On Thu, Jan 22, 2009 at 01:45:14PM -0500, Roscoe Primrose wrote:
I think the front end in my Argonaut 509 is dead. Noise on 80M last
night was S0 on the 509, the same antenna hooked up to my FT817ND was
S6-S8... The 509 still passes signal, but the levels are just way
down. When I got the 509, the T/R relay was stuck in receive, so the
front end being fried wouldn't be surprising.
The front end dual gate FET is an MPF132, is there a source for MPF132s,
or a substitute available anywhere? I can't find a cross-reference for
it anywhere...
A well published upgrade for the 509 (and 505, 515) was to replace the MPF132
with a 3N211 or the RCA equivalent. It's a drop in replacement, but you really
should realign the front end when you do it.
The 3N211 has much higher gain, lower noise and built in diodes for
static/overload protection.
Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
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