[ARC5] ARA 46104 receiver sensitivity

[Kenneth G. Gordon]

OK. I did the following:

First of all, I have no electronic means (so far) of measuring actual average signal level. All I 
can do is to look at the scope, with the sweep rate set to as slow as possible, ignore the 
obviously random spikes, and guesstimate the remainder. Even so, I think I am pretty close. 

So, I connected my scope to the audio output jack in parallel with the 500 ohm speaker.

Audio and RF gains at maximum, BFO off.

Average no-signal noise level as measured on the scope approximately 110 mV.

Turned on the signal generator, set it for 1 KHz first at 30% modulation and a signal level of 
0.3 microvolts tuned to 2.0 MHz. 

(I used 1 KHz at first instead of 400 Hz since it is seemed to be easier for me to make it out 
on the scope. I then reset it to 400 Hz. since the 1 KHz setting didn't seem to make any 
difference.)

Measured average signal-plus-noise level, approximately 350 mV.

V2/V1 ratio approximately 3.2

S+N/N ratio approximately 10.103 db

Reset signal generator output to 1 microvolt

Measured average signal-plus-noise level approximately 15 V.

V2/V1 ratio approximately 13.6 (1500 mV divided by 110 mV)

S+N/N ratio, approximately 22.670778 db

Do these figures seem reasonable? These are actually what I am getting. I went over the 
procedure several times to be certain.

The only thing I am uncertain about is the "average" levels. But, it seems to me that if my 
guesstimation is off, it should be off for both with and without input, so it should balance out.

Ken W7EKB