Topband: best core material?

Mon Aug 5 15:31:49 EDT 2013

Hi, Jim

Well, seems that I may  have borrowed the 40X10 dimensions from somewhere.
Interesting thing, is, if you are into modeling things with EZNEC, as I am,
you can play with the dimensions quite a bit. The gain goes down as the loop
area is reduced, placing more demand on the preamp. My 40X10 loop did really
well with an old AMECO tunable tube preamp. No, my loop was not as tall as
John’s but worked really well. I had Dacron ropes on the ends, so I could
re-orient it like leading a cow !  Would like to have built one rotatable,
but don’t think I’m going to have that opportunity.

Sure you  can use a larger core, especially if you use 73  material. The two
tubular cores that I used were almost ¼ in ID X 0.45 OD. I just taped them
together to make a binocular core. They were what I had available -73 mat’l.

I understand about neuropathy!  I have it pretty bad in my right hand and
some in my right leg. We recently found some lesions on my cervical spinal
cord.

Really scary bad news!! 

Enjoy the loop!

73,

Charlie, K4OTV

From: James Rodenkirch [mailto:rodenkirch_llc at msn.com] 
Sent: Monday, August 05, 2013 2:53 PM
To: Charlie Cunningham
Subject: RE: Topband: best core material?
Importance: High

I was going with the "standard" dimensions mentioned in the ON4UN book,
Charlie - 18' high, 28' wide at the base....BUT I really wanted to reduce
the height so your dimensions work far more better for me.

OK - I'm convinced on using binocular but that BN-73-202 core sure looks
small!

Is there a slightly larger one I could use (I have a sever case of
neuropathy so handling small thing is next to impossible! The XYL won't even
let me wash dishes 'cuz she's afraid I'll mishandle that stuff!)

If I'm winding a 4:1 turns ratio for a toroid I assume I do the same for a
binocular, just use less turns....i.e., instead of 28 to 8 for a toroid, 8
to 2 for a binocular???

> From: charlie-cunningham at nc.rr.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 14:45:12 -0400
> 
> BTW, Jim
> 
> I think you will be pleased with that loop! Mine was 40' long X 10' high
> and it was an excellent receive antenna for 160, 80, 40 and 30 m. If you
> model it in EZNEC, you will find that the impedances and cardioid patterns
> stay fairly constant as you go higher in frequency, but the gain goes up
> with increasing frequency. It helped me to hear and work Kazakhstan on
> 80m, when I couldn't copy on the 80m GP. It opened lots of additional
paths
> on 160 as well.
> 
> 73,
> Charlie, K4OTV
> 
> 
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James
> Rodenkirch
> Sent: Monday, August 05, 2013 2:29 PM
> To: Charlie Cunningham; 'BY THE LAKE'; topband at contesting.com
> Subject: Re: Topband: best core material?
> 
> Yes to both, Charlie - a friend of mine has a calculator to figure the
exact
> turns ratio BUT, at a web site I found for this antenna (used during an
FO0
> dxpedition) the ratio was defined as 8 turns in the primary, 28 turns in
> the secondary (for 75 ohm cable so for 50 ohms it'll be something else but
> still fairly close to your mentioned 4:1 ratio)
> 
> > From: charlie-cunningham at nc.rr.com
> > To: rodenkirch_llc at msn.com; magoo at isp.ca; topband at contesting.com
> > Date: Mon, 5 Aug 2013 14:24:05 -0400
> > Subject: Re: Topband: best core material?
> > 
> > BTW, Jim
> > 
> > I assume that 18:1 is the impedance ratio, and the turns ratio is of the
> > order of 4:1 or so
> > 
> > Charlie, K4OTV
> > 
> > -----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
> > > >
> > > >
> > > > -----
> > > > No virus found in this message.
> > > > Checked by AVG - www.avg.com
> > > > Version: 2013.0.3392 / Virus Database: 3209/6552 - Release Date:
> > 08/05/13
> > > > 
> > > 
> > > 
> > > 
> > > -----
> > > No virus found in this message.
> > > Checked by AVG - www.avg.com
> > > Version: 2013.0.3392 / Virus Database: 3209/6552 - Release Date:
> 08/05/13
> > > 
> > 
> > _________________
> > Topband Reflector
> > 
> > _________________
> > Topband Reflector
> 
> _________________
> Topband Reflector
> 