Re: [IRCA] Cable work

["Chuck Hutton" <charlesh3@xxxxxxx>]

I'm lazy. Rather than epoxying beads together, I just buy the binocular
cores like the BN73-202 or 2873202.

The former is only $.31 in singles from Newark. It makes the best
transformer I've measured for Beverage matching - low loss, wide bandwidth.


Chuck

-----Original Message-----
From: irca-bounces@xxxxxxxxxxxxxxxx [mailto:irca-bounces@xxxxxxxxxxxxxxxx]
On Behalf Of Gil Stacy
Sent: Sunday, August 26, 2007 11:35 AM
To: Mailing list for the International Radio Club of America
Subject: Re: [IRCA] Cable work

"What I didn't do is space the
toroid so it was centered in the box, nor were the windings exactly opposite
to each other on the toroid."

A retired electronics pro that I know tested xfrmers with  a spectrum
analyzer with built in tracking generator and discovered that he had  losses
above 1000 kc on his transformers with opposing windings on J or 75 mix.
His best results occurred with the secondary windings centered on top of the
primary, overlapping.
His test results were outstanding from LW up.

For a transformer, I have followed Gary Breed's (k9ay) method of using two
FB77-6301 Ferrite beads epoxied together to make a small bino core.  9 turns
of #24 mag wire and 3 turns for the RX side.  I saw his note on topband.
My buddy tested this core and found MW performance to be very good, but LW
had more losses than the 114J or 75 core.  While the small twin bead xfrmr
did not measure quite as good in the MW band as the toroid core, one would
not notice the difference at the headset.  These beads are quite small in
comparison with the 114 cores and cost $5/dozen.  The FT 114J's are $3.75
per. http://www.amidoncorp.com/pricing/  If you are looking for a more
compact transformer for strictly MW, the beads are the way to go.
73 Gil NN4CW

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