Looking for a nice superhet Rx design for 75M/40M, using 12V fil. &
plate tubes. Not needing anything fancy, schematic and any addional info
appreciated, if anyone can point me to this. Thanks.


Ed K7AAT

Ed wrote:

Looking for a nice superhet Rx design for 75M/40M, using 12V fil. &
plate tubes. Not needing anything fancy, schematic and any addional info
appreciated, if anyone can point me to this. Thanks.


Ed K7AAT

Try some of the links found he

http://www.duntemann.com/12vtubes/12vtubesindex.htm

-Bill

Looking for a nice superhet Rx design for 75M/40M, using 12V fil.
&
plate tubes. Not needing anything fancy, schematic and any addional
info appreciated, if anyone can point me to this. Thanks.


Ed K7AAT


Try some of the links found he

http://www.duntemann.com/12vtubes/12vtubesindex.htm

-Bill


Thanks, Bill. I can't find any good info on an HF superhet circuit,
but there's lots of good info on that site, anyway. Appreciate it.



Ed

The site does have reference to a superhet.

Colin K7FM

"COLIN LAMB" wrote in news:Eqque.8243$jX6.7991
@newsread2.news.pas.earthlink.net:

The site does have reference to a superhet.

Colin K7FM




Yes, I saw the Japanese site.... had an FM/AM broadcast radio circuit.
I suppose I could work with their circuits, but I was looking for a design
that was already closer to my needs (CW detection). Another reference to
"superhet" circuit was a dead link, for me. It looks like my best chance
to find what I'm looking for is to try to find those back issues of QST
which were referenced.


Ed

Ed wrote:

Looking for a nice superhet Rx design for 75M/40M, using 12V fil. &
plate tubes. Not needing anything fancy, schematic and any addional info
appreciated, if anyone can point me to this. Thanks.

My suggestion is that you get out the Sam's Photofacts book on car radios
and look at some of the vibrator-free tube car radio designs. It should
not be too hard to change the loopstick and/or tuning cap for 75M and 40M.

The problem you'll have is that the IF is wide as hell, but that's part
of the fun. Be sure to add a BFO!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
Ed wrote:

Looking for a nice superhet Rx design for 75M/40M, using 12V fil. &
plate tubes. Not needing anything fancy, schematic and any addional info
appreciated, if anyone can point me to this. Thanks.


My suggestion is that you get out the Sam's Photofacts book on car radios
and look at some of the vibrator-free tube car radio designs. It should
not be too hard to change the loopstick and/or tuning cap for 75M and 40M.

The problem you'll have is that the IF is wide as hell, but that's part
of the fun. Be sure to add a BFO!
--scott

12V plate tubes are rather rare, perform poorly compared to most anything else.
They are very low power, low gain, and low frequency. Typical amplification
factor is 10 or less. With the exception of the R392, which used 28V tubes,
and some automobile radios from the late '50s to early '60s, I don't recall that
they were used for much of anything... which is why they are rare.

There were a whole pile of different types made, pentagrid converters, sharp and
remote cutoff pentodes, triodes with diodes, pentodes with diodes, twin triodes,
.... the most amusing thing was the "power" tubes that had maximum output ratings
of 20mw!

The typical automobile radio used the following tube lineup:

RF: 12AF6 - Sharp cutoff pentode
Mixer: 12AD6 - Pentagrid converter
IF: 12AF6 - Sharp cutoff pentode
Det/AGC/1st audio: 12AE6 or 12AJ6 - medium mu triode/ twin diode
Audio amp: DS-501 Delco Germanium PNP transistor.

In a car radio, the RF/Mix/LO was tuned by a very fancy rig that moved the
slugs in the coils. The IF was 256KHz, with a 4KHz bandwidth...Real Hi-Fi!

Somewhere in my archives I have a Sams Photofact for the 12V tube radio that
is in my '60 'vette. By 1960, all transistor car radios were already
on the scene in Corvettes and Cadillacs.

In the R392, the 28V tubes in the RF section are generally bad, and kill
the sensitivity of the radio above 14MHz.

Is there a particular reason that you want to use this style of tube?

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

-Chuck

Chuck Harris wrote:

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

--
Ah, yes, _The Dying Earth_: a wonderful title, greatly spoiled by the
book.

-- Nix, in a newsgroup inhabited by a better class of people

"Mike Andrews" ) writes:
Chuck Harris wrote:

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

But given the topic, I'm always surprised that people don't treat switching
supplies like those cars of old. Look in the old ARRL mobile manual (and
a later edition just might have a receiver using those 12v tubes), and
there was always material about filtering the alternator noise.

Make it go through feedthrough capacitors, put in tuned circuits in
series with the 12V (to null out the whine), and good shielding. These
are the things that apply to switching supplies, though too often they
are so treated as black boxes that nobody considers such things.

As for 12v tubes, you most certainly saw converter using them. SOmeone
was asking about 12v Nuvistors a while back, and the next to last edition
of the ARRL VHF Manual, late sixties or so, has a converter using one.


Michael

Michael Black wrote:

As for 12v tubes, you most certainly saw converter using them. SOmeone
was asking about 12v Nuvistors a while back, and the next to last edition
of the ARRL VHF Manual, late sixties or so, has a converter using one.

We are not talking about normal radio tubes that have 12V heaters, we are
talking about special tubes that have 12V heaters, and a 30V maximum plate
voltage rating. These special tubes were designed to use normal car battery
voltages as their plate voltages.

-Chuck