Link Coupled Antenna Tuner

[Ralph W3GL]

Dave / John...

Careful, HRO is liable to puke all over you guys and cause this thread
to disappear...

Now what was the so called subject?  Something to do with balanced tuners
using "butterfly" caps as I recall...

Only balanced tuner using a "butterfly" (dual differential) cap might be the Johnson "Match Box".  I think what he means, for the younger techs in here is what is called a Dual Ganged Split Stator Capacitor...

Back in the day (late 40's when I got back on the air) I used a couple of 47
lamps with short leads and clips attached on both sides of the feeder to check
balance.  Had a 0-5 Amp in series with the surplus RG-8 to the link to measure output power (about 775 watts as I recall).  Old Bud coil had a 5 turn link taped
at each turn. I still have that coil in line!

VSWR meters were unheard of,  just tuned for max current to the link...
Anyone remember the "Twin Lamp"?

[KD3CN]

<sup>"Dave / John...

Careful, HRO is liable to puke all over you guys and cause this thread
to disappear..."</sup>


Ralph, perhaps HRO already puked on everyone?  See the quote below.

^{"Well, it’s obvious that no one has a clue so I have attached my correct HB circuit below. I just wanted to see if anyone could see the mistake and it wasn’t a small one either."}

HRO should be more careful of the number 5 rule in the 'rules and regulations' of this forum.

Let's treat everyone with respect here.

[W2VW]

****

Watch it, the next animated gif might have something coming out of a different orifice

****

Noooooo. It was not bogus. It was a 124' doublet being used on 1.885 mhz. The point is very large current and voltages can be found when one uses short radiators.

It was bogus if your meters were reading 18 RF amps when your actual power input was much less than that. Unless it was like Don said and you figured out a way to solve the energy crisis. It doest really matter why it was happening it was still wrong for an accurate output power measurement, but I fully understand your point.

Take a deep breath.

You are assuming the ammeter is still being used at a 50 ohm j0 point. It is not. The antenna coupler is an impedance transformation device.

Same concept as measuring current in the primary of your 4-1000's filament transformer. You would not expect it to read 21 amps like it would on the secondary.

Don't feel bad. Several talented individuals have had trouble with this concept.

[WQ9E]

You are assuming the ammeter is still being used at a 50 ohm j0 point. It is not. The antenna coupler is an impedance transformation device.

For a real world example of the level of current you don't need an ammeter.  Just feel (very carefully) how hot many "legal limit" tuners get when trying to match an electrically short (and thus low impedance) antenna on 160 and 80 meters.  I vaguely recall QST did a review of several tuners matching various loads including very low impedance loads on 160 which will definitely test the current capability of the tuner.

[W2VW]

Yes, valid point, but even so, if you could accurately measure the input impedance of you feedline (the secondary transformation impedance) it still wouldn't be 18 amps.

One CAN compute load impedance by modeling the antenna and plugging those numbers into a feedline transformation calculator.

18 R.F. amperes measured was accurate except for the lack of the ammeter being mounted on a steel plate.

It

was

NOT

a

bogus

reading.

It's really 18 amps of R.F. The same 18 amps you would get with a 16 kilowatt carrier at 50 ohms only it's a 1500 watt test carrier.

That's the kind of current you get with a low resistive impedance. Same reason cheap tuners melt.

[The Slab Bacon]

<snip> "See, this is where it doesn't make any sense. Why would you load up into an electriclly short and low resistive antenna? Now I understand exactly what you are saying, but why try to use an antenna that is too short for that band?"
<snip>

Because some of us dont have the room for a full sized antenna! ! the trick of it all is learning how to make it work. I run a 60' flat top and NOONE has an trouble hearing me on 75 or 160! !

I run balenced feeders from the antenna to a 4:1 (yes 4:1) homebrew balun at the back wall of the basement and about 6-7' of coax from the balun to the tuna. I use a HB 1:1 balun for 160 only to help keep the feedline current down. With 500w of carrier on 160, I have melted the ends of the coax and burned the PL-259s and SO-239s to a crisp.

Both baluns are HB and totally indestructable, and swept for the frequencies and  designed for the imedances they are facing. they also both exhibit minimal loss!

However I have figgered how to make it all work, (minimizing the I-R losses is the key) and noone has ever complained of not being able to hear me.

As far as why would you want to run a short antenna, the answer is very simple: Sometimes you just gotta do what you gotta do!! Creative antennas are much more affordable than increaseed house payments!!

                                                             The Slab Bacon

[flintstone mop]

It makes sense that the lower the frequency and the more the antenna is compromised that an RF ammeter would indicate the outrageous readings.
It seems that from 80M on up it's a little easier to accomplish a reasonable antenna.
160M is a very demanding band for antenna performance and high melting RF amps.

Fred

[W2VW]

I think it would be better to just short your "short" antenna feedline together and use it as single wire then connect a suitable ground and possibly bury a few short radials in the yard instead of super heating the couplers.

Not an option.

The angle of radiation would be too low.

This requires an extensive ground system or raised radials to be efficient. That's not happening.

The signal would now propagate directly through all the neighbor's houses. Max current would be right above ground.

The short doublet works pretty well once all the weak links are removed.

[The Slab Bacon]

A shortened "marconi" type of antenna is totally unacceptable for the reasons Dave mentioned. (I tried it some years ago) After melting and smoking supposed "legal limit" tunas, burning baluns and exploding ferrites, I figgered out how to make it work. Nothing even gets even a little warm, hence little to minimal losses. I have even experimented with pissweak low power (7w) and still been heard.

If you must run a short antenner it is totally doable, It's just a matter of coordinating the whole system to work in harmony. This usually involves some homebrewing and not buying and using storebought items. Every part needs to be designed to take the heavy currents with minimal losses.

It also never hurts to have a little horsepower behind it

Since I am a ragchewer and not a DXer, a high angle radiator is much more desirable for my application.

                                                           The Slab Bacon

[The Slab Bacon]

Actually most of the people I talk to are too far for low angle groundwave. What I really want is all high angle skywave. the only 2 peple that are close enough for groundawave are close enough that they can hear me tuning up on a dummy load.

Low angle groundwave creates more problems for me and the houses in my neighborhood are only 20' apart  

Keeping this in mind, you learn to play the angle of refraction game.

I can understand your wanting a balance of both, but that is "situation specific" and not the case in my situation. 

Keeping in mind that a "half sized" antenna should only be 3db down from a full sized one, if wverything else is working properly, you shoudn't be more than 1/2 an "S" unit down on the other side. Factor in having plenty of horsepower, and tons of dense audio and no one can tell the difference on the other end.

Many times late at night I have been in a roundtable with a bunch of weaker stations, I always end u the "pivot man" as everyone keeps sending it back to me.
Why:.......because I'm the only one they all are hearing.

No one (at least noone with good sense) runs a shortened or comprimised antenner because they want to, those of us that do do it because we have no other choice.
A compromised antenna still beats the hell out of none at all! 

[K3ZS]

For 160M I have a 135 ft doublet fed with about 160 ft of ladder line.     It radiates much better when using the feedline and antenna as an end-fed.     The problem is that it picks up all the noise from the house, the reason the antenna is 160 ft from the house.    Using it as a short dipole the signal-to-noise is much better.   My best solution would be to put up an inverted L and feed it from a separate tuner for transmitting and switching to the dipole to receive.

[k4kyv]

Yeah, I don't know how you could protect the ammeters connected to the feeders on the coupler’s output under those circumstances. Unless maybe add resistors in an attenuator network and then short across them and the meters after checking for balance, etc. I’ve never use ammeters on the output before.

The Gates BC1-T has a built-in rf ammeter in the output circuit.  I use an outboard L-network to match the finicky 50-70Ω ricebox-esque load requirements of the Gates to the long length of coax running to the 2nd L-network at the base of the tower.  But after losing two perfectly good thermocouple rf ammeters I disconnected the meter.  Turns out if I lose antenna load, by accident first time when the antenna changeover relay malfunctioned and by human error second time when I forgot to re-close the antenna switch, a huge circulating current builds up between the output of the transmitter and the unloaded L-network, enough to wipe out the thermocouple in the meter.

[Steve - WB3HUZ]

I think what often confuses some people is the difference between groundwave and skywave on the different HF bands. Things work a lot different down on 160 meters, etc. If you have too high of a radiation angle you can easily overshoot stations close by in the skip zone within the same state, but stations far away come in really strong.

Please explain how this could happen. Most dipoles in use on 160 meters are ultimate high angle radiators - most of the signal is radiated straight up at 90 degrees. I've worked stations as close as a few miles right on out to hundreds or miles. There was never a skip zone.

[k4kyv]

I think what often confuses some people is the difference between groundwave and skywave on the different HF bands. Things work a lot different down on 160 meters, etc. If you have too high of a radiation angle you can easily overshoot stations close by in the skip zone within the same state, but stations far away come in really strong.

Please explain how this could happen. Most dipoles in use on 160 meters are ultimate high angle radiators - most of the signal is radiated straight up at 90 degrees. I've worked stations as close as a few miles right on out to hundreds or miles. There was never a skip zone.

If you have too low a radiation angle you can easily overshoot stations close by in the skip zone within the same state, but stations far away come in really strong.  A low-to-the-ground dipole shoots the signal straight up.  If the dipole is raised to approximately a halfwave above ground, then the null begins to appear at high angles.  The dipole is a good local antenna unless it is too high.  A high dipole takes on similar skywave characteristics to those of a vertical.

Up to a wavelength or so, a vertical radiates at lower angles and always has a null straight up.  The main lobes from short verticals are higher than those of taller verticals, so the taller ones are better for DX, but even a short vertical has decent low angle radiation and has a null at 90°.

I use a quarter wave vertical on 160, and also can load my 80m dipole on 160 as a shortened (quarter wave) dipole. It is approximately a quarter wave high on 160.  It does fairly well all over N. America, but the vertical usually out performs it beyond about 200 miles.  Closer in, less than 100 miles, the dipole is head and shoulders above the vertical.  I used to regularly talk to a couple of AM'ers in Nashville, about 50 miles away, on 160.  With the vertical, I was readable, but the local electrical noise was well audible in the background.  With the dipole I was full quieting.  They said I was about 30 dB stronger on the short dipole than on the full size quarter wave vertical with 120 quarter wave radials.

[Steve - WB3HUZ]

Exactly Don. I found about the same thing when comparing a vertical-T and a dipole on 160 meters (it was the same set of wire, just configured differently achieve the two antennas).

Any dipole less than one-quarter wavelength above the ground (that's any dipole less than about 130 feet on 160 meters) will radiate maximum at 90 degrees - straight up. Yes, there is still radiation at lower angles too, it is less however. The point is, you can never have too high a radiation angle and cause your signal to skip over someone on 160 meters or most other bands. You can have too low and angle and skip over, especially on the higher bands.

[Steve - WB3HUZ]

The Army figured out what? That there are skip zones on 160 meter? Nonesense. Show me the documentation that shows such. I've never had a skip zone on 160 meters using a dipole. Further, anyone using a dipole on 160 that is less that 120 feet high will have a take-off angle too high according to you. But, I've never heard any of the hundreds of people using such dipoles on 160 ever complain about skip zones or display one when I worked them. Your  comments just don't square with reality and any of the commonly understood propagation and antenna pattern measurement data.

[W2PFY]

Any dipole less than one-quarter wavelength above the ground (that's any dipole less than about 130 feet on 160 meters) will radiate maximum at 90 degrees - straight up.

Ok, this is a question that maybe someone would have an answer for? If the takeoff angle is 90 degrees could that take off angel be manipulated by placing a reflector perhaps driven out of phase at some given angle to lower the take off angle? If it works for broadcast stations using phasers to modify the patterns vertically, why can't a 160 meter signal be squeezed horizontally for a better take off angle. Please remember that I am somewhat a technician at this and not an engineer? Therefore, perhaps a dumb question    

[Steve - WB3HUZ]

Comparing 10 meters and 160 meters is like comparing apples and dump trucks.    And no, I don't believe you, since nothing you've said squares with well known propagation knowledge or my experience in over three decades of operating on 160 meters.

Terry, placing a reflector under a low dipole will only increase the radiation straight up (at 90 degrees) if it does anything. For all other angles, the pattern is formed by reflection off the ground at some linear distance from the antenna (increases as the take-off angle lowers), so the reflector has no effect.

Further, anyone using a dipole on 160 that is less that 120 feet high will have a take-off angle too high according to you. But, I've never heard any of the hundreds of people using such dipoles on 160 ever complain about skip zones or display one when I worked them.

No, that is not what I said. Many people (hams) are unaware that they even have a dead spot between their normal ground wave distance and DX range called the skip zone. Depending on whether the band goes long or short at night that “skip zone” can vary on 160 a lot. Sometimes the dead spot can be just a few miles or 100 miles. It just depends on band conditions. What I said or meant was that if you have too high of an angle you can overshoot people within the skip zone because many hams are unaware that using ordinary dipoles or doublets wont produce a high enough angle to eliminate the “dead zone” They automatically think because the have a horizontal antenna their signal is shooting straight up and the angle is high enough. Well, that is often not the case. Unless you apply full NVIS techniques the chances are you will a dead spot and just not know it.

NVIS techniques can also be applied to some of the higher HF bands during the day as well, but it depends on the yearly band conditions. I’ll tell you exactly how I know and learned all of this. During one of the sunspot cycles years ago I operated on 10 meters during the day and made all of the usual AM contacts across the country and overseas. At that time I was using an ordinary dipole. As most people know during the peak sunspot times you can only work stations that are far enough away. You normally will never reach anyone within your same state or next state away, etc. They have to be far enough away. You can’t work anyone within the “skip zone” unless it’s the occasional backscatter which happens in the early evening hours when the sun starts to go down.

Right?

Wrong! That is what I use to think. I had just ended a QSO with another station one day across the country on 29.000Mc. It was in the middle of the day around noon I think and the next thing I heard was KI5SG (my old call) this is W5PYT calling, Brian can you hear me? Needless to say I was at a loss for a moment. My first thought was “did I just switch over to 40 meters and not remember doing it?” How in the world could I be hearing Bob just down in Texas when I’m in Oklahoma? He went on to tell me, after the initial shock, that when he was in the Merchant Marines and the Navy they used NVIS techniques while on certain islands to reach other operators on nearby islands. They were often too close and were in the skip zones on those higher bands during the day so they figured out how to work those other operators within those skip zones to communicate.

I eventually did some research and found the Army’s old NVIS manual which has had a couple of appendixes thru the years, and it was very helpful in understanding how to work around the propagation. You can believe what you want, but there is a “skip zone” at night on 160 meters.

[ka3zlr]

"apples and Dump Trucks"  now that's Funny..

73
Jack.

[Steve - WB3HUZ]

I can't take credit for it. I first heard it from Thom - KA1ZGC. It's very appropriate here.

"apples and Dump Trucks"  now that's Funny..

73
Jack.

[flintstone mop]

I can't take credit for it. I first heard it from Thom - KA1ZGC. It's very appropriate here.

"apples and Dump Trucks"  now that's Funny..

73
Jack.

I like "cinders and ashes" better or "bust my boiler"

Fred

[Steve - WB3HUZ]

It's apples and dump trucks because you used an example OF youR experience on 10 meters to try to prove youR point about 160 meters. It's bogus and you've made the assumption not others. You claim a skip zone exists yet provide no evidence or data. I have actual experience that showed no skip zone.  I've had several hams visit my house while running a mobile setup and in QSO with me. They never faded out.

You also seem confused about near in signal loss when using a vertical. Of course near in signal loss wil occur when using a vertical since the vertical has a null at the high angles. This will not occur when using a dipole.


Apples, dump trucks, dipoles and verticals. Provide some data already.

Its apples and dump trucks because people automatically just assume that because it's 160 meters there is no skip zone. People generally don't think that about the higher HF bands because it so noticeable. All the HF bands have a skip zone. The difference is that on 160 it covers a much shorter distance and happens at night instead, but it is there regardless.

[W2VW]

dump trucks

Don't forget about the groundwave on 160 with a ver-trickle. There will be some close in coverage that works better than with a horizontal antenna. This is especially true in daytime.

[Steve - WB3HUZ]

Nevertheless, there is a skip zone on all of the HF bands. NVIS is used primarily from 2 MHz on up, but down to 1.8 MHz is basically the same. Dipoles do radiate at high angles, but they don’t radiate directly strait up in the air at 90 degrees like many people think. Depending on their orientation and height above ground some dipoles can radiate at angles as low as 30 degrees. The higher the dipole is above ground the more lobes it will produce.

Maybe on the HF band, but 160 meters is not an HF band.   

I assumed nothing. It's been well known for many decades (more like a century) that any horizontal antenna less than one-quarter wavelength above ground will have a take-off angle of 90 degrees - straight up. The fact that you continue to dispute this tells me you are either completely ignorant of this fact or you just like arguing.

You claim there is a skip zone on 160 meters but provide no evidence or data. If there is a skip zone, how would I hear a mobile station continuously from more than 100 miles from my station to my front door? There is no skip zone at 50-70 miles as shown by the mobile example. Further, I regularly work stations 50-70 miles from my location and they are generally the loudest signals received.

If you knew more about NVIS, you would know that if the frequency used is below the critical frequency but not so far below as to experience undue D and E layer absorption, and high angle radiators are used, full coverage within a 100-200 mile radius is obtained. This is exactly why the military uses NVIS, to avoid the skip zone. So, please don't pull a few quotes from an old Army manual and act as though that's the entire story.

[Steve - WB3HUZ]

LOL. Now you are just being silly. Jokes go in the QSO section.