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Long Wire Antenna for HF

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#1
Greetings,

I'm looking for advice on a long wire antenna for HF operations. I'm look at the 20 meter band as my place to start. I have a PL-259 connector and a spool of speaker wire from Radio Shack. The idea I had was to run the wire directly into the connector and then use a rope to put the antenna up in a tree. The radio I'm using is the FT-817. I'm leary about high SWR so I want to get this right before I make a mistake.
 

ka3jjz

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#2
Well let's start with the antenna itself. I doubt you really want a longwire for a transmit antenna - they tend to be very directional off either end, and not particularly efficient radiators. And true longwires are 1 wavelength or better long - hope you have the physical space for it...and I haven't even talked about grounding yet...

A good old fashioned dipole will do nicely. There are TONS of places to read up on how to build a dipole - including our own antenna wiki...here's a nice basic article on the subject...

Antenna Primer Part 2

best regards..Mike
 
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#3
Hi Mike,

Thanks for the input. The reason I was thinking long wire was for something field expedient that I could throw in my cargo pocket and move out to the next site quickly. I know the long wire isn't the best choice for radiating. I'm very interested in very mobile operating. I will definately be reading the link you sent.
 

ka3jjz

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#4
You would probably do better with antennas such as the PAR (that have ham-only designs, not just the well known SWL version...); I would go join the FT817 yahoo group and get some recommendations.

A dipole really needs 2 points from which to suspend it - and I suspect you won't always have such available. The QRP (yes, that radio is low power) guys make an art form out of antennas which are field-deployable

best regards..Mike
 
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#5
Get three insulators, 52 (the dipole is 51 feet long, the extra is for making the connections) feet of 18 ga. wire, 17 feet of 300 ohm tv twin lead, and 35 feet of RG174. Use that to make a light weight pocket carry-able G5RV Jr. it will work 40, 20, 15, 10 and maybe even 18 and 12 meters without a tuner.
 
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#6
The G5RVJR will not work those bands without a tuner unless you are counting on lots of loss in the RG-174 to bring the match down. You can tune the balanced feedline length to give a reasonable match on 10m but thats about it. The full size G5RV will give a good match on 20m and you need a tuner everywhere else. I would not recommend long runs of RG-174 on HF except into a well matched load otherwise much of your power will be used to heat up the tiny coax.

On the other hand a cousin of the G5RV called the ZS6BKW is computer designed to match on 40m and up without a tuner and these work just great. They are about 94ft long with a 450ohm or 300ohm balanced line matching section about 41ft long. A Google search will find all the dimensions of the ZS6BKW and I found its best to use the recommend length of wire and cut the balanced feedline to get the best match on 40m, then the other bands just fall into place.
prcguy



Get three insulators, 52 (the dipole is 51 feet long, the extra is for making the connections) feet of 18 ga. wire, 17 feet of 300 ohm tv twin lead, and 35 feet of RG174. Use that to make a light weight pocket carry-able G5RV Jr. it will work 40, 20, 15, 10 and maybe even 18 and 12 meters without a tuner.
 
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#7
Greetings,

I'm looking for advice on a long wire antenna for HF operations. I'm look at the 20 meter band as my place to start. I have a PL-259 connector and a spool of speaker wire from Radio Shack. The idea I had was to run the wire directly into the connector and then use a rope to put the antenna up in a tree. The radio I'm using is the FT-817. I'm leary about high SWR so I want to get this right before I make a mistake.
Back to the original idea. IT WILL WORK FINE. The only thing I would add is a small, low power tuner and an SWR meter. Something small so you can keep things compact and simple. That will allow you to string up whatever length wire you have room for at the time. Short, long, super long.

A simple wire strung between the car and a tree, or your camp and a tree will work fine. You don't have to make it complex to have it work.

You will work plenty of people without difficulty. Sounds like fun!



 
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#8
If you are set on a very simple antenna then that 'random length' end fed wire is probably about as 'simple' as it get's. The problem with antennas like that is that you have to make then compatible to the transmitter, and then finding a tree to throw them into. Oh mercy, there are a lot of "if's" and "but's" with that!
One solution to -part- of that problem is a very versatile 'tuner'. (Finding that tree is your problem.) Then you need another pocket to put that tuner into, right?
Can you find a length of wire that will result in a low 'SWR'? Sure, but that doesn't mean it's going to radiate very well. It'll produce -a- signal, but who knows how good of a one?
The simplest solution is to throw lots of money at it (sort of like the military??). But if you 'discover' some 'miracle' of an antenna, please let us know, okay?
- 'Doc

You can make almost anything work if you want to bad enough. Good luck.
 
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#9
A simple random length wire can work fine but you need an adequate counterpoise in addition to the tuner. Otherwise the coax between the tuner, the microphone cable and anything connected to the radio will become the other half of the antenna and will try to radiate.

Its also good to have multiple counterpoise wires running away from each other to cancel radiation because a single counterpoise wire in most cases makes a random wire antenna into a dipole. The single counterpoise wire is the other half of a dipole and is about the same as using an inverted V with one element laying on the ground, not so good.

A few weeks ago I was in a hurry to get a field antenna up for a 5min test on 40m with a 20w military manpack radio and I tossed about 60ft of wire in a tree and ran a 2ft ground cable to the center of a chain link fence for the counterpoise. It worked really well and the 20w radio with internal antenna tuner was doing as good as some 100w stations in the same area.
prcguy

Back to the original idea. IT WILL WORK FINE. The only thing I would add is a small, low power tuner and an SWR meter. Something small so you can keep things compact and simple. That will allow you to string up whatever length wire you have room for at the time. Short, long, super long.

A simple wire strung between the car and a tree, or your camp and a tree will work fine. You don't have to make it complex to have it work.

You will work plenty of people without difficulty. Sounds like fun!



 
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#10
A simple random length wire can work fine but you need an adequate counterpoise in addition to the tuner. Otherwise the coax between the tuner, the microphone cable and anything connected to the radio will become the other half of the antenna and will try to radiate.
So what? Who cares. At 10 watts you're not going to get RF burns.

Its also good to have multiple counterpoise wires running away from each other to cancel radiation because a single counterpoise wire in most cases makes a random wire antenna into a dipole. The single counterpoise wire is the other half of a dipole and is about the same as using an inverted V with one element laying on the ground, not so good.

A few weeks ago I was in a hurry to get a field antenna up for a 5min test on 40m with a 20w military manpack radio and I tossed about 60ft of wire in a tree and ran a 2ft ground cable to the center of a chain link fence for the counterpoise. It worked really well and the 20w radio with internal antenna tuner was doing as good as some 100w stations in the same area.
prcguy
+1

Keep it simple and learn as you go.
 
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#11
The G5RVJR will not work those bands without a tuner unless you are counting on lots of loss in the RG-174 to bring the match down. You can tune the balanced feedline length to give a reasonable match on 10m but thats about it. The full size G5RV will give a good match on 20m and you need a tuner everywhere else. I would not recommend long runs of RG-174 on HF except into a well matched load otherwise much of your power will be used to heat up the tiny coax.

On the other hand a cousin of the G5RV called the ZS6BKW is computer designed to match on 40m and up without a tuner and these work just great. They are about 94ft long with a 450ohm or 300ohm balanced line matching section about 41ft long. A Google search will find all the dimensions of the ZS6BKW and I found its best to use the recommend length of wire and cut the balanced feedline to get the best match on 40m, then the other bands just fall into place.
prcguy
Ok, I'll tell my watt meter it better start showing some reflected power OR ELSE! 300 some contacts, 37 states, and several VEs with that antenna, a 12 AH gel cell charged by solar and an 817 mainly on 20 and 40 last field day.
 
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#12
I have a G5RV JR and at the end of the twinlead its about 10:1 on 40m and pretty bad on most other bands.
The 35ft of RG-174 is acting as an attenuator and loosing a lot of power on the high VSWR bands while smoothing out the match. That just means you made all those contacts with less power at the antenna than you thought.

The G5RV is also a marketing idea and not designed by Louis G5RV, they just cut his 20m antenna in half and it resonates somewhere near 10m with a good match to 50/75 ohm coax.

Ive used G5RVs for many years and after discovering the ZS6BKW I can say its a much better antenna for most hams since it truly matches on most bands from 40m on up where the G5RV and it's half pint JR version do not.
prcguy




Ok, I'll tell my watt meter it better start showing some reflected power OR ELSE! 300 some contacts, 37 states, and several VEs with that antenna, a 12 AH gel cell charged by solar and an 817 mainly on 20 and 40 last field day.
 
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#13
And YOU know that if you stick a so called antenna tuner on the end of the coax the transmitter sees a load it is happy with but the mismatch is still there on the antenna side of the tuner and so are the losses in the coax. All the tuner does is keep the transmitter happy so the protection circuits will not turn the power output down. The power that makes it to the antenna MAY be higher because the transmitter is putting out full power instead of folding back, but all the mismatch losses are still there.

Antenna tuners are not some kind of magic bullet. The only way for a tuner to reduce line losses is to remote mount it at the feed point of the antenna, not at the transmitter.

BTW, do you know what a field strength meter is and how to use one to compare antennas?
 
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#14
Yes I know the tuner is making the radio happy and coax losses are still there, especially high loss from RG-174 under high VSWR conditions. That's why I use very low loss balanced line on multiband wire antennas whenever possible which substantially reduces feedline loss even at very high VSWR.

Yes, I know how to use a field strength meter but I prefer using a spectrum analyzer to see the differences in precise .1dB steps. I used to be the rangemaster at an antenna/RCS test range so I am a little familiar with antenna testing and comparison.
prcguy


And YOU know that if you stick a so called antenna tuner on the end of the coax the transmitter sees a load it is happy with but the mismatch is still there on the antenna side of the tuner and so are the losses in the coax. All the tuner does is keep the transmitter happy so the protection circuits will not turn the power output down. The power that makes it to the antenna MAY be higher because the transmitter is putting out full power instead of folding back, but all the mismatch losses are still there.

Antenna tuners are not some kind of magic bullet. The only way for a tuner to reduce line losses is to remote mount it at the feed point of the antenna, not at the transmitter.

BTW, do you know what a field strength meter is and how to use one to compare antennas?
 
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#15
Ah, but that tuner, while it certainly isn't a 'cure-all', does make some really 'not-good' antennas USABLE, which is the whole point. As you say, it doesn't 'correct' anything, but it does make the transmitter 'happy' and so it'll put out full power.
Line losses. We may be talking about different things there. A tuner won't change any 'line losses' at all. Those losses are inherent to the feed line being used.
That RG-174 has the highest losses of any coaxial feed line that I'm aware of. It isn't bad for -very- short runs, interconnections of 'modules' in a radio, but for a feed line it's terrible.
I can't speak for 'prcguy', but I do know what a field strength meter is. I also know their limitations. They certainly can make somethings easier to 'measure', but unless you use them in a very controled way, they don't always tell you very much that's really usable/accurate. If you know what they do and how, a florescent light bulb can tell you as much in most cases. :)
- 'Doc
 
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#16
The thing that sparked this side thread was a statement about a G5RV JR having a good match and not needing a tuner and my main point is the G5RV JR does not have a good match anywhere and the length of RG-174 used with it is matching via high loss. If you know this and proceed to make contacts that's great but it doesn't make a G5RV JR useable without a tuner on its own.

To take this further, on doublet antennas fed with balanced line all the way to a proper tuner for that purpose, the system loss can be very low and practically all the power gets radiated even though antenna to feedline VSWR is very high.

As an example, you can take a resonant 80m dipole matched well to 50 ohm coax, take a field strength measurement, then replace the coax with 600ohm balanced line and a tuner and the resulting field strength will be nearly the same even though the antenna to feedline match is really high. Yea you can measure a very small loss in field strength but its probably not going to be detectable by other operators.

What you have also done in this case is taken a mono band 80m antenna and turned it into a very useable multiband antenna, which would not work very well multiband if fed with coax due to the high loss on other bands.
prcguy


Ah, but that tuner, while it certainly isn't a 'cure-all', does make some really 'not-good' antennas USABLE, which is the whole point. As you say, it doesn't 'correct' anything, but it does make the transmitter 'happy' and so it'll put out full power.
Line losses. We may be talking about different things there. A tuner won't change any 'line losses' at all. Those losses are inherent to the feed line being used.
That RG-174 has the highest losses of any coaxial feed line that I'm aware of. It isn't bad for -very- short runs, interconnections of 'modules' in a radio, but for a feed line it's terrible.
I can't speak for 'prcguy', but I do know what a field strength meter is. I also know their limitations. They certainly can make somethings easier to 'measure', but unless you use them in a very controled way, they don't always tell you very much that's really usable/accurate. If you know what they do and how, a florescent light bulb can tell you as much in most cases. :)
- 'Doc
 
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#18
Quote from jhooten: "it will work 40, 20, 15, 10 and maybe even 18 and 12 meters without a tuner".

Sorry if I read that as having a good match on those bands. BTW, is 18 meters a new amateur band?

PS, no panties on today, I'm going commando.
prcguy




Go back and quote where I said it was a good match. Unwad your panties and reread. Then show me the quote. You cannot.
 
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#19
I'm with prcguy on this one. The G5RV is a crappy antenna. Here's an interesting experiment that anyone with a few active brain cells can try with their G5RV. Insert a VSWR meter between the (required) tuner and the coax feedline of the G5RV. Tune the (required) tuner for best match at the transmitter, and measure the VSWR on the coax. With your VSWR measured, calculate the additional loss on the coax.

Declaring an antenna is working good by virtue of the DX worked is not really a valid measure of performance. I've worked across the country on 80 meters while mobile, and I KNOW that my antenna is less than 5% efficient on that band. DX is worked all the time on less than 1 watt ERPs.

If you're serious about maximizing performance on a multiband antenna, a G5RV isn't the way to go. You can replace the balan with a tuner at that point, and that alone will make a huge difference. If you're looking for something cheap and easy, a G5RV will radiate. But you'd be surprised at just how low your ERP is on some bands. Whatever floats your boat...
 
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#20
The op said he was looking for "field expedient that I could throw in my cargo pocket and move out". Stuffing even that micro tuner from MFJ in the pocket of the BDU and letting it beat me in the leg is not my idea of a fun day.

Anything you can come up with that meets his requirements is going to be a compromise. Yes the RG-174 is a compromise. It serves two purposes. It attenuates the reflected power as mentioned. It also keeps the size and weight down to meet the stated requirements. He is asking for something for quick deployment and easy transport and the best you guys can come up with is a full size rhombic.

I meant 17 meters and you know it.

Ok, before the fire, I had 240 feet of 12 gauge sky blue wire strung between to 100 foot tall pines roughly nw to se. It was fed with 70 feet of 450 ohm window line, a 1to1 balun and enough RG=8 to get to the autotuner in the shack. I was Alaska on 15 meters away from working 5 band DXCC on that antenna and 40 states worked on 160. Was it the best antenna for the job? No, but it let me make contacts. Would I want to coil it up and put it in a cargo pocket and take a hike? NO!

Same with the 817. It is not the radio I want to work a traffic net or contest with. But to put in a pack to take on a day hike, pulling it out at the lunch stop with a small antenna to hang on what ever support is available and make a few contacts it is a tool for the job.

So, do any of you geniuses have a suggestion for the op that meets his requirements or not?
 
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