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 help with my cobweb 
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Post help with my cobweb
Hi guys

I'm just in the middle of building my cobweb and the lowest swr I can manage to get on
20 meters is 1.5 which stays the same from 14.100 to 14.350 is this swr 1.5 ok to use regualy
Without damaging my radio ??

Sorry if I sound thick guys but I'm still at the learning stage :)

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Sun Jul 31, 2011 2:07 pm
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 help with my cobweb 
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Post Re: help with my cobweb
Its not ideal and I'm bound to be shot down but most radios won't mind a SWR of 1.5. Further down the line most amps wont mind a SWR of 2 and some can run up to 3 without issue.

if my cobwebb has 1.5 on 20m I'll be quite happy.

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Sun Jul 31, 2011 2:19 pm
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 help with my cobweb 
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2e1hje wrote:
Its not ideal and I'm bound to be shot down but most radios won't mind a SWR of 1.5. Further down the line most amps wont mind a SWR of 2 and some can run up to 3 without issue.

if my cobwebb has 1.5 on 20m I'll be quite happy.



Thanks mate well at least I know its usable like that if I can't get it any lower :)

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Sun Jul 31, 2011 2:24 pm
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 help with my cobweb 
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im going to give it another try before i set it at 1.5 if i cant get it any lower i will use it at 1.5 then :)

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Sun Jul 31, 2011 2:38 pm
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 help with my cobweb 
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Post Re: help with my cobweb
Well no luck so its staying at 1.5

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Sun Jul 31, 2011 3:11 pm
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 help with my cobweb 
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Post Re: help with my cobweb
You may find that once you get it up in the air the SWR drops slightly. - that depends on how low you are doing your testing.

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Sun Jul 31, 2011 3:14 pm
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 help with my cobweb 
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2e1hje wrote:
You may find that once you get it up in the air the SWR drops slightly. - that depends on how low you are doing your testing.



Iv got it mounted on a 6 foot scaff pole in the middle of the garden just well I build it
Then when its finished it will be going up on a 21 foot pole!!
Its conected to my radio via a 10 meter length of rg58

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Sun Jul 31, 2011 3:28 pm
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 help with my cobweb 
Silent Key

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Post Re: help with my cobweb
An SWR of 1.5:1 shouldn't harm the radio.

But I would be more concerned to find out why 1.5 is the minimum, and importantly why it doesn't seem to vary much across the band. Those are not typical for the CobWeb.

Is it the folded dipole design, or my single-wire design?

Steve G3TXQ


Sun Jul 31, 2011 3:45 pm
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 help with my cobweb 
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G3TXQ wrote:
An SWR of 1.5:1 shouldn't harm the radio.

But I would be more concerned to find out why 1.5 is the minimum, and importantly why it doesn't seem to vary much across the band. Those are not typical for the CobWeb.

Is it the folded dipole design, or my single-wire design?

Steve G3TXQ


Yes this is the folded dipole twin wire design mate iv had a little play with it
And got the swr down a lil bit just below 1.5 now so better haha it duz vary now the swr
Creeps up towards to nearly 2 on 14.350

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Sun Jul 31, 2011 4:00 pm
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 help with my cobweb 
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Post Re: help with my cobweb
and is it different at height?

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Sun Jul 31, 2011 4:05 pm
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 help with my cobweb 
Silent Key

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Post Re: help with my cobweb
The twin wire versions are a bit trickier to tune: you have two things to juggle - the lengths of the elements and the shorting positions. If adjusting for the best length still leaves you with a moderate value of minimum SWR, the shorting positions are wrong.

For those who want the technical "nitty gritty" it's here:
http://www.karinya.net/g3txq/folded_dipole/

73,
Steve G3TXQ


Sun Jul 31, 2011 4:06 pm
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 help with my cobweb 
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Post Re: help with my cobweb
2e1hje wrote:
and is it different at height?

Not had it any higher than 6 foot up to yet mate !!
I was led to beleve that the cobweb swr would be the same weather
6 foot or 20 foot up in the air ! I could give it ago tho and see if it makes
a difference ya never know do you lol

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Sun Jul 31, 2011 4:10 pm
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 help with my cobweb 
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Post Re: help with my cobweb
G3TXQ wrote:
The twin wire versions are a bit trickier to tune: you have two things to juggle - the lengths of the elements and the shorting positions. If adjusting for the best length still leaves you with a moderate value of minimum SWR, the shorting positions are wrong.

For those who want the technical "nitty gritty" it's here:
http://www.karinya.net/g3txq/folded_dipole/

73,
Steve G3TXQ


i think im going to strip it right back and re start the who thing by using your design the single wire version :)

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Sun Jul 31, 2011 4:26 pm
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 help with my cobweb 
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Post Re: help with my cobweb
Infact I'm going to stick with the folded dipole one that I'm building and find oit what's wrong with it
And fix it instead of letting it beat me haha,I'm going to chek the shorting points first !!

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Sun Jul 31, 2011 5:33 pm
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 help with my cobweb 
Silent Key

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Post Re: help with my cobweb
How did you decide where to place the shorting points on the antenna as it is now?

Steve G3TXQ


Sun Jul 31, 2011 5:43 pm
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