[HBR] Wow! A Rare One!

[hbr@mailman.qth.net]

Thanks to Byron Tatum I now have a nice example of what both of 
us thought was  an early G2DAF receiver, well known to those who 
drool over the older RSGB handbooks, probably a few thousand 
built in the late 60's and in a later version, after that.   

But that's not what it is.   It's a contemporary design by A.J. 
Shepherd, G3RKK but probably rather less common.   It's also 
featured in the RSGB handbook 4th edition under the name 
"Amateur-bands-only double superhet."  It was likely built in 
considerably smaller numbers than the G2DAF, probably around 
1968.   The physical layout is somewhat similar but the design isn't 
as advanced.  A good way to think of it is as a UK version of Ted 
Crosby's HBR-series but bandswitching and with an Eddystone 
dial.   14 tubes (I think) counting the VR-150/30.  

It's a double-conversion design, 1.62 Mcs 1st IF, 85 kcs 2nd IF.   
The RF stage is a 6EH7, 1st mixer 6AJ8 triode-pentode with the 
triode working as the LO.   6CU7 2nd mixer, two stages of 6BA6 
IFs, pretty conventional after that.   I haven't looked at all the 
details but mine seems to be a near-faithful reproduction of the 
handbook model.  Boy is that a nice dial -- no wonder people pay 
such prices for them.  This unit was built with the Electroniques 
manufactured front end assembly; the dial scale appears to be 
commercially made and must have come with the front end.

Construction technique is only fair but the metalwork's pretty good 
so it will re-kit nicely.   Steel chassis -- a good idea for these sets 
with big power transformers.  The original meter has been replaced 
with a smaller one on a plate; I think I can take care of that from 
stock.  (The square Simpson meters will fit perfectly.)  Couple of 
minor missing parts -- nothing challenging.   It was surely built in 
the UK as even the small parts are UK make.  Many small parts 
are salvaged from dismantled equipment.

Wouldn't you like to know the stories of some of these old sets?

Pictures are at:

http://timbreblue.com/walt/g3rkk1.JPG
http://timbreblue.com/walt/g3rkk2.JPG
http://timbreblue.com/walt/g3rkk3.JPG
http://timbreblue.com/walt/g3rkk6.JPG

Then at:

http://timbreblue.com/walt/g3rkk5.JPG

is another pic showing the current very early state of the general 
coverage HBR project.   The lower knob is the 10 Mcs and 0.5 Mcs 
bandswitch, the upper one is the 1 Mcs steps.  The subchassis is 
the synthesizer for the LO; the shaft from the 1 Mcs bandswitch 
operates the cams for the slug rack.  There are 10 crystals 
grouped around the switch on the front of the synthesizer, 24.7 
Mcs-33.7 Mcs.  Under the synthesizer chassis are 7.55 and 8.05 
Mcs crystals (0.5 Mcs steps) and 10 and 20 Mcs for the 10 Mcs 
steps.  

The second-to-last mixing is with the 5.2-5.7 Mcs linear tunable 
oscillator already built with the dial and cap from an LM frequency 
meter but not yet installed.  (Calibrated directly to 10 cps, tho end-
to-end accuracy probably will only be +/- 500 cps or so.)  The 
receiver is a single conversion design, with an IF of 6.553 Mcs.   
The two IF stage sockets are on the left.  

Except for the tunable oscillator no wiring has been done yet -- got 
a lot of metal work to do first!

Maybe *next* winter there'll be time to work on some of these 
projects!

Well ... a G3RKK re-kit would go pretty fast ... and I do need to do 
paintwork in the summer when it can be done outdoors.

Walt 
KJ4KV