Contact G0MRF and get some of those big honk'n 58mm 3C90 toroid ( Suitable
for tx matching transformer or antenna matching to 800W)
£7.80 - Back in stock from 7/Jan/04
We use these and they rock.
73 Scott
----- Original Message -----
From: "Warren K2ORS/WD2XGJ" <[email protected]>
To: "rsgb lf reflector" <[email protected]>
Cc: "LWCA LF Reflector" <[email protected]>
Sent: Thursday, February 02, 2006 2:41 PM
Subject: LF: Keeping the smoke in
Hello the list,
I've heard that the secret to keeping things going in electronics is
to make sure you don't let the smoke out (that's what makes it all work
apparently).
I have again failed to do so. After rewinding my toroidal loop
transformer in the ATU, I had a core overheating problem. The core is 3
stacked FT-290-77 ferrites.
After setting the Decca up on QRSS for an hour or so I noticed a problem
with the rf output current, it was pulsing up and down as if the Decca guard
circuit was cutting in to protect the PA. So I through the breaker and went
out and opened the tuner box. Smoke poured out. Bad news. I checked the
temperatures with a non-contact infra-red thermometer and the toroid core
was 343 Farenheit. The Curie temperature for type 77 ferrite is 200 C (which
is 392 Farenheit). Not sure yet if the core is permanently damaged, I'm
still waiting for it to cool down.
All credit to Laurence who managed to get a loop to work at this
power level! And especially with the currents he dealt with in the parallel
wire loop configuration.
I guess I need a bigger core than the 3 stacked FT-290-77s any
suggestions out there?
--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm
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