[TenTec] Argonaut 509 Bias Mod

[Stuart Rohre]

Byron,
I "think" the pop on strong stations on the 509 is audio derived AGC.  
As I recall, and I am going from uncertain memory, rigs with audio 
derived AGC have to use a large capacitor which charges up.  The pop is 
an artifact of that design.  It "may" improve if the capacitors are 
updated to fresh ones.  Look for an electrolytic typically.  This is a 
problem not only on the 509 but also on many simple kit QRP rigs today 
with that type of AGC.  A work around might be to add an RF attenuator 
to cut down the signal level of extremely strong stations.

Stuart
K5KVH