I looked at that kit-assembly a week back I asked 4Z4RB the same question,
about the apparent missing mounting holes, and if he would supply the heat
spreader.
His response was "I can supply a pre drilled copper slab heat spreader for
an additional 73 usd all drilled and ready for the amp board with all
mounting screws - 4z4rb". No other specifics.
I use W6PQL's kits for the VHF-UHF bands and his ultimate sequencer, and 48V
DC SS switches on mine.
For the HF version, it is almost cheaper to buy the assembeled pallet from
someone like Communications Amps LLC.
Bobby and the guys make a nice product, and are now showing full legal limit
designs (parallel pallets or quadrature designs I'm not sure) for HF and 2M
too.
I understand they will be at K5AND BBQ BAsh in a couple weeks showing their
wares.
http://www.commamps.com/
The neutron flash has already gone off.
73 Mike K9MK
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Mike Tubby
Sent: Wednesday, September 18, 2013 4:58 PM
To: Jim Valdes
Cc: amps@contesting.com
Subject: Re: [Amps] MRFE6VP61K25HR6
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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