Author Topic: Wire antennas anyone?  (Read 1213 times)

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Offline K4TQF

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Re: Wire antennas anyone?
« Reply #15 on: April 13, 2014, 06:35:00 AM »
RE: "perfect antenna.png"

Looking at that drawing, I assumed you meant 130' in height. Is that what you are saying? Or, are you giving that as total feedline length?

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #16 on: April 13, 2014, 08:32:50 AM »
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RE: "perfect antenna.png"

Looking at that drawing, I assumed you meant 130' in height. Is that what you are saying? Or, are you giving that as total feedline length?

To get the best performance with a 1/2 wavelength antenna the feedline length should be a 1/4 wavelength long. That would be for the lowest band you design the antenna to operate. In this case it was for 1.800Mc. Then for a full wavelength antenna the feedline should be a 1/2 wavelength long.



Offline KM1H

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Re: Wire antennas anyone?
« Reply #17 on: April 14, 2014, 03:13:03 PM »
Im another who has no use for a PITA tuner that means retuning for even simple in band QSY's :mad:

OWL is a drag in more ways than one and not everyone lives in the desert with no rain and ice storms. There is really no such thing as a non radiating OWL and local noise pickup can be intense in many areas.

With good quality RG6 almost free for the asking in many places putting up a multiband wire dipole is simple and any half decent vintage rig can tune even all of 80/75M. Ive run 1200W at both ends of the band with it. A good coax balun wound on a couple of 31 mix toroids takes common noise into the noise.

Carl

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #18 on: April 15, 2014, 08:17:20 AM »
Antennas with OWL will not radiate when using them on the frequency they are cut for or if you use a balanced tuner when not on that frequency or band. Say like the one in my pic, on 1.8Mc when it folds back the 130' feedline is pretty much invisible. The only time it will radiate is when changing frequencies or bands and that’s why you need a balanced tuner to eliminate it. It can radiate during tuning as you change bands, but once tuned and equalized (balanced again) it won’t.

I agree that OWL is a PITA when you don’t live in a location where you have the room for it like most of us, but if you do and can put it up without any obstacles then it’s the only real way to go. Even in my limited space location I’m still using OWL and it is a PITA because of it, but it’s still better than using coax if you can make it work.

Offline K4TQF

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Re: Wire antennas anyone?
« Reply #19 on: April 15, 2014, 10:34:34 AM »
Well... I have one of those AEA HF antenna analyzers. Unfortunately, it is for coax... the specs say 0-1000 ohms, but the I/O is an N connector with a SO-239 adapter...
I suppose I could experiment with some baluns & known impedances and plot the known to compare with the unknown, homemade OWL.  I think trying to use it thru a tuna
connecting it to the 50 ohm input and the OWL to the balanced output would throw off the readings. Again, I could use a known dummy load and look at how the analyzer would behave.
Just thinking out loud :confused:
MD

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #20 on: April 15, 2014, 11:18:28 AM »
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Well... I have one of those AEA HF antenna analyzers. Unfortunately, it is for coax... the specs say 0-1000 ohms, but the I/O is an N connector with a SO-239 adapter...
I suppose I could experiment with some baluns & known impedances and plot the known to compare with the unknown, homemade OWL.  I think trying to use it thru a tuna
connecting it to the 50 ohm input and the OWL to the balanced output would throw off the readings. Again, I could use a known dummy load and look at how the analyzer would behave.
Just thinking out loud :confused:
MD

Unfortunately those analyzers will not work with OWL fed antennas. As far as the modern tuners go, you would need a 4:1 toroid balun inside for connecting it to OWL. Many of them do have that now, but they leave a lot to be desired. The best way is to just build your own balanced tuner that doesn't need any balun.

Offline KM1H

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Re: Wire antennas anyone?
« Reply #21 on: April 15, 2014, 06:23:38 PM »
Quote
I agree that OWL is a PITA when you don’t live in a location where you have the room for it like most of us, but if you do and can put it up without any obstacles then it’s the only real way to go. Even in my limited space location I’m still using OWL and it is a PITA because of it, but it’s still better than using coax if you can make it work.

A coax fed antenna doesnt require an external tuner in many cases and VSWR loss is low on 160-40M for many ham runs. Use a roof mounted 10-20M ground plane where the vertical polarization can be useful; many AMers get nosebleeds on those bands.  :lol:  I operate 160-6M on CW, SSB, and AM, all coax and not a tuner in sight. CW/SSB only above that.

Quote
Unfortunately those analyzers will not work with OWL feed antennas. As far as the modern tuners go, you would need a 4:1 toroid balun inside for connecting it to OWL

That assumes the load is a perfectly resistive 200 Ohms and if the OWL is 600 Ohms we already have a problem. The tuner doesnt tune the antenna either and once the operating frequency becomes reactive the feedline is no longer a perfect 1/4 wave and the feedline starts to radiate unless you have an automatic tracking tuner. Change bands and the feedline is part of the antenna which is the real reason many think their antenna works so well....it has a horizontal and vertical component and at some point it becomes purely a vertical with T top loading which cancels the horizontal component.

Except on paper an OWL fed antenna is a compromise.

Carl
KM1H

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #22 on: April 15, 2014, 06:40:20 PM »
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A coax fed antenna doesnt require an external tuner in many cases and VSWR loss is low on 160-40M for many ham runs.

B.S. :lol:

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Except on paper an OWL fed antenna is a compromise.

It's only a compromise when using one antenna compared to needing separate antennas for each band or for two bands like 80/10 and 40/15.

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #23 on: April 16, 2014, 06:10:58 AM »
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Use a roof mounted 10-20M ground plane where the vertical polarization can be useful; many AMers get nosebleeds on those bands.

Verticals on the higher HF bands stink unless you are trying to work the occasional stuff overseas. That probably explains why after all these years I've never heard you on the air before. I've used verticals on 20 thru 10-meters before and they were awful for working AM here in the U.S. I've also used 80-meter coax fed dipoles on 10-meters and 40-meter coax fed dipoles on 15-meters, but the bandwidths were so narrow that if the transceiver didn't have a built in auto tuner to keep it's 50-ohm output happy it wasn't happy. And, trying to use them without a tuner on the tube stuff wasn't much better and you had to have one to try and bring the receive level back up when you moved too far away from it's resonate point.

Granted, a center-fed Zepp fed with OWL will leave a lot to be desired on the higher HF bands because of no gain, but at least they will work for someone who only has the room for one antenna and it will still work better than separate coax fed dipoles any day of the week.

Anyway, what works the best on the higher HF bands is a horizontal Yagi with at least 3 elements. 8dB to 9dB gain will do more good than anything. I still use my 10-meter mono band Yagi on the tower, but I'd like to have a tri-bander or one that even has 12 and 17-meters then use the my Zepp on 40-meters on down.

P.S. And yes, everyone uses the term "tuner" when the correct term is antenna coupler. It doesn't really tune the antenna, it simply matches and couples your source Z to it. Using the term 'tuner" is just a bad habit we have all falling into.

Offline K4TQF

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Re: Wire antennas anyone?
« Reply #24 on: April 16, 2014, 07:13:34 AM »
OK, using the "open wire feeder impedance calculator" ( You are not allowed to view links. Register or Login ) using 14GA wire (1.6MM)      I don't see much change in impedance from 2ft spacing ( 700 ohms) to 5 ft spacing (843 ohms )    600 ohms was achieved @ 9.4 inch spacing. This seems much more manageable.

Offline W5HRO

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Re: Wire antennas anyone?
« Reply #25 on: April 16, 2014, 07:42:08 AM »
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OK, using the "open wire feeder impedance calculator" ( You are not allowed to view links. Register or Login ) using 14GA wire (1.6MM)      I don't see much change in impedance from 2ft spacing ( 700 ohms) to 5 ft spacing (843 ohms )    600 ohms was achieved @ 9.4 inch spacing. This seems much more manageable.

600-ohms is what most hams do and will work fine, its just better to use wider spacing whenever possible. The wider the gap is at the antenna feed-point (not the transmitter end) then the higher Z you will have there. The higher the better. You can use a wider spacer between each leg of the antenna and then "V" the end of the feeder up to it, but having a sharp 90 degree angle straight down always works best.

I'd use at least 1' spacing minimum since you have the room for it. The Z at the transmitter end will change anyway as you change bands. Try and make it work without any external antenna coupler first on the lowest band you will use it on. Just connect it directly to the link coil's output of your push-pull amp. It will be a step down at that point anyway.

If you have room for a full-wave loop you could try that too. Also remember the curtain antenna that guy put up in his historic district after they complained about his modern tower?

Offline K4TQF

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Re: Wire antennas anyone?
« Reply #26 on: April 16, 2014, 10:03:21 AM »
Quote
Also remember the curtain antenna that guy put up in his historic district after they complained about his modern tower?

Yes, I remember that. The only complainers I'll have are the deer. Our house is on a paved city street. The 3.5 wooded acres that the shack sits on is west of  a gravel road behind the house. So, it's well out of view of any tourists and there are no houses on the gravel road. Passers-by would have a hard time seeing #14 black wire back in the woods. Heck, I can't even see the 100' pines out the rear windows of the house. The shack is about 120' from the house. I'll be posting the shack progress pix I had on the old forum. Maybe I can get a Google Earth screen grab to give a better perspective.
TNX, MD 

Offline KM1H

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Re: Wire antennas anyone?
« Reply #27 on: April 17, 2014, 06:48:50 PM »
I only use verticals on 160 and 80 supplemented by 180' high inverted V's. Until I downsized the contest aluminum from 4 high stacks of 4 el on 10, 15, 20; and 4/4 on 40 you would have heard me on any band if you were active during my waking hours. These days it is nothing on 40 as I rebuild the 2/2 into Leeson Moxons and 10/15/20 use HB 4/4/3 el monobanders. Im usually in bed by 10-11 PM Eastern time these days. Lots of the guys from the other place have worked me 160-10M and there were a couple of good nights to the West Coast during the winter when I stayed up to 1AM. Needed a lot of smoke since most of those guys dont hear well, the Beverages here helped to get perfect copy on the 100W stations.

OTOH switching between the main station and the expanding AM side of the basement is a royal PITA so I wont be using the antennas requiring rotators. Currently there is a 75M sloper with 40/15 hanging from it as an inverted V and I run the 180' high 160/80/75 single feedline Vee on a switch.

In the past Ive had excellent results with verticals 20 to 10M US and DX and the current projects are converting a pair of freeby Hi Gain CB 5/8 wave. One for 20/17 will be mounted at one side eave and the other 15/12/10 on a chimney mount about 55' away. With elevated radials they should do well enough.

Still trying to figure out to get a station in the FR, BR, and maybe the attic wired in and easily antenna switched.

Carl

Offline K4TQF

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Re: Wire antennas anyone?
« Reply #28 on: April 25, 2014, 11:14:31 AM »
So, I've ordered this OWL kit:  You are not allowed to view links. Register or Login     Am I allowed to post a commercial link?

I have a roll of 14ga THHN and a roll of Dacron rope, ( black, so the hysterical district snoops don't see it) I've ordered two center spacers for the antenna, so as to separate the dipole at least double the width of the feed line for a higher impedance feed point. (Y)

I'll mount these to the wall  to bring the feedline into the shack:  You are not allowed to view links. Register or Login
Am I allowed to post a commercial link?

Now, all I need to do is figure 130' from the output of the tuna/transmitter to the antenna... in order to make the feedline reach and allow the antenna to work at optimum height above ground. BTW, I have very poor soil over here in the Ozarks... I may wind up needing  a reflector either parallel with the antenna or on the ground ! :icon_crazy:


Offline W1AC

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Re: Wire antennas anyone?
« Reply #29 on: April 26, 2014, 09:11:24 AM »
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What you want is a really high impedance at the antenna feed point (not the shack end) and then a low impedance (600-ohms or less) at the shack end where it connects to your tuner or equipment.

I'm confused: why is that a "good thing"? Most antennas are well below that value, and even a folded dipole is nominally 300 ohms at the feedpoint. Getting a higher feedpoint impedance would mean introducing reactance or using a transformer, correct?

Bill, W1AC