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 My first doublet 
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Post My first doublet
Managed to get a doublet up yesturday before the rain set in. Had a quick listen last night and all seemed ok.
My question is how far away from the support poles should the ends of the doublet be?
Ive managed to just squeeze in 88ft but im thinking now that maybe the ends are to close to the poles and that I should have hung the ends down a bit.
The ends of the antenna are probably only 6 inches from the support poles. Is this to close?
Thanks in advance
Mark.


Fri Jun 27, 2014 10:16 am
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 My first doublet 
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Post Re: My first doublet
By the way I should have added, the support poles are metal poles one straight into the ground and the other bolted to the end of the house.


Fri Jun 27, 2014 12:17 pm
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 My first doublet 
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Post Re: My first doublet
Shouldn't make much difference.

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Fri Jun 27, 2014 12:22 pm
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 My first doublet 
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If you don't see any big blue flashes between the ends of the doublet and the poles it's far enough :)

Steve G3TXQ


Fri Jun 27, 2014 1:15 pm
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 My first doublet 
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G3TXQ wrote:
If you don't see any big blue flashes between the ends of the doublet and the poles it's far enough :)

Steve G3TXQ


I was going to put something like that, very similar to what my setup is and I don't have any issues.

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Fri Jun 27, 2014 1:20 pm
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 My first doublet 
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Post Re: My first doublet
Many thanks for the replys guys. Seems a very noisy antenna to be honest, not what I was expecting. Seems a constant s5 to s7 of noise all the time :-(
Im not sure if it's something possably interfering from the local shops or bank as these are very close to me.
will compare it later on when there all closed.


Fri Jun 27, 2014 4:00 pm
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 My first doublet 
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Post Re: My first doublet
Depends on what band you are listening to. I use a 100 foot doublet and on 80M the noise it between 5 and 7 most of the time on ssb, but the signals are way above the noise anyway. What I'm trying to get at is that the antenna might be quite efficient and you are hearing more noise than you expect.

Normally as you go up in frequency the noise reduces, especially above 40M. Don't condemn it just yet, give it a try.

By the way, I'm listening on 60M at the moment and the background noise is S5 and the static crashes are peaking 20db over S9, so someone is having a good old storm somewhere. I do live in a rural area as well.

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Fri Jun 27, 2014 4:32 pm
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 My first doublet 
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Post Re: My first doublet
Just had a listen now all the shops have shut and gone home. 10, 15 and 20m seems to all have about s3 to s4 of noise even though the bands seem quiet to me apart from a bit going on on 20 but 40m has about s8 of noise with lots of g stations. Does this sound about right? I thought 10 would be s0 at the moment?
Ive tried swapping patch leads over and disconecting the earth from the power supply plug but no different.
Am I looking for a problem thats not there?


Fri Jun 27, 2014 7:35 pm
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 My first doublet 
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Post Re: My first doublet
That all sounds about right to me, I've just checked 40 and I've got about S6-7 of background noise in between the static crashes and 10M I've got a steady hiss of S3 which is quite normal for me here. As I say, I live in a rural area so what you are getting there doesn't sound too bad at all. How are you feeding the doublet? You don't need an additional earth if you are using a doublet because it is a balanced antenna system, so the RF earth is not needed.

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Fri Jun 27, 2014 8:02 pm
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 My first doublet 
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Im feeding it with 300 ohm ribbon feeder (20 metres in length) straight through a hole in the wall into the shack to a sem tranzmach balanced atu. It seems to tune ok on all bands with a bit of messing. Might just be me getting used to the tuner. Ive got the tuner and separate swr meter in line.


Fri Jun 27, 2014 8:50 pm
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 My first doublet 
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It sounds like you are good to go, give it a try, I'm sure it will be fine.

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Fri Jun 27, 2014 9:01 pm
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 My first doublet 
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Post Re: My first doublet
Thanks for your help paul, I'll stick with it and see how I get on over the next couple of weeks.
Mark


Fri Jun 27, 2014 9:16 pm
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 My first doublet 
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I just noticed, you need to reconnect the earth to the power supply plug if that is the 13 amp plug you have removed it from, as that is your safety earth. Good luck, post back and lets us know how you get on.

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Fri Jun 27, 2014 9:41 pm
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 My first doublet 
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Post Re: My first doublet
Yes thanks already done after it made no difference.
Ive since noticed a bit of rf in the shack. I can feel it on the mike plug on transmit and also the swr alters slightly if i touch the casing of the swr meter or tuner ? I'm thinking maybe I need to earth the tuner or use a balun outside and bring coax into the shack instead of ribbon feeder?


Fri Jun 27, 2014 11:44 pm
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 My first doublet 
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Post Re: My first doublet
That is indicating the feeders are not balanced. You need a 1:1 Balun just outside then run the coax from the end of the open line into the tuner, preferably using RG213 of no more than a few metres to keep the losses down, because there will be a high SWR on some bands.
I built this Balun that has a pair of FT240-43 glued together and the wiring is about 9 turns of 18SWG sleeved with PTFE. You could get away with just one core, but I had two available so it's made it a bit of a belt and braces job.

Forgot to mention, that might help reducing the noise if the open wire line is balanced, it will stop the line picking up unwanted noise.

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Sat Jun 28, 2014 5:56 am
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