Envelope-to: dave@picks.force9.co.uk
Delivery-date: Mon, 04 Jul 2005 15:28:37 +0100
From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>
To: "Steve McDonald" <jsm@gulfislands.com>
Cc: "LF \(Rsgb LF Group\)" <rsgb_lf_group@blacksheep.org>
Date: Mon, 4 Jul 2005 15:28:44 +0100
Message-ID: <NKEMLGOEKANPNJOBFBAFGEJBCFAA.g4wgt@tiscali.co.uk>
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Subject: LF: RE: G0MRF 300w Tx PA mods
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Hi Steve & LF,

On 28th January 2005 you included the following statement in your e-mail.

""I think Scott has found that anything over 43V at 15A is getting
very scary as the cores will saturate all of a sudden...""

It seems that t has just happened to my PA, although my readings were
showing 36 volts at 14 Amps (504 watts), I was testing again & tweaked the
volts up a bit from 34 volts at 12 Amps (408 watts), it only stayed on about
30 seconds & failed.

During testing after the mods were carried out I bench tested into 50 ohm
dummy load & achieved 645 watts so I felt that I could procede a little
higher into the antenna, the antenna readings looked fine using Jim's
(M0BMU) LF Tuning Meter. So I wonder, was it core saturation??

The core I am using is the original which came with the kit from David
(G0MRF).

Any thoughts or ideas ??

Regards,

Gary - G4WGT - IO83qp

Web : http://myweb.tiscali.co.uk/wgtaylor


-----Original Message-----
From: Steve McDonald [mailto:jsm@gulfislands.com]
Sent: 28 January 2005 22:50
To: g4wgt@tiscali.co.uk
Subject: Re: G0MRF 300w Tx PA mods


Gary - it sounds like you are getting similar results as we are with our
'west coast half-killowatt' amps. I am wondering what toroid you are using
in the output xfrmr? Both Scott (VE7TIL) and I are using salvaged TV cores
which seem to be OK up to a limit...they all appear to be slightly
different. I think Scott has found that anything over 43V at 15A is getting
very scary as the cores will saturate all of a sudden...be careful with
yours and get as much cooling on it as you can. I am thinking of rewinding
another output xfrmr with the same turns ratio but with two cores stacked
together. Good luck with yours.

Steve / VE7SL

Web: "THE VE7SL RADIO NOTEBOOK" at   http://www.imagenisp.ca/jsm
[L.F. Loops] [Tuna Tin DX] [H.F. Maritime DX] [Crystal Radio DXing]
[2200m Band] * NEW [CQ Crossband - 2200m To HF] [NDB DX] [Boatanchors]

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