I've had good success winding matching transformers for terminated RX loops,
on these cores with wire-wrap wire.
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Thursday, November 27, 2014 4:11 PM
To: topband@contesting.com
Subject: Re: Topband: [time-nuts] Minicircuits 10% discount in December
On Thu,11/27/2014 11:14 AM, Tim Shoppa wrote:
> The 2873000202 73 material binocular core, I buy those by the hundreds
> from Newark and hand them out like a human Pez dispenser at local
> radio club meetings. They are amazing things. Not only do I use them
> for 160M and other RF applications, but I have using them in small
> step-up applications too up to the 10W level!!!
The single turn resonance of this core is around 10 MHz, with a Z at
resonance of about 120 ohms. Like any other ferrite core, winding turns will
increase L as N squared, increase C as N, thus moving the resonance down in
frequency. I'd guess that 8 turns would move the resonance fairly close to
160M with Z in the range of 4-5K ohms. The catch is that the i.d. is pretty
small, so the choke would need to be wound with something like one pair out
of CAT5 cable.
Fair-Rite considers this a suppression part, not an inductive part, although
it is widely used for winding transformers for MF RX antennas.
The laws of physics don't change with what we call something, so this will
be a fairly lossy transformer. For RX transformers, it may not matter (and
the low Q may even help), but don't be surprised when you see the added
resistance beyond what the turns ratio predicts. :)
73, Jim K9YC
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|