[ARC5] BC-459 Frequency Jump

[Mark K3MSB]

Last year I was having trouble with my BC459A on 40M in that it would jump
frequency quite a bit during a QSO.

I (re)cleaned the unit and resoldered every solder joint I could get to.
This greatly helped the problem.

Now, every now and then,  the unit will start to jump in frequency, but a
quick "thump" to the front panel clears up the issue nicely.  I can use the
radio for hours afterwards with no problem.

Yesterday my friend N3CU called me early in the morning for an SKN QSO.
He recorded part of my transmission:

www.k3msb.com/temp/K3MSB_40M_ARC5_1.mp3

Afterwards, we were chatting on the phone and he said the drift issue was
greatly cleared up from the last time he heard my BC459.   I asked him to
clarify, and he said there was some frequency change when I initially
started.

What I did was slightly readjust my TX frequency before I started sending
(which is not on the above audio).  We did some subsequent experiments and
apparently there is a slight frequency shift when I initially start
transmitting, but not during an exchange.

I asked him to record my transmission when I deliberately went key down for
10 seconds, then sent a normal exchange,  then again went key down for
about 10 seconds.   Here is what is sounded like:

www.k3msb.com/temp/K3MSB_40M_ARC5_2.mp3

I'm not sure why there is a frequency change when I go key down for a long
time.  I can't hear it during a normal exchange.  My Plate, Screen, and
Oscillator voltages show no drop.  I'm using a HB power supply with the
typical voltage divider as per the manual (the 28V supply is seperate).

This does not happen on 80M using my BC-696A fed with the same power supply.

Comments welcome!

73 Mark K3MSB
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