SB-100: S-meter Sensitivity

[Skipp Tullen]

Dear Group Members,

Like many of us, I began feeling nostalgic about the SB-100/SB-200  
station I owned in the mid-to-late 1960s, and subsequently gave to a  
ham radio friend in the mid-'70s. I now own another SB-100 and SB-200  
combination that I've repaired, aligned, and put on the air. (BTW,  
both relays have been replaced with modern units.)

Despite my having replaced the 6AU6 RF amplifier in the receiver  
section of the SB-100 with a 6HS6, the rig requires 80 microvolts of  
signal on the 40 meter band to produce an S-9 signal strength  
reading. In addition, the AGC threshold seems rather high, as  
evidenced by little or no signal strength reading on ordinary 40 M  
background noise that reads S-4 to S-6 on, for example, a TS-450S-A/T.

Are these low S-meter readings characteristic of the SB-100 design,  
or do I need to look further into the circuitry for some subtle  
problem? If you wish to reply directly, kindly use     
skipp at tullensound.com    for your response. I thank you, in advance,  
for your expertise.

With good wishes,
Skipp, K2PXQ



Skipp Tullen
Recording Engineer/Producer
Tullen Sound Recording
26 Altamont Court
Morristown, New Jersey 07960-5325
(voice: 973-539-8120)




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