A 60' flat top for 160 and 75m!

[The Slab Bacon]

With operating condx on 75 being horrible at best lately, I wanted to see what 160 was like. I have been running a 60' long folded dipole on 75 for years now with pretty good results. Having only a postage stapmp sized lot that was all that I could put up. Many of you have worked me on 75 and heard how well it did on that band. so I decided to see if I could get it to play on 160. It was a bit of a challenge, but it did!

A compromise antenna will always be a compromise, but it is still better than none at all!! You will NEVER be the channel master, but at least you will be there and copyable. So far as the initial testing and trying have shown, the results are quite favorable. With pretty terrible condx on 160 the last 2 nignts I have been able to work everyone that I could hear, and the signal reports that I have received have been pretty much the same as as i was hearing the stations that were giving them. I will update this as condx improve and i do more testing. I was in QSO last night with W3SLK, N3IBX, K2PG, WA4DWW, KD2XA,and AC4BV. They were all hearing me exactly the same as I was hearing them. Propagation was piss poor and spotty. Worked W1IA, K2DK, KK4AM, K2PG and others on friday night.

Initial testing is showing that you will also need to have "antennas by Eimac" working for you as well as I was running "legal limit" power level for the testing. Although I worked W1IA friday a week ago running 100w power level. Better plan on having some reserve power to get the job done.

The secrets that make it work are simply minimizing your losses and getting absolutely as much RF power as you can TO the antenna! You MUST run balanced line feeders, at least 14ga at minimum, 12 or 10ga would work even better. You MUST use a ROBUST tuner capable of handling an extreme mismatch and EXTREMELY HEAVY FEEDLINE CURRENT without heating up or arcing over. Remember that heat = loss, anything that is getting hot is absorbing your power and dissipating it. I had a real battle getting the tuna to survive the ordeal, but a major redesign made it work and run kool as a cucumber. Design your tuna / balun, and feedlines to handle at least 3-5 times the load that you would expect and you will be fine. DONT EVEN THINK ABOUT USING AN MFJ OR NYE VIKING STOREBOUGHT TUNA FOR THIS ONE!! You will HAVE to build a strapping hb tuna for this one.

I will make up a descent drawing of the whole system ans scan it in next week so I can post it along with some of the continuing test results here. It is doable!!!

                                                                                        The Slab Bacon

[Steve - WB3HUZ]

Congrats Frank. Where there's a will, there's a way. Hope to hear you on 160, maybe tonight.

[Jim, W5JO]

I hope to hear any of you on 169.  I haven't heard a peep from the East yet out here in the South of Oklahoma.

[Steve - WB3HUZ]

Not much westward action on 160 this season for me too - although I have worked stations as far west as Wisconsin, Indiana, Illinois. Several evenings over the Thanksgiving weekend, I noticed heterodynes underneath the east coast stations on 1885. On evening, the heterodynes were very noticeable. During a break in the east coast transmissions, I thought I heard a station mention Tucson, so maybe some far west was coming through.

Many of us are running dipoles, which aren't the best for longer distance contacts on 160. I've considered putting up an Inverted-L for the AM DX.    That said, I've worked Bill-KD0HG more than once on 160 using a dipole, so it can be done. Suggest we take a listen every once in a while for stations on the opposite coast, or set up some calling times.

[WA1GFZ]

Frank was making the trip to Ct. last night. I will be interested to see how he improves the set up to eliminate losses.

[W2JBL]

Frank- you were quite strong on 160 last night, especially considering the band was "long" and i was having trouble with K1KBW and N3IBX, i'd say you are doing a very good job down there. welcome to the peacful shores of 160!

[The Slab Bacon]

Murphy's law will always bite you in the butt. I get everything working and the band craps out! Oh well, szht happens. 160 has been just about as bad as 75 for the past few days. Long skip, high noise, spotty propagation and weak signals. I will keep everyone abreast of the progress after a few more nights of testing.

                                                              The Slab Bacon

[W3FJJ]

Hey Frank I heard you saturday, around 4pm testing and you were s-9, q-5 to conowingo,
We should have a good daytime path, Look forward to working ya om, keep up the good work!

Chuck

[Tom WA3KLR]

I did a quick antenna and transmission line simulation of Frank KB3AHE’s 60 foot long folded dipole at 1.9 MHz.

See it in the topic "160 Meters Transmission Line Study  - SWR and Losses"

http://amfone.net/Amforum/index.php?topic=9122.40

[Tom WA3KLR]

Frank 'AHE,

If you can give me some refined numbers, I will re-do the study and see what difference there is:

1. Your actual antenna height at the 2 ends and middle.
2. The wire size used on the folded dipole and the wire spacing used.
3. The wire size used on the ladder line and the spacing used.
4. The actual length of the transmission line.

Thanks,

[WA1GFZ]

Tom take a look at linear loading by running a folded dipole with an open at the center opposite the feed point. I wonder if that would raise the Z a bit?

[WA1GFZ]

http://www.bushcomm.com.au/
Check out the multiple wire antennas
Frank look at the pictures and see how the length is increased. They use a balun and load resistor to get a better match but you can replace both with the tuner.

[WA1GFZ]

http://www.arraysolutions.com/Products/bushcommantennas.htm

A better picture of the interface to open wire line. Notice feedline drives 2 elements for low R. At the ends the two elements connect to the center that comes back to the feed point where the load resistor is located. you would not use the load resistor having a tuner.

[Tom WA3KLR]

Well Frank ‘GFZ, thinking about the situation, what my antenna suggestion for Frank ‘AHE is to change from the folded dipole to single wire flat top, same length, but with 30 foot danglers straight down at each end.  Same 600 Ohm ladder line feed.

This would have half-wave resonance on 75 meters and so would have good performance and low loss tx line there.

On 40 meters, this is basically two half-waves in-phase, not at resonance, but near.  Again low loss on tx line (SWR 10.2:1) and good performance.

On 160 meters at 1.9 MHz., feed point impedance is 8.4 – j1070 Ohms.  SWR 299:1, but again low tx line loss ~ 0.6 dB, which is 0.9 dB less than the feed line loss for the folded dipole.  The antenna itself appears to have about 14 ½ dB. better radiation efficiency than the 40 m. folded dipole on 160 m.  Looks about 2 ½ dB. worse than a full-sized 160 m. half-wave dipole at same height (40 feet).  So, signal about 15 ½ dB. better than the folded dipole system, including the 0.9 dB less tx line loss.  The current at the antenna feed point (with 1500 Watts) is 12 ½ Amps instead of 23 Amps with the folded dipole system.  R.f. voltage (with 1500 Watts) in the 12 ½ to 16 kV range across the tx line end to end.

Again, this is what the simulation says.

[WA1GFZ]

Tom,
I hope Steve and Co. save your work here. How about the Bushcom thing with linear loading?
Do you see any advantage with longer conductors folded back on themselves at close spacing?
Delete the balun and load resistors and just feed with open wire line.  Then back to the folded dipole do you gain anything by having the ends open to each other when they fold back to the center?

[Tom WA3KLR]

I like the photo that shows 3 wires in parallel on each side of the Bush BBA-100 dipole.  I was going to suggest to Frank putting up 2 wires spaced about 6" to 1 foot apart to reduce some antenna loss.

As I recall the Bush folks are running that one down to 3 MHz with 90 feet length.  That would scale to 142 feet at 1.9 MHz.  Looks like the 3 wires are spaced more than 1 foot apart.

I haven't studied the antennas you mention though. 

Those kinds of antenna designs are meant for frequency hopping and tuner-less operation.  They have a nice SWR curve across the HF spectrum, but the radiation efficiency has to be real bad on many frequencies.  As hams working one frequency at at time with a tuner, we can have our cake and eat it.  Best not to copy the design but use some of the construction ideas.
 
Depending on how high Frank's antenna is, how easy to let down, and what else is in the vicinity below the ends, maybe he could do the suggested change as a temporary experiment without much difficulty.

[Steve - WB3HUZ]

Adding end-loading capacity hats to the folded back design will further lower the resonant frequency. A zero-land ham did some work with the idea several years ago. With only a 25 foot long antenna and a single six foot long end-loading "capacity hat”, the antenna resonated at around 10 MHz. The feedpoint impedance was very close to 50 Ohms. This works out to about a one-half sized antenna referenced to a half-wave dipole. So on 75 meters, a 60 foot long antenna would be about right. How much the end-loading would help on 160 meters can only be seen running another simulation.

[WA1GFZ]

It's like building a motor. If you can't add bore add stroke.

[The Slab Bacon]

It's like building a motor. If you can't add bore add stroke.

Oooooo I like when you talk dirty!!

[The Slab Bacon]

Seriously, Tom, the ant is 120' of wire folded back on itself, spaced at 10 or 11".
But it does not form a complete loop. It is fed at the bottom and has a second bogbone insulator where the wires come back together at the top. It is about 35' off of the ground. The antenna is made of 14ga stranded copper wire, and the feeders are about 65' of 14 ga crappy brown stuff. (I am planning 12 ga stranded feeders as soon as I get a chance to make them.

I have about a 10' jumper of RG-8 between the tuna and the balun (1:1). The 23 amps of feedline current is prolly in the ballpark, as the coax jumper gets notocably warm after repeated long "old buzzard" transmissions. I am going to replace it with a piece of LDF-450 when I get a chance.

I was on for a while yesterday evening around 5:30 with W3HM. He was hearing me very well and remarked that it was working pretty well for a short antenna.
I really dont want to change the overall configuration of the ant as it works so well on 75m. As soon as I get a chance to sketch it up I will scan it in and post a full drawing of it here. Condx and activity on 160 lately have sure not been "the promised land" So as  use it more I will get a better feel for how well it is working.

                                                                The Slab Bacon

[WA1GFZ]

Frank,
I prefer solid wire for feeders. I think they hold shape better. My #10 solid feeders have been FBOM since 1983. Check your Balun temp 23 amps input sounds like a lot of current for the number of turns on that thing.
Now Tom can simulate your antenna....

Tom, notice the Bushcom  feed line interface to two outside wires of the three.
At the far end the three wires are tied so the return is the one center wire.
This would lower the resistance at the feed line interface.

[Tom WA3KLR]

Frank ‘AHE,

Thanks for the updated details.  I re-did the model for your 40 meter folded- but open dipole and there is a big difference in the performance at 160 meters.  Your antenna is 13 dB better than when the top wire was one closed loop (my simulation yesterday)!  How did you know to do this?  So your antenna (only) is about 1 ½ dB worse than the antenna I was suggesting, at 160 meters.  Your transmission line loss is 4.4 dB though, using the “450 Ohm Window” line option of the W9CF program for your “crappy brown stuff”.  This does not include the losses in the 10 feet of RG-8 or the 1:1 balun.

If you were running 1500 Watts into the system at 1.9 MHz., the current at the transmitter output is 25 Amps, 13 Amps at the antenna feed point, with your feed line.  The highest voltage is 19 kV r.m.s., occurring in the middle of the line.  The balun is seeing 2.5 – j738 Ohms at the ladder line connection.

As far as 75 and 40 meters:
             Antenna feed point Z   450 Ohm SWR    Z at balun/ladd.    Ladder line loss
  1.9 MHz.     3.21 – j1548 Ohms         1800:1        2.5 – j738 Ohms         4.4 dB.
  3.9 MHz.     11.8 – j345 Ohms               61:1      18.6 – j447 Ohms            1 dB.
7.29 MHz.     89.1 + j2054 Ohms           110:1     * 352 + j2567 Ohms          4 dB.

The baluns don’t work well at high impedances. It’s best to put the 1:1 balun between the transmitter and tuner where the impedance is 50 Ohms.  The tuner should then “float” on some wood or something to reduce the capacitance to the desk if metal and spaced from other metal gear to the sides.  Grounding wires to the transmitter, but not the tuner.  If this is effective, you will see a change in the tuner settings because the transmission line input impedance should change due to becoming more balanced and isolated from ground.

Changes to improve 160 meters, not as dramatic as I thought yesterday – If antenna system is changed, the total improvements on 160 may be about 6 - 7 dB. due to a number of incremental changes:
1 ½ dB. for the “75 meter” antenna I suggested.  It’s feed point impedance also helps to further reduce ladder line losses.
 5 ½ dB. for reduced transmission lines, balun and tuner losses.  Balun moved to transmitter output, and employ a beefy 600 Ohm line like Frank ‘GFZ described.

So the main thing would be to change out the ladder line and move the balun, with the present antenna.

This is what I see from the p.c. side of things Frank.

[WA1GFZ]

Very cool Tom, then 3 wires (bushcom) should be even better. BTW 1500 watts out at 50 ohms is just under 6 amps.  If the coax is hot then there is a problem. BB transformers really don't like high reactance and high Z.
Sounds like it is time to move the balun to the 50 ohm side and build a tuner of a different configuration.
6 0r 7 dB gain would make a big difference.

I guess the first thing to fix is the fed line. Home depot sells bare by the foot. Largest size is #4.
1/4 inch copper tubing would be lighter though. I don't think you have to go to 600 ohm Z.
#10 at 4 inches is about 400 ohms.

[The Slab Bacon]

Velly intelesting! I do plan on making some heavier feeders, however i am somewhat limited by the weight of the conductors. I do not use a center support
(I wish I could) so I am somewhat limited by their weight. I would love to use something beefy like #4, but I would have to use an engine block for a bob weight at the far end to pull it straight. #12 or even 10 may be doable, but that is prolly about the limit dur to weight.

At least we know that it is working as it is, as you were able to hear me last night.
Your end fed works very well as you had one of the best signals into my qth last night. Especially for running only a 100w power level. As condx was crapping out as I signed last night, you were still much stronger into Baltimore than Joe (GMS) was.

this whole setup is far from finished as it is still a work in progress. I will be still tweaking and improving as we go. At least I proved that it was doable and that is the main thing I wanted to do with this experiment. I dont expect to be the channel master with a short antenna. Everyone seems to be able to hear me, and that is all that I could ask for.

                                                         the Slab Bacon

[WA1GFZ]

Frank,
I use #10 and it isn't all that bad to support. #8 is my antenna which isn't bad either.