"Dale Parfitt" wrote in message
news:FNl0e.16399$b_6.6287@trnddc01...
I had posted this elsewhere, and it has created some interesting feedback.
Based on Wes W7ZOI's Progressive RX from the late 1980's. A wonderfully
balanced design to which I added some bells and whistles I like in a
receiver.
These are some shots of my almost finished 1980's theme HF receiver.
All stainless hardware, teflon wiring. Rock stable VFO, homebrew xtal
filters ( 5/2/5/0.5), selectable and defeatable AGC, notch filter, tone
control, QSK input,built in front end BP filters for each band,
preselector,
AM/USB/LSB/CW.
Enjoy:
http://www.parelectronics.com/pics/W7ZOI11%20copy.jpg

http://www.parelectronics.com/pics/w7zoi13jpg.jpg

http://www.parelectronics.com/pics/w7zoi14.jpg

http://www.parelectronics.com/pics/w7zoi15.jpg

Dale W4OP
for PAR Electronics, Inc.

Dale -

Very nice. Looks like you built the RX .. that I am still designing since
1980 and reading Wes' articles. :-)

I see you used a 9 MHz IF.
Any particular reason that you used separate (LO) oscillators for each band
(rather than a single oscillator with switchable crystals) ?

The cabinet look a bit like some LMB enclosures.

Greg
w9gb

"gb" wrote in message
...
"Dale Parfitt" wrote in message
news:FNl0e.16399$b_6.6287@trnddc01...
I had posted this elsewhere, and it has created some interesting
feedback.
Based on Wes W7ZOI's Progressive RX from the late 1980's. A wonderfully
balanced design to which I added some bells and whistles I like in a
receiver.
These are some shots of my almost finished 1980's theme HF receiver.
All stainless hardware, teflon wiring. Rock stable VFO, homebrew xtal
filters ( 5/2/5/0.5), selectable and defeatable AGC, notch filter, tone
control, QSK input,built in front end BP filters for each band,
preselector,
AM/USB/LSB/CW.
Enjoy:
http://www.parelectronics.com/pics/W7ZOI11%20copy.jpg

http://www.parelectronics.com/pics/w7zoi13jpg.jpg

http://www.parelectronics.com/pics/w7zoi14.jpg

http://www.parelectronics.com/pics/w7zoi15.jpg

Dale W4OP
for PAR Electronics, Inc.

Dale -

Very nice. Looks like you built the RX .. that I am still designing since
1980 and reading Wes' articles. :-)

I see you used a 9 MHz IF.
Any particular reason that you used separate (LO) oscillators for each
band
(rather than a single oscillator with switchable crystals) ?

The cabinet look a bit like some LMB enclosures.

Greg
w9gb

Hi Greg,
I did not deviate a lot from Wes's original PR design- and that used a 9 MHz
IF. I also had a bunch of xtals for the filters- so just stuck with it. It
also allowed the 49M LO to double as the 160M L.O.
F.A.R. circuits had the L.O. boards already made up, so I went with that. No
reason I suppose, if one had an osc. that would paly well over the entire
range w/ good spectral purity that a single L.O. and PIN diodes could not be
used for switching. Would have saved on some SMA connex!
The side rails and cabinet, and matching speaker cabinet (not shown) are
from a junker SB-303 I found on E Bay ( have another for the mating TX once
I recover). All the rest- front panel, subchassis, rear panel awere done in
my machine shop.
I know of the LMB you are talking about - nice stuff, but hard to come by in
larger sizes these days I suppose.
They were steel I thnk, whereas the Heath stuff is aluminum which I find a
lot easier to machine.
Dale W4OP

"gb" ) writes:


I see you used a 9 MHz IF.
Any particular reason that you used separate (LO) oscillators for each band
(rather than a single oscillator with switchable crystals) ?

Surely because it works out to be simpler.

People often make the mistake that extra circuitry is bad because it
complicates things, but the reality is often that extra circuitry simplifies
things.

Back in the days of tubes, their bulk and filament current (or slow
startup if you switch the filament) meant that one did give thought
before adding another tube. It probably was simpler to switch crystals
than switch oscillators, and compared to the cost of tubes and sockets,
the switch was relatively cheap.

Once transistors came along, their size, low current and instant on
meant the game changed. If adding another transistor in an IF stage
meant that all the stages were running at a lower level, better to
do. It added little to the cost, and pretty much nothing to the current
drain.

If you switch crystals, you limit layout. You need that switch near
the crystals (and in some cases may need two poles per position), or
you need to use relays (I've seen it done in mods to tube equipment)
or diode switches. Those diodes can often cause some problems, depending
on choice and useage. Switching crystal oscillators means none of this
applies, and the cost of the transistor and passive components is
nothing compared to the cost of the crystal.

This is a theme of some of Hayward's work. Various times, he's described
transceivers, and not only is he using separate IF strips for receive
and transmit, but he's got a separate IF filter for each function. His
reasoning is that it makes the chain cleaner by not having the switching.
Given the cost of commercial filters, I'm not sure that's the best choice,
but certainly there is a tradeoff. If adding a few dollars for an extra
RF stage rather than switching tuned circuits requires a cheaper switch,
or makes it easier to do the switching, it may be worth spending those
few dollars rather than fuss too much.

Jerry Vogt (I"ve spelled that wrong) who seemed to be connected
with Hamtronics (at least, he wrote about their stuff for Ham Radio magazine)
pointed out in an article about preamps that a manufacturer needs to
cut costs. They skimp on parts because any single part saved is
multiplied by the number of units built. But a hobbyist building a single
unit doesn't have that multiplier. If they toss in an extra bypass
capacitor here, or build each stage into a metal box for shielding,
the cost is right there. They don't have to worry about 10,000 more
capacitors, or whatever.

Michael VE2BVW

That's very well said!

The "optimum" design is, as you say, very much a matter of the
particular situation. In my career doing circuit design, I've worked for
a company where products were custom or nearly custom -- a production
run of 10 was a big deal. In that situation, if I could save half an
hour of design time by using a $20 part instead of a $5 part, it was a
very good trade. I've also designed a product for a mass near-consumer
market. There, a week of extra work spent in getting a few pennies out
of the production cost was worthwhile. We all have to remember that:

1. There's no one best way for everybody, every project, or every market
or situation.
2. What's best for the mass manufacturers, or for that matter another
homebrewer, isn't necessarily the best for us.
3. The best way to do a design is constantly changing, as both techology
and our own situations (e.g., the amount of time and money we have) keep
changing.

Design is a creative process, and there's a lot of art as well as skill
in it. Finding a better way to do something requires both, and knowing
the appropriate time to declare it "good enough" requires art, skill,
and discipline too.

Roy Lewallen, W7EL

Michael Black wrote:

"gb" ) writes:



I see you used a 9 MHz IF.
Any particular reason that you used separate (LO) oscillators for each band
(rather than a single oscillator with switchable crystals) ?


Surely because it works out to be simpler.

People often make the mistake that extra circuitry is bad because it
complicates things, but the reality is often that extra circuitry simplifies
things.

Back in the days of tubes, their bulk and filament current (or slow
startup if you switch the filament) meant that one did give thought
before adding another tube. It probably was simpler to switch crystals
than switch oscillators, and compared to the cost of tubes and sockets,
the switch was relatively cheap.

Once transistors came along, their size, low current and instant on
meant the game changed. If adding another transistor in an IF stage
meant that all the stages were running at a lower level, better to
do. It added little to the cost, and pretty much nothing to the current
drain.

If you switch crystals, you limit layout. You need that switch near
the crystals (and in some cases may need two poles per position), or
you need to use relays (I've seen it done in mods to tube equipment)
or diode switches. Those diodes can often cause some problems, depending
on choice and useage. Switching crystal oscillators means none of this
applies, and the cost of the transistor and passive components is
nothing compared to the cost of the crystal.

This is a theme of some of Hayward's work. Various times, he's described
transceivers, and not only is he using separate IF strips for receive
and transmit, but he's got a separate IF filter for each function. His
reasoning is that it makes the chain cleaner by not having the switching.
Given the cost of commercial filters, I'm not sure that's the best choice,
but certainly there is a tradeoff. If adding a few dollars for an extra
RF stage rather than switching tuned circuits requires a cheaper switch,
or makes it easier to do the switching, it may be worth spending those
few dollars rather than fuss too much.

Jerry Vogt (I"ve spelled that wrong) who seemed to be connected
with Hamtronics (at least, he wrote about their stuff for Ham Radio magazine)
pointed out in an article about preamps that a manufacturer needs to
cut costs. They skimp on parts because any single part saved is
multiplied by the number of units built. But a hobbyist building a single
unit doesn't have that multiplier. If they toss in an extra bypass
capacitor here, or build each stage into a metal box for shielding,
the cost is right there. They don't have to worry about 10,000 more
capacitors, or whatever.

Michael VE2BVW