[AMRadio] Open Wire - was AMRadio Digest, Vol 46, Issue 24


jeremy-ca km1h at jeremy.mv.com
Wed Nov 14 12:41:32 EST 2007


----- Original Message ----- 
From: "Robert Nickels" <W9RAN at oneradio.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Wednesday, November 14, 2007 11:10 AM
Subject: Re: [AMRadio] Open Wire - was AMRadio Digest, Vol 46, Issue 24


> Ben Dover wrote:
>> I personally love the stuff. Coax has it's place, but often it's not the
>> best solution to the problem.
>>
>>
> I've always used coax, but wanted to give open wire a try, and so far I'm 
> very pleased with it.  But let's talk tuners for a minute, assuming that 
> we're not directly coupling to a balanced plate tank.  I've been running 
> 1500 watts PEP into a Heathkit SA-2060 with it's 4:1 balun without 
> incident, but I've heard all the stories about  core saturation, etc. 
> How much advantage would a "real" balanced line tuner (e.g. a link-coupled 
> tuner or Johnson Matchbox) have?   Then antenna by the way is 130 ft, 
> center fed, and primarily used on 75 meters.


Bob, the KW Matchbox has a limited range on 80M and is reportedly quite 
inefficient.

You can upgrade your Heath (or is that Heat) tuner with a stack of T400A-2 
cores, some #12 or 10 teflon wire and HV tape.  Calculate the turns from the 
Amidon or Micrometals site specifically for 3.8 MHz, it will maintain 
excellent balance 160-20 as well as less loss.

>
> Also, having read comments by Cebik and others - any thoughts on 
> homebrewing high-power balanced tuners?


Other than trying to find the components that can handle the power go for 
it. The design should be High C to minimize loss. I believe there was a 
built to order commercial tuner available that was pricey but built to 
perform. Id probably go for one of those big edge wound fixed coils and a 
big switch, or a pair if you cant find a 2 section one. I wouldnt trust a 
rotary over such a wide range of unknowns.

Good luck

Carl
KM1H



>
> Thanks and 73,
>
> Bob W9RAN
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