[TenTec] Argosy I "Thump"

[Jerry Volpe]

Yes, the audio 'thump' is caused by the audio AGC being derived from the 
audio waveform rather than the IF itself. However there are numerous 
benefits to this scheme including the fact that the audio filters (the 
primary source of CW bandwidth limiting) and the notch filters remain 
inside the AGC loop itself which (if you read the Orion threads) is a 
very good thing.

Many have played with the AGC time constants but my general opinion (as 
an RF engineer) is that no matter what constants you choose you will 
always be working with a compromise, depending on changing operating 
conditions. Probably the best 'fix' is to add the RF Gain mod. Ten-Tec 
has a Technical Note on this mod although they no longer provide the 
parts. Basically you replace the AF Gain control with a concentric 
control (requires concentric knobs like found on the Scout, 526, 
Paragon, Omni V, etc.) and insert the new variable resistance with a few 
other parts into the AGC system allowing you to decrease the GAIN of the 
Argosy for very strong signal reception. The 'thumpin' you are referring 
to is only noticeable with very strong signals so reducing the gain 
reduces and/or eliminates the thumping.

There was an Argosy with this RF mod on a commercial auction site this 
past week. I think it is gone now but you can look at past items and see 
what I am referring too.

73,
Jerry, KG6TT
Fairfield, CA