[HBR] Where Is Everyone?

[Walter A. Hutchens]

Darrell asked:

> Boy has this group been quiet! What's going on out there? Who's building
> what?

I can offer in mitigation that I have built a home brew receiver over the 
winter -- another one of those 'transformerless' ones I like.   Seven tubes: 
35W4 rectifier, band imaging 80-40, 12AT7 push-pull mixer, 12AU7 p-p 
oscillator, 2 x 19JN8 IF stages, triode half of 1st 19JN8 AGC bias 
rectifier, triode half of 2nd 19JN8 AGC (plate) detector, 1/2 12AU7 signal 
(plate) detector,  19JN8 1st audio stage, triode half BFO, 1/2 12AU7 2nd 
audio.  LO tunes 1350-1950, IF is 5400 kcs.

This is really an excellent receiver; for a fairly simple design it's 
essentially faultless.   There are spurious responses at 3600/7200 kcs 
where the LO harmonics pass through the IF; a half lattice crystal filter 
isn't the ultimate in selectivity.   Sensitivity is probably not 'super' but 
that's a trade-off on 80/40 ... it's ample for use with a normal 80/40 ham 
antenna.   Stability is good enough that you can turn it on, tune in a 
sideband QSO and not retune -- or maybe once.  I haven't tried measuring 
anything but it sounds good on any signal under any conditions.   

It still needs a few small tweeks -- the S-meter won't quite go to full scale 
because of a minor error in the bridge circuit design, the AGC needs two 
resistors changed, the AGC threshold pot is too high value, there's no 
headphone jack and no mute switch.   I need to draw the circuit diagram.

It's good enough that I'm fooling with a design for a double conversion 
general coverage receiver using the same circuit (but slightly different 
frequency conversion scheme) as the back end.   And I think I have a 
workable SIMPLE synthesizer idea for the first conversion.   The BC-1335 
crystal set consists of 120 FT-243's 5675-8650 kcs in 25 kcs steps.   
Multiply by 10 and you have 250 kcs steps (bands) covering 30 Mcs.   
Hetrodyne with another (single) crystal harmonic to whatever frequency 
range is convenient for the first conversion.   
														
The slick design would be to put one or two crystals for each ham band 
inside and switch those with the band (similar to KWM-2) but I'm going for 
easy rather than slick -- just a socket on the front panel and I'll put the 
crystals in a drawer with a chart.   

Walt Hutchens
KJ4KV