[Collins] 51J4 Alignment Question

[Carl]

Most likely to compensate for tube degradation and minimize time in a 
service shop.

Many other receivers had one of the IF cathode resistors selected in 
production.

Carl
KM1H


----- Original Message ----- 
From: "Grant Youngman" <nq5t at tx.rr.com>
To: "Collins at listserve.com" <collins at listserve.com>; 
<collins at mailman.qth.net>
Sent: Wednesday, August 21, 2013 1:04 PM
Subject: Re: [Collins] 51J4 Alignment Question


Just to follow up on my question.  My receiver is an early one, and does not 
have the IF gain control.

Finished the alignment of the receiver, and measured the gain from antenna 
terminal to IF output.  3 uV RMS in at the antenna terminals yields 250 mV 
RMS at the IF output port.  The alignment spec for receivers with the IF 
gain control is 270mV out.  I figure that's close enough not to worry about. 
I think someone also indicated that the IF output signal was loaded down by 
the detector and was badly distorted and not very sinusoidal (?).  I did not 
find that to be the case.

Which still begs the question … why did Collins feel the need to add the IF 
gain control in the first place?  I can only suppose it had to do with the 
fact that some contracting officer put it in a specification somewhere along 
the line.

Grant NQ5T

>
>> I've been reading over the alignment instructions for the 51J4 getting 
>> ready to touch mine up.  In manual section 5.3.17 (1962 manual), it gives 
>> instructions for setting IF gain.  My question is whether the input 
>> (antenna terminal) and output (IF output) voltages indicated are peak or 
>> RMS.  I presume it doesn't actually matter as long as both measurements 
>> are taken the same way, but thought I would ask.  I think I've also seen 
>> a comment in a posting somewhere that it isn't worth worrying about and 
>> that the IF gain should just be set to maximum.  Any input on this?
>>

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