Topband: (no subject)

[RPARKES197@aol.com]

Tom W8JI wrote
>>There is one rule that always works.
Set your gain with use of preamplifiers or attenuators so you can just 
comfortably hear a noise increase when the antenna is connected, and a 
definite decrease with it removed.  If your receiver can not take you 
comfortably into the noise without overloading on the strongest 160 signals, 
then you need to buy another receiver or have your receiver repaired...or 
give up working some weak signals.<<

This is similar to what I used to do on SHF systems and we called it Noise 
Overide.
We used 'a rule of thumb concept' to monitor the Rx noise from the detector 
output on a scope and then add the preamp with the gains set so the noise 
level doubled and no more.   This way you can be sure you get the maximum 
sensitivity (ie the noise figure of the preamp) and you did not decrease the 
dynamic range of the system anymore than necessary.  For LF situations a 
Preamp reads as antenna since in SHF systems the antenna noise is swamped by 
the preamp NF. 
The noise can be seen on a scope or heard on phones but it will show an 
increase when the antenna is connected.  
If it does not show an increase then something is not working and you are not 
seeing the antenna noise (or environment noise) overiding the receiver noise.

best 73s

Bob Parkes
G3REP