Topband: best core material?

[Charlie Cunningham]

When I did mine, I had used up all my binocular cores that were large
enough, so I taped two tubular cores together side-by-side to make a
binocular core. A little more room to wind, and maybe a little less
inter-winding capacitance?

73,
Charlie, K4OTV



-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James
Rodenkirch
Sent: Monday, August 05, 2013 2:20 PM
To: Shoppa, Tim; BY THE LAKE; topband at contesting.com
Subject: Re: Topband: best core material?

 
 I wasn't going to use a binocular core, Tim - I was going to use the Amidon
FT-140-43 OR the FT-140-77 IF it made any noticeable difference....is there
some magical reason to use binocular vice standard "round"?
 
 
> From: tshoppa at wmata.com
> To: rodenkirch_llc at msn.com; magoo at isp.ca; topband at contesting.com
> Subject: RE: Topband: best core material?
> Date: Mon, 5 Aug 2013 18:12:48 +0000
> 
> If receive only, you will do just fine using the 2873000202 binocular 73
material core that Tom mentions.
> 
> I think this corresponds to Amidon part number BN-202-73. Newark stocks
the part under the original Fair-Rite 2873000202 number.
> 
> Tom shows 2:5 ratio but I've done other ratios just fine.
> 
> I am very very impressed with the 2873000202 core, in fact I also use it
in some DC-DC converters and the core just barely gets warm at the 10 watt
level. Whenever I've accidentally transmitted into my receive antenna, the
transformer survives just fine, it's the terminating resistor that goes up
in smoke. I try not to make a habit of it :-)
> 
> Tim N3QE
> 
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James
Rodenkirch
> Sent: Monday, August 05, 2013 2:04 PM
> To: BY THE LAKE; topband at contesting.com
> Subject: Re: Topband: best core material?
> 
>  Sorry - didn't make it crystal clear that this is a Delta shaped variant
of a EWE antenna!!!!
>  
> My bad for not utilizing all of the necessary verbiage to make that
clear....you see it in ON4UN's latest book on page 7-104.
>  
> 
> 
> 
> > From: magoo at isp.ca
> > To: rodenkirch_llc at msn.com
> > Subject: Re: Topband: best core material?
> > Date: Mon, 5 Aug 2013 14:00:48 -0400
> > 
> > A full-wave delta loop would have the transformation done with a 1/4 
> > wave line of 75 ohm cable. This must be something other than a full-wave
loop?
> > 
> > Bill VE3NH
> > ----- Original Message -----
> > From: "James Rodenkirch" <rodenkirch_llc at msn.com>
> > To: <topband at contesting.com>
> > Sent: Monday, August 05, 2013 1:33 PM
> > Subject: Topband: best core material?
> > 
> > 
> > >
> > > I have a schematic for a delta shaped loop that shows I'll need an 
> > > 18:1 transformer to transform the 950 ohms of the antenna to 50 ohms 
> > > (feeding it with 50 ohm coax).
> > >
> > > One transformer diagram shows an FT-140-43 core being used.
> > >
> > > BUT, looking over some of Tom's, W8JI, write-ups, I see where he 
> > > uses 73 material instead.
> > >
> > > I see where 77 material replaced 73 material so -- is an FT-140-77 
> > > the mo betta way to go?
> > >
> > >
> > > Thanks, in advance, for any advice/info.  Jim Rodenkirch K9JWV
> > >
> > >
> > >
> > > _________________
> > > Topband Reflector
> > >
> > >
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