to read the paper.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 17, 2024, 01:57:22 PM Here is the network for the parallel equivalent Z. The coupling is light. Easier to implement. Increased coupling is possible, just decrease the Q of primary/secondary sides. The antenna equivalent Z highlighted in box
and the shunt C to resonate is absorbed into the shunt C that results from solving the link coupling equations. Plotted the return loss as REAL RETURN LOSS as a positive number. Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 17, 2024, 06:50:05 PM You can convert your series antenna Z to its parallel equivalent. This provides yet another solution. The basic configuration follows the link coupled topology from the QST paper discussed as resonant primary non resonate secondary, see figure. However, the author of this paper did not address the complex load. If you convert series to parallel then the 69 pF cap is in shunt with the balanced line and secondary winding and a new set of primary and secondary inductance values emerge. As well, the k factor can change as desired as you alter the matching bandwidth or Q of the source and load side of the link coupled network. Joe, Could you please try once more with the attached scheme which is the usual 'balanced link coupled tuner'? Greetings Stefano Transmission line end impedance parallel equivalent Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 19, 2024, 11:33:53 AM sim smith provides a solution with k = 1. This simplifies the prior posted equation and I suppose you can choose a Q for the primary and secondary loop within some constraints. Need to visit those details. Anyway, if you get a k of 1, great. A k of 0.8 or greater is needed otherwise the match deteriorates as shown in this plot. I assume one is able to enter a desired k into sim smith. Nicely done.
Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 19, 2024, 10:19:30 PM Hi Stefono,
What band is this monoband antenna for? And, you might consider using 300 ohm instead of 600 ohms for your feedline impedance. This lowers the high voltages on the feedline and thus a lower voltage stress on your link antenna output components (inductors and capacitors  potential arcing of capacitors). Let us start with above and move on from there. What do you think? Chuck Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 20, 2024, 12:07:34 AM sim smith provides a solution with k = 1. This simplifies the prior posted equation and I suppose you can choose a Q for the primary and secondary loop within some constraints. Need to visit those details. Anyway, if you get a k of 1, great. A k of 0.8 or greater is needed otherwise the match deteriorates as shown in this plot. I assume one is able to enter a desired k into sim smith. Nicely done. Yes, you are correct a k of 1 was used for the analysis you can enter the desired k. Here is a plot of the ideal power delivered to the 600 ohm transmission line vs k, with a transmitter output of 100 watts.Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 20, 2024, 01:16:05 PM W4AMV,
I read the QST article you reccommended me and saw that it is for linked coupling of the tube output to 50 Ohm. It is advised to keep K less than 0.4 and when did that the Q should be 12 or more. Anyway in that article both parts of coupler are considering as resistive. In order to use those equations I have to cancell the reactive part of the ladder line. This is not however the mainstream technic. I see now that things become easier with k=1 but still the series cap is a must. This cap is not involved in any balanced linked couple tunner consideration. Joe, I have studied very carefully your program's results but I can't understand why the LI which is on the ladder side facing 118 Ohm is smaller than LR which is on the link side facing 50 Ohm. Normally should be opossed. Chuck, It is for the low band as I have mentioned in my first post. 300 Ohm line seems much better in calculations but it is not very safe because the wires (12 gauge) have to be less then 2'' closed together, this distance needs more spacers per foot and is unsafe to winds, rain and snow. In conclusion I think that the parallel cap must be on the edge of a sufficient for the frequency inductor to keep the Q and the circulating currents low and the line should touch the inductor where the resistance is correcttly transformed. I wonder if I can manage to use a not so big inductor without sacrificing much gain. My tuner should look like the one in the photo http://amfone.net/Amforum/index.php?topic=36685.0 where the antenna set up including the OWL length is like mine. I only wish not to have so many turns in the main inductor. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 20, 2024, 05:57:30 PM Perhaps you can clarify with a schematic the exact circuit topology you desire. The limited view of the hardware requires quite a bit of extrapolation!
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 20, 2024, 07:20:14 PM After a careful re read of your post, is this the topology desired?
No tuning on the secondary implies the secondary reflected Z will also be complex and reactance cancellation on the primary should permit the primary port Z to be 50 + j0. Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 20, 2024, 10:16:36 PM Stefono, When you say low band do mean 160 meters? Thank you. Chuck Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 21, 2024, 09:41:20 AM Hi aa5wg...
per prior posts, looks like... 80 meters phone. (per example 2.1225uH for 3750Khz) Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 21, 2024, 10:28:31 AM If the topology is the one I mentioned earlier... Where the link is required to absorb the antenna reactance (inductive) and there is NO tuning on the balanced transmission line side, then this results in the schematic attached. Note, counter intuitive, the link inductance is larger than the balanced side inductor. There is only the 50 ohm side of the tuner with a series cap to tune out the reflected impedance. The result is the consequence of absorbing the reactance of the termination. Obviously different results will occur dependent on the 600 ohm side of the balanced line Z and the selection of circuit Q values. Finding a set of component values is easy using the Matlab script and the full linked coupled equation from the prior post. You might consider the balanced tapped inductance with link as I think showed in your photo. K1JJ tuner. I have not analyzed this from design to component value. Perhaps someone has already.
Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 21, 2024, 12:56:19 PM If the topology is the one I mentioned earlier... Where the link is required to absorb the antenna reactance (inductive) and there is NO tuning on the balanced transmission line side, then this results in the schematic attached. Note, counter intuitive, the link inductance is larger than the balanced side inductor. There is only the 50 ohm side of the tuner with a series cap to tune out the reflected impedance. The result is the consequence of absorbing the reactance of the termination. Obviously different results will occur dependent on the 600 ohm side of the balanced line Z and the selection of circuit Q values. Finding a set of component values is easy using the Matlab script and the full linked coupled equation from the prior post. You might consider the balanced tapped inductance with link as I think showed in your photo. K1JJ tuner. I have not analyzed this from design to component value. Perhaps someone has already. I think Alan's schematic and analysis is the most sensible approach to this question. Phil  AC0OB Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 21, 2024, 04:52:12 PM If the topology is the one I mentioned earlier... Where the link is required to absorb the antenna reactance (inductive) and there is NO tuning on the balanced transmission line side, then this results in the schematic attached. Note, counter intuitive, the link inductance is larger than the balanced side inductor. There is only the 50 ohm side of the tuner with a series cap to tune out the reflected impedance. The result is the consequence of absorbing the reactance of the termination. Obviously different results will occur dependent on the 600 ohm side of the balanced line Z and the selection of circuit Q values. Finding a set of component values is easy using the Matlab script and the full linked coupled equation from the prior post. You might consider the balanced tapped inductance with link as I think showed in your photo. K1JJ tuner. I have not analyzed this from design to component value. Perhaps someone has already. W4AMV, The attached is the usual set up (jj tuner) which I am also intending to use. The link coil value is known for the frequency as 4.3uH but could be used larger with the addition of a capacitor in series with the coil link to ground. The balancing inductor and it's parallel capacitor are resonating the also known 120+600jx ladder line impedance. The question is what is the critical L and C values for transforming 120+600jx to 50+0jx with a reasonable Q and efficiency factor? Chuck, Yes, it is for 160m. Frequency is not that critical because by using terms in wave length all can be scaled with a reactance calculator and the wave length scale factor. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 21, 2024, 06:44:43 PM I did not do an extensive derivation of Tom's tuner.
However, there are notes in the attached as to the procedure applied. To do it justice, need to consider the tapping of the main balanced inductor and probably treat it as a symmetric tapped inductor (auto transformer). I simplified and allowed the inductor to be larger than required to adopt tapping if needed. You can get by with a smaller size if desired. The element values and response are attached. You need to build and verify your coupling coefficient, k. Easy to do. You need close to unity, 0.85 should be fine and not difficult to achieve. If a smaller k is desirable to aid in construction, could visit the script in Matlab. The main inductor floats...balanced... did not show it that way, got lazy. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 21, 2024, 08:11:57 PM After back of the envelope inductor size and value, I suspect you are not going to be happy so here is another run....
Change the 270 uH to 54 uH, change the 4.3 uH to 1 uH and the tune cap to 276 pF. The same range of K is desirable. The return loss is still quite fine from a min of 15 dB to a best case of over 30 dB. A larger L (than 54 uH) however, would be more flexible so as to accommodate symmetric tapping. In any case you could start with this set of values. Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 21, 2024, 10:34:33 PM "The question is what is the critical L and C values for transforming 120+600jx to 50+0jx with a reasonable Q and efficiency factor?"
From your circuit diagram above and posted pictures, it appears you are wanting some type of air coil RF transformer system, unbalanced in, balanced out. I ran some calcs on MatLab as well and here is my put. Updated 9/22: Calculated Coil Values and Dimensions PhilAC0OB Title: Re: Balanced linked tuner turns ratio Post by: Steve  K4HX on September 22, 2024, 11:21:20 AM If I'm seeing your photo correctly, it appears you are tapping WAY down on the coil. If so, you may want to consider the series tuning arrangement rather than the your current arrangement, parallel tuning.
W4AMV, I read the QST article you reccommended me and saw that it is for linked coupling of the tube output to 50 Ohm. It is advised to keep K less than 0.4 and when did that the Q should be 12 or more. Anyway in that article both parts of coupler are considering as resistive. In order to use those equations I have to cancell the reactive part of the ladder line. This is not however the mainstream technic. I see now that things become easier with k=1 but still the series cap is a must. This cap is not involved in any balanced linked couple tunner consideration. Joe, I have studied very carefully your program's results but I can't understand why the LI which is on the ladder side facing 118 Ohm is smaller than LR which is on the link side facing 50 Ohm. Normally should be opossed. Chuck, It is for the low band as I have mentioned in my first post. 300 Ohm line seems much better in calculations but it is not very safe because the wires (12 gauge) have to be less then 2'' closed together, this distance needs more spacers per foot and is unsafe to winds, rain and snow. In conclusion I think that the parallel cap must be on the edge of a sufficient for the frequency inductor to keep the Q and the circulating currents low and the line should touch the inductor where the resistance is correcttly transformed. I wonder if I can manage to use a not so big inductor without sacrificing much gain. My tuner should look like the one in the photo http://amfone.net/Amforum/index.php?topic=36685.0 where the antenna set up including the OWL length is like mine. I only wish not to have so many turns in the main inductor. Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on September 23, 2024, 12:05:46 PM "The question is what is the critical L and C values for transforming 120+600jx to 50+0jx with a reasonable Q and efficiency factor?" From your circuit diagram above and posted pictures, it appears you are wanting some type of air coil RF transformer system, unbalanced in, balanced out. I ran some calcs on MatLab as well and here is my put. Updated 9/22: Coil Values and Dimensions PhilAC0OB Phil, What k factor did you use for your analysis Joe Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 23, 2024, 02:04:46 PM "The question is what is the critical L and C values for transforming 120+600jx to 50+0jx with a reasonable Q and efficiency factor?" From your circuit diagram above and posted pictures, it appears you are wanting some type of air coil RF transformer system, unbalanced in, balanced out. I ran some calcs on MatLab as well and here is my put. Updated 9/22: Coil Values and Dimensions PhilAC0OB Phil, What k factor did you use for your analysis Joe I used a k = ~0.8 assuming the coils were placed end to end and separated by 1/8 inch. The coupling is highly dependent on how you place and orient the adjacent coils. One could conceivably have a coilovercoil (primary over secondary) arrangement, for example, by increasing the diameter of the primary to 2.25," decreasing the number of primary turns to 7, and decreasing the length to 10mm close wound. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 23, 2024, 03:09:18 PM W4AMV,
It is important to keep the link coil value at 4.3uH. The balance inductor (54uH) seems to be very big with your calculation considering 1uH link coil. Phil, This is what you attached is what I had also in my mind from the begining. To cancel the +jx and then to transform the resistance with the coupled inductors. In the meantime I started read more and more and found out that the gurus (Cebik ect) proposed a better way. They add turns to the balance inductor in order to increase its inductance and connect the capacitor from edge to edge. This lowers the Q and the losses because the circulating currents 'see' a lower rf resistance. They definitely find the right turns ratio somewhere in the inductor. I didn't meet anywhere this you and me thought which is to cancel any positive or negative reactance from the OWL and then to care for the resistance with the linked coupler. It is possible they didn't do so because they designed a multipurpose tuner for many bands and not a single band narrow use one as in my case. I am thinking after your post to mix somehow both technics, to triple the balance inductor (3x9uH=27uH) to get better efficiency with less circulating currents and resonate the parallel sircuit with the capacitor at 1.85Khz. Using the 300pf caps in series with the OWL legs I'll have to deal only with the 120Ohm OWL's resistance and I'll find the right points on the balance inductor (I hope around 8T/9uH) to get an efficient matching. Schematic attached. Steve, Around 15 years before I constructed a link coupled tuner like this but for an endfed Zeppelin resonant low band antenna. In that time my OWL was 1/4 wl. The result was that 40005000Ohm from antenna edge was transformed to about 6080Ohm at OWL edge before the tuner. I started with the parallel configuration (wrong for this low resistance) and found a matching point on the balance inductor but very closed to the link, as in the photo you saw. After some thinking I decided to try the series topology and cut the inductor in the middle, connected there the OWL and I never managed to get a good matching again. I even added a cap in series to the link coil but nothing. So before I split the inductor I'll try all the ways with the cap in parallel. Series will be my last decision. Joe, My balance inductor is on a 4" PVC form and the link over it on a 5" PVC form. I leave the forms in both as far they don't get any heat, I don't know if this influences the efficiency/Q of the inductors. I can't also guess the K factor. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 03:18:27 PM This is series tuned per Steve suggestion.
The balanced link inductance value is constrained by the reactance presented at the 600 ohm end of line port. The k is 0.95. Smaller k limits return loss, however, you could get by with 0.8. That requires a larger inductance balanced side inductor. At 0.8, 18 uH. Re tune the balanced C and the return loss is in excess of 30 dB. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 03:19:47 PM And the other arrangement is:
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 04:20:32 PM Joe,
My balance inductor is on a 4" PVC form and the link over it on a 5" PVC form. I leave the forms in both as far they don't get any heat, I don't know if this influences the efficiency/Q of the inductors. I can't also guess the K factor. WHY NOT MEASURE IT? IT IS EASY. DO YOU HAVE ANY TEST GEAR? YOU WILL NEED TO MEASURE INDUCTANCE AT 1.8 MHZ. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 23, 2024, 04:58:03 PM W4AMV,
I have a LCR meter for inductance and capacitance measures. I also have a grid dip meter and an osciloscope 100Mhz double trace. I can test the effieciency with some laser gun temperature tests. How I could measure the K factor with these instruments? Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 05:32:29 PM The GDO will work fine.
You will need to resonate the PRIMARY, that is the larger inductor. Use your LCR meter to get an approximate inductance reading, will neglect the fact that the LCR does not take a reading at 1.8 MHz, but lower. Now using the L reading, figure out the shunt C needed to resonate the PRIMARY L at 1.85 MHz... All this is done with the LINK OPEN circuited. Now use the GDO to measure the resonate frequency of the primary with the LINK open and then measure the primary again resonate freq with the link shorted. Keep wires and all that connection stuff as short and direct as possible. The calc for K is as follows: K = SQRT (1(Fopen/Fshorted)). So clearly if the freq with the link shorted moves HIGH.... compared to Fopen, then K is approaching 1. Any questions, flame away... Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 23, 2024, 05:54:36 PM If it is so straigtful I'll try to measure K factor first to a simulation sircuit much smaller dimensions but same frequency and then to the final one.
Thank you very much for the knowledge you shared to me. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 06:21:28 PM Great. No problem. Keep in mind the GDO is one of those instruments that requires skillful art to provide accurate measurements. Couple it to the coil under test at a distance where you get a nice dip. But then BACK AWAY as much as possible and accept a more feeble dip. The GDO, oscillator can be PULLED a bit and that upsets the measurement. Once I get the dip, I carry the GDO over to my frequency counter and jot down the number. If you have no counter, maybe use your receiver to pick up the GDO signal and record its digital reading or lastly try reading the GDO dial as best you can.
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 23, 2024, 07:18:52 PM I am very familiar with the GDOs. I own 3 different portable/batteries ones which I used to measure in many instances.
I also have a frequency meter to check whether it dips or oscilates in the right frequency. Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 23, 2024, 07:47:52 PM The 1/4 wavelength feedline connected to a halfwave doublet will provide high voltage at the feed point of the transmission line.
This is called voltage feed which favors the parallel configuration for the link antenna coupler. ARRL antenna books from the 1950's and 1960's provide inductor and capacitor data to build this antenna tuner in the parallel configuration per your desired band. Chuck Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 23, 2024, 09:01:22 PM Here is DMOD solution, Phil...
Quite reasonable. The series caps are fixed, not series tuned, however serve to cancel the reactance of the Z balanced port. The shunt C is tuning and fine adjustment. A k of 0.9 is preferred, you can get by with 0.85, dropping to 0.8 is still an acceptable 16 dB return loss. Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 24, 2024, 02:58:19 AM Note, these are for 2" Dia. coils. in a linear, side by side arrangement.
If you use other diameter coils or coils with different wire gauge, the coil parameters such as number of turns, length of coil, diameter, wire gauge and winding pitch will need to be recalculated. I think the coaxial Tp over Ts configuration probably gives the highest coupling coefficient k; for example, having the Tp coil 2.25" to 2.5" and the Ts coil 2" in a coaxial configuration. Phil  AC0OB Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 24, 2024, 10:03:37 AM The 1/4 wavelength feedline connected to a halfwave doublet will provide high voltage at the feed point of the transmission line. This is called voltage feed which favors the parallel configuration for the link antenna coupler. ARRL antenna books from the 1950's and 1960's provide inductor and capacitor data to build this antenna tuner in the parallel configuration per your desired band. Chuck The antenna where I used the 1/4wl feedline was a Zepp not a doublet. It was fed on the edge where the voltage and the resistance were very high. So on the end of the 1/4wl line appeared low voltage and resistance so series feeding was the propriate way but for some reason it didn't fit to my needs. Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 24, 2024, 09:05:39 PM The neat thing about the link antenna coupler is its flexibility to make the appropriate impedance match for the complete antenna system (one half the doublet, feedline length and antenna tuner). This system theoretically works best at multiples of 1/4 wavelengths at any given band. These lengths change when using different bands. Thus, having the flexibility to tune the capacitive or inductive reactance via parallel or series tune is achievable with link coupling. Parallel tuning is used for a high voltage point at the tuner or series tuning for a high current point at the tuner.
When the total antenna system length (one half of doublet, length of transmission line plus antenna tuner) is a measurement of multiple 1/8 wavelengths instead or 1/4 wavelengths extra high reactance is present and it may be difficult to tune out this extra high inductive or capacitive reactance. When this happens a rule of thumb is to shunt (connect) across the left and rights sides of the transmission line an additional variable reactance at the output of the tuner. This is going to be a variable capacitor to tune out the excessive inductive reactance or a variable inductor to tune out the excessive capacitive reactance. The transmission line impedance dictates the theoretic maximum value for this shunt inductor or capacitor. Example: A 600 ohm open wire feed line would have a theoretical maximum reactance of 600 ohms for the shunt inductor or capacitor. 600 ohms worth of capacitance at 3.5 MHz is just less than 80 PF. 600 ohms worth of inductive reactance at 3.5 MHz is about 27 uH. It is best if these shunt capacitors and inductors are variable. This same link antenna tuner works great for the end fed ZEPP antenna fed with open wire feedline. Another neat thing about link antenna coupling is there are no ferrite transformers that can saturate/heat up under reactive loads. Antenna systems always have resistive and reactive components such as inductive or capacitive reactance. This is why we need to "tune" the "antenna system" for maximum flexibility and efficiency. Chuck Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 25, 2024, 07:31:52 AM W4AMV, Phil, Chuck and all,
Ithink that should be better to make a test tuner with a dimensionally small but sufficient inductor (50uH+), a link coil with the right reactance for the frequency loading it with 120 Ohm resistor in series with 52uH inductance and check the possibilities. I'll try first with 270pf caps in series with the load (120+600jx) to precancel the inductive reactance. I'll also try without the caps and check if the OWL impedance can be handled by the parallel cap in cooperation with the inductor. I'll also check the efficiency and measure the K factor. It is true that my case is 'special' because of single band use and 3/8wl as total length of one leg of the dipole+OWL. In case the results are dissapointing, I'll rethink about using the single band super efficient cap loaded dipole antenna. Thank you all for simulations suggestions and possible solutions. Stefano Title: Re: Balanced linked tuner turns ratio Post by: KL7OF on September 25, 2024, 08:47:58 AM I have followed the thread with some interest....... I have nothing to contribute, but I am very interested in how the tuner works after construction. Good Luck. Steve
Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 25, 2024, 10:58:09 AM Build a link antenna tuner with correct capacitor and inductor values for the band in use. Make sure you can change from parallel to series tune with your tuner. Don't use larger inductors that are greater in value for the band in use. This will degrade the tuners performance. Don't use resistors because they will give you false performance indications. Rather, use the antenna system (antenna, feedline and tuner) which provides true conditions for the tuner. The input inductor for the tuner, that receives power from the transceiver or transmitter, should have a variable capacitor in series connected to ground. Sometimes it makes a difference if the this capacitor is first or after the inductor.
Chuck Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 26, 2024, 04:38:51 PM W4AMV, Phil, Chuck and all, Ithink that should be better to make a test tuner with a dimensionally small but sufficient inductor (50uH+), a link coil with the right reactance for the frequency loading it with 120 Ohm resistor in series with 52uH inductance and check the possibilities. I'll try first with 270pf caps in series with the load (120+600jx) to precancel the inductive reactance. I'll also try without the caps and check if the OWL impedance can be handled by the parallel cap in cooperation with the inductor. I'll also check the efficiency and measure the K factor. It is true that my case is 'special' because of single band use and 3/8wl as total length of one leg of the dipole+OWL. In case the results are dissapointing, I'll rethink about using the single band super efficient cap loaded dipole antenna. Thank you all for simulations suggestions and possible solutions. Stefano Why not try a full size, unitscale link coupled tuner with this circuit, which uses a 2.5" Primary link coil OVER a 2" Secondary coil. These component values and sizes have been verified by simulation. This Coaxial arrangement should provide the highest coupling coefficient. See coil detail notes in lower lefthand corner. This is essentially what you requested graphically in a previous post. PhilAC0OB Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 26, 2024, 08:03:08 PM Wrong circuit design. A variable capacitor needs to be added to the input inductor. This will give you much more flexibility in tuning the antenna coupler, matching.
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 26, 2024, 08:33:38 PM For some reason I can't reply any more. :X
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 26, 2024, 08:37:12 PM That's good, I can post but I can't attach the photos of my just finished tuner. I'll try to find out what is wrong and come back with the photos.
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 26, 2024, 08:47:58 PM Just a test photo, nothing to do with this conversation.
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 26, 2024, 08:49:38 PM I found out the reason but I'll fix it tomorrow and I'll add the photos of what I have done till now.
Excuse me for the inconvinience. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 27, 2024, 08:33:18 AM Phil, Joe, Steve, Chuck and all,
I fixed my problem with attachments. My photos archives were jpeg and I had to transform them to jpg. I hope this time to get attached. The main inductor is 34 turns 1/8'' spacing 3/8'' copper tube on a 5.5" pvc form and the link coil is 4 turns 3/8'' spacing 3/8'' copper tube on a 7'' form. Due to dog house small dimensions I can't get any bigger. In any case I'll adjust OWL or antenna length to get the most efficient taping. Plenty of taps for experimenting tunings. Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 27, 2024, 05:21:31 PM Phil, Joe, Steve, Chuck and all, I fixed my problem with attachments. My photos archives were jpeg and I had to transform them to jpg. I hope this time to get attached. The main inductor is 34 turns 1/8'' spacing 3/8'' copper tube on a 5.5" pvc form and the link coil is 4 turns 3/8'' spacing 3/8'' copper tube on a 7'' form. Due to dog house small dimensions I can't get any bigger. In any case I'll adjust OWL or antenna length to get the most efficient taping. Plenty of taps for experimenting tunings. When you say 5.5" and 7" forms, are those length dimensions? If so what are the coil diameters? Phil Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 27, 2024, 09:57:49 PM 5.5'' and 7'' are the diameters from center to center of the 3/8'' tubes. The dimensions are 21.2'' for the 34 turns coil and 2.1'' for the 4 turns link coil.
Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 28, 2024, 12:56:55 AM 5.5'' and 7'' are the diameters from center to center of the 3/8'' tubes. The dimensions are 21.2'' for the 34 turns coil and 2.1'' for the 4 turns link coil. Your 5.5" Dia. 34turn Output coil has an inductance of 35uH and an XL of 415 ohms. About 220pF in parallel will tune it to 1.85MHz. Your 7" Dia. 4turn Input coil has an inductance of 3.5uH and an XL of 41 ohms or 9 ohms below the 50 ohm target. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 28, 2024, 06:52:32 AM I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance.
I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 28, 2024, 10:31:48 AM I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance. I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing. The design is based on the self inductance of primary and secondary. The mutual inductance is controlled by the coupling factor and so these items are chosen somewhat independent of each other. No issue, just put a tiny squeeze on the L if need be. Initial values might compromise best case return loss slightly. Title: Re: Balanced linked tuner turns ratio Post by: KC2ZFA on September 28, 2024, 01:11:42 PM possibly a naive question: all those designs here have low to very low L/C ratios, is that desirable ?
peter Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 28, 2024, 04:31:41 PM Hi Peter,
What values would you propose for L and C in a sircuit like the one in the attachment? Single band use p.e 1850Khz, 50Ohm to 120+600jx impedance. Stefano Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 28, 2024, 04:55:23 PM The L/C ratio is driven by the complex line Zo with the antenna attached and the desired matching bandwidth, that is operating Q. A good treatment of the details is in the handbook, example the '63 treatment in the chapter on transmission lines. See copy of excerpt attached. There in Ch 13, the series and parallel balanced line tuning is addressed.
Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 28, 2024, 08:04:05 PM I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance. I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing. The design is based on the self inductance of primary and secondary. The mutual inductance is controlled by the coupling factor and so these items are chosen somewhat independent of each other. No issue, just put a tiny squeeze on the L if need be. Initial values might compromise best case return loss slightly. In my calcs, the calculated coil inductances were for free coils by themselves. If one is concerned with the Mutual Inductance, then M ~ = (Ns X Np X Area)/length of coil. M also is = k X SQRT(Ls X Lp) where k is the coefficient of coupling. If k ~= 0.9 for a coaxial set of coils, then M = 0.9 X SQRT(3.5uH X 35uH) = 0.9 X 11.1uH = 10uH. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on September 28, 2024, 08:51:19 PM Even if it is a coaxial set up, the two coils have a distance of 3/4'' between them so K could be less then 0.9. I used 4 turns for the link coil because this number was right in a previous linked tuner I made for an EFHW (4000Ohm +). In that case I had the link coil (4 turns) around the cold side of the long inductor (44 turns). It worked perfectly without capacitor in series to ground. In that case coupling was much better and K was for sure closer to 0.9. The long inductor was factory made and I managed a very tight coupling, may be less then 3/8''. In any case if I'll count around 10uH when in place then with a var. cap and 1300pf in series to ground I'll adjust it to the desire XLS. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 28, 2024, 09:06:05 PM Some more comments on this and to put this design approach in perspective.
Choosing Lp and Ls might be driven by the loaded Q of the primary and secondary inductance. On the 50 ohm side, a Q of unity is realized at 1.8 MHz with an inductive reactance of 50/(6.28*1.8 MHz) or 4.4 uH, hence its value. On the balanced side consider the magnitude of the Z termination, about 612 ohms, At a Q of unity, Ls would approach a value of 54 uH. However, if the reactance of 600 ohms is tuned out at 1.8 MHz, the remaining 112 ohms is set by an inductance of 10 uH. A range of 1054 uH with suitable C to tune the reactance is reasonable. It is the coupling factor, k, that will significantly alter the final quality of the match and the return loss. Recall in the earlier designs of balanced matching tuner systems, a swinging link was always touted as an ideal final adjustment. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 28, 2024, 09:08:03 PM Should be 120 ohms, real, anyway still ~ 10 uH.
Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on September 28, 2024, 09:43:29 PM Alan  W4AMV, good material.
[/quote] Title: Re: Balanced linked tuner turns ratio Post by: KC2ZFA on September 29, 2024, 01:16:16 PM as the handbook text posted above says, as a first approximation use the LC values of the transmitter plate tank.
the 160M B&W balanced (for pushpull PA) coils are 94 uH and resonate at the bottom of 160 with 90 pF. The handbook recommendation is that the LC tuner tank resonates at 80% of the intended operating frequencies so max of 100120 pF would be used in a parallelfeed balanced link tuner for 160 using the B&W hdvl or tvl coils depending on power. From what Stefanos is seeing at the input end of his ladder line he should use the parallel configuration. and make the link variable to dispense with the capacitor on the link side. Title: Re: Balanced linked tuner turns ratio Post by: DMOD on September 29, 2024, 05:44:03 PM If Charles and Peter have some analysis and schematics they would like to submit, I am sure we could all benefit.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 30, 2024, 06:08:04 PM This is sort of a work in process. I found it interesting to look at the linked coupling transformer modeled as its "conductively coupled equivalent circuit". The results for a simple impedance matching system are interesting. More to follow while digging deeper.
Title: Re: Balanced linked tuner turns ratio Post by: Tom WA3KLR on September 30, 2024, 07:30:30 PM I'm just diving into this thread. 1.4 picofarads at 160 meters; 60,000 Ohms? Doesn't look like a comma to me at 7:30 p.m.  tired.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on September 30, 2024, 07:53:56 PM Hi Tom... Yes sir... Keep in mind, there just numbers. Some notions are counter intuitive. Not necessarily practical. However, it is the concepts and making sense of the mechanics so that practical and useful design paths are obtained.
Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on October 01, 2024, 07:33:42 AM as the handbook text posted above says, as a first approximation use the LC values of the transmitter plate tank. the 160M B&W balanced (for pushpull PA) coils are 94 uH and resonate at the bottom of 160 with 90 pF. The handbook recommendation is that the LC tuner tank resonates at 80% of the intended operating frequencies so max of 100120 pF would be used in a parallelfeed balanced link tuner for 160 using the B&W hdvl or tvl coils depending on power. From what Stefanos is seeing at the input end of his ladder line he should use the parallel configuration. and make the link variable to dispense with the capacitor on the link side. 94uH inductance is much but logic for a 160m final PA which can vary from 100010000 Ohm depending on plate voltage to current, Q of the tuning network and working class. When the impedance, as in my case, is considerably low the inductance in conjuction with the proper capacitance can be much smaller. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 01, 2024, 05:58:34 PM This is sort of a work in process. I found it interesting to look at the linked coupling transformer modeled as its "conductively coupled equivalent circuit". The results for a simple impedance matching system are interesting. More to follow while digging deeper. Added the interactive Smith chart tuning tool which was the motivation in using the T equivalent transformer arrangement. The added pages now become more realistic You could embellish all this with parasitic components if desired. This is now version ONE. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 01, 2024, 08:29:16 PM Used the tune feature in the Smith chart tool with the ideas presented in the paper pdf and constraining to values close to those discussed in the thread. However, kept the k factor realistic at k ~ 0.5. There is an asset in using the series cap input in order to achieve a reasonable response for small k factor.
Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on October 02, 2024, 05:24:27 AM 5.5'' and 7'' are the diameters from center to center of the 3/8'' tubes. The dimensions are 21.2'' for the 34 turns coil and 2.1'' for the 4 turns link coil. Stefano, From your link coil dimensions, 4 turn link coil= 3.73uh, 34 turn coil= 37uh, k=.9 Circuit L is the feed point impedance vs frequency of a modeled centered fed 160 meter dipole at 100 feet, with an overall length of 247 feet of #12 copper wire, sweep from 1.8 MHz to 2 MHz. T1 is a 1/8 wavelength at 1.9mhz of 600 ohm line. The antenna can be match to 50 ohms across the 160 meter band. Shown are the values of C1 and C2 for matching at 1.8, 1.9 and 2Mhz. Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on October 02, 2024, 05:28:26 AM Match 1.9 MHz
Title: Re: Balanced linked tuner turns ratio Post by: ka1bwo on October 02, 2024, 05:31:20 AM Match 2Mhz
Title: Re: Balanced linked tuner turns ratio Post by: DMOD on October 02, 2024, 07:23:52 PM Simulations and S graphs are nice but I think what experimenters really need and want are real schematics and component values.
PhilAC0OB Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on October 02, 2024, 10:02:38 PM Hello to all.
Below are component values for the 160 meter (1.8 MHz) link antenna tuner calculated for a 600 ohm feedline. Because this link input coil (connected to the transceiver or transmitter) is fixed (cannot be tuned) you need to add a variable capacitor in series with this coil to achieve input tuning flexibility. This variable capacitor can be connected ahead or after the inductor. If it is after the coil then is is connected to ground. If it is placed in front of the coil then the coil is grounded. Some times it can be placed in parallel with the input inductor. Each antenna farm is unique and testing of the input variable capacitor placement is required to determine it's electrical location. INPUT components: 1. Input link capacitor value is 1768 pf. A variable 300  500 pf capacitor with added (padded) home brew or commercial capacitors in parallel will get you up to the 2500 plus pf range. 2. Input link coil is calculated at 4.4 uH. OUTPUT components. SERIES circuit configuration: 1. Total inductance is 106 uh. 2. Total capacitance is 74 pf. Use a 150 pf variable capacitor. PARALLEL circuit configuration: 1. Total inductance is 27 uH. 2. Total capacitance is 295 pf. Use a 500 or 600 pf variable capacitor. If the total antenna system length is a multiple of 1/8th wavelengths instead of the desired multiples of 1/4 wavelengths then you may need to connect a capacitor or an inductor to the left and rights sides of the transmission line at the output of the tuner. This is called a shunt capacitor or a shunt inductor. 1. The shunt capacitor is calculated at 147 pf. Use a 300 pf variable capacitor. 2. The shunt inductor is calculated at 53 uH. Make this inductor variable with taps. Above components with less challenging values can be achieved with a 300 ohm transmission line. The 300 ohm transmission line also lowers the high voltages encountered at the antenna coupler in the parallel configuration which is dependent upon total antenna system electrical length. Lowering these voltages helps prevent high voltage induced arcing of the capacitors. 73, Chuck Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on October 03, 2024, 04:55:03 AM PARALLEL circuit configuration:
1. Total inductance is 27 uH. 2. Total capacitance is 295 pf. Use a 500 or 600 pf variable capacitor. If the total antenna system length is a multiple of 1/8th wavelengths instead of the desired multiples of 1/4 wavelengths then you may need to connect a capacitor or an inductor to the left and rights sides of the transmission line at the output of the tuner. This is called a shunt capacitor or a shunt inductor. 1. The shunt capacitor is calculated at 147 pf. Use a 300 pf variable capacitor. 2. The shunt inductor is calculated at 53 uH. Make this inductor variable with taps. I am exactly on Chuck's road. If I am lucky and this is the value I'll need then I have doorknobs 150pf few Kvars, I have also increased the link coil inductance by bringing the turns much closer each other. Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on October 03, 2024, 07:12:36 AM I will see if I can recalculate the output series components using capacitors instead of inductors. This may make it easier for component selection. Give me a little time to crunch the numbers.
It is VERY important to utilize the input variable capacitor. You need four tires to operate your car efficiently and the same goes for the link antenna coupler regarding this input variable capacitor. 1. Try not to use door knob capacitors. They can heat up and turn the tuner into a microwave oven. Fixed home brew plate capacitors work much better; they run cool. 2. Be careful when decreasing the spacing of the coil windings. This increases inner winding capacitance and some times messes things up. The output windings work well when spacing is the diameter of the wire or tubing in use. If possible, use 1/4 inch or 3/8 copper tubing or flat copper stock to make parallel 300 ohm open wire feeders. It may be possible to make a four wire open wire feeder that uses smaller wire to accomplish the preferred 300 ohm impedance for open wire feeders. 73, Chuck Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 03, 2024, 09:08:47 PM Hi Stefano,
Given your current link coupled physical configuration per your prior pictures, would recommend you take a measurement of the coupling value, k. This significantly drives the possible solutions and component values of the tuner. Some of this can be accommodated by the series C on the link side. However, knowing in advance what k is possible helps target a closer set of all component values. Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 06, 2024, 08:34:54 PM Here is an Excel SS. Not fancy, but seems to correlate well with measurements on push pull link coupled tanks that I have constructed in the past. Any issues, please let me know.
Title: Re: Balanced linked tuner turns ratio Post by: WA4WAX on October 07, 2024, 03:25:11 PM See article by O J Russell. Good luck.
https://www.worldradiohistory.com/UK/PracticalWireless/50s/PW195508.pdf Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 08, 2024, 11:38:50 AM See article by O J Russell. Good luck. https://www.worldradiohistory.com/UK/PracticalWireless/50s/PW195508.pdf Excellent and thanks. Another is: https://www.worldradiohistory.com/ArchiveElectronics/50s/Electronics195205.pdf W. Bruene from Collins Radio had some nice pieces on the subject. 73' Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on October 13, 2024, 02:57:50 PM Attached are two pictures of two circuits for tuning the link antenna coupler in series or current feed as it is sometimes called.
The inductor and capacitor values are calculated values to resonate the antenna system. The calculated capacitor values should be doubled for better antenna coupler tuning. Example: 1. 74 pf should be doubled to approximately 150 pf. 2. 37 pf should be doubled to approximately 75 pf. I should of added the input side of the link antenna tuner and not just the output side as shown in the two pictures. Will make an update to the pictures to reflect the entire link antenna circuit, soon. 73, Chuck Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on October 13, 2024, 03:01:55 PM W4AMV,
Thank you for posting those good articles. 73, Chuck Title: Re: Balanced linked tuner turns ratio Post by: Opcom on October 14, 2024, 10:08:34 PM Phil, Joe, Steve, Chuck and all, I fixed my problem with attachments. My photos archives were jpeg and I had to transform them to jpg. I hope this time to get attached. The main inductor is 34 turns 1/8'' spacing 3/8'' copper tube on a 5.5" pvc form and the link coil is 4 turns 3/8'' spacing 3/8'' copper tube on a 7'' form. Due to dog house small dimensions I can't get any bigger. In any case I'll adjust OWL or antenna length to get the most efficient taping. Plenty of taps for experimenting tunings. This thing is beautiful! Could you please show pictures of how the coil taps are made to the tubing, with the wing nuts and all. That is, are they screws which are soldered, or something else? I've never seen anything like it. Title: Re: Balanced linked tuner turns ratio Post by: AMLOVER on October 15, 2024, 07:50:22 PM Hi Patrick,
First stage. The copper tube was first winded around the PVC form 5'' diameter. The copper turns were winded very closed together without any space between them in the begining. It is easy to distant them later but very dificult to bring them close back together if for some reason they get further then should be. The black teflon spacer tube turns were winded in between the copper turns and they will create the right distance 1/4''. Copper tube turns are fastened on the PVC form with few 1/2'' long inox 'memory' screws to create a model for the turns right position in order to rewind them later in the same exactly position. Two lines are made by pen and so the wholes will be drilled in a straight line. The copper tube is drilled only on its upper side and the male part of the bronze spacers are screwed into the wholes to stay stable for later soldering. Those exagon bronze spacers are 3/4'' long with one male and one female side like the ones we use to keep PCBs higher of the sassis in our constructions. The copper tube is 3/8'' and the male part of the bronze spacer is shorter, just 1/4'' long. Second stage. The inox 'memory' screws which fastened the copper tube turns in place are unscrewed and the inductor gets free to move away from the PVC form. With the inductor away from the PVC form is time for soldering the bronze spacers on the copper tube turns with the boutane gun. When everything is soldered in place and the copper is cool, gets a good cleaning from dirts and is painted with some primer and a final satin grey color. 2 hours later the inductor is dried and repositioned back on the PVC form. It has to be fastened in the same place as before by using the 'memory' inox screws screwed back in their predrilled wholes. The black teflon spacer tube will be rewinded back on the end and that's all. This spacer tube could also left away but is important to form the right space in the first stage. In the female part on the top of the bronze spacers are screwed male 'butterfly' screws to fasten the OWL edges easily by hands. Very soon the tuner will be ready and make few measurements/tests before real antenna is connected. More photos will come soon. Stefano Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 18, 2024, 12:11:25 PM Hi Chuck. I set up the circuit shown as the series tuned inductor pair, the circuit of picture # 2. Assume that the topology I provide is correct and the primary (link) is the Q = 1 at 1.85 MHz, the swept responses for coupling coefficient, k, are attached. It is interesting to note how significant the k value shifts center frequency and the quality of the match. This is a "sensitive" configuration. Perhaps a series C on the link is warranted. A swinging link is also a possible solution. This sweep at k = 0.45, the next is swept k.
Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 18, 2024, 12:13:00 PM The swept k response. The k at ~ 0.4 to 0.5 is best. Smaller and greater produces a degradation.
Title: Re: Balanced linked tuner turns ratio Post by: aa5wg on October 18, 2024, 02:21:28 PM Alan,
You are correct. The variable input capacitor to the link coil is needed. It is part of the design. And, this input variable capacitor arrangement, in the past, performed better than a swinging link coil by itself. Thank you for the nice pics of your work. I should mention: 1. Try not to put any physical material between the coil windings. This degrades the air dielectric. 2. An exception to this are some fiberglass products like G10 FR4. I still need to upload pics of the complete link antenna tuner circuit and not just the output section that I uploaded earlier. 73, Chuck Title: Re: Balanced linked tuner turns ratio Post by: W4AMV on October 18, 2024, 10:02:28 PM Yes Chuck. I tried 2 cases. A k of 0.3 and a k of 0.65. A reasonable variation which I was able to adjust for a SWR of less 1.2:1 by adjustment of the series C with the link. Only a small change was required in the resonating capacitor value. That range in k required the
variable cap in series with the link to shift 3:1 in value. Of course the k is fixed in any construction. A more important result is what range in balanced termination Z can be accommodated by the series link tuning and tapping position of the balanced inductor? Title: Re: Balanced linked tuner turns ratio Post by: Opcom on October 20, 2024, 12:22:31 AM Thank you Stefano, that is a very wellengineered method. AMfone  Dedicated to Amplitude Modulation on the Amateur Radio Bands
