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 coax choke 
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Post coax choke
looking renewing my coax for my ocd will also be making a choke anyone recommend a good quality flexible coax only short run so losses not important.

Many Thanks In Advance

Andy....


Sat Jul 28, 2012 7:27 pm
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 coax choke 
Silent Key

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Post Re: coax choke
What power level? And what diameter do you need to be able to bend it to?

Steve G3TXQ


Sat Jul 28, 2012 9:08 pm
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 coax choke 
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100w at the moment maybe go to 400w later on and 2 1/2 inch pipe. im getting a lot of rf in the shack and the sdr radio doesnt like it.


Sun Jul 29, 2012 7:13 am
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 coax choke 
Silent Key

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Post Re: coax choke
Andy,

RG-58 is rated to about 350W continuous at 30MHz and would probably be OK for anything other than a 100% duty-cycle mode. RG-400 would be my choice if you needed a bit more "headroom".

But be aware that any air-cored choke will only be effective over a relatively narrow bandwidth; ferrite cored chokes are much more effective for wideband applications. More details here:
http://www.karinya.net/g3txq/chokes/

Look at how narrowband air-cored chokes are, and see how they can actually increase Common Mode current in some situations.

73,
Steve G3TXQ


Sun Jul 29, 2012 8:10 am
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 coax choke 
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Post Re: coax choke
Think the best for me might be beads on my coax i have lmr400 what do you think 6 or 10.

Many Thanks

Andy.


Sun Jul 29, 2012 5:29 pm
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 coax choke 
Silent Key

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Post Re: coax choke
What frequency range are you trying to cover?

Steve G3TXQ


Sun Jul 29, 2012 6:35 pm
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 coax choke 
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40m is the one i get most shack rf with.


Sun Jul 29, 2012 7:29 pm
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 coax choke 
Silent Key

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You would need an absolute minimum of 10 beads, preferable a lot more.

Beads are not as effective as multiple turns on a ferrite toroid. 12 turns of RG-58 or RG-400 on an FT240-31 core would make a very effective choke for 40m.

73,
Steve G3TXQ


Mon Jul 30, 2012 9:26 am
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 coax choke 
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12 turns it is then.
Many Thanks for all you help & patience


Mon Jul 30, 2012 12:10 pm
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 coax choke 
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That is on a core though and NOT airwound

billy

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Mon Jul 30, 2012 12:12 pm
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 coax choke 
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yes on the FT240-31 ?


Mon Jul 30, 2012 12:58 pm
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 coax choke 
Silent Key

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Post Re: coax choke
Correct. Available here:
http://www.ebay.co.uk/itm/FT240-31-HUGE ... 43b1fe56fc

Steve G3TXQ


Mon Jul 30, 2012 1:24 pm
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 coax choke 
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Cheers Steve going to get a couple, Any idea on where i can get RG400?


Mon Jul 30, 2012 2:37 pm
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 coax choke 
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i picked up some 1588's today Ā£2.00 each from haydon comms in Brierley hill :yahoo:

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Mon Jul 30, 2012 3:21 pm
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 coax choke 
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M1DRK wrote:
Cheers Steve going to get a couple, Any idea on where i can get RG400?


http://www.gigatronix.co.uk/default.php?_minc=show_part_template_1&__utma=173680181.2091883133.1343673054.1343673054.1343673054.1&__utmb=173680181.4.10.1343673054&__utmc=173680181&__utmz=173680181.1343673054.1.1.utmcsr=%28direct%29|utmccn=%28direct%29|utmcmd=%28none%29&_lang=&gpdb_product_id=7616&

Have never used them though.

You could also try eBay

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Mon Jul 30, 2012 9:22 pm
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