[Boatanchors] Calibrating S-Meters & Marconi Attenuator

[Al Klase]

W8KZW wrote:
> I have read that "the proper way to set up the S-meter would be to use a
> signal generator set to 500uV and a 20 dB inline 50 Ohm attenuator".
>   
I can't see where that any different form setting a "proper" signal 
generator to 50uV.  Perhaps there was som other instrument involved that 
was happier reading 500uV or the impedance of the generator was not near 
50 ohms.
> My question is, is the 500uV peak-to-peak, peak, or RMS?
>   
That would be RMS.
> Also, I have picked up a wonderful Marconi attenuator, with both input and
> output labeled "75 Ohm".  At frequencies ranging from audio through 30 Mhz,
> can I use it with a signal generator and HF receiver, both of which are 50
> ohm devices, without too much of an impedance mismatch bump that would
> render readings worthless?
>
> Finally, should I consider an impedance matching network for the front of
> the attenuator and another  for behind it?  Any ideas on what that circuit
> would look like?
>
>   
S-meters are NOT precision instruments.  The difference between 50 and 
75 ohms, for instance, is going to be completely lost in the sauce.  
Just come close to 50uV.  Some receivers claim 100uV for  S9.

Regards,
Al

-- 
Al Klase - N3FRQ
Flemington, NJ
http://www.skywaves.ar88.net/