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 Cobwebb construction advice 
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Post Cobwebb construction advice
Hi
I bought the components to build my own cobwebb antenna including the hardware kit and ready built balun box including the wire kit as i wanted to ensure the best chance of sucess as possible. I was quite meticulous with the construction so i was a bit miffed when i put the antenna analyser on and found it was no where near the resonant frequencies on any band.
The balun box comes with a stauff clamp fitted which takes a 25mm dia tube. This is the size of the alum tube that comes with the hardware kit. So i connected the balum box directly to the 1m peice of tube that came with the kit.
Could this have affected the swr and frequency.
The ant is mounted on a 12m tiltable mast so its not an easy job to trim the wires but obviously i know i have to but want to iron out any other problems.
Thanks
Phill m0ank


Fri Oct 27, 2017 3:47 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Pics?

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Fri Oct 27, 2017 4:03 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Cut 150 mm off the aluminium and put in a piece of fibreglass to return the tube to the correct length
and you need to be aware that height above ground will affect resonance and any buildings etc

I tuned mine at 6 foot abive grouind and raiseing to 30 foot shifted resonace about 50 khz, just cant remember whether it was higher or lower.

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Fri Oct 27, 2017 4:07 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
which version is it?

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Fri Oct 27, 2017 4:12 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Sangoma wrote:
which version is it?



Its the g4ztr version
Thanks


Fri Oct 27, 2017 5:24 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
From here then http://www.hamgoodies.co.uk/cobwebb-balun-box
How far out is it and on what bands ,normally you start on one band and work your way through them one at a time starting at 20m .
Looks like he didn't have issues with the metal pole on the balun box, silly question but you are using fiberglass for the spreaders.
I tuned mine 6 foot off the floor to start with.

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Fri Oct 27, 2017 5:41 pm
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Post Re: Cobwebb construction advice
If I read that right, a 1m length of aluminium tube to hold the balun box is a badddd idea! :shock:

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Fri Oct 27, 2017 5:42 pm
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 Cobwebb construction advice 
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Well you would think so but it obviously isn't doing any harm going on his results.

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Fri Oct 27, 2017 5:46 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
M0MNM wrote:
If I read that right, a 1m length of aluminium tube to hold the balun box is a badddd idea! :shock:

yup, I cut off 150mm and added a piece of fibreglass 200mm long to support the balun box no more tuning problems
all pruned in 20 minutes 6 foot off the floor.

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Fri Oct 27, 2017 5:56 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Err double post

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Its not the class of licence the amateur holds thats important but the class of bias the prat applies to his amplifier


Fri Oct 27, 2017 6:01 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Thanks all ill try replacing the alum with fibreglass tomorrow
Yes using fibreglass for spreaders .
Got some spare so easy to do


Fri Oct 27, 2017 10:20 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
M0ANK wrote:
Thanks all ill try replacing the alum with fibreglass tomorrow
Yes using fibreglass for spreaders .
Got some spare so easy to do

Can you link to where you got the fibreglass spreaders please?

Ta.

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Sat Oct 28, 2017 8:34 am
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 Cobwebb construction advice 
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M0YDC wrote:
M0ANK wrote:
Thanks all ill try replacing the alum with fibreglass tomorrow
Yes using fibreglass for spreaders .
Got some spare so easy to do

Can you link to where you got the fibreglass spreaders please?

Ta.

It was sandpiper aeriels matey
Awww.sandpiperaerials.com/shop
Thanks


Sat Oct 28, 2017 9:42 am
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
Well that seems to have worked. Cut 150mm off and inserted a length of fibreglass tubing and all tuned up on a pole 6 ft from the groung. Will put it on the mast for final tweeks tomorrow.
Thanks everyone
Phill m0ank


Sat Oct 28, 2017 12:12 pm
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 Cobwebb construction advice 
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Post Re: Cobwebb construction advice
M0ANK wrote:
Well that seems to have worked. Cut 150mm off and inserted a length of fibreglass tubing and all tuned up on a pole 6 ft from the groung. Will put it on the mast for final tweeks tomorrow.
Thanks everyone
Phill m0ank

:good:

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Its not the class of licence the amateur holds thats important but the class of bias the prat applies to his amplifier


Sat Oct 28, 2017 1:27 pm
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