[R-390] Noise when warm ('390A)

[Roy Morgan]

At 11:50 PM 9/11/2005, Dennis Wade wrote:

>It goes away when the antenna is unplugged  (sigh).
>Is there any failure mode anyone can think of that would only be
>apparent when the antenna is connected?


YES. Static electricity building up on the antenna can make such noises.

Put an RF choke or moderate value resistor (100 K or so) from the antenna 
to ground to see if it goes away.

The R-390 antenna input transformer primary is isolated from ground for DC, 
so if you do not have one side grounded (which most of us do) then static 
electricity on the antenna can build up. (The neon lamp in the antenna 
relay is across the UNbalanced antenna input jack.)

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --