[Collins] R-388 Y112

[Al Parker]

Hi folks,
    Stan & I are aware of the function.   I don't want to do the 51-J4
filter mod., just make the phasing unit work OK.  Problem is that I have a
bad xtal in mine & haven't found anyone to make one (tho' must admit
haven't tried all possibilities).  I put out a want on the list a few mo.s
ago with no results, so Stan & I are looking for alternatives.  Looks like
the cheap ceramic resonators won't do the job, but at <$1 ea. I'll try one
after my next Mouser order.  I did pick up a Murata 455kc filter a while
ageo, may try that in an SP-600 to see what it'll do, realizing that it's
not a filter application as such, and not knowing just what ckt chgs are
needed.
    We're looking for thoughts.
tnx, 73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info


Message: 6
Date: Sat, 17 Dec 2005 11:18:39 -0600
From: Gerald <geraldj at ispwest.com>

On Sat, 2005-12-17 at 06:41 -0600, Stanley Adams wrote:
> Al Parker and myself were mulling over the options that are there when
the
> main xtal filter (Y112) is nolo-worko.
>
> Short of finding another 500kc 8 kc filter what is a fellow to do?
> KIWA option is out of the picture.  Does anyone know or suggest a
cheaper
> avenue?  Murata Ceramic filters only work up to a CF of 456, so I do not
> think that this will be of any help.
>
> Where are all the experts here?
>
The crystal in the R-388 is NOT a bandpass filter. Its a single crystal
filter that acts more like a notch with an adjacent narrow pass band.
The radio's bandpass is determined by the IF transformers, not the
crystal. That notch is tuned and maximized with the crystal phasing
control. The receiver works very well with the crystal switched out.

There is a module that makes a 51J-3 (R-388) into a 51J-4 that holds up
to three mechanical bandpass filters. Its noticeable from the front
panel by a little lever sticking out from behind one of the other knobs
to the left of the main dial.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer