(Michael Black) wrote in message ...
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.

Agreed! However, there's something to be said for both the exact copy
and modification approaches.

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.

But OTOH some of the mods turned out to be very worthwhile, such as
the 898 dial on the HBR-16 and the product detector mods. There were
also some problems that were only shaken out by the construction of
many copies.

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.

Yep, a whole packet of photos, layout templates and other stuff could
be had.

Another point was that the HBR series were designed around
then-current-production parts obtainable by mail order. A builder
could get every needed part that way, if necessary, and some did just
that.

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.

Agreed in part. But within their limitations they are a sound design.
And if you can get the parts, they are "duplicatable" with limited
tools and test equipment.

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.

They used a first IF around 1700 kHz (for decent image rejection on
all of HF with only one RF stage) and a second IF at 100 kHz.

The first IF isn't as broad as you might think, particularly in
versions that used two IFTs. Certainly it's much narrower than the
tunable-first-IF designs that followed.

There was good reason forty
or so years ago to use such a design, but that hasn't been true for
a long time.

The 1957 QST article "What's Wrong With Our Present Receivers" pretty
much makes the case for the use of single-conversion and xtal filters
in the low-HF range. The 1965 "Miser's Dream" receiver demonstrated
the principle, but was not a wire-for-wire "duplicate me" article. And
the filters weren't cheap - 1959 price for the Hycon Eastern 2215 kHz
filters was $44 *each*.

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.

The HB-67, in the ARRL Handbook of 1967, for example.

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.

I approach the challenge the other way: Look at the readily-available
parts and see what can be built with them. Of course, "readily
available" varies with the builder!

But there's nothing like getting on the air with a 100% homebrew
station. Even kitbuilt isn't quite the same.

73 de Jim, N2EY