Re: {Collins} Collins 51J4 and 651S-1 AGC points

On Jul 24, 2010, at 9:11 PM, Richard Knoppow wrote:
I measured the input impedance of my R-388 at 4mhz using a General Radio 1650-A bridge....about 48 ohms

Ah,  a NOBLE instrument.

... the signal generator is calibrated for a 50 ohm load. If the impedance its working into is not known the voltage is also not known so the measurement was necessary to get anything meaningful.

I have read that the Collins factory procedure for the S-line receivers at least, was to run the generator into the receiver with no further matching. The assumption was that the receiver had an input impedance close enough to 50 ohms to get meaningful results for sensitivity.

I have noted with amusement on the R-390 list (in the past) folks cite sensitivities like 0.321 microvolts.



Roy Morgan
K1LKY Since 1958 - Keep 'em Glowing!

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