Balanced linked tuner turns ratio

[AMLOVER]

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 push-pull 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 100-120 pF would be used in a parallel-feed 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 1000-10000 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.

[W4AMV]

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. 

[W4AMV]

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.

[ka1bwo]

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.  

[ka1bwo]

Match 1.9 MHz

[ka1bwo]

Match 2Mhz

[DMOD]

Simulations and S graphs are nice but I think what experimenters really need and want are real schematics and component values.

Phil-AC0OB

[aa5wg]

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

[AMLOVER]

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. 

[aa5wg]

I will see if I can re-calculate 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  

[W4AMV]

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.

[W4AMV]

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.

[WA4WAX]

See article by O J Russell.  Good luck.

https://www.worldradiohistory.com/UK/Practical-Wireless/50s/PW-1955-08.pdf

[W4AMV]

See article by O J Russell.  Good luck.

https://www.worldradiohistory.com/UK/Practical-Wireless/50s/PW-1955-08.pdf

Excellent and thanks. Another is:

https://www.worldradiohistory.com/Archive-Electronics/50s/Electronics-1952-05.pdf

W. Bruene from Collins Radio had some nice pieces on the subject.
73'

[aa5wg]

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 smoother 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



 

[aa5wg]

W4AMV,

Thank you for posting those good articles.

73,
Chuck