[Collins] WTB diode pack

[Dr. Gerald N. Johnson]

On Mon, 2009-04-13 at 11:14 -0700, Dutch Maure WB7DYW wrote:
> Gang,
> I am in need of a balanced modulator pack for a KWM-2A, any available??
> I know about the separate diodes at Radio Shack but would prefer OEM if possible..
> 
> 
> 73's Dutch WB7DYW
> 
> 
>       
Those are tough to find. Over the various production runs several
different parts have been used. FA4000e, FA4200e, CA6987, FA4200e, and
FA4311e. Searching by part number, brings up several federal RFQ that
apparently weren't ever filled. 

I think that a quad of Avago 5082-2835 schottky diodes will have better
diode match (especially if they are all from the same batch) than the
best of the FA family by Fairchild in junction diodes and far better
than any "matched" 1N34 used in the early production.

Except that the small package is inconvenient to connect, Avago and
others make a diode quad especially for double balanced mixers. The
number isn't popping up right now. It even can have the leads ordered to
fit the Collins schematic. Maybe I'll get some and add leads someday and
a blob of potting to make modulator replacements.

And going more afield, probably the common MCL SBL-1 rated for 100 KHz
to a few hundred MHz would work well, but I don't know if the balance
adjustments would function to improve the carrier suppression. The
output impedance matching may be far off also.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer