[BC] Harmonics...

[Thomas G. Osenkowsky]

> I recently had a problem where the third harmonic was about 13 dB too
> high.  This was definitely coming out of the antenna yet the
> transmitter into a dummy showed the harmonics almost
> non-existent.  The problem turned out to be a corroded connection in
> an ATU of a D.A.

I had a client with a 2 twr DA on 990 Khz. 500W daytimer, Audimax->
Fairchild passive EQ module->Volumax. Pre-NRSC days. The CE of
a station about 15 miles away on 960 Khz called me to say they sold
spots to a car dealership about 10 miles North of them and they couldn't
listen to 960 because of our splatter. I thought this was unusual because
we didn't process heavily, the Vanguard II had a modified transformerless
audio input and was stable.

I visited my client and heard what sounded like arcing type of splatter, not
monkey chatter. It turned out to be a poor roller contact on one of the
common point matching coils. Cleaned it up, splatter gone.

I had another case of a 2.5kw ND daytimer with a B.E. AM2.5 tx. I would
always have to retune it for minimum VSWR. One day it wouldn't stay on the
air past 800W. When I entered the tx shack I smelled something bad. Turned
out
to be arcing due to a loose bolt/nut in the ATU. Metal got hot and
intermittent.
New hardware, now very stable.

Tom Osenkowsky, CPBE