160 on a Wing and a Prayer

[K9ACT]

I am in the process of re-tooling my 810 rig for 160; that's the easy part.

Sooner or later, I have to face the inevitable facts that have neither an antenna nor a tuner designed for the job.

The antenna is a 75 meter dipole up high and clear of trees, fed by a 400 ohm ladder line.  I live in a forest and a longer antenna, at least symmetrically so, is not an option.  The tuner is an old Heathkit that does not have 160 capability.

The combination works to my satisfaction on 80, 40 and 20.  Unlike the antenna, this is a solvable problem but the question is, would a proper tuner make a usable 160 antenna out of the 80 meter dipole.

I tried my Kenwood and low power MFJ tuner on 160 and it seems to work but 25 watts is not 250 watts.  I tried using the bal line input and tying the two ends together and got about the same results.  When I say it worked I mean a few locals could hear me.

Assuming the answer to the above it yes, does anyone have any suggestions on modifying the Heathkit for 160?

Is it a matter of adding some lump L or C somewhere or do I need to start from scratch or buy a new one?

Is the ladder line/dipole a one way compromise?  Like you can make a big antenna smaller but not bigger?

Does using it with a tuner require that the two halves of the flat top be the same length.  I could extend one end several hundred feet if this would help and not hurt what already works.

Maybe I should just give up? In my 69 years, I have spent about ten mins on 160 and that was running the above test.

js

[Pete, WA2CWA]

Which Heathkit tuner do you have?

[Sam KS2AM]

Sooner or later, I have to face the inevitable facts that have neither an antenna nor a tuner designed for the job.

The antenna is a 75 meter dipole up high and clear of trees, fed by a 400 ohm ladder line.  I live in a forest and a longer antenna, at least symmetrically so, is not an option.  The tuner is an old Heathkit that does not have 160 capability.

Unlike the antenna, this is a solvable problem but ...

Does using it with a tuner require that the two halves of the flat top be the same length.  I could extend one end several hundred feet if this would help and not hurt what already works.

js

It sounds like you do have some room to work with and perhaps an antenna with different geometry is what you need to get a real 160 antenna up.  What about putting up a horizontal loop ?   At 1885 kc a square loop is 133 ft per side.  It can be rectangular or triangular or another shape if that suits the geography better (mine is a trapezoid).


Sam / KS2AM

 

[KL7OF]

My experierence is that more wire is better than any tuner when going to 160 meters...if you can add some additional wire to your existing antenna or put up a longer wire (even if it is low)  you will have better results than trying to tune a short wire with a tuner for 160...  my 2 cents...good luck....Steve

[k4kyv]

Before I put down my  radial ground system I used the 80m dipole on 160 as a quarter wave dipole.  It was a matter of getting the feedline the right length so that parallel tuning would work.  You want to avoid a length that is midway between current and voltage feed.  Once you  get it tuned up you will find that the Q is high and the tuning very sharp.  On mine, it is like being crystal controlled; I can move maybe +/- 5 kc/s in either direction before the tuner needs readjusting.  Since my tuner is at the base of the tower that was a real PITA, so I rigged up a reversible DC motor to operate the tuner and I would seek  minimum reflected power.

The antenna worked quite well across the entire band all over north America.  I suspect I was helped considerably by the height off the ground, approximately 110 ft. average height.

But when I finally got the radial system installed, the quarter wave vertical was much better, except when working some friends I had in Nashville, about 50 miles airline  from here.  They told me that the dipole was about 30 dB stronger than the vertical, and that made a  difference between being buried in the urban electrical hash and being well above the noise.  The dipole was a better high angle radiator, while the vertical has a skip zone.

But one of my friends is SK now, and others are not active, so there is no-one in Nashville that I talk to on 160, so I haven't used the dipole on that band for years, although I  still have the tuner.

[K0UL]

Dear JS,
   I had exactly the same problem several years ago. I put up a 75 meter dipole, fed with 450 ohm "CBS", which worked"somewhat".About that time I acquired a Viking Valiant and thought I would like to "try 160". What to do?? I decided to add a length of wire to each end to convert the 75 dipole to a 160 G5RV. It works GREAT!!
   Coupler?? I built a "JJ Special". No problem since.
       
                                        Tom  K0UL

[w3jn]

The K1JJ tuna I built also works on 160 with my 75 dipole, albiet barely.  The ant is W7FG ladderline feeding a 130' or so fan dipole (lengths of fan elements are all the same). 

I thought I'd hafta tap way out on the coil but to my surprise I had to tap way IN.  The coil is a 25 uH or so out of a BC xmitter, the cap is a 500 pF vac variable, input link is 1 turn of 1/2"X1/8" thick STRAP.  The cap is tapped at the outermost ends of the coil, the ant taps are each +/- 1 turn from the center.  This makes for stupendous circulating current and modulates the vac variable with a bit of a ringing sound!  Nevertheless it does get me on 160, but 1885 is about the absolute lower limit.  I did put a 50 pF fixed vac cap in parallel and could get down to about 1830 (not that I really want to). 

Your tap situation of course will be different according to your feedline length, etc.

[WA1GFZ]

Notice the conductor size of John's tuner. hammy hambone will melt

[AF9J]

Jack,

Like some others have said, the more wire the better, with a tuner that can handle the voltages. I've been doing 160 since my college days in the late 80s.  For a few years it was my favorite band.  If you can't do a dipole or a loop, you can run your 75m dipole in a T configuration. but you will at the very least, need some kind of counterpoise that's electrically close to 1/4 wave on 160, if you;re not running a diplle or a loop.  You can always add wire to your dipole,in the direction you do have space, and use it as an off-center fed dipole (as long as your system can handle the impedance). 

73,
Ellen - AF9J

[WB2YGF]

But when I finally got the radial system installed, the quarter wave vertical was much better, except when working some friends I had in Nashville, about 50 miles airline  from here.  They told me that the dipole was about 30 dB stronger than the vertical, and that made a  difference between being buried in the urban electrical hash and being well above the noise.  The dipole was a better high angle radiator, while the vertical has a skip zone.

Is it possible there was also attenuation due to cross polarization?  I know on 10M AM it is an issue for ground wave - don't know about 75.

[K9ACT]

Which Heathkit tuner do you have?

Tuner is model 2040.

js

[Steve - WB3HUZ]

You should go with series feed if you are tapped that far in.

The K1JJ tuna I built also works on 160 with my 75 dipole, albiet barely.  The ant is W7FG ladderline feeding a 130' or so fan dipole (lengths of fan elements are all the same). 

I thought I'd hafta tap way out on the coil but to my surprise I had to tap way IN.  The coil is a 25 uH or so out of a BC xmitter, the cap is a 500 pF vac variable, input link is 1 turn of 1/2"X1/8" thick STRAP.  The cap is tapped at the outermost ends of the coil, the ant taps are each +/- 1 turn from the center.  This makes for stupendous circulating current and modulates the vac variable with a bit of a ringing sound!  Nevertheless it does get me on 160, but 1885 is about the absolute lower limit.  I did put a 50 pF fixed vac cap in parallel and could get down to about 1830 (not that I really want to). 

Your tap situation of course will be different according to your feedline length, etc.

[Pete, WA2CWA]

Which Heathkit tuner do you have?

Tuner is model 2040.

js

I figured it was the SA-2040. If you Google "SA-2040 on 160" you'll find the question has been asked a number of times over the last 8 or 9 years (based on the dates of the queries. No one really had an answer other then increasing the values of the two variable caps and also increasing the inductance and current carrying capacity of the variable inductor. The SA-2060/2060A is basically the same as the SA-2040 except it covers 1.8-30 MHz. Get a copy of the manual or parts list and schematic and try to find similar parts to convert your SA-2040.

[WA1GFZ]

John I think you would be better off with more primary turns so maybe you could move the taps out a bit.

[w3jn]

Works, not gonna screw with it

[W2VW]

You will need feedline, a coupler and dipole wire material which has large conductor sizes. This is especially true at QRO where things will cook.

I got pretty good results with 124' center fed with #8 feeders and a honking coupler. I kept going larger until the R.F. ammeter at the coupler's output showed no further improvement. I even worked Yerp on 160 phone 2 winters ago.

It's all in the resistive loss of the wire and circulating current in "tuner" components. When you model a doublet like the one suggested the radiation resistance will be in the single digits. This means you have to deliver your R.F. power into several ohms instead of the usual 50 or 70. This in in addition to providing a conjugate match. BTW, center of the dipole can be made of heavier wire than out toward the ends.

My coupler morphed into a version of the balanced balanced tuner as described by AG6K on his web page. I landed up using a vacuum variable and inductors wound from refrigerator ice maker supply line. Roller inductors are NOT necessary in that tuner design and are a weak link in this application.

There are still some old threads on here with a lot of good information. Frank KB3AHE has been on 160 with a 40 meter dipole and did OK. Tom WA3KLR had a thread going on relative signal reports a few years back. The Jumbo Joint tuner will certainly work. I opted to use something else after doing the link coupled thing with undersized components for a time.

If you can see your way clear to tack 20 feet of wire on each end (even if it has to bend sideways and head towards ground) matching becomes easier and losses go down. The voltage part of the antenna doesn't radiate a whole lot anyway. This should not ruin performance on 80. 

Start by making careful R.F. current measurements at your existing coupler's output. The meter will be in the center of a conjugate match so it will pretty much measure only radiation resistance load+conductor dissipated losses AND some circulating current. In other words the reactance at that point should not mean much to the ammeter reading. Use a easily repeated carrier level for the testing. I liked a 1 kw carrier as that found weaknesses in the system pretty quickly. If you keep the feedline and doublet lengths the same, any increase in R.F. current measured will show how your work is paying off. The reading also helps you visualize what is going on when factored into numbers obtained my modeling the antenna and then taking the modeling figures and plugging those into a feedline transformation calculator.

[W2VW]

The AG6K deal has the advantage of working OK for receive on bands where the tuner isn't matched AND allows for easy DC grounding of the entire antenna. This grounding isn't a substitute for a safety disconnect but it does give rain static somewhere to go.