[HBR] RE: HBR 2006 and a question

[Walter A. Hutchens]

Jim said:
>I think the big attraction was that they were general-purpose all-band HF
>ham receivers that were extensively documented and 'buildable'. HBRs were
>more complex than regens or simple supers (and outperformed them) but not
>so complex as to require extreme skill/experience in construction. Nor
>did they use unusual parts. And they were easy to modify - note that W6TC
>didn't originally use the 898 dial - that was an adaptation by another.
>
>Most of all they practically screamed "BUILD THIS RADIO" and "YOU CAN DO
>IT" at you from the magazine pages.

It's just about impossible to fault this design for the 'market' that Ted 
Crosby was trying to reach.   Others have listed the main points: parts off 
the shelf from standard sources, performance comparable to the upper-
middle price range receivers of the time except for the lack of 
bandswitching, lack of any critical circuits or difficult adjustments, ease 
of extending by winding other coils, using a better dial, substituting used 
parts if desired (85 kcs 'command set' transformers vs. 100 kcs Millers, 
command set tuning cap ...), and more.

EVERY design incorporates some compromises.   The W6TC receivers accept 
the inconvenience of plug in coils and higher warm-up drift than can be 
achieved with a fixed-coil or partly-crystal controlled front end but they 
deliver a BUILDABLE receiver that would make QSO's as well as what most 
hams could have bought at the time and better than most of them.    The 
things have a potfull of front panel controls but nearly any tube that would 
light up will work fine (where most ham designs assume new tubes) and you 
could optimize the gain distribution for either weak signals or crowded 
band/many strong signals.

The 3500 kcs crystal band edge marker was perfectly adequate for the 
operational calibration of these receivers; you couldn't read the dials 
closely enough to require any more than a band edge check when changing 
coils, anyway.   And there were the advantages of no problem getting a 
strong calibration signal nor of identifying what signal you had, since only 
one would be heard per set of coils.   

Look at the 'simple receiver' designs of the 60's Handbooks:   All of them 
with more than three tubes will outperform the HBR-series on one or more 
points, most often selectivity.   But they're nearly all so limited in some 
other area that they're closer to "an experimenter's receiver with which you 
could make some QSOs" than "a station receiver with plug-in coils."    Take 
the 'Advanced 6-Tube Receiver' of the 1969 handbook as the best of 
breed: Single conversion on 80 with a crystal controlled converter for other 
bands -- not too bad so far.   The mixer is a 7360.   But audio AGC and no 
way to switch off the BFO make it useful only for SSB/CW.   Sorry, that's 
not a station receiver.   With a Collins mechanical filter for selectivity, it's 
not inexpensive, either -- or even 'moderately priced.'

The only real station receiver is the DCS-500 of 1960 +/-.   That's a decent 
design (also using plug in coils) but  requires four crystals ('surplus') for 
selectivity plus one more in a transistorized 100 kcs calibrator and has 
modified IFTs and some relatively complex/critical circuitry.   The main 
thing you get in exchange for much less 'buildability' is several steps of 
variable selectivity -- a poor trade-off, in my opinion.   There's no product 
detector, so receiving SSB would require you to use the old technique of 
backing down the RF/IF gain and in this design that requires switching off 
the AGC.   

Yes, the design glitches could be fixed.   But if you're qualified to do that, 
you don't really need a Handbook design, do you?   The DCS-500 is 
basically a fine 1950 station receiver design realized with 1960 parts.

All those handbook receivers uses unbuffered triodes as local oscillators.   
It's not easy to do that without getting enough oscillator pulling to reduce 
intelligibility of a sideband signal, and they don't; the 'Advanced 6-Tube 
Receiver' (7360 mixer with the LO driving the deflection plates) might be 
satisfactory.   The W6TC ECO LO does not have the problem.   All except 
the DCS-500 are single conversion designs but you have to build a crystal 
controlled converter if you want more than one or two bands.   

Look beyond the handbooks and there are exactly two serious candidates 
for a home built station receiver:   the G2DAF sets which are close to the 
complexity of the Collins S-Line receivers (but EXCELLENT), and the 
premixed design of W5OMX, Col. Dave Curtis.   There's NO chance that you 
could build a two tube project and then tackle either of these with a good 
chance of success -- and the price would have been in the ballpark of a 
used Collins A-line or Drake receiver.   

W6TC was a gifted radio designer.   Does anyone know what he did in 'real 
life'?

Walt 
KJ4KV