[Collins] 51J parts

[Ed Wirtz]

Hi, Guys,

All of you are correct in your respective analyses re. the coil modules for 
the 51J series of receivers. I have two R388s here and two 51J4s. They are 
all alike in that in the variable RF rack, each of the three coils for bands 
4-7, 8-15, and 16-30 are coded with a color dot on top of the coil form. 
White for bands 4-7, black for bands 8-15 and gray for bands 16-30. All of 
these coils are taper wound so it would really be a job to homebrew one.

All of the cores used in the RF section are alike while there are two 
different length slugs used in the variable IF.

I attempted to use a coil and core from the 4-7MHz range in my 8-15MHz 
range. It tunes OK at 8MHz but does not make it at 15MHz.

Larry, it seems that the coil you sent me won't work well enough to allow 
the RF to track across the band spread but thanks for the effort. I learned 
alot from trying to use it. I'll keep it in stock for another time.

Bill, I'm still waiting for the parts you sent me to arrive. I'll let you 
all know how things come out after I get them installed and checked out.

Thanks to all of you that responded to my problem. I hope I can return the 
favor in the future.

73,

Ed, KØBKA
----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: "Lawrence Mayhew" <lmayhew4 at comcast.net>
Cc: <collins at mailman.qth.net>
Sent: Wednesday, April 30, 2008 1:35 PM
Subject: RE: [Collins] 51J parts


> On Wed, 2008-04-30 at 10:51 -0700, Lawrence Mayhew wrote:
>> While we are on the subject of the L-105 coil for the 51J series, may I 
>> ask
>> about the "tuning slugs"? Somewhere I got the idea that the slugs in the
>> tuning rack were not all the same permeability. I can't confirm it in the
>> technical literature. Anyone have an experienced opinion?
>> Regards,..........Larry in Seattle
>>
> I think they are different permeability. Higher for IF and LF, lower for
> higher frequency front ends. Notice that besides different sizes, they
> are different colors.
>
> There's not enough data out that I have for the 51J family to confirm
> that, but I have a full set of R390A drawings on CD-ROM and I have
> looked up the slugs and they do have different permeabilities (mostly
> powdered iron variations) for different applications. I know those I've
> picked up surplus have a range of material colors, but unfortunately few
> are identified with part numbers so finding them good homes is very
> difficult.
>
> I wouldn't be surprised to find that each core permeability is assigned
> a different physical size (diameter or length) in a radio just to make
> it easier for manufacturing and service depots to tell the slugs apart.
>
> -- 
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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