[HBR] Another Receiver Project -- HBR-4, Part 6

[waltah at earthlink.net]

Well, I'm listening to it -- sort of.   With full volume I can hear 
signals, but the S-meter barely moves.

80 meters is working.   The 18 Mcs crystals I had oscillated over 
100 kcs high and were given to hopping to another mode/frequency 
nearby; it looked to me like they had been opened and 'adjusted.'   
I found a 6 Mcs rock that runs fine 3rd overtone at 18,046 kcs.   
Also two for 9.5 Mcs that should oscillate 3rd overtone at 28.600 or 
so -- close enough to test 20 meters.   (Crystals are 14 Mcs above 
high end of band.)

The ICM crystals -- correct frequencies for 80, 40, 30, 20, and 10A -
- should be here next week.   I really don't think I'll need them 
before then. 

The bandswitch and front end tuning coils are from an FT-101 so 
there's the potential for 11 bands, 160 through 10D, including 30 
and an 'aux' band that must be 10 Mcs or higher.   

Overall gain is very low, especially in the IF stages.   I tweeked the 
design in the direction of low gain, all the way through -- chiefly by 
using relatively large cathode resistors.  Now I will go back and 
adjust the other way.  

Coupling between the 6JH8 beam deflection mixer and the IF's 
probably isn't right either.   It's resonant and approximately 
balanced (output from plates is push-pull) but the match to the 
crystal filter is doubtful.   The filter response is 'bumpy' -- I don't 
know if that means load too high or load too low.

These tubes require both beam balance -- the beam needs to be 
centered between the plates by DC bias on the deflection plates -- 
and RF balance -- the two halves of the plate tank look 'equal.'   I 
do have the latter but the DC balance adjustment circuit isn't there. 
For initial testing I picked a tube that balanced better than the 
others and let it go at that.   That'll have to be fixed since there's an 
RTTY signal at 9001 kcs or so and accurate balancing will give 
considerable reduction of IF feedthrough.

The beam tube may need more drive.   That will wait until the IF 
gain and mixer-filter coupling are straightened out because more 
drive will mean more problems with spurious responses.

It sounds good but you can't tell much by that until the signal levels 
are correct.   

Walt 
KJ4KV