Envelope-to: dave@picks.force9.co.uk
Delivery-date: Fri, 03 Feb 2006 01:07:23 +0000
From: Warren K2ORS/WD2XGJ <k2ors@comcast.net>
To: rsgb_lf_group@blacksheep.org
Date: Fri, 03 Feb 2006 01:06:56 +0000
Message-Id: <020320060106.3108.43E2ACB00009174D00000C2422007358340B97010D0A020E06979D0E03@comcast.net>
Subject: Re: LF: Re: Keeping the smoke in
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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" <sthed475@telus.net>
> Contact G0MRF and get some of those big honk'n 58mm 3C90 toroid   ( Suitable
> for tx matching transformer or antenna matching to 800W)
> Ł7.80 -   Back in stock from 7/Jan/04
> 
> We use these and they rock.
> 
> 73 Scott
> 
> ----- Original Message -----
> From: "Warren K2ORS/WD2XGJ" <k2ors@comcast.net>
> To: "rsgb lf reflector" <rsgb_lf_group@blacksheep.org>
> Cc: "LWCA LF Reflector" <lowfer@lwca.org>
> 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
> >
> 
>