10-27-2008, 03:45 PM
A more accurate test of the set's performance would be to measure the AGC voltage coming off of the detector of each set, receiving the same station with the same antenna. The AGC action of the set masks the true gain of it, but the output of the detector tells how much gain the set had before the detector. I'm sure that the 116 has lots more gain than the 650, but the AGC in it pulls back more on the reins, and that causes the 116 to appear to have the same gain.
Get a VTVM, and connect it to the detector outputs in as nearly the same on each set, then see what it says. There should be a difference.
This is why you need an indicator of receiver output when you align it. The audio output of a radio is no accurate indicator of resonance when you are peaking the alignment. True, it was the way you indicated before the late thirties, but VTVM's were almost unknown much before the forties. It's even possible with a 20,000 ohm per volt meter to measure the detector's output. On a 20 volt scale for instance, the resistive load of the meter would be 400,000 ohms, and the detector could survive with that easily. If you look at the circuits of the old Hammarlund communication sets, the "S" meter is actually a straight voltmeter across the detector output.
Get a VTVM, and connect it to the detector outputs in as nearly the same on each set, then see what it says. There should be a difference.
This is why you need an indicator of receiver output when you align it. The audio output of a radio is no accurate indicator of resonance when you are peaking the alignment. True, it was the way you indicated before the late thirties, but VTVM's were almost unknown much before the forties. It's even possible with a 20,000 ohm per volt meter to measure the detector's output. On a 20 volt scale for instance, the resistive load of the meter would be 400,000 ohms, and the detector could survive with that easily. If you look at the circuits of the old Hammarlund communication sets, the "S" meter is actually a straight voltmeter across the detector output.
