Have had a look at the board - looks okay, but general observations and
recommendations from building several on 50/70/144MHz:
* I can't see where the fixing holes are on the PCB?
* you need a precision machined copper spreader about 3/8" thick and 6"
x 4" in size between it and the main heatsink - PE1RKI makes these
* the gates of the FET are delicate, the source/drain is robust
* check the bias circuit and ensure that it is clamped at 3V3 or similar
to ensure that under no circumstances can you get high DC bias which
will kill the FET (you want about 2.7V on the gates)
* it will only want a watt or two of drive - use a *big* attenuator on
the input
* ensure your radio is not attenuating its output power using ALC that
can 'spike' and over drive the FET
* use a VSWR sensor on the output to trip your controller and remove the
+12V TX to the board
* use a controller/sequencer to ensure your change-over relay is over
before applying drive - see W6PQL and others
* first time up use a small power supply (eg. 50V @ 10A current limited)
to set the bias and perform initial check out
Mike G8TIC
On 18/09/2013 19:30, Jim Valdes wrote:
> I'm interested in a 1KW solid stare amp. I see an EBAY listing
> from4Z4RB for a Single device 1KW LDMOS-FET Linear Amplifier Board,
> EBAY 150951055048 . It is populated w/o the FET. Does anyone have any
> experience with the board or the FET?
> Thanks,
> Jim (WA1GPO)
>
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