I don't know if it matters much, but I believe it is not 4:1 UNUM but rather
4:33 to 1.
I had a chat with Balun Design (I forget his name!) about it when I considered
replacing the matching unit on mine with something from him.
I will soon have an extra matching unit. My 4:33 to 1 was wound a bit poorly,
wires not evenly spaced around the core and so it would overheat at 1.5KW.
Hy-Gain/MFJ replaced it, but I have yet to install the new unit. I'll be taking
it down in the next week or so to prepare for a move though.
73,
Art
--- On Wed, 8/1/12, Dan Hearn <n5ardxcc@gmail.com> wrote:
From: Dan Hearn <n5ardxcc@gmail.com>
Subject: Re: [TowerTalk] Rebuilding AV640 matching network.
To: "Grant Saviers" <grants2@pacbell.net>
Cc: towertalk@contesting.com, "K8RI" <K8RI-on-TowerTalk@tm.net>
Date: Wednesday, August 1, 2012, 10:18 AM
My Times Wire and Cable catalog shows a power rating of 9kw for 142 and
11.5 kw for 143 at 10mhz . The ratings are less at 50mhz, 3.5kw and 4.6kw.
I have been using 142 on legal limit chokes for several years. Take a look
at the chokes from Balun Designs and DXE. they use the stuff.
Dan, N5AR
On Tue, Jul 31, 2012 at 8:16 PM, Grant Saviers <grants2@pacbell.net> wrote:
> RG304 but get out your wallet, if you can find it! 0.28" od
> http://www.awcwire.com/Part.aspx?partname=RG304
>
> Also RG142 dbl silver braid is close to QRO all bands, same as RG303.
> 1900 volt max.
>
> Grant KZ1W
>
> On 7/31/2012 7:38 PM, K8RI wrote:
> > The AV640 matching network is relatively simple, a current, or choke
> > balun wound on 2 ferrite core, and I believe a 4:1 transformer wound on
> > two cores.
> >
> > #31 material should work well with RG303 for the current balun, but it
> > appears to be a bit anemic for handling the legal limit. I think the
> > same core material will work for the 4:1 transformer.
> >
> > Is there another relatively compact/small coax that is rated for the
> > full legal limit?
> >
> > 73
> >
> > Roger (K8RI)
> >
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
> _______________________________________________
>
>
>
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>
--
Dan Hearn
N5AR
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