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160 and Small Antennas




 
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Steve - WB3HUZ
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« on: September 29, 2006, 11:47:28 PM »

From previous thread in QSO section VJB wrote:

Quote
I was hoping to find a write up for a short vertical.

W3R hasn't got the property for much of a doublet, and if I expect to get the 300-G on from there I need a 160 ant of some kind.

Advice any and all apc.

How much room do you have, both horizontally and vertically? If you have some room horizontally, an Inverted L of some sort might be the easiest. As far a pure vertical, top loading (or as close to the top as possible) is supposedly the most efficient. A top capacity hat is probably also in order. A T antenna may also work, since it is essentially a top loaded vertical.

But if you already have room for a 75 meter dipole, you can make that antenna work on 160.

What say?





http://www.amwindow.org/tech/htm/160smallants.htm
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WA3VJB
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« Reply #1 on: September 30, 2006, 01:47:19 AM »

The longest path is barely 60 feet, and we ran a 40m dipole fed with open wire line that worked pretty well, on 40.

Running the 32V2.

The tuna let us squeeze 75m out of it, but 160 / 300-G was a no way.

Took it down for the summer and ready to put something aloft again.

Have room for a pole and ground radials up to about 40 feet max, and can guy but it has to all be temporary-looking.

Any possibility out of a wire wound pipe ? Great big coil of wire on a stick.

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Steve - WB3HUZ
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« Reply #2 on: September 30, 2006, 09:40:57 AM »

Wow! That's tight. Yes, a big coil will work. I used to have info on using a stretched slinky as a vertical radiator. Another approach would be a vertical with a big coil near the top, with a top capacity hat (you could make the guys act as the capacity hat) could work pretty well with 40 feet.

As always, the radials will make or break the system. I'd put the majority of the effort there.
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WA3VJB
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« Reply #3 on: September 30, 2006, 10:32:54 AM »

Ergh, pretty much a Warren 160M mobile antenna that happens to be sitting on the ground.
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #4 on: September 30, 2006, 11:19:12 AM »

With only 60' of space, I imagine there is building absorption everywhere (bad for verticals) plus the hope of putting down a 1/4 wave 160M radial field are nil. This alone will chop maybe 15db off your vertical signal. Not to mention the local high angle suck out for the close in guys.

I wud do this:  Put up a 60' flat top with the ends dropping down close to the ground, ala HUZ's 160M suggestion.  Feed it with open wire and use a good quality homebrew SERIES tuner to handle the low impedance. ( I assume the total flat top and side legs  equal 60' + 40' + 40' = 140' total = little more than 1/4 wave.

Use #8 wire from HomeDepot for the complete flat top and feeders.

If you build a strapping tuner to handle the low impedance current and the antenna is not too absorbed by buildings, my guess is you will be within 5db of a full size perfectly matched coax fed dipole that is completely flat, of the same height.  That's not too bad at all.

But with a 12 ohm input impedance or so, it is easy to give it all back via losses from thin wire and crappy tuners in this unique situation, so don't cheap out there.

***  If you use a center support for the flat top, you don't need feedline spacers! Just pull the openwire tight and keep it spread about 2' apart. This will cancel FB. I did this on 75M for a wire Yagi and it was fine.  Thus, you have a more transparant looking dipole for the neighbors, w/o spreaders.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
flintstone mop
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« Reply #5 on: September 30, 2006, 11:37:48 AM »

Hello Friends,
The HUZ man had a very nice dipole that he made into a T and worked very well on 160M, but it sounds like your sqeezed for "horizontal space". Ya'll don't yell at me BUT CushCraft has a very nice 40 foot vertical for 160M........top loading.....capacity hat for $200.00. You can read any reports about the cushcraft on eHAM.com... I HAD the 30 foot Unihat which didn't mind close in objects and compared favorably on a wooded lot against a dipole 90 feet in the air. That was unfortunatley a $500.00 antenna not including the Phillystran wire and 4 ground mounted supports. I also had an "L" ant on this property and I "A-B-C'd" it against the Unihat and the Dipole. The real test would have been with a Ham over 500 miles away, I guess.
It sounds like you need to use the vertical space of your property to do 160M. An unshortened dipole for 75M can work on 160M with a big a## tuner.
I hope we hear you on 160 before the aerial planting season is over. For some of us that usually happens on the cold windy day in January...........hi

Fred
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Fred KC4MOP
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« Reply #6 on: October 01, 2006, 09:10:26 PM »

I have been stuck with a 60' flat top for years now, It works fairly well on 75, as most of you dont have any trouble hearing me, even running experimental pissweak low power. Like Tom said you need to have strapping feeders to minimize the feedline loss and get as much of the rf as you can up to the antenna instead of heating up the feedline.

I have experimented with this setup on 160. With 100w, people can hear me, but I'm pretty pissweak.  Running the 4x1 transmitter no one had any trouble hearing me, but the tuna was groaning from the heavy feedline current. I plan to do some experimenting this fall to come up with a better matching network and see how it plays out. Maybe a 1:4 or 1:6 UnUn or something of that nature. I will do more experimenting this fall and post he results here if I come up wih anything interesting.

                                                                          The Slab Bacon
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Steve - WB3HUZ
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« Reply #7 on: October 01, 2006, 09:28:44 PM »

Quit messing around with those ferrite thingies. Build a nice link coupled balanced tuner and be done with it. Copper tubing and a cap and you're ready.
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The Slab Bacon
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« Reply #8 on: October 01, 2006, 09:34:25 PM »

Quit messing around with those ferrite thingies. Build a nice link coupled balanced tuner and be done with it. Copper tubing and a cap and you're ready.


But, but, its fun to watch the ferrite rings explode!! Grin Grin
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Steve - WB3HUZ
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« Reply #9 on: October 01, 2006, 09:43:41 PM »

Bang, lookie there!
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WA1GFZ
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« Reply #10 on: October 01, 2006, 09:46:02 PM »

Frank,
Check out measure's site. Build some strapping L networks to drive that low Z.
I would think a link tuner would have a problem driving a low Z. Maybe series tuned??.
I'm glad a number of hams have this problem because I'm in the same boat at the new place with 160 or so feet of span.  The lowfers do it so we should be able to make something strap.
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The Slab Bacon
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« Reply #11 on: October 01, 2006, 09:50:39 PM »

Bang, lookie there!

Thats right!! I'll be wavin my hand in the breeze!!
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The Slab Bacon
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« Reply #12 on: October 01, 2006, 09:54:32 PM »

Frank,
Check out measure's site. Build some strapping L networks to drive that low Z.
I would think a link tuner would have a problem driving a low Z. Maybe series tuned??.
I'm glad a number of hams have this problem because I'm in the same boat at the new place with 160 or so feet of span.  The lowfers do it so we should be able to make something strap.


Frank,
         I know that is idefinately doable. It is just a matter of finding out what works best and has the lowest loss. that is the fun of experimenting!! I had loads of fun blowing up baluns and tunas years ago! Grin Grin
 
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WA1GFZ
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« Reply #13 on: October 01, 2006, 10:08:00 PM »

The most efficient low frequency EMI test antenna I have ever seen is the parallel plate. two 10 foot long 2 feet wide metal plates 50 ohm drive on one end and a 50 ohm load on the other end. It can make a quite a near field
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Steve - WB3HUZ
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« Reply #14 on: October 01, 2006, 10:36:08 PM »

Quote
I would think a link tuner would have a problem driving a low Z. Maybe series tuned??.


Never had a problem, just tap down on the coil or go series with the caps. The roller inductor approach seems far too complex for what you get - a tuner that STILL needs a balun. And running the balun on the input side doesn't help. Neither the current balance in the output conductors nor the voltage across the balun are any different when the balun is put at the input or
output of the tuner.

Go with the simple link design. It has 70 plus years successful use behind it.
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WA1GFZ
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« Reply #15 on: October 02, 2006, 08:29:45 AM »

Steve.
I use a BB transformer on th einput of my tuner. I have RF amp meters in each leg and there is a balance. Also the same current flows if I connect the Johnson Match box but the L network tuner has a lot more range. All in what your junk box produces. Step down with a link seems hard. fc
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Steve - WB3HUZ
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« Reply #16 on: October 02, 2006, 11:14:37 AM »

Different strokes. I just like the KISS approach.

Quote
Step down with a link seems hard.

Seventy years of success sez different.

As far as baluns and tuners, read the following.

http://eznec.com/misc/ibalun.txt


Here's what I'd do if I had Frank's setup.


 ______________  _______________
|______________  _______________|
               | |
               | |
               | |
               | |
               | |
               | |  Big A$$ Feeders
               | |  #8 or larger
               | |
               | |
               | |
               | |
               | |
          _____________
         |             | WX-proof box with
         |             | heavy-duty series
Coax to  |             | fed link coupled
station  |             | tuner (directly below center of antenna)
<------- _______________     

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WA1GFZ
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« Reply #17 on: October 02, 2006, 11:45:15 AM »

Steve,
1.How much spacing between conductors
2. How do you think it will work on higher bands?
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Steve - WB3HUZ
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« Reply #18 on: October 02, 2006, 01:01:27 PM »

I think Frank is using a 2-4 inch spacing. But spacing is not critical.

Don't see why is wouldn't work on the higher bands. At those frequencies, the length is closer to 'normal.'  Cheesy
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flintstone mop
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« Reply #19 on: October 02, 2006, 02:18:00 PM »

Hello
I built the K1JJ tuner and no regrets on this end for a cannot break or over heat tuner. I built last Winter.  And I was getting sick from the cancer growing inside of me!!!. There is info and pics somewhere on this forum.
Fred
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Fred KC4MOP
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« Reply #20 on: October 02, 2006, 02:28:32 PM »

I think Frank is using a 2-4 inch spacing. But spacing is not critical.

Don't see why is wouldn't work on the higher bands. At those frequencies, the length is closer to 'normal.'  Cheesy

Actually I'm using the crappy brown stuff (14 ga) I am planning to make up some home brew ladder line this winter somewhere #10 or 12. I feed it into a home brew 4:1 balun and a very short (about 6 or 8') run of coax to my big strapping homebrew single ended tuna. It has worked very well on 75 for some time now.

It works ok-fine on the uppa bands, but I seldom use it there as I have a small tribander on the top of the tower.
                                              The Slab Bacon
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Steve - WB3HUZ
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« Reply #21 on: October 02, 2006, 03:50:51 PM »

Frank:

Have you ever made an old buzzard and then went outside and checked for heating on the feedline? Might be interesting. Also, why a 4:1 balun? Seems the stepdown would only make the task on the tuner even greater (taking an already low impedance and making it even lower).

Just thinking out loud here.
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The Slab Bacon
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« Reply #22 on: October 02, 2006, 04:24:53 PM »

Frank:
Have you ever made an old buzzard and then went outside and checked for heating on the feedline? Might be interesting. Also, why a 4:1 balun? Seems the stepdown would only make the task on the tuner even greater (taking an already low impedance and making it even lower).

Just thinking out loud here.

Good thoughts. I have checked the balun for heating and it does not heat at all, but I have never checked the feedline. Hmmmm........................

The reason that I chose a 4:1 came after much experimentation and testing: I wound / built many different 1:1 designs (that is really what I was looking for) and swept them from 10 ohms to 500 ohms and 1.5 - 15Mhz. I found that most of the 1:1's for kind of flakey as you got away from their 50 ohm characteristic impedence. They did not stay 1:1, and added a noticable amount of reactive component of their own when you started getting away from 50 ohms. (I knew that my antenna was nowhere near that impedence)

I twisted up several different 4:1 designs and found that they worked much better. They seemed to give a much more accurate inpedence match, and added less/no reactive component of their own. The 4:1's gave a real accurate 4:1 ratio no matter what the input or output impedance was. Keeping in mind that I had to still run a short (about 6') piece of coass to get from the balun to the tuna, I have always felt that if you have to sin and run a high SWR through coass, it is always better to sin in the direction of a low impedence.

Keeping in mind that coass is nothing more than a capacitor, the capacitive reactance loss is going to be a lot less in a low voltage high current situation I did what I did and it worked. I rolled up a strapping 4:1 with heavy wire and tons of ferrite and I lived happily afta.

All seemed well and good till I tried to use it on 160 with the big rig last year. Something kept changing and I constantly had to keep retuning the tuna. The coass amd pl259s were getting very hot, so I knew that the current in the short coass was very high. I also blew out a 10A rf ammeter while doing the initial testing. I will figger this thing out in time and post the results here.
                                                             The Slab Bacon
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Steve - WB3HUZ
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« Reply #23 on: October 02, 2006, 04:36:42 PM »

Interesting. It's all about working and if the 4:1 works better, you go it. Can't argue with your signal.

One MORE thing (I keep thinking of things), do you notice having to retune with it's raining or snowing. From what I've read (and from some observations during use) the impedance and loss of the brown crap ladder line can change when wet (in some cases drastically). Going with some strapping open wire line will remove this potential problem. 
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Ed/KB1HYS
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« Reply #24 on: October 02, 2006, 05:54:46 PM »

Sincer were talking odd antenna setups.  this is what I've got.

Two Tall Pines, about 65 ft to my wire.  They are only 50 or so feet apart, straddling the house. 

I have an 80 meter dipole which drops the ends quite far.  I think I could get a 160 m dipole up with some creative zigging around some other trees.  Feed point would still be up around 65 ft or so.

The problem is, I am limited for feedline.  I can't run ladder line directly to the shack/tuner, so what I have now is coax to the attic, a coax choke feeding cheap brown TV twinlead.   

Whats a better way to transition from the coax to ladder line in the attic with a shack in the basement??
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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