[ARC5] S+N/N ratio results.

[Glen Zook]

Unfortunately, when the load on the input is significantly lower than the actual design impedance, the apparent sensitivity of the unit will almost always require a higher level of signal.  That is, a stronger signal is required with the lower impedance than would be required if the input impedance is properly matched.

This fact is quite evident in receivers like the Collins 75A-1 when a coaxial cable fed antenna is attached.  Adding a balun with a 6:1 (even a 4:1 TV balun works very well) or some sort of "antenna tuner" between the coaxial cable and the receiver antenna input improves the apparent sensitivity of the receiver greatly.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Kenneth G. Gordon <kgordon2006 at frontier.com>


Hmmmm....now you guys have me wondering: I have been using some sort 
of pad (one of those that was with my URM-25) between my HP-8640B and 
the receivers I have been "messing with" since this exercise began.

It is one of those 50 ohm jobs that is in the small box with BNCs on both 
ends.

I did this since the only thing I know about the input impedances of the 
receivers is that it is "high", and I figured that such a box would give me a 
more accurate figure of what the SG is actually putting out.

I guess I had better go look more closely at it.

Sigh....this probably changes everything I have tried to do up to this point 
and I'll have to do it all over again.

Ken W7EKB
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