(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

N2EY wrote:
Ken Scharf wrote in message ...


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.


All of those things can be dealt with. To me the big problem with the
basic HBR design is the stability of the tunable HFO.


I prefer the variable first IF
and a crystal controled first oscillator. (Like the drake 2B).


Me, too. There are some pictures on the HBR site of a receiver I built
about 30 years ago using that principle. It worked very well, and cost
me almost nothing to build.


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).


In the 1965 ARRL Handbook there is a receiver described (the HB-65)
which is almost exactly what you are describing, except it used the
100 kHz Miller IFTs. The 85 kHz cans are probably much easier to come
by these days.


The final IF would be 85khz (guess where those IF cans came from).


Swords into plowshares...


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.


Nothing wrong with Compactrons, but you are begging for trouble with
that scheme because the layout and section-to-section stray
capacitances will make it difficult to isolate the various stages. The
skirt selectivity of the IF amp will be compromised as well. The
layout will also be a compromise.


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!).


The basic idea is very sound if the Compactrons are used differently.


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.


Yep! Note, however, that except for the 6-9.1 MHz version they have
plate shapes that won't yield a linear dial on the ham bands. The
6-9.1 MHz version is almost pure straight line capacitance, and is
only 62 pf per section or so.
I would think you want a 'stright line frequency' where the capacitance
changes as the square of the rotation. IE: at half open position the
capacitance is down to 1/4 of the value available at full mesh.

For the ultimate, though, use the capacitor from an ARC-5 tx, BC-221
or LM freq meter. Nice gear drives and an even bigger dial than the rx
versions. Only one section though, but good for "unit oscillator"
construction of the HFO. (Only needs to cover the range 5.2-5.7 MHz)

I have a few of those ARC-5 tx caps in my junk box, and at least one
with the dial drive. It binds just a bit though as if the drive shaft
is slightly bent. Just enough to be noticed while turning it with a
good sized knob attached.
With such a design, it would be a good idea to use a Pullen mixer and
no RF stage in the 80/40 bandimage section (at least). There's also
the problem of secondary images - you need a lot of selectivity in the
front end and 1.7 MHz IF section to avoid signals 170 kHz from the
desired one seeping into the second IF. The 2B used a 455 kHz
first-fixed-IF for this reason. IM performance is compromised by the
fact that the selectivity is so far from the antenna.
With a good 'roofing' filter ahead of the final mixer you should be able
to knock down the images from the 1.7mhz if before reaching the 85khz
one. I have three 1.7mhz double tuned cans available, with all three in
series top coupled with gimick caps I should be able to achieve enough
selectivity to avoid secondary image problems. The use of a 455khz IF
is also a good idea, and I have a few Collins mech. filters that could
be used there as well (a 2.0khz bw out of an R390, a 2.7khz that looks
like an S line filter, and a large unit of 1.8khz bw that came out of an
if adaptor for an HRO-50 or 60).


With proper layout and shielding I don't see a problem using the 6AR11
in the two stage IF. Hell, they were designed for use at 47mhz in a
dual stage TV if where cross coupling would be even more of a problem!
The 6AR11 is an excellent semi-remote cutoff amplifier with good
overload and cross mod specs equal to the pentodes used in the HBR.

Some alternatives to consider:

1) Get some xtals in the 1700 kHz range and build a filter or filters
so that the 85 kHz IF is not needed. Perhaps a variable-bandwidth
filter using a multigang variable capacitor could made, using 4
crystals and a three-gang capacitor. This approach solves the
secondary image problem, too.

2) Have a single tuning range of 3.5 - 4.1 MHz and the fixed IF at 455
kHz or thereabouts. Would require dual conversion on 40 but would also
allow use of standard 455 kHz IF filters. Or make your own from
FT-241A crystals (which is what I did way back when).

3) Use the filters and heterodyne xtals from a junked transceiver as
the basis of a homebrew rx. Hangar-queen/basket case HW-100s, -101s,
and SB-line units show up on ePay and at 'fests for quite low prices -
far below what the filters and xtals would cost separately. Other
types of transceiver can also be good parts sources (Tempo One comes
to mind - nice VFO mechanism in them, and the IF is 9 MHz IIRC). KJ4KV
turned an early-version FT-101 into a pretty interesting receiver this
way.

As for a new design with todays parts, well I have several ideas here
begging to be tried. I have quite a few 'Samples' from Analog Devices
including many DDS chips. The 400mhz DDS parts would make a great HFO
for a single conversion receiver with an IF at 9mhz (again more junkbox
filters, including about 1/2 dozen 9mhz 3.2khz 8 pole units out of
Gonset Sidewinder rigs purchased at Dayton years ago). Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector. Probably use MC1350's or ancient CA3028's as the IF amps.
The front end would use a quad DFET (Siliconix) switching mixer that
was in the handbook for several years driven at twice the required HFO
frequency (to get push-pull drive using a D Flipflop). Bowing to the
junkbox, the front end would be a double or triple tuned filter using
toriods bandswitched using a standard coil tuner chassis as the switch.
(The toriods fit nicely in the tuner strips). An 8051 series micro
drives the DDS, frequency display on 7 segment LEDs (I have enough of
these to choke an alligator) and a rotary encoder drives the micro to
select frequency.

Maybe I'm crazy, but I still wonder about puting in a second conversion
down to 85khz to use those ARC5 IF cans! Anything wrong with a hybrid
radio using the latest IC's and microprocessors along with 60's
compactrons! (Just what kind of bandwidth will a properly aligned 85khz
if strip using arc5 cans give?)

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box. (Also
some IRF531 mosfets which might make a good linear final for about 25
watts a pair....though maybe not to 30mhz....).

I've rambled enough....
73's

Besides the HBR website, the HBR reflector offers receiver ideas that
range far beyond the classic W6TC HBR series designs.

(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.)


I haven't used an 898 yet but with the template (which I have) it
shouldn't be too difficult except for that huge rectangular hole in
the panel.

So many great hollowstate rx ideas!

Indeed!

N2EY wrote:
Ken Scharf wrote in message ...


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.


All of those things can be dealt with. To me the big problem with the
basic HBR design is the stability of the tunable HFO.


I prefer the variable first IF
and a crystal controled first oscillator. (Like the drake 2B).


Me, too. There are some pictures on the HBR site of a receiver I built
about 30 years ago using that principle. It worked very well, and cost
me almost nothing to build.


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).


In the 1965 ARRL Handbook there is a receiver described (the HB-65)
which is almost exactly what you are describing, except it used the
100 kHz Miller IFTs. The 85 kHz cans are probably much easier to come
by these days.


The final IF would be 85khz (guess where those IF cans came from).


Swords into plowshares...


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.


Nothing wrong with Compactrons, but you are begging for trouble with
that scheme because the layout and section-to-section stray
capacitances will make it difficult to isolate the various stages. The
skirt selectivity of the IF amp will be compromised as well. The
layout will also be a compromise.


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!).


The basic idea is very sound if the Compactrons are used differently.


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.


Yep! Note, however, that except for the 6-9.1 MHz version they have
plate shapes that won't yield a linear dial on the ham bands. The
6-9.1 MHz version is almost pure straight line capacitance, and is
only 62 pf per section or so.
I would think you want a 'stright line frequency' where the capacitance
changes as the square of the rotation. IE: at half open position the
capacitance is down to 1/4 of the value available at full mesh.

For the ultimate, though, use the capacitor from an ARC-5 tx, BC-221
or LM freq meter. Nice gear drives and an even bigger dial than the rx
versions. Only one section though, but good for "unit oscillator"
construction of the HFO. (Only needs to cover the range 5.2-5.7 MHz)

I have a few of those ARC-5 tx caps in my junk box, and at least one
with the dial drive. It binds just a bit though as if the drive shaft
is slightly bent. Just enough to be noticed while turning it with a
good sized knob attached.
With such a design, it would be a good idea to use a Pullen mixer and
no RF stage in the 80/40 bandimage section (at least). There's also
the problem of secondary images - you need a lot of selectivity in the
front end and 1.7 MHz IF section to avoid signals 170 kHz from the
desired one seeping into the second IF. The 2B used a 455 kHz
first-fixed-IF for this reason. IM performance is compromised by the
fact that the selectivity is so far from the antenna.
With a good 'roofing' filter ahead of the final mixer you should be able
to knock down the images from the 1.7mhz if before reaching the 85khz
one. I have three 1.7mhz double tuned cans available, with all three in
series top coupled with gimick caps I should be able to achieve enough
selectivity to avoid secondary image problems. The use of a 455khz IF
is also a good idea, and I have a few Collins mech. filters that could
be used there as well (a 2.0khz bw out of an R390, a 2.7khz that looks
like an S line filter, and a large unit of 1.8khz bw that came out of an
if adaptor for an HRO-50 or 60).


With proper layout and shielding I don't see a problem using the 6AR11
in the two stage IF. Hell, they were designed for use at 47mhz in a
dual stage TV if where cross coupling would be even more of a problem!
The 6AR11 is an excellent semi-remote cutoff amplifier with good
overload and cross mod specs equal to the pentodes used in the HBR.

Some alternatives to consider:

1) Get some xtals in the 1700 kHz range and build a filter or filters
so that the 85 kHz IF is not needed. Perhaps a variable-bandwidth
filter using a multigang variable capacitor could made, using 4
crystals and a three-gang capacitor. This approach solves the
secondary image problem, too.

2) Have a single tuning range of 3.5 - 4.1 MHz and the fixed IF at 455
kHz or thereabouts. Would require dual conversion on 40 but would also
allow use of standard 455 kHz IF filters. Or make your own from
FT-241A crystals (which is what I did way back when).

3) Use the filters and heterodyne xtals from a junked transceiver as
the basis of a homebrew rx. Hangar-queen/basket case HW-100s, -101s,
and SB-line units show up on ePay and at 'fests for quite low prices -
far below what the filters and xtals would cost separately. Other
types of transceiver can also be good parts sources (Tempo One comes
to mind - nice VFO mechanism in them, and the IF is 9 MHz IIRC). KJ4KV
turned an early-version FT-101 into a pretty interesting receiver this
way.

As for a new design with todays parts, well I have several ideas here
begging to be tried. I have quite a few 'Samples' from Analog Devices
including many DDS chips. The 400mhz DDS parts would make a great HFO
for a single conversion receiver with an IF at 9mhz (again more junkbox
filters, including about 1/2 dozen 9mhz 3.2khz 8 pole units out of
Gonset Sidewinder rigs purchased at Dayton years ago). Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector. Probably use MC1350's or ancient CA3028's as the IF amps.
The front end would use a quad DFET (Siliconix) switching mixer that
was in the handbook for several years driven at twice the required HFO
frequency (to get push-pull drive using a D Flipflop). Bowing to the
junkbox, the front end would be a double or triple tuned filter using
toriods bandswitched using a standard coil tuner chassis as the switch.
(The toriods fit nicely in the tuner strips). An 8051 series micro
drives the DDS, frequency display on 7 segment LEDs (I have enough of
these to choke an alligator) and a rotary encoder drives the micro to
select frequency.

Maybe I'm crazy, but I still wonder about puting in a second conversion
down to 85khz to use those ARC5 IF cans! Anything wrong with a hybrid
radio using the latest IC's and microprocessors along with 60's
compactrons! (Just what kind of bandwidth will a properly aligned 85khz
if strip using arc5 cans give?)

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box. (Also
some IRF531 mosfets which might make a good linear final for about 25
watts a pair....though maybe not to 30mhz....).

I've rambled enough....
73's

Besides the HBR website, the HBR reflector offers receiver ideas that
range far beyond the classic W6TC HBR series designs.

(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.)


I haven't used an 898 yet but with the template (which I have) it
shouldn't be too difficult except for that huge rectangular hole in
the panel.

So many great hollowstate rx ideas!

Indeed!

Ken Scharf wrote in message ...
N2EY wrote:
Ken Scharf wrote in message ...

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.


Yep! Note, however, that except for the 6-9.1 MHz version they have
plate shapes that won't yield a linear dial on the ham bands. The
6-9.1 MHz version is almost pure straight line capacitance, and is
only 62 pf per section or so.

I would think you want a 'stright line frequency' where the capacitance
changes as the square of the rotation. IE: at half open position the
capacitance is down to 1/4 of the value available at full mesh.

That only works with a tuning range of about 2:1. The type of ham band
rx being described has a much more limited tuning range, and needs an
almost-linear capacitance curve to get a linear dial.

For the ultimate, though, use the capacitor from an ARC-5 tx, BC-221
or LM freq meter. Nice gear drives and an even bigger dial than the rx
versions. Only one section though, but good for "unit oscillator"
construction of the HFO. (Only needs to cover the range 5.2-5.7 MHz)

I have a few of those ARC-5 tx caps in my junk box, and at least one
with the dial drive. It binds just a bit though as if the drive shaft
is slightly bent. Just enough to be noticed while turning it with a
good sized knob attached.

Somebody hammered on the shaft to get the knob off, or it was dropped.
Ruined unless you machine a new shaft. *sigh*


With such a design, it would be a good idea to use a Pullen mixer and
no RF stage in the 80/40 bandimage section (at least). There's also
the problem of secondary images - you need a lot of selectivity in the
front end and 1.7 MHz IF section to avoid signals 170 kHz from the
desired one seeping into the second IF. The 2B used a 455 kHz
first-fixed-IF for this reason. IM performance is compromised by the
fact that the selectivity is so far from the antenna.

With a good 'roofing' filter ahead of the final mixer you should be able
to knock down the images from the 1.7mhz if before reaching the 85khz
one.

Exactly!

I have three 1.7mhz double tuned cans available, with all three in
series top coupled with gimick caps I should be able to achieve enough
selectivity to avoid secondary image problems. The use of a 455khz IF
is also a good idea, and I have a few Collins mech. filters that could
be used there as well (a 2.0khz bw out of an R390, a 2.7khz that looks
like an S line filter, and a large unit of 1.8khz bw that came out of an
if adaptor for an HRO-50 or 60).

NICE!

With proper layout and shielding I don't see a problem using the 6AR11
in the two stage IF. Hell, they were designed for use at 47mhz in a
dual stage TV if where cross coupling would be even more of a problem!

Not really. The TV applications were broadband and low gain compared
to what you're trying to do at HF. And the manufacturers could do a
whole bunch of not-obvious tricks and PC board prototypes to get what
they wanted.

The 6AR11 is an excellent semi-remote cutoff amplifier with good
overload and cross mod specs equal to the pentodes used in the HBR.

I agree 100% - it's just that cascading them at 85 kHz may prove
troublesome.

OTOH, in a 455 kHz design where the selectivity comes from the xtal
filters, you may be OK.

Some alternatives to consider:

1) Get some xtals in the 1700 kHz range and build a filter or filters
so that the 85 kHz IF is not needed. Perhaps a variable-bandwidth
filter using a multigang variable capacitor could made, using 4
crystals and a three-gang capacitor. This approach solves the
secondary image problem, too.

2) Have a single tuning range of 3.5 - 4.1 MHz and the fixed IF at 455
kHz or thereabouts. Would require dual conversion on 40 but would also
allow use of standard 455 kHz IF filters. Or make your own from
FT-241A crystals (which is what I did way back when).

3) Use the filters and heterodyne xtals from a junked transceiver as
the basis of a homebrew rx. Hangar-queen/basket case HW-100s, -101s,
and SB-line units show up on ePay and at 'fests for quite low prices -
far below what the filters and xtals would cost separately. Other
types of transceiver can also be good parts sources (Tempo One comes
to mind - nice VFO mechanism in them, and the IF is 9 MHz IIRC). KJ4KV
turned an early-version FT-101 into a pretty interesting receiver this
way.

As for a new design with todays parts, well I have several ideas here
begging to be tried. I have quite a few 'Samples' from Analog Devices
including many DDS chips. The 400mhz DDS parts would make a great HFO
for a single conversion receiver with an IF at 9mhz (again more junkbox
filters, including about 1/2 dozen 9mhz 3.2khz 8 pole units out of
Gonset Sidewinder rigs purchased at Dayton years ago).

The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.

Very good idea. The best filter goes first, then "cleanup" filters.

Probably use MC1350's or ancient CA3028's as the IF amps.
The front end would use a quad DFET (Siliconix) switching mixer that
was in the handbook for several years driven at twice the required HFO
frequency (to get push-pull drive using a D Flipflop). Bowing to the
junkbox, the front end would be a double or triple tuned filter using
toriods bandswitched using a standard coil tuner chassis as the switch.
(The toriods fit nicely in the tuner strips). An 8051 series micro
drives the DDS, frequency display on 7 segment LEDs (I have enough of
these to choke an alligator) and a rotary encoder drives the micro to
select frequency.

And the LEDs glow!

Maybe I'm crazy, but I still wonder about puting in a second conversion
down to 85khz to use those ARC5 IF cans! Anything wrong with a hybrid
radio using the latest IC's and microprocessors along with 60's
compactrons! (Just what kind of bandwidth will a properly aligned 85khz
if strip using arc5 cans give?)

The original design gave a decent SSB passband if the rods were pulled
up. But the shape factor isn't the best and the selectivity winds up
so far from the antenna....

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.

Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.

The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.

73 de Jim, N2EY

Ken Scharf wrote in message ...
N2EY wrote:
Ken Scharf wrote in message ...

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.


Yep! Note, however, that except for the 6-9.1 MHz version they have
plate shapes that won't yield a linear dial on the ham bands. The
6-9.1 MHz version is almost pure straight line capacitance, and is
only 62 pf per section or so.

I would think you want a 'stright line frequency' where the capacitance
changes as the square of the rotation. IE: at half open position the
capacitance is down to 1/4 of the value available at full mesh.

That only works with a tuning range of about 2:1. The type of ham band
rx being described has a much more limited tuning range, and needs an
almost-linear capacitance curve to get a linear dial.

For the ultimate, though, use the capacitor from an ARC-5 tx, BC-221
or LM freq meter. Nice gear drives and an even bigger dial than the rx
versions. Only one section though, but good for "unit oscillator"
construction of the HFO. (Only needs to cover the range 5.2-5.7 MHz)

I have a few of those ARC-5 tx caps in my junk box, and at least one
with the dial drive. It binds just a bit though as if the drive shaft
is slightly bent. Just enough to be noticed while turning it with a
good sized knob attached.

Somebody hammered on the shaft to get the knob off, or it was dropped.
Ruined unless you machine a new shaft. *sigh*


With such a design, it would be a good idea to use a Pullen mixer and
no RF stage in the 80/40 bandimage section (at least). There's also
the problem of secondary images - you need a lot of selectivity in the
front end and 1.7 MHz IF section to avoid signals 170 kHz from the
desired one seeping into the second IF. The 2B used a 455 kHz
first-fixed-IF for this reason. IM performance is compromised by the
fact that the selectivity is so far from the antenna.

With a good 'roofing' filter ahead of the final mixer you should be able
to knock down the images from the 1.7mhz if before reaching the 85khz
one.

Exactly!

I have three 1.7mhz double tuned cans available, with all three in
series top coupled with gimick caps I should be able to achieve enough
selectivity to avoid secondary image problems. The use of a 455khz IF
is also a good idea, and I have a few Collins mech. filters that could
be used there as well (a 2.0khz bw out of an R390, a 2.7khz that looks
like an S line filter, and a large unit of 1.8khz bw that came out of an
if adaptor for an HRO-50 or 60).

NICE!

With proper layout and shielding I don't see a problem using the 6AR11
in the two stage IF. Hell, they were designed for use at 47mhz in a
dual stage TV if where cross coupling would be even more of a problem!

Not really. The TV applications were broadband and low gain compared
to what you're trying to do at HF. And the manufacturers could do a
whole bunch of not-obvious tricks and PC board prototypes to get what
they wanted.

The 6AR11 is an excellent semi-remote cutoff amplifier with good
overload and cross mod specs equal to the pentodes used in the HBR.

I agree 100% - it's just that cascading them at 85 kHz may prove
troublesome.

OTOH, in a 455 kHz design where the selectivity comes from the xtal
filters, you may be OK.

Some alternatives to consider:

1) Get some xtals in the 1700 kHz range and build a filter or filters
so that the 85 kHz IF is not needed. Perhaps a variable-bandwidth
filter using a multigang variable capacitor could made, using 4
crystals and a three-gang capacitor. This approach solves the
secondary image problem, too.

2) Have a single tuning range of 3.5 - 4.1 MHz and the fixed IF at 455
kHz or thereabouts. Would require dual conversion on 40 but would also
allow use of standard 455 kHz IF filters. Or make your own from
FT-241A crystals (which is what I did way back when).

3) Use the filters and heterodyne xtals from a junked transceiver as
the basis of a homebrew rx. Hangar-queen/basket case HW-100s, -101s,
and SB-line units show up on ePay and at 'fests for quite low prices -
far below what the filters and xtals would cost separately. Other
types of transceiver can also be good parts sources (Tempo One comes
to mind - nice VFO mechanism in them, and the IF is 9 MHz IIRC). KJ4KV
turned an early-version FT-101 into a pretty interesting receiver this
way.

As for a new design with todays parts, well I have several ideas here
begging to be tried. I have quite a few 'Samples' from Analog Devices
including many DDS chips. The 400mhz DDS parts would make a great HFO
for a single conversion receiver with an IF at 9mhz (again more junkbox
filters, including about 1/2 dozen 9mhz 3.2khz 8 pole units out of
Gonset Sidewinder rigs purchased at Dayton years ago).

The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.

Very good idea. The best filter goes first, then "cleanup" filters.

Probably use MC1350's or ancient CA3028's as the IF amps.
The front end would use a quad DFET (Siliconix) switching mixer that
was in the handbook for several years driven at twice the required HFO
frequency (to get push-pull drive using a D Flipflop). Bowing to the
junkbox, the front end would be a double or triple tuned filter using
toriods bandswitched using a standard coil tuner chassis as the switch.
(The toriods fit nicely in the tuner strips). An 8051 series micro
drives the DDS, frequency display on 7 segment LEDs (I have enough of
these to choke an alligator) and a rotary encoder drives the micro to
select frequency.

And the LEDs glow!

Maybe I'm crazy, but I still wonder about puting in a second conversion
down to 85khz to use those ARC5 IF cans! Anything wrong with a hybrid
radio using the latest IC's and microprocessors along with 60's
compactrons! (Just what kind of bandwidth will a properly aligned 85khz
if strip using arc5 cans give?)

The original design gave a decent SSB passband if the rods were pulled
up. But the shape factor isn't the best and the selectivity winds up
so far from the antenna....

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.

Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.

The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.

73 de Jim, N2EY

The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

The big problem with DDS is getting a good anti-aliasing filter on the
output to satisfy Mr. Nyquist. Trying to build a good 'brick wall' low
pass filter is insane. Running the DDS with a clock many times greater
than the highest output frequency helps, with an injection frequency of
39mhz on 10 meters with a 9mhz if a 400mhz DDS clock is 5x the Nyquist
requirement. Rather than using a low pass filter, I'd use switchable
bandpass filters, much more rejection of unwanted spurs and a cleaner
output. Not as simple to build, you have to switch filters to change
bands, but hey, I can always GANG several tv tuner chassis for my
band switch! (I knew those old TV sets I caniblized would come in handy!)


Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.


Very good idea. The best filter goes first, then "cleanup" filters.

Actually those filters are identical. But another idea is a double
conversion with both 9mhz and 455khz if's. Then by tuning the second
conversion oscillator you can 'overlap' the bandpass of both sets of
filters to use only a portion of them, and if you also move the bfo
frequency you can move the position of the signal within the resulting
bandpass.


The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.


Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.
My junk box has a few 1625 size sockets, two ceramic 'plate' types and a
large saddle mount. Actually these sockets are easy to find and not too
expensive. Antique Electronic Supply has them, and they show up on Ebay
often. No need to use ones out of ARC5 xmtrs.

I also have a good number of 6AG7 tubes, they would make a good driver
stage for the 1625s. (BTW 6AG7 is sorta an octal version of the 6CL6).
If I used a single 1625 in the final, it would be good for about 25
watts output without straining. Then if I needed more power, I'd build
a linear amp using a 2 or 3 811A's (that's 340-410 Watts PEP output).
Not a full gallon, but the extra few db ain't worth the cost! I have
some 813's in the junkbox, but the sockets for them are costly, and they
have such HIGH output capacitance that making a good tank circuit in a
single ended amp is rather a pain. Still a grounded grid tetrode
circuit looks interresting! (cathode driven with normal g1 and g2 voltages).


The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.
If you have enough filters you can put separate filters in the tx and rx
chains, and even use double conversion on the rx but single conversion
on tx. Then you can use a separate tunable bfo for the receiver. The
bandwidth and center frequency of the tx filter can be selected for good
audio, while the rx filter(s) for selectivity. Tx bandwidth is a
function of audio channel filtering, alc, and NOT overdriving anything.

The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

The big problem with DDS is getting a good anti-aliasing filter on the
output to satisfy Mr. Nyquist. Trying to build a good 'brick wall' low
pass filter is insane. Running the DDS with a clock many times greater
than the highest output frequency helps, with an injection frequency of
39mhz on 10 meters with a 9mhz if a 400mhz DDS clock is 5x the Nyquist
requirement. Rather than using a low pass filter, I'd use switchable
bandpass filters, much more rejection of unwanted spurs and a cleaner
output. Not as simple to build, you have to switch filters to change
bands, but hey, I can always GANG several tv tuner chassis for my
band switch! (I knew those old TV sets I caniblized would come in handy!)


Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.


Very good idea. The best filter goes first, then "cleanup" filters.

Actually those filters are identical. But another idea is a double
conversion with both 9mhz and 455khz if's. Then by tuning the second
conversion oscillator you can 'overlap' the bandpass of both sets of
filters to use only a portion of them, and if you also move the bfo
frequency you can move the position of the signal within the resulting
bandpass.


The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.


Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.
My junk box has a few 1625 size sockets, two ceramic 'plate' types and a
large saddle mount. Actually these sockets are easy to find and not too
expensive. Antique Electronic Supply has them, and they show up on Ebay
often. No need to use ones out of ARC5 xmtrs.

I also have a good number of 6AG7 tubes, they would make a good driver
stage for the 1625s. (BTW 6AG7 is sorta an octal version of the 6CL6).
If I used a single 1625 in the final, it would be good for about 25
watts output without straining. Then if I needed more power, I'd build
a linear amp using a 2 or 3 811A's (that's 340-410 Watts PEP output).
Not a full gallon, but the extra few db ain't worth the cost! I have
some 813's in the junkbox, but the sockets for them are costly, and they
have such HIGH output capacitance that making a good tank circuit in a
single ended amp is rather a pain. Still a grounded grid tetrode
circuit looks interresting! (cathode driven with normal g1 and g2 voltages).


The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.
If you have enough filters you can put separate filters in the tx and rx
chains, and even use double conversion on the rx but single conversion
on tx. Then you can use a separate tunable bfo for the receiver. The
bandwidth and center frequency of the tx filter can be selected for good
audio, while the rx filter(s) for selectivity. Tx bandwidth is a
function of audio channel filtering, alc, and NOT overdriving anything.

Ken Scharf wrote in message ...
The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

The big problem with DDS is getting a good anti-aliasing filter on the
output to satisfy Mr. Nyquist. Trying to build a good 'brick wall' low
pass filter is insane. Running the DDS with a clock many times greater
than the highest output frequency helps, with an injection frequency of
39mhz on 10 meters with a 9mhz if a 400mhz DDS clock is 5x the Nyquist
requirement.

I agree 100%.

Rather than using a low pass filter, I'd use switchable
bandpass filters, much more rejection of unwanted spurs and a cleaner
output. Not as simple to build, you have to switch filters to change
bands, but hey, I can always GANG several tv tuner chassis for my
band switch! (I knew those old TV sets I caniblized would come in handy!)

A good scrounger approach if you can find tuners with good contacts!

Here's another approach, shamelessly copied from Elecraft: Bandswitch
the low-level circuits with small latching relays and some logic
circuitry (a PIC or TTL can easily do the job). These relays are
available from Digi-Key - Omron is one mfr. - and are not too
expensive in quantity.


Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.


Very good idea. The best filter goes first, then "cleanup" filters.

Actually those filters are identical. But another idea is a double
conversion with both 9mhz and 455khz if's. Then by tuning the second
conversion oscillator you can 'overlap' the bandpass of both sets of
filters to use only a portion of them, and if you also move the bfo
frequency you can move the position of the signal within the resulting
bandpass.

Good ideas but getting less and less simple.

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.

Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.
My junk box has a few 1625 size sockets, two ceramic 'plate' types and a
large saddle mount. Actually these sockets are easy to find and not too
expensive. Antique Electronic Supply has them, and they show up on Ebay
often. No need to use ones out of ARC5 xmtrs.

Agreed. The ARC-5 ones are good for submounting, though.

I also have a good number of 6AG7 tubes, they would make a good driver
stage for the 1625s. (BTW 6AG7 is sorta an octal version of the 6CL6).

Oh yes, used them in several rigs.

If I used a single 1625 in the final, it would be good for about 25
watts output without straining. Then if I needed more power, I'd build
a linear amp using a 2 or 3 811A's (that's 340-410 Watts PEP output).

But will 25 watts drive a two- or three-hole 811A amp in grounded
grid? All of the data I've seen says you need about 15 watts per 811A
in GG. Grid Driven requires a lot less (about 5W) but then you need a
grid tank, etc.

Not a full gallon, but the extra few db ain't worth the cost! I have
some 813's in the junkbox, but the sockets for them are costly, and they
have such HIGH output capacitance that making a good tank circuit in a
single ended amp is rather a pain. Still a grounded grid tetrode
circuit looks interresting! (cathode driven with normal g1 and g2 voltages).

I always thought the big advantage of GG was elimination of the need
for screen and bias supplies.

The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.

If you have enough filters you can put separate filters in the tx and rx
chains, and even use double conversion on the rx but single conversion
on tx.

Sure, but by that time you're actually building a separate transmitter
and receiver that share a VFO and not much else.

Then you can use a separate tunable bfo for the receiver. The
bandwidth and center frequency of the tx filter can be selected for good
audio, while the rx filter(s) for selectivity. Tx bandwidth is a
function of audio channel filtering, alc, and NOT overdriving anything.

Agreed!

But since I'm primarily a CW op, the problem is greatly simplified in
some ways. My current homebrew transceiver uses a different het scheme
for tx and rx, sharing a common VFO. Both paths are single conversion.
Requires that the het xtals be dead-on freq (handled by trimmers
across each xtal).

73 es GL de Jim, N2EY

Ken Scharf wrote in message ...
The big question with DDS is the spectral purity of the output. Even
weak artifacts can cause all kinds of birdies and other troubles in
today's RF environment. This is one reason so many folks find the old
designs so appealing - they are "clean" except for the obvious things
like images.

The big problem with DDS is getting a good anti-aliasing filter on the
output to satisfy Mr. Nyquist. Trying to build a good 'brick wall' low
pass filter is insane. Running the DDS with a clock many times greater
than the highest output frequency helps, with an injection frequency of
39mhz on 10 meters with a 9mhz if a 400mhz DDS clock is 5x the Nyquist
requirement.

I agree 100%.

Rather than using a low pass filter, I'd use switchable
bandpass filters, much more rejection of unwanted spurs and a cleaner
output. Not as simple to build, you have to switch filters to change
bands, but hey, I can always GANG several tv tuner chassis for my
band switch! (I knew those old TV sets I caniblized would come in handy!)

A good scrounger approach if you can find tuners with good contacts!

Here's another approach, shamelessly copied from Elecraft: Bandswitch
the low-level circuits with small latching relays and some logic
circuitry (a PIC or TTL can easily do the job). These relays are
available from Digi-Key - Omron is one mfr. - and are not too
expensive in quantity.


Thought I'd use
three IF stages with a filter between EACH stage and a final one before
the detector.


Very good idea. The best filter goes first, then "cleanup" filters.

Actually those filters are identical. But another idea is a double
conversion with both 9mhz and 455khz if's. Then by tuning the second
conversion oscillator you can 'overlap' the bandpass of both sets of
filters to use only a portion of them, and if you also move the bfo
frequency you can move the position of the signal within the resulting
bandpass.

Good ideas but getting less and less simple.

The above radio would probably end up being a transceiver (cause the
extra circuity isn't much) but the finals would end up being 1 or 2 1625
bottles 'cause I have at least a dozen of 'em in the junk box.

Great bottles but the sockets are a pain. Unless you hack up an ARC-5
tx.
My junk box has a few 1625 size sockets, two ceramic 'plate' types and a
large saddle mount. Actually these sockets are easy to find and not too
expensive. Antique Electronic Supply has them, and they show up on Ebay
often. No need to use ones out of ARC5 xmtrs.

Agreed. The ARC-5 ones are good for submounting, though.

I also have a good number of 6AG7 tubes, they would make a good driver
stage for the 1625s. (BTW 6AG7 is sorta an octal version of the 6CL6).

Oh yes, used them in several rigs.

If I used a single 1625 in the final, it would be good for about 25
watts output without straining. Then if I needed more power, I'd build
a linear amp using a 2 or 3 811A's (that's 340-410 Watts PEP output).

But will 25 watts drive a two- or three-hole 811A amp in grounded
grid? All of the data I've seen says you need about 15 watts per 811A
in GG. Grid Driven requires a lot less (about 5W) but then you need a
grid tank, etc.

Not a full gallon, but the extra few db ain't worth the cost! I have
some 813's in the junkbox, but the sockets for them are costly, and they
have such HIGH output capacitance that making a good tank circuit in a
single ended amp is rather a pain. Still a grounded grid tetrode
circuit looks interresting! (cathode driven with normal g1 and g2 voltages).

I always thought the big advantage of GG was elimination of the need
for screen and bias supplies.

The biggest headache I've encountered in transceiver design is finding
a heterodyne combination that works in both directions and uses
available components. All of the classic ones are compromises in one
way or another, either on rx or tx.

If you have enough filters you can put separate filters in the tx and rx
chains, and even use double conversion on the rx but single conversion
on tx.

Sure, but by that time you're actually building a separate transmitter
and receiver that share a VFO and not much else.

Then you can use a separate tunable bfo for the receiver. The
bandwidth and center frequency of the tx filter can be selected for good
audio, while the rx filter(s) for selectivity. Tx bandwidth is a
function of audio channel filtering, alc, and NOT overdriving anything.

Agreed!

But since I'm primarily a CW op, the problem is greatly simplified in
some ways. My current homebrew transceiver uses a different het scheme
for tx and rx, sharing a common VFO. Both paths are single conversion.
Requires that the het xtals be dead-on freq (handled by trimmers
across each xtal).

73 es GL de Jim, N2EY

If I used a single 1625 in the final, it would be good for about 25
watts output without straining. Then if I needed more power, I'd build
a linear amp using a 2 or 3 811A's (that's 340-410 Watts PEP output).


But will 25 watts drive a two- or three-hole 811A amp in grounded
grid? All of the data I've seen says you need about 15 watts per 811A
in GG. Grid Driven requires a lot less (about 5W) but then you need a
grid tank, etc.

The 15 watt figure is close, I think the offical handbook rating was 12
watts per tube in GG. The higher figure was with an UNTUNED input
without any impedance matching network (just the way most 811 gg amps
were built, since the average exciter provided about 100 watts output
who cared?).

TWO 811A's should easily be driven by a 25w out exciter with a good
matching network between the amp and the exciter, it might be pushing it
to drive three (But you can get 35w pep out of a single 1625, or use two
of them in the final for 50w output in AB1).

BTW the 1625 used to be the last cheap final left. Fair Radio had new
ones for $4.50 up till last year. Now they only have used ones left for
$3.00. Everyone has discovered that 6159's are really 25v heater 6146's
and the price has jumped from a few bucks to the $18 range. The US made
811A's are drying up (and you have to be carefull of those Chinese
tubes, some are OK, others don't last long). I remember back in the
60's when BA was selling NOS surplus 1625's for $0.25 each! (Should
have bought several gross and put them in storage, but not on a
teenagers budget).



Not a full gallon, but the extra few db ain't worth the cost! I have
some 813's in the junkbox, but the sockets for them are costly, and they
have such HIGH output capacitance that making a good tank circuit in a
single ended amp is rather a pain. Still a grounded grid tetrode
circuit looks interresting! (cathode driven with normal g1 and g2 voltages).


I always thought the big advantage of GG was elimination of the need
for screen and bias supplies.


The 813 isn't such a great tube in pure GG. Most of the spec's I've
seen show it as only 200 watts or so output in GG. Problem is the tube
just doesn't have much power gain in GG. If you bias it as a tetrode
the power gain goes way up, you can still run it 'cathode driven' to
avoid neutralization though.