[TenTec] Re: TenTec Digest, Jupiter SENSITIVITY

[Allan Henry Kaplan]

Bruce and others,
Below perhaps 12 meters, atmospheric noise absolutely overwhelms the 
sensitivity of modern receivers.  By that, I mean that scientific 
studies by CCIR have shown conlusively that atmospheric noise below 25 
MHz is MUCH STRONGER than a sub-microvolt signal.  Especially for 80 
meters, it is easy to determine if a receiver has adequate sensitivity.

Temporarily disconnect the antenna and set RF Gain on MAX.  Turn up 
audio to a convenient level of noise output. Now restore the antenna 
connection.  On a receiver with sufficient sensitivity for HF, the audio 
output noise level will increase (quite a lot on 80 meters!).  You have 
just demonstrated that the receiver hears the external noise well above 
its internal noise.  It will be IMPOSSIBLE to hear any signal lower than 
the external noise.    Jupiter will easily pass this test, as should the 
  746 PRO.   Make your choice based on some factor other than sensitivity!

This is not some theory-in-the-clouds notion, but a time-honored 
practical test with solid theoretical underpinning.
Hope this helps,
73 de W1AEL (retired from Ten-Tec engineering)


  Bruce, N8CZZ wrote,
>  My concern is that the specs for the Jupiter 
> on  receive sensitivity is not as good as the 746 PRO. This concerns me 
> because I like to work 80 meters DX and signals are not that strong. "
> 
Member, TT Worshipers Cult