[HBR] Help with old home-brew receiver

[hbr@mailman.qth.net]

In a message dated 3/23/03 9:40:24 PM Eastern Standard Time, 
waltah@earthlink.net writes:

> Well ... We may have a winner.   QST, March, 1956, p. 39, "A Nine 
>  Tube Amateur Band Receiver With 3-Kc. Selectivity", by Emory E. 
>  Toops, Jr., W9HLH.   

(Homer Simpson mode ON)

DOH!!!!!!!

(Homer Simpson mode OFF)

Dunno how I missed that one, but I agree 100% with Walt. The rx may be based 
on the 1956 article, or it may be the original with modifications. Got the 
mag right here, too close a match to be anything else.

>  This is a double conversion receiver with the 
>  tubes as listed by Kevin except that there's a 6BA6, there's no 
>  6BY6, and there's no 12AU7.

It's possible the unidentified tube is a 6BA6.
>  
>  The tube lineup in the W9HLH receiver is:
>  
>  6AQ5 Audio Output
>  12AX7 1st Audio/BFO
>  6AL5 Detector/AVC/ANL
>  6BJ6 x2  85 Kcs IF's
>  6BE6 x2 1st & 2nd mixer
>  6BA6 RF
>  6C4 Local Osc.
>  
>  The 1st IF freq. is 1600 kcs and consists of just one transformer 
>  located between the two mixer stages.   The 6BE6 2nd mixer is self-
>  excited, with a crystal at 1685 kcs.   
>  
>  That looks like it, though there are obvious questions about the 
>  12AU7 and 6BY6.   The 6BY6 is probably a substitute for a 6BE6 -- 
>  the basing is the same.   I'd guess the unidentified tube is the 6BA6 
>  RF stage -- if so it will be nested in with the coils.   The 12AU7 ... Q-
>  multiplier?    Selecto-ject?   The TNS (twin noise squelch) used a 
>  12AX7 I think?   

All good possibilities. Another is that the noisy 6BE6 first mixer was 
replaced by a 12AU7 a la Pullen, and the 6BY6 added as a product detector. Or 
the 12AU7 may be the product detector. 12AU7 could also be a tube to drive an 
S meter (external?).
>  
>  The author describes his goal as coverage of 80 through 10 meters, 
>  simple to construct, and use as many parts as possible from a BC-
>  453.   He describes use of the IFTs, BFO coil, nine bypass caps 
>  (ugh ...) and resistor terminal boards from the command set.

I know others have had bad luck with Command set caps, but mine just keep on 
working. But I agree they need to be checked before applying power. Changing 
them all as a preventive is certainly a good idea. Only three ARC-5 cans are 
used, not a big job. 
>  
>  "No S-meter was included because it was considered an 
>  unnecessary expense."   The receiver is tuned with a National UM-15 
>  three gang 15 mmf/section variable cap.
>  
>  Congratulations, Kevin -- you snagged a *rare* one!   And that's a 
>  good sound design;  it should be quite usable on the lower bands in 
>  any case and on 20 and up according to the builder's degree of 
>  fanaticism.   
>  
Agreed!  Now all you need is a power supply and speaker. Article says a 90 ma 
transformer is more than adequate. 

73 de es sri for the earlier confusion

Jim, N2EY