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Re; L-band Gear



How are the PA module and PCB grounded? The best way is to mount both on a
flat piece of aluminum or the back of a heat sink with some thin aluminum or
brass sheet under the PCB to increase the height to match the pins on the
PA.

73,

John, KD6OZH

>Date: Fri, 22 Oct 1999 18:36:38 -0400
>From: Jim Sanford <wb4gcs@home.com>
>Subject: [amsat-bb] L-band Gear
>
>Hi:
>I've been working on a Down East Microwave 1296 transverter setup for
>several years.  One vexing problem:  the 2303 PA  (1/5 - 3 watt
>amplifier) oscillates at nearly full output, with no input.  Providing
>input reduces the spur amplitude, and provides a little output on the
>channel frequency.  This is NOT local oscillator feedthrough, it happens
>when there's nothing connected to the input except a 50 ohm load or the
>input is open circuited, or the input is connected to the transverter.
>
>I've replaced the module -- same symptoms.
>
>I've replaced and added additional chip bypass caps on the various DC
>lines.  Same symptoms
>
>The power supply is filtered with a choke at the board.  Same symptoms.
>
>I've placed the assembly in the open, in a shielded box, and in a
>smaller shielded box.  Same symptoms.
>
>So, has anybody else had this or similar problems? If so, how solved?
>Any ideas???
>
>Thanks & 73,
>
>Jim
>wb4gcs@amsat.org


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