Hi Scott,
The 58 mm 3C90 has smilar permeability to the type 77 I am using but 58 mm is
considerably smaller than the 3" cores I am now using.
--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm
-------------- Original message ----------------------
From: "Scott Tilley" <[email protected]>
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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