[Collins] R388 51j-3

[DAN COTSIRILOS]

What about the sensitivity issue that Dennis was saying. Dan





----- Original Message ----- 
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
To: "DAN COTSIRILOS" <dcsfree@worldnet.att.net>
Cc: <collins@mailman.qth.net>
Sent: Tuesday, January 27, 2004 3:53 PM
Subject: Re: [Collins] R388 51j-3


> Its not the crystal filter, its the IF transformers that can be stagger
> tuned. The crystal filter only allows for a notch or narrow passband for
> CW. The phase response of the IF transformers can be significantly
> better than the Collins mechanical filters of that era.
> 
> Other than the first IF stage on the filter module instead of the
> chassis, the J-3 and J-4 are identical everywhere else and with the same
> quality in all the front end tubes should have the same practical HF
> sensitivity. The sensitivity should be set by the mixers before the IF
> (and those are fairly noisy mixer tubes).
> 
> But the mechanical filters in the R-390A were cheaper than the IF
> transformers and keeping them properly aligned in the R-390.
> 
> I've felt the 390 would be a nicer sounding receiver than the 390A also. 
> 
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> -- 
> Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
> Reproduction by permission only.
>