Tim Wescott ) writes:
Ken Scharf wrote:

wrote:

The HBR web site:

http://www.qsl.net/k5bcq/HBR/hbr.html


I've built three HBR's. It's a nice receiver.

73,
Darrell, WA5VGO

This is something I thought of building several times, but with
extensive modifications. I just don't care for the classic superhet
with the first oscillator a vfo. This requires calibration of each
band, and also tracking adjustments. I prefer the variable first IF
and a crystal controled first oscillator. (Like the drake 2B). My
idea of a receiver project would be to add an additional rf/mixer
front end to the HBR with a first if of 3.5-4.1 (and 6.9-7.5). The
second IF would be 1.7khz (so it's an 80/40 band image front end).
The final IF would be 85khz (guess where those IF cans came from).
Being a compactron nut, the front end would use a 6AR11 rf amp/mixer,
and the 85khz IF would use another 6AR11. A 6AV11 for the product
detector and bfo, 6AF11 for the AF stage and agc amp. Other tubes for
the rest of the rig TBD. Also thought of using toriods in the front end
and bandswitching them by mounting them in a standard turret tuner
chassis ripped out of an old TV set. (I've got some real old junk in my
junk box!).

I have several ARC-5 rx three gang variable
caps, these have a real nice vernier drive on them. Just attach a
larger dial, or a drive pulley for a slide rule dial and you have
something as nice as the Eddystone.

(I sold an Eddystone I had in the junkbox a few years ago on ebay, it
fetched about $130 IIRC. Nice dial, but a RPITA to cut out the front
panel and mount correctly.)

That introduces problems because that wide 1st IF encourages
intermodulation unless you really ride the gain budget. The Galaxy V
avoids this by using single-conversion with a 9MHz IF. It uses a single
5-5.5MHz VFO that's premixed with the crystal oscillator output for all
bands except for 20 and 80 (and 20 tunes backwards, in traditional 9MHz
IF fashion).

And your point brings up that once you start modifying something, it's
not the original.

I've seen some of the HBR articles, and followup letters, and the author
did make comment about people "making receivers just like mine, but with
a few changes...". He made the point that he had put effort into making
receivers that not only worked, but could be duplicated, and once someone
started messing with them it tempted problems. One reason they were
popular (though I have no idea how that translates to actual figures)
was that the author had put so much effort into it all, and if I'm
remembering, there were extras like chassis layout patterns that
could be had for a nominal fee.

To some extent, I question building one today. Not only is there
the issue of getting the specific parts, but receiver design has
changed a lot. Are they double conversion? I can't remember, but if
so, they used a fairly broad section at the first IF, before dropping
to the final IF and it's selectivity. There was good reason forty
or so years ago to use such a design, but that hasn't been true for
a long time.

Putting a converter ahead of a tuneable receiver had reason years ago,
but that too has changed.

And if one is going to shift the conversion scheme around to make
it a converter into a tuneable receiver, one might as well start
with any of the numerous designs that did just that.

Of course, there can be reasons of nostalgia for building one,
in which case the tracking down the parts becomes part of the
process, rather than an impediment to building a receiver.

Michael VE2BVW