[R-390] Error in article in HSN 45 (Summer-Fall 1998)

[Larry H]

While researching a different project, I came across an article in the HSN
# 45 (Summer-Fall 1998) that is an error.  I  know it's been a very long
time since it was published, but since they are now online for everyone to
easily see, I thought it was necessary to alert you. I looked through the
HSNs after it and the forum archives and did not find any correction, so
I'm letting you know now.  The article is titled:

'SUPPLEMENTARY GROUNDING OF THE R-390A ANTENNA TRIMMER'.

and starts on the bottom of page 3.  It says you should ground the gear on
the top of the antenna trimmer cap that mates to the gear on the antenna
trimmer shaft.  That is absolutely wrong.

The antenna trimmer gear is at AGC voltage level.  Same for the mating gear
on the AGC trimmer adjust shaft.  But, the shaft itself is at ground
potential.  Nice design, huh.  Well in order for this to work, the gear on
the AGC trimmer adjust shaft is electrically insulated from the AGC trimmer
adjust shaft, which is grounded.

Grounding the gears at this point totally disables the AGC on the RF amp
and adds a 270 K ohm load to the AGC line.  This seriously disables the AGC
function.

Regards, Larry