20M Struggle

[K1JJ]

  Can you say which long side is the front and which is the rear?

Glad to help, Rob.

On your loop model, the rear is the driven 80' length and the front is the opposite 80' side.


Let us know how the 22 foot,  20-10M open wire dipole works out.  Get it up as high as possible. At 35' high it will work like a dream on all three bands for the USA.  Higher will only lower your angles more.  Angles of 15 degrees on 20M are very useful for DX.  Down to 7 degrees on 10M are FB too.  You can get these angles if the dipole is up in the 50' high area or more.


Most hams are satisfied with the patterns I described for the loop for 10-20M. But when you see the difference in performance using a high dipole that produces CLEAN figure eight patterns, you will be amazed how competitive you are against the triband Yagi boys, especially the trap tribanders.  If you get ambitious, put a reflector behind it for your favorite band and direction to make it a 2el Yagi. (Beam it east from w5?) Your ears will improve markedly. Raise and lower the ref on pulleys for versatility.  The other bands will not see it at all.

You could even have three different reflectors hung together or one at a time.

T

[K5UJ]

Okay Tom FB thanks again!  Well, I have been dramatically reevaluating the antenna plan.  I'm gg to go ahead and try to get the loop higher up, but I've decided to take down the gap titan and put up a 50' pushup mast in its place.  I'll attach pulleys on it to hold ropes and insulators to hold up part of the inv. L, and one end of the 22' dipole.  the other end will be held by a 2nd 50' pushup mast that will primarily old up the feedpoint of the loop.  this will give a dipole facing southwest and north east.  I will also put a short pvc arm on the mast that replaces the titan and  use that to hold up a pulley with a rope/insulator holding a wire that will hang down to make a 1/4 wave vertical on 40 and I'll use the titan's counterpoise.  This should give me all of the coverage but much better efficiency compared to the Titan, which as a multiband vertical did not do very well so I only used it on 40 cw, 20 and 17 and 15.  It was very poor on 10 and 80.   There's something about the design of caps, stubs, and linear loading that caused problems.  There simply is no such thing as a single antenna that works well all across HF.   I think we all know that here.   

73

Rob K5UJ

[K1JJ]

Good, Rob.

Always nice to see someone who takes action.  It's too bad 10 & 15M aren't wide open to see how well this system will work at 50' for you. You will be amazed what you can do on 20M with it.  I'll bet when you call CQ on 20M, you will almost always get a reply. Hams tend to call louder stations cuz they think THEY will be loud too and get a good report...   Also, many apt dwellers have so much noise, they can't hear but the loudest stations, or have given up calling anyone that is not loud due to poor response.

Anyway, sounds like a good plan you have now.

Looking forward to the 20M reports.  BTW, are you gonna use the same tuner or build a dedicated one for 10-20M?

T

[K1JJ]

Rob,

Thinking about it, I have a suggestion about the loop....

Since you will no longer use it on 10-20M, 160M is too lossy, and you may have that vertical for 40M, I'd replace the loop. 

For 75M, if you can get it a little higher, then all the better for an openwire center fed dipole.  If space is a problem, just make the legs as long as possible and drop the ends down vertically. It might even work decently on 160M too, with longer dropped legs.  Two small center loading coils are also a solution to bring up the input impedance for 160M operation. You could use simple coax if only for 75M when loaded, too.

Then use the tuner dedicated to 10-20M with the ant 22' ant.


Also, the loop takes up your whole lot. There is no hope of isolation for other antennas. A simple 75M dipole, even though the RF footprint is similar, you may be able to put something at right angles to minimize things. With the rectangular loop, you're scewed.

Just something to think about, OM.

T

[K5UJ]

Okay Tom thanks; I'll use the same tuner.  Interesting thoughts re the loop.  Well, I'd certainly save money on supports with a dipole 

The only way to fit the dipole would be to have one about 95-100 feet long running east to west so north and south would be off the sides and about 6 feet dangling down on each end.   From your description I kind of like the pattern of the loop on 40 but yeah, it's a cloud burner on 75.  And I do operate on 75 a lot more than on 40.  I'll have to think about this.  Any idea of the efficiency of the 100' dipole on 75 at 35-40 feet and the efficiency and pattern of the same thing on 40? 

tnx

Rob K5UJ

[Steve - WB3HUZ]

Put up that 100 foot long dipole, except add 10-15 feet on the ends and let them hang down vertically. Now you have a full-sized half-wavelength dipole on 75 meters. The little bit hanging down on the end has minimal effect on the pattern or efficiency

[K5UJ]

Put up that 100 foot long dipole, except add 10-15 feet on the ends and let them hang down vertically. Now you have a full-sized half-wavelength dipole on 75 meters. The little bit hanging down on the end has minimal effect on the pattern or efficiency

I've given this some thought while sitting in the parking lot of the Jewel before going in for groceries and what I decided I'd do is time honored ham experimentation.  I'm gg to go ahead with the plan as is, and do some testing/operating/measuring then clip the loop wire and isolate the unused part and see what life is like with all dipoles.     That's the great thing about wire antennas--you can have it both ways with a pair of dikes--if you screw up, you just have to do a little stripping, twisting and some work with silver solder and a torch and everything is right back like it was.

Rob

[WQ9E]

Rob,

Just a quick note:  I have been using an 80 meter full wave horizontal loop for my vintage gear operations for about 5 years now.  The loop is roughly square although the sides are not exactly even and the highest corner is around 35 feet high and the lowest corner is around 30 feet high.  It is fed at one corner with RG-8 using a homebrew reversible L network at the operating position.  I also use it for local work on 160 with the coax shield and center shorted where it goes up vertically (although I did work several S. Americans and Hawaii during a recent 160 contest). 

It seems to work fine on the higher bands also (both stateside and EU) on 40 thru 10 but it doesn't compare with my Quad on the higher bands.  The loop is noticeably quieter than the 160 meter Carolina windom I used earlier and the Hy Tower I also use currently. 

Of all the antennas I have used over the years, the loop definitely scores high on low maintenance and versatility.  The Carolina Windom I used earlier with the vintage gear worked pretty well but I don't think its line isolator would have held up to the Desk KW.

Just an additional data point to help with your decision.

Rodger WQ9E

[K5UJ]

Thanks Rodger; I hope no one get's offended by this but I think those carolina windoms are so-so antennas (they work so-so on a bunch of bands).  They are an example of the multi-band snake oil being sold. 

My guess with the loop i have is that on 75, it is too low and the short sides are too short.  Therefore it is marginally a loop and that's why it works better (more loopy) on 40 with a slightly lower t.o. angle and more pattern to the east and west.  On 75, it would probably be okay if it were twice as high and all sides closer to equal.  I kind of hate to give it up on 40 but I could perhaps gain the east west with the 1/4 w. vertical on 40.   part of the game is choosing carefully because there's a limit to what I can have in a small patch of property.  Go over the limit and everything plays poorly.   Hence...the experimentation.

73

Rob

[K1JJ]

Rob,

I like your idea of using all dipoles. Also consider Steve's suggestion of the hanging ends for the 75M dipole with the dimensions he gave. That will be the best antenna you cud put up for 75M on your lot. 

Heck, since the 75M dipole is now gonna be a 1/2 wave antenna fed with openwire, use it on 40M too as two-half waves in phase. Hopefully it is broadside in the right direction  (NE?) cuz the pattern narrows to a sharp figure 8.

Otherewise find a way to stick in a 40M dipole. It is very hard to beat a dipole on 40M. It is down only 4-5 db from a full-size 3el Yagi at the same height. A single vertical cannot compete with that.

Your ideas are starting to gel. You gonna be whirl-wide!

T

[K5UJ]

Rob,

I like your idea of using all dipoles. Also consider Steve's suggestion of the hanging ends for the 75M dipole with the dimensions he gave. That will be the best antenna you cud put up for 75M on your lot. 
Heck, since the 75M dipole is now gonna be a 1/2 wave antenna fed with openwire, use it on 40M too as two-half waves in phase. Hopefully it is broadside in the right direction  (NE?) cuz the pattern narrows to a sharp figure 8.
Otherewise find a way to stick in a 40M dipole. It is very hard to beat a dipole on 40M. It is down only 4-5 db from a full-size 3el Yagi at the same height. A single vertical cannot compete with that.
Your ideas are starting to gel. You gonna be whirl-wide!
T

Thanks; it will be a few weeks as I need to schedule some time off and order a few supplies (dacron rope).  I usually get everything ready to go (everything measured and cut, soldered etc.) before I take time off.  The low band dipole is going to have to be broadside to the south and north.  No room to put up one right angled to that and if I tried to cram one in, there'd be too many dipoles in a small space ergo, the 40 m. vertical, which I might also setup as a 75 m. inverted L with some sort of switchable insulator at the 33' point.   Hmm but if I ponder this for a while I may think of something 
Oh yeah, be careful of comparisons between antenna x and a yagi--those dB comparisons may be true on tx but half the job is receiving and a yagi, lp, quad always beats a simple dipole or vertical hands down on receive.


73

Rob K5UJ

[flintstone mop]

WOW! Page 3
I have a dream! somewhere in my reading. It was either QST or the ER mag that there was an article about using vacuum relays to reduce the length of a dipole for a different band. I don't know if it was on a resonant 50 ohm system or open ladder line.
The writer did his home work and bypassed the DC lines going to the vac relays. And the "control lines" didn't seem to bother the actual antenna element.
I'll do some research through Google or ARRL and report back.
Any one ever read about anything like this?

Fred

[K1JJ]

[Oh yeah, be careful of comparisons between antenna x and a yagi--those dB comparisons may be true on tx but half the job is receiving and a yagi, lp, quad always beats a simple dipole or vertical hands down on receive.

73
Rob K5UJ

Yep, I'm always talking about raw forward gain on transmit when referring to 4-5 db over a full size Yagi at the same height. Signal to noise ratio is a different matter.  The front to back of a Yagi on receive reduces the noise from the full rear hemishere. Even the sides are sharper.  In fact, my high 75M Yagi/Loops hear slightly better into Europe than the terminated beverages. Using a simple dipole to receive puts the Beverage way in front in comparison.


Question:  How long would the 75M flat top be (and dropped legs to equal 123')  if you oriented it NE/SW?  Give us the numbers and maybe Steve can model that to see how close it comes to a full size flat top.   Just the orientation (and side nulls) may make it more worthwhile to do when compared in the end.  I mean, if the shortened flat top is down 1 db but the side nulls are down 15-20 db, the better choice is the shortened flat top oriented in the desired direction.

T

[K5UJ]

to get n/e off the side the flat top would have to be no more than ~45 feet long;  the narrow sides of the lot face east n/e unfortunately, but I could throw a big signal at K4KYV and into the Gulf and Brazil 

Rob

[K1JJ]

to get n/e off the side the flat top would have to be no more than ~45 feet long;  the narrow sides of the lot face east n/e unfortunately, but I could throw a big signal at K4KYV and into the Gulf and Brazil 

Rob

Maybe you'll be OK since low dipoles tend to exhibit a BROAD figure 8, almost omni-directional at the lower angles.  Come up with the flat top dimensions at max span and maybe Steve can re-model it to give the exact vertical drops needed to resonant on 3850, in case you wish to feed it with coax.

T

[K5UJ]

Hmm, the flat part would probably be 88 to 90 feet, leaving 15 on each end to dangle down.  or they could be strung out horizontal to make a [ looking dipole.  not interested in coax except for unbalanced antennas i.e. verticals fed against ground.  anything balanced I want to use for more than one band.  no room for luxury of all monoband antennas, so it's got to be ladderline and bal. tuner.  That's okay, the big boys do the same thing with their curtains, they just have bigger tuners and more dipoles 

R.

[K1JJ]

Hmm, the flat part would probably be 88 to 90 feet, leaving 15 on each end to dangle down.  or they could be strung out horizontal to make a [ looking dipole.  not interested in coax except for unbalanced antennas i.e. verticals fed against ground.  anything balanced I want to use for more than one band.  no room for luxury of all monoband antennas, so it's got to be ladderline and bal. tuner.  That's okay, the big boys do the same thing with their curtains, they just have bigger tuners and more dipoles 

R.

OK, openwire fed, 88' long flat top. How high at the center and at the ends?    Maybe by extending the dropped ends to the ground we can get a working 160M dipole there too. It may require series tuner feed on 160M, but wud be a good local 160M ant too. 75M would work well and 40 would be a sharp figure 8.   On 40M, the height would start to make it less omni-directional, however, and your NE/SW wud suffer.  It wud happen even with a 1/2 wave 40M dipole, however.

I wud say a total of 160' (88 flat top and 36' on each end) would do the trick on all bands, 160-40M. The ends wud drop down near to the ground, but that's OK.  On 75M you still have the majoity of 88' flat in the air. You will be amazed how well that system will work on all three bands.

T

[Steve - WB3HUZ]

Lat night, I modeled just 88 feet and then 88 feet with 15 feet ends hanging down vertically last night on both 80 and 40 meters. I'll post the results when I get home tonight since it was late and I can't remember the numbers.    I'll also have some pattern plots.

The above arrangement would propably be too short to work effectively on 160 meters, unless you built a really strapping tuner and some home-made open-wire feedline with #10 or larger conductors. I'll run some numbers on 160 too, just to see what would happen.

[WA1GFZ]

I'm told a 44 foot lazy H works great 40 through 10M Vertical spacing 22 feet.

[K5UJ]

Lat night, I modeled just 88 feet and then 88 feet with 15 feet ends hanging down vertically last night on both 80 and 40 meters. I'll post the results when I get home tonight since it was late and I can't remember the numbers.    I'll also have some pattern plots.

The above arrangement would propably be too short to work effectively on 160 meters, unless you built a really strapping tuner and some home-made open-wire feedline with #10 or larger conductors. I'll run some numbers on 160 too, just to see what would happen.

That'll be interesting to see thanks.  Ends and middle would be about 40' high.  I do have the inverted L on 160 which seems to be a pretty good ragchew antenna.  I have doubts about the dipole being worthwhile on 160.  Too low for one thing; and too small, too much loss at the ends near ground....a matching network might make it look okay to the rig but that's another trap you have to watch out for...the right network can match a coat hanger on 160 but ur antenna is still a coat hanger 

Losses in a tuner would probably be high.   

Rob

[Steve - WB3HUZ]

If you already have an inverted-L for 160, then you are set. The low, short dipole will not work any better, especially if you have a decent groud system under the L.

[WA1GFZ]

Tuners can have low loss but need to be large and fugly

[K1JJ]

For a small lot, the additional inverted L for 160M will add interaction and needs radials.  It has both horizontal and vertical components.  There is also a 40M vertical, 75M dipole and 10-20M dipole too.  Yikes.

Clean house first - start with a clean field.  Then lengthen the 75M dipole drop legs and make it work 160-40M. (36' end drops and openwire fed)   Then put up that 10-20M openwire fed 22' flat top and that's it. TWO antennas with figure 8's on all bands.  Minimal interaction.  All horizontally polarized. Great performance.

If ya really want an inverted L on 160M, then tie the openwire together of the 75M dipole and feed against ground. It will work a little like a vertical 'T' against ground.  Still, only TWO *unrelated* antennas to muck up the RF field.... a good compromise.  Each antenna sees nothing to interact with.

** Another point:  The 22' flat top would make a great vertical 'T' on 40M . Tie the feeder leads together at the ends and feed against ground.**

T

[ke7trp]

Rob. You are talking about the antenna I use and I even posted the EZnec of it..   Open wire fed, Flat top and ends turned down.

Clark

[K5UJ]

If you already have an inverted-L for 160, then you are set. The low, short dipole will not work any better, especially if you have a decent groud system under the L.

Yes, I mentioned the 160 L back at the beginning of the month but you all probably forgot or missed it.  I mentioned it in passing.  It's an inverted L with 101 radials and a tuner out at the feedpoint for 1985 KHz.  feedline is ldf4-50.   the f/p Z is 14 ohms in the middle of the band at the vswr null (~3.5:1 or so).  the driven part is around 120 feet long.  I plan to lengthen that and get the vertical part higher this fall.  The radials vary from 10 feet to 120.     

R.