Older ARRL Handbooks
 

ken scharf wrote:
HERE'S the link http://www.io.com/~nielw/3tubrcvr/3tubrcvr.htm
Oh, nearly forgot....
With a little head scratching, you can replace the 6K8 with a 6u8, 6ea8,
6x8 (etc) triode/pentode. Use the pentode as the mixer and the triode
as the oscillator. In many cases the inter-electrode capacitance inside
the tube will provide enough coupling from the oscillator to the mixer,
but you might need to use a gimick capacitor (twisted wires) from the
pentode grid to the oscillator plate. Other tricks are to connect the
pentode screen to the oscillator plate, or in the case of the 6x8, the
pentode grid 3 to the oscillator grid.

The 6c8 may be replaced by ANY dual triode (such as 12au7, 12at7, 12ax7,
6sn7,6sl7, etc....)

I think we may be in business, here. Went through my selection of
tubes, and there's a 6X8 and a 12AX7A among them. Three other tubes
looked like they had promise - two 12AV6 and a 6BU6.

After I'm done with this post, I'm going to Google Images to see if I
do indeed have 2000 ohm headphones. I want to make sure, because
elsewhere I found a crystal shortwave radio that uses them as well.
That might serve my needs better, although it won't have those cool
glow in the dark tubes.


Ralph

Older ARRL Handbooks
 

After using Google images to track down pictures of 2000 ohm
headphones, I am satisfied that those are what I have. (Eight sets, in
fact.) Found out the one tube is a 6BJ6, not a 6BU6, but it does still
seem usable. Going to ask if I can make some trades with tubesandmore,
so I can find a good home for some of the headphones and possibly get
the tube sockets and transformers I need for my project.

Thanks again to everyone who has helped. Time for me to go do some
math. (Ugh!)


Ralph

Older ARRL Handbooks
 

Today, I am reminded that Google is my friend. After much digging and
prodding, I found what I was looking for. It seems the National SW-54
receiver is as close to what I want as possible without me having to do
math. It dates back to the 50's, uses tubes, (in fact, I already have
three of the five in it) covers a good amount of the SW band, and will
drive either my 2000 ohm headphones or a 4" speaker. BAMA had the
manual, but it wouldn't give it up, so I had to go to the mirror site
to get it. Everything I need is in it - schematics, parts list,
pictures of the assembled receiver. Not exactly the ideal radio for a
first try, but nothing good ever came easy, did it? ;-)

Thanks again to everyone who offered advice and suggestions. I'll be
sure to post when I have it together and let everyone know how I made
out.

Time to scrounge for parts.


Ralph

Older ARRL Handbooks
 

julian814 wrote:
After using Google images to track down pictures of 2000 ohm
headphones, I am satisfied that those are what I have. (Eight sets, in
fact.) Found out the one tube is a 6BJ6, not a 6BU6, but it does still
seem usable. Going to ask if I can make some trades with tubesandmore,
so I can find a good home for some of the headphones and possibly get
the tube sockets and transformers I need for my project.

Thanks again to everyone who has helped. Time for me to go do some
math. (Ugh!)


Ralph

You can just measure the resistance of the phones with an ohm meter.
The result will be close enough to the impedance (I think in the era
they were made they didn't even measure impedance, just the resistance).


Also, I have a lot's used 12au7's. If you need a few you can have some
for the cost of postage.

Older ARRL Handbooks
 

julian814 wrote:
Today, I am reminded that Google is my friend. After much digging and
prodding, I found what I was looking for. It seems the National SW-54
receiver is as close to what I want as possible without me having to do
math. It dates back to the 50's, uses tubes, (in fact, I already have
three of the five in it) covers a good amount of the SW band, and will
drive either my 2000 ohm headphones or a 4" speaker. BAMA had the
manual, but it wouldn't give it up, so I had to go to the mirror site
to get it. Everything I need is in it - schematics, parts list,
pictures of the assembled receiver. Not exactly the ideal radio for a
first try, but nothing good ever came easy, did it? ;-)

Thanks again to everyone who offered advice and suggestions. I'll be
sure to post when I have it together and let everyone know how I made
out.

Time to scrounge for parts.


Ralph

Ocean State electronics has EXACT replacement coil forms for the beast.
(sockets are another story!) They have NORMAL socket type plug in coil
forms too. (the national coil forms have different pin spacing than
standard tube socket type coils).

Older ARRL Handbooks
 

julian814 wrote:
Today, I am reminded that Google is my friend. After much digging and
prodding, I found what I was looking for. It seems the National SW-54
receiver is as close to what I want as possible without me having to do
math. It dates back to the 50's, uses tubes, (in fact, I already have
three of the five in it) covers a good amount of the SW band, and will
drive either my 2000 ohm headphones or a 4" speaker. BAMA had the
manual, but it wouldn't give it up, so I had to go to the mirror site
to get it. Everything I need is in it - schematics, parts list,
pictures of the assembled receiver. Not exactly the ideal radio for a
first try, but nothing good ever came easy, did it? ;-)

Thanks again to everyone who offered advice and suggestions. I'll be
sure to post when I have it together and let everyone know how I made
out.

Time to scrounge for parts.


Ralph

OPPS, I confused the sw-54 with the sw3-5 series.
This one is a "modern" superhet. Do you have the IF transformers, band
switch and coils?

I have a complete band switch and coil assembly from an old Lafayette
short wave receiver. It is a 4 band assembly with rf, osc, and mixer
coils intended for use with a 3 gang 365pf/section tuning capacitor.
I was thinking of using this in some project (that never happened), but
it sounds like just what you want. The coils have slug tuned tracking
adjustments, and the oscillator and mixer coils also have trimmer
capacitor tracking too.

If you can use this let me know.

Older ARRL Handbooks
 

ken scharf wrote:
julian814 wrote:
Today, I am reminded that Google is my friend. After much digging and
prodding, I found what I was looking for. It seems the National SW-54
receiver is as close to what I want as possible without me having to do
math. It dates back to the 50's, uses tubes, (in fact, I already have
three of the five in it) covers a good amount of the SW band, and will
drive either my 2000 ohm headphones or a 4" speaker. BAMA had the
manual, but it wouldn't give it up, so I had to go to the mirror site
to get it. Everything I need is in it - schematics, parts list,
pictures of the assembled receiver. Not exactly the ideal radio for a
first try, but nothing good ever came easy, did it? ;-)

Thanks again to everyone who offered advice and suggestions. I'll be
sure to post when I have it together and let everyone know how I made
out.

Time to scrounge for parts.


Ralph

OPPS, I confused the sw-54 with the sw3-5 series.
This one is a "modern" superhet. Do you have the IF transformers, band
switch and coils?

I have a complete band switch and coil assembly from an old Lafayette
short wave receiver. It is a 4 band assembly with rf, osc, and mixer
coils intended for use with a 3 gang 365pf/section tuning capacitor.
I was thinking of using this in some project (that never happened), but
it sounds like just what you want. The coils have slug tuned tracking
adjustments, and the oscillator and mixer coils also have trimmer
capacitor tracking too.

If you can use this let me know.

PS, if you use this you'll have to change the tube lineup to take full
advantage of all the coils. Replace the 50c5 with a 35c5 and add
another 12ba6 for an rf amplifier. Actually you should use all 6v tubes
and a power transformer. Those AC/DC sets are "undertakers labs"
approved shock hazards. An "isolation transformer will fix that of course."

The schematic of the receiver the coil switch assembly came from is here
http://bama.edebris.com/manuals/lafayett/ha700/

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I'm starting to think I should just settle for that crystal shortwave
set I found on the Antique Radio website. Less headaches.

No idea where to get the coils for the SW-54, so I guess that's out.
Besides, since this is my first real attempt at making a radio, I
should probably go for something simpler.

Going back to Google to see if I can find more on some of the tubes I
have. I keep thinking I should be able to make a regenerative receiver
with some amplification with the two 12AV6 tubes I have.

Ralph

Older ARRL Handbooks
 

Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

Older ARRL Handbooks
 

julian814 wrote:
Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

http://www.lindsaybks.com/bks/twin/index.html