Envelope-to: dave@picks.force9.co.uk
Delivery-date: Thu, 05 May 2005 17:14:56 +0100
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From: "hamilton mal" <g3kev.ham@virgin.net>
To: rsgb_lf_group@blacksheep.org
References: <NKEMLGOEKANPNJOBFBAFMEENCDAA.g4wgt@tiscali.co.uk>
Date: Thu, 5 May 2005 13:45:29 +0100
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Subject: LF: Re: RE: Re: Re : tests.
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----- Original Message -----
From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, March 28, 2005 8:48 PM
Subject: LF: RE: Re: Re : tests.


> Hi Mal & LF,
>
> I am using the G0MRF 300 watt Tx but since blowing several PA mosfets I
> decided to carry out the M0BMU PA mods using the original toroid & I can
now
> run a cool PA up to 650 watts into dummy load bench testing. I put it on
air
> into antenna & started with 280 watts & on following tests gradually
> increased to 420 watts (still cool) with antenna current up to 2.3 Amps it
> was at this time I got corona/arcing on the spiral top load so I stopped
> tests until I have the time to lower the mast & carry out a visual
> inspection of the area of arcing so as to effect a cure. I suspect that I
> may have too little clearance between the spiral & the metal fixing
> hardware, an inspection will be carried when work & family permit.
>
> Regards,
>
> Gary - G4WGT - IO83qp
>
Hi Gary.
I have found soak testing into a dummy load different to loading into the
resonant antenna. The antenna is more critical and tricky and seems more of
a problem using high voltage low current than low voltage high current.
I built my tx a few years ago when 136 khz became available,  it was the low
V type and it worked well over the years but recently tried different hi
spec FETS 23A/600V. I ran it up to 50v at 20a but it does not appear to be
as stable as the low voltage tx.  I think others might have experienced this
also.
How does the phase meter work that you built. I have a couple of nice meters
here that would be suitable and hope to build one. One thing I do need are
some diodes. If you have any spare from your project and want to sell a few
let me know. I have everything else.
73 de Mal/G3KEV
>
>
>
>