Envelope-to: dave@picks.force9.co.uk
Delivery-date: Fri, 03 Feb 2006 01:23:39 +0000
From: Warren K2ORS/WD2XGJ <k2ors@comcast.net>
To: rsgb_lf_group@blacksheep.org,  rsgb_lf_group@blacksheep.org
Cc: "Alan Melia" <alan.melia@btinternet.com>
Date: Fri, 03 Feb 2006 01:22:30 +0000
Message-Id: <020320060122.8083.43E2B0560003663A00001F9322092299270B97010D0A020E06979D0E03@comcast.net>
Subject: Re: LF: Re: Keeping the smoke in
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Hi Alan,

    I will look at it tomorow as it was too hot to handle today! I don't know if 
the core is intact or has fractured as it is covered with fiberglass tape. The 
fiberglass tape has turned yellow from the heat!

--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm

 -------------- Original message ----------------------
From: "Alan Melia" <alan.melia@btinternet.com>
> Hi Warren, an excursion to high temperature should not affect the ferrite as
> this is sintered at quite high temperatures to make the ring. What might
> suffer is the epoxy (usually) coating which may burn up and created a lossy
> shorted turn (guess, I have no experience of this) A quick solution might be
> to bung it in a beaker of cooking oil !! That will act as insulation as well
> !!
> Just think you could be the first station with an oil cooled antenna
> transformer !!
> 
> Cheers de Alan G3NYK
> 
> 
> ----- Original Message -----
> From: Warren K2ORS/WD2XGJ <k2ors@comcast.net>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: 02 February 2006 23:10
> Subject: Re: LF: Re: Keeping the smoke in
> 
> 
> > Hi Mike,
> >
> >    I don't think that the cores were damaged from the last incident. I was
> able to run the 250 watt transmitter through it with no problem and no
> measureable reflected power. I understand that Laurence also used 3 stacked
> FT-290-77s but actively cooled it. A cooling fan is not easy to do in my
> case since the tuner is in a weathertight box.
> >
> > --
> > 73 Warren K2ORS/WD2XGJ
> > FN42hi
> > http://www.w4dex.com/wd2xgj.htm
> >
> >  -------------- Original message ----------------------
> > From: "MIKE REID" <we0h1@msn.com>
> > > What cores did Laurence use and what wire size & type? Sorry to hear she
> failed
> > > again. Maybe the cores got damaged the other day with no external
> indications
> > > like cracking or? I don't recall you having trouble with the transformer
> when it
> > > was dry and Teflon is way better than cotton so that leads me to think
> the cores
> > > were no good after the first heat cycle/failure.
> > >
> > > Mike
> > > WE0H
> > >
> > >   ----- Original Message -----
> > >   From: Warren K2ORS/WD2XGJ
> > >   To: rsgb lf reflector<mailto:rsgb_lf_group@blacksheep.org>
> > >   Cc: LWCA LF Reflector<mailto:lowfer@lwca.org>
> > >   Sent: Thursday, February 02, 2006 4:41 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<http://www.w4dex.com/wd2xgj.htm>
> > >
> > >
> >
> >
> >
> >
> 
>