One - Do- Tree... Tests with the 2x2x2 40M Yagi stack

[WA1GFZ]

Wow Tom, That is a long coax run. I could get into the shack with about 50 feet of cable on each loop. All I would need to do is replace a basement window with a lexan panel. Then I could dial it in from the operating position.
So the balun plus 70 feet should be close to 1/2 wavelength electrical of about 80 feet of RG11. My old quad was very close to 50 ohms at 12 feet spacing on 20M so didn't need the quarter wave stub. I did need it on 15 and 10M though. I'm getting a good match directly to 50 ohm coax at 20 feet spacing.
Jack I think Tom is using 70 ohm cable to the shack.
Jack are you feeding the top or bottom?

[W9GT]

Wow Tom, That is a long coax run. I could get into the shack with about 50 feet of cable on each loop. All I would need to do is replace a basement window with a lexan panel. Then I could dial it in from the operating position.
So the balun plus 70 feet should be close to 1/2 wavelength electrical of about 80 feet of RG11. My old quad was very close to 50 ohms at 12 feet spacing on 20M so didn't need the quarter wave stub. I did need it on 15 and 10M though. I'm getting a good match directly to 50 ohm coax at 20 feet spacing.
Jack I think Tom is using 70 ohm cable to the shack.
Jack are you feeding the top or bottom?

I'm feeding the bottom corner of the driven element and shorting or stubbing an addtl length across the bottom corner of the parasitic element.

73,  Jack, W9GT

[K1JJ]

Couple of questions Tom....do you use 1:1 or 4:1 baluns (or something else)?  is the coil at the end of the RG-11 section?  Do you cut the RG-11 for 1/4 wave at operating freq (considering vel factor)?  I would guess, as a matter of scale, then my proposed 20' spacing would be fine for 40M.  

My tower guys were cut with vel factor of galv. guy line and addtl cap on ends considered, however, there are some series effects due to the cap across the insulators and between the sections.  Phillystran would be the best solution, but it is expensive for the size I need (equiv of 5/16" EHS) 11,000lbs.

73,  Jack, W9GT

Jack,

This is for 75M:

I use a simple 16 turns of RG-11/U  (1:1 balun) wound on a 4" ABS plasdick pipe.  (Same technique for the 40M Yagis) The "stub" coil is a real coil, 4" diameter using silver plated edge wound stock - low loss.  The stubs were cut to 142 degrees including vel factor. I had originally wanted to use a remote vac variable, but the tests showed I needed inductance instead. After winding the balun, I was short coax to the tower so just used a coil - all the same in the end as long as you can tune that reflector for max f-b.

Frank, 70' of coax is not that long on 75M, just like 35' or so on 40M.  This includes the balun turns. It's only about + - 20' to the tower from the eles on 75M. Yes, I use 75 ohm hardline buried underground to the shack. The run from the tower alone to the shack on the 2x2x2 stack is about 440'. This doesn't include the hardline run up the tower and the phasing distribution lengths. I don't sweat loss of hardline at 7mhz. The TO angle is the most important thing  - even forward gain is no big deal.  Running a long feeder to get away from the house noise is another good trade-off.

Jack, I know some guys use and like Phillystran, but I wud never use it here for a tall tower. I stick with steel all the way. I sometimes use Philly for critical VHF boom trussing and and wire array supports. It's good to have an invisible support for other antennas in the area.

Hope to get on 75M tonight - as well as maybe a short 40M session. Maybe we'll see ya all there.

T

[WA1GFZ]

Yup, this weekend I changed the 30 dB pad in front of my station to 20 dB.
If I use HUZ stub length I could do switching at about 15 feet on the tower.
I suppose I could mount a water proof box for relays. I want to keep my losses as low as possible. I'm thinking of a twisted pair for the stub. maybe Teflon wire rather than coax. I bet that #12 teflon we bought is under 100 ohms Z.
 

[Steve - WB3HUZ]

Yes, a NEMA box on the tower will be FB.

JJ killed me on 80 tonight. I could hear FB but was PW on TX most of the time. Some pretty interesting stuff was worked. I'll let Tom tell you about it.

[K1JJ]

Yes, a NEMA box on the tower will be FB.

JJ killed me on 80 tonight. I could hear FB but was PW on TX most of the time. Some pretty interesting stuff was worked. I'll let Tom tell you about it.

Yes, fun session tonight on 75M. Very low angle as shown by the reference dipole comparisons. A number of celebrities stopped by.

Don't sweat the TX part, Steve. Guru Trogladite says it very honorable thing to hear much better than transmit.  Just like rat dog with large ears and tiny mouth....  TX easy to improve - RX vely hard to make better.


Here's the highlight of the week. Sri Lanka called in on 75M. It took me a couple minutes to get his call and info, but it was worth it. I didn't realize at the time Sri Lanka is a large island SE of India, about 8600 miles away!  The heading is about 33 degrees, right thru Europe, so the delta loops were on the right path:

4S7NE
Nelson Ranasinghe  18 Katana Housing Scheme  Demanhandiya 11270, SRI LANKA


Steve, after you  left I got a call from an older Russian near Moscow. He said that my FT-1000D was a museum piece. He had one too and was just joking  - cool guy.  He talked and mentioned "kilocycles" a few times I told him HE's a museum piece since he still says "kilocycles. That was one of the first times I heard a Russian crack up and laugh out of control on the air...  I told him they haven't made FT-1000D's since the Berlin Wall fell down.  It went on like this for 10 minutes. That was the funniest QSO I ever had with a Russian station. They are usually very serious with westerners.  I'm gonna work over a few more and see what happens...

T

[WA1GFZ]

I drove the simulator after football last night. I have a working switched stub with good results but the stub is shorter than Steve's. Maybe due to my simulator skills in loading coax but anyway it seems to play. Only about 9 feet in length so swinging it to the tower could be a problem.  Sounds like you had a ball.

[K1JJ]

I drove the simulator after football last night. I have a working switched stub with good results but the stub is shorter than Steve's. Maybe due to my simulator skills in loading coax but anyway it seems to play. Only about 9 feet in length so swinging it to the tower could be a problem.  Sounds like you had a ball.

Your suggestion to add a 1/2 wavelength extension to the 9' stub coax to bring it to the ground for tuning will work FB. I wouldn't worry about stub lengths at all. Ya gotta eventually get it to the shack somehow anyway - might as well be partly stubs and feeders.  Just remember that Tom Vu has over 600' of total feeder to the stack but can still hear a pin drop in Eu...  

Yep, we did have a ball last night.  You never know who's gonna call in just like Forrest Gump's box of chocolates.   Last night Steve said it's like fishing - sometimes you hook a marlin, but most of the time it's blue gills...

I'm still happy about that Sri Lanka marlin last night.  That was the first one ever on 75M for me after over 25 years of DXing on that band. The path wasn't the homo-easy type like working the VK's at sunset.   It was at 10PM going through Norway,  Russia, a tip of western China, around and down over the Himalayas, through India to Sri Lanka. Cool stuff! Lots of northern attenuation and if he was only 3db weaker I wouldn't have heard him at all. Right on the threshold of my hearing here and I love those types of contacts.  So, I'll just turn the notebook page, bury the entry in my notebook and lose it - don't need no stinkin QSL - I know I worked him and that's good enuff...

We'll see what the next few nights bring.

T

[Steve - WB3HUZ]

Where are you feeding the loops Frank?

[WA1GFZ]

I'm feeding them in the center of the bottom. I don't see any advantage in running coax up to the apex by simulation. Any suggestions? As I said my loop size is very close to yours. I don't have the numbers here at work but the bottom is slightly longer than the sides.

[Steve - WB3HUZ]

OK. So you are going with horizontal polarization.

Yes, the top or bottom feed doesn't seem to make much difference.

[W9GT]

I wonder if the varying length of sides vs bottom of a delta loop, or making all sides equal in a square or diamond makes much difference?  I recall seeing an article about a rectangular loop with long top and bottom lengths vs much shorter sides. (sort-of looking like a big fat folded dipole).  I have seen all sorts of loop configurations, even circular elements, but I'm not clear on how the shape affects the pattern.  I believe that the polarization is determined by whether you feed a vertical element or a horizontal element, however, if you feed a corner of a rectangular loop, is it still horizontally polarized?  In my case the elements are square, but tipped to become a diamond shape.  I feed it at the lower corner of the diamond.  Loops are really pretty effective antennas and seem to be quieter than dipoles.  Many guys are using horizontal loop "cloud warmers" on 75 and 160 with decent results, at least out to several hundred miles.

I know my loops need to be optimized, but they sure do seem to work well on 40!  I wish I had the room to put up a couple for 75 or even 160.

Here's some more food for thought.  What about multi-turn loops?

73,  Jack, W9GT

[K1JJ]

Jack,

For 2el or more, I've found the most important thing with loops is to configure them to take advantage of the highest average height possible based on your supports. If you can put the flat side up, then do it. If you can make the base longer than the sides, then do it... both will increase avg height.

For array use, I don't think there's anything magical in any particular shape. I've used both quads and deltas on 75M and both kick ass cuz they're up high and have a great TO angle.... and they're tuned for max f-b precisely.

Sounds like your exisiting loops are vertically fed. I wud feed them in the bottom middle and go horiz fed- at least try it and see. If you see no diff, I wud stay horiz.  Use a reference ant and carefully compare them, of course, or you'll never see the diff just by getting reports day to day..

(Yes, the corner fed loop is vert polarized)

T

[Steve - WB3HUZ]

Used as a single element, the quad has the most gain of any loop shape, except for a perfect circle. The difference between it and a delta loop is supposedly on the order of a dB or so.

Multi-turn loops are a good design for small transmitting or receiving loops, but I don't see any advantage if you have a full wavelength sized loop. You may get some impedance transformation that could be useful in some cases, and if you were feeding the thing with open wire on multiple bands, it may be easier to match/tune.

[WA1GFZ]

I lost a good loop article when I moved to Ca. it was a study done by the Army right after nam where they tested a number of loop configurations and feed methods. One cool designs I heard about was the loop antenna in the tail of an F16. A GD guy told me it worked pretty well down to 6 MHz.

Jack, looking at simulation the input Z shifts around as the height of the loop changes and agree with HUZ there is only about 1 dB loss moving away from a circle. My loops are about 25 to 30 feet tall so the top is at 55 feet and bottom at 25 to 30 feet. This accepts 50 ohm coax feed with two spaced 20 feet. my 2:1 VSWR points are 6.9 to 7.2 MHz. Reflector is a bit long.  So I get my average height taller by making the loops shorter. I have a 3 element design that is only 15 feet tall and since it is closer to a folded dipole the input Z isn't bad. 10 foot spacing sounds weird but it sure has some FBOM front to back.
I can't make vertically polarized loops work. They have a low radiation angle but FB and gain stink. My old quad was configured as a diamond fed at the bottom it worked very well for 19 years.

[Steve - WB3HUZ]

The vert pol loops do produce a nice low take off angle. But usually, the gain is down so much that the horiz pol still beat it, except at the very lowest angles.

I lost a good loop article when I moved to Ca. it was a study done by the Army right after nam where they tested a number of loop configurations and feed methods. One cool designs I heard about was the loop antenna in the tail of an F16. A GD guy told me it worked pretty well down to 6 MHz.

Jack, looking at simulation the input Z shifts around as the height of the loop changes and agree with HUZ there is only about 1 dB loss moving away from a circle. My loops are about 25 to 30 feet tall so the top is at 55 feet and bottom at 25 to 30 feet. This accepts 50 ohm coax feed with two spaced 20 feet. my 2:1 VSWR points are 6.9 to 7.2 MHz. Reflector is a bit long.  So I get my average height taller by making the loops shorter. I have a 3 element design that is only 15 feet tall and since it is closer to a folded dipole the input Z isn't bad. 10 foot spacing sounds weird but it sure has some FBOM front to back.
I can't make vertically polarized loops work. They have a low radiation angle but FB and gain stink. My old quad was configured as a diamond fed at the bottom it worked very well for 19 years.

[WA1GFZ]

I couldn't figure out how to phase 2 vertical polarized loops and get it to radiate in one direction. maybe end fire?? It does have an interesting take off angle but around 6 dBi gain.
Weird WX here today, Rain, thunder and wind. I bet it notches things colder.

[K1JJ]

Good wind test for the 40M stack today.  Gusts 45-50mph - probably higher up at 190'.  The new sidearms did their job. No twisting or turning detected. The boom and el alignments still look perfecto.  

Amazing what a little steel placed in the right spots can do.  [caw mawn]


T

[Steve - WB3HUZ]

Phasing for the vertical feed would be no different than horizontal feed - about 135 degrees, plus or minus your exact installation. It's end-fire in either case.

I couldn't figure out how to phase 2 vertical polarized loops and get it to radiate in one direction. maybe end fire?? It does have an interesting take off angle but around 6 dBi gain.
Weird WX here today, Rain, thunder and wind. I bet it notches things colder.

[WA1GFZ]

Gee, you are right I just got the sim to run and it has a good FB. Only about 6 dBi gain but a nice lobe at 15 degrees. Everything above 30 degrees is attennuated.

[Steve - WB3HUZ]

If you want only low angles, it's the way to go. Probably makes a good RX antenna. All that high angle stateside stuff would be gone.

[K1JJ]

Hmmmm....

In a closely packed residential neighborhood, I think a vertically polarized lobe (15 degrees TO) will do more to warm the neighbor's houses and BA's than anything else...    Stick wid horizontal.

T

[Steve - WB3HUZ]

I agree. Other than possibly being better on receive, the loops up at about one-half wave and fed for horizontal polarization will beat the vertical polarized version.

[WA1GFZ]

It would be cool to dial the shape charge with delay lines....
I think my simulation shows a bit more gain at 15 degrees.








HUZ, Congress, with their cradle to grave benefit package

[W9GT]

That was my thought Frank.  Seems like you could change the phase by adjusting the feed line lengths to each loop to adjust the pattern around the azimuth.  Don't know how much variation you could achieve, but would be an interesting concept anyway.

73,  Jack, W9GT