[Boatanchors] Re: Collins R-388 vs 51J4

[Jim Wilhite]

I had an R388 some years back, an older one.  I don't remember the 
contract number for sure but it was early.

I tried the TV balun to antenna input and measured the sensitivity after 
tweaking the coils.  I then removed the balun and retweeked the coils 
with a 50 ohm dummy load across the antenna terminals and the difference 
was nil, not enough to quibble about.  I used an URM 25 F to make the 
measurements and a VTVM across the detector for the indicator.  I used 
the panel meter to set the signal to mid-scale when I needed.  The 
sensitivity was below the book value on all bands.  This was a stock 
unit and not modified in any way.

Wonder why it worked out that way?

Jim/W5JO





> My 51J-2 has the higher impendance antenna input.  It
> is one of the receivers that I reference in my article
> on using TV baluns on the older receivers.
>
> Glen, K9STH
>
>
> --- Bill Cotter <n4alg at qx.net> wrote:
>
> Examining the 51J4 schematic on the CCA site, the 51J4
> uses the identical Hi-Z input design as the R-388 and
> 51J3 use.
>
>