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LF: Re: RE: Re: Re : tests.

To: [email protected]
Subject: LF: Re: RE: Re: Re : tests.
From: "hamilton mal" <[email protected]>
Date: Thu, 5 May 2005 13:45:29 +0100
Delivery-date: Thu, 05 May 2005 17:14:56 +0100
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----- Original Message -----
From: "Gary - G4WGT" <[email protected]>
To: <[email protected]>
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




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