[Collins] 51J series input coil antenna requirements.

[Dr. Gerald N. Johnson]

On Thu, 2008-05-01 at 18:46 +0000, Bill Kirkland wrote:
> There is an archived letter from me that lists the differences between the 
> 51J(j-2), the j-3(r388) and j-4.  There are differences in the antenna 
> circuit between the j/j-2 and the j-3/j-4 but not between the j-3 and j-4.  
> As Jerry points out, the J-4 is a modified J-3 - mechanical filter module.
> 
> The 51j or 51j-2 uses a balanced (differential) input and is transformer 
> coupled. There is
>   no antenna trimmer cap.
> 
> The j-3 and j-4 use a capacitor coupled singled ended input and have the 
> antenna
> trimmer cap.
> 
> 
> Bands 2 and 3 do NOT use the coils in the RF rack, but rather the coils in 
> the IF rack.
> Bands 2 and 3 use 1 conversion stage with the PTO as the mixer.  Band 1 is 
> up converted
> to a high band, and then goes through 2 more mixer stages.
> 
> 
Is it normal for the R388/J-3 RF stage to be unstable on bands 3 and 4
when the antenna tuner is peaked or is my few few feet of wire too short
an antenna to load the stage at those frequencies? E.g. should I try to
fix it or is it not broke?

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer