I saw an eBay listing for a Lear ADF. It looked surprisingly like a Bendix
T-12B, also known as an ADF-201B. This particular model has the tuning dial
right in the center of the front panel, and it is a solid state unit. The
only difference it that the Bendix unit uses a 140kHz I.F. I do have service
information for this model.

Pete

"elaich" wrote in message ...
Does anybody know of a small, easy to obtain receiver that can receive 85
kcs? Tube type, surplus OK.

I have an old Lear ADF that was cut out of a plane decades ago. The cables
were whacked off, and I can't find a schematic. Someone did send me a
schematic of a set very close in model to the one I have, so I do have
that. However, most of the circuitry in the radio is dedicated to the DF
capacity, which I don't need or want. There are three subchassis, and
probably 15 tubes.

I want to use the small tuning head, which has an 85 kcs IF output, to
feed
something like a Q-5er that would serve as IF and audio.

If I can't find one, I have an R-11a that I could feed the tuning head
output into it's IF strip.

I'm trying to kludge up a homebrew longwave/BCB DX rig.

Uh, oh..........we are talking about a different radio than the Bendix unit.


"elaich" wrote in message ...
Registered User wrote in
:

An alternative to rewiring the filaments is to build a power supply
using a 24 V transformer. My Q5-er supply uses back-to-back 25.2V
transformers to feed the rectifier/filter circuit. The filament
voltage is taken from between the two transformers. A 6.3-0-6.3V
transformer supplies 6 & 12 volts.

If I'm going to use the remote rotatble ferrite bar antenna (and I
definitely want to) I'm going to need 28 VAC 400 Hz. Does anybody know of
a
schematic for an oscillator circuit? I looked online and couldn't find
anything.

elaich wrote:


I'm going to use the Lear tuning head to feed the 85 kc IF of the R-11a. My
big problem will be voltages. The R-11 uses 14 volt tubes, wired in series
pairs. That was for the plane's 28 volt system. I'll have to rewire them in
parallel and feed them 12 volts. I haven't looked at the Lear yet, but it
probably uses the same idea.



The ARC book shows the 12-24 volt re-wire options. The Type 12 system,
of which all that series is part of, was designed for both voltages.
Its not difficult, at all, to swap a few wires to change the voltage.
If you need the sheet, I think I can scan it into a TIF.

de K3HVG

Pete KE9OA wrote:
I saw an eBay listing for a Lear ADF. It looked surprisingly like a Bendix
T-12B, also known as an ADF-201B. This particular model has the tuning dial
right in the center of the front panel, and it is a solid state unit. The
only difference it that the Bendix unit uses a 140kHz I.F. I do have service
information for this model.



If the folklore passed on to me in about 1965 is correct, Motorola
bought the Lear ADF design and made it the ADF-12. Bendix got the
design from Motorola and came out with the ADF-T12-series. There
certainly are striking similarities as one might expect. Tye worst of
the lot is/was the synthesized ADT-T12D. It is an abomination. We took
the "D" out of our aircraft and re-installed a "C" model.

de K3HVG
also: N95JP

I've seen HRO's for less than $50.00 at hamfest without coils! The VLF
coil might be hard to find but you'd end up with less stuff and less
work!

--

73
Hank WD5JFR
"elaich" wrote in message
...
"Henry Kolesnik" wrote in
news:qK0Lk.5910
:

An HRO 7 will tune down to 50 Kc with the proper coil set and I'd
guess
that some of the other HROs will too!

Jeez, if I had an HRO 7, I wouldn't need to do this to begin with!
LOL!

I'm going to use the Lear tuning head to feed the 85 kc IF of the
R-11a. My
big problem will be voltages. The R-11 uses 14 volt tubes, wired in
series
pairs. That was for the plane's 28 volt system. I'll have to rewire
them in
parallel and feed them 12 volts. I haven't looked at the Lear yet, but
it
probably uses the same idea.

Weren't R-11's fairly common? A Google search turns up only one page
on the
entire Internet that even mentions them. There are a couple of the
Lear
tuning heads on eBay. That surprised me.

"Henry Kolesnik" wrote in message
...
I've seen HRO's for less than $50.00 at hamfest without coils! The VLF
coil might be hard to find but you'd end up with less stuff and less work!

--

73
Hank WD5JFR

Hi Hank. You're right, but I've never seen a set of LF coils for the HRO
despite seeing (and owning) several HRO's. Then you need to factor in the
expense of the additional room you have to build to house the thing, seems
terribly expensive to go to all that trouble to replace a DBM, a low pass
filter and a one transistor crystal oscillator to build an up converter. Use
whatever you've got for the IF.

W4ZCB

Hi Harold
My way is travelling a random path and finding whatever is fast, cheap
and available because if I look too long the urge soon goes away. There
are too many distractions along the path, and at times create a greater
urge. So one has to drop the lesser urge and pursue the greater urge.
It too, can be sidelined.
Another options is a frequency selective voltmeter, they used to be real
cheap but now not so because I think the VLFers have their eyes on them.
I still see the odd one at hamfests for about $20.00.
Yes I agree that a transistor osc. or a 6BE6 would do the trick.
I kept one HRO for sentimental reasons and to waste gravity and
somewhere in a box I have stored some odd ball coils. I'll have to see
if I have LF. I might because interest in LF and VLF is one of my
chronic diseases that is currently in remission.

--

73
Hank WD5JFR
"Harold E. Johnson" wrote in message
news:y1lLk.343105$TT4.248866@attbi_s22...

"Henry Kolesnik" wrote in message
...
I've seen HRO's for less than $50.00 at hamfest without coils! The
VLF
coil might be hard to find but you'd end up with less stuff and less
work!

--

73
Hank WD5JFR

Hi Hank. You're right, but I've never seen a set of LF coils for the
HRO
despite seeing (and owning) several HRO's. Then you need to factor in
the
expense of the additional room you have to build to house the thing,
seems
terribly expensive to go to all that trouble to replace a DBM, a low
pass
filter and a one transistor crystal oscillator to build an up
converter. Use
whatever you've got for the IF.

W4ZCB

Another options is a frequency selective voltmeter, they used to be real
cheap but now not so because I think the VLFers have their eyes on them. I
still see the odd one at hamfests for about $20.00.

WOW! I have a HP-312/313 pair that I paid a couple hundred for, but I
wouldn't let them go for twice that.

Yes I agree that a transistor osc. or a 6BE6 would do the trick.
I kept one HRO for sentimental reasons and to waste gravity and somewhere
in a box I have stored some odd ball coils. I'll have to see if I have
LF. I might because interest in LF and VLF is one of my chronic diseases
that is currently in remission.

If I want to use WWVB, I can use the 312 (With a surplus filter to keep the
59 KHz from the video monitor 2 floors away out of it) or a little TRF/PLL
RX I built for that maybe 20 years ago. Interestingly, my loop, (100 turns
on a 32 inch bicycle rim) resonates at 60 KHz with a big ARCO trimmer, but
resonates right at 24 KHz for NAA with just a alligator clipped on 1890 pF
silver mica. I monitor that with a simple DBM/crystal oscillator (with a 96
KHz oscillator and a divide x 4 74AC74). Lots of signal. I used to monitor
with an old Rustrak paper tape recorder, but a few years back, Radio Shack
had a special on for Metex Voltmeters that had an RS-232 output and a piece
of software that would send a reading to a file on the computer. Now I just
throw away the parts of the file that are uninteresting and save the SID's.

Interesting part of the spectrum, I also did a BC-453 conversion solid state
and to 136 KHz several years back, that was a learning experience but not
terribly interesting.
W4ZCB

Harold E. Johnson wrote:

Hi Hank. You're right, but I've never seen a set of LF coils for the HRO
despite seeing (and owning) several HRO's. Then you need to factor in the
expense of the additional room you have to build to house the thing, seems
terribly expensive to go to all that trouble to replace a DBM, a low pass
filter and a one transistor crystal oscillator to build an up converter. Use
whatever you've got for the IF.

Making coils for the HRO is not too big a deal as long as you don't need them
to look original.
---scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

That explains why the old T-12B that I had was a Motorola unit. All of the
T-12Cs (I have five of them) are Bendix units. I did have a T-12D a while
back. What a brick! I bought it, along with a batch of KR-85s from one of
the local airports. I kept only one of the
KR-85s.........not a bad radio, but those bandswitches take a bit of time to
clean.

Pete

"k3hvg" wrote in message
...
Pete KE9OA wrote:
I saw an eBay listing for a Lear ADF. It looked surprisingly like a
Bendix T-12B, also known as an ADF-201B. This particular model has the
tuning dial right in the center of the front panel, and it is a solid
state unit. The only difference it that the Bendix unit uses a 140kHz
I.F. I do have service information for this model.



If the folklore passed on to me in about 1965 is correct, Motorola bought
the Lear ADF design and made it the ADF-12. Bendix got the design from
Motorola and came out with the ADF-T12-series. There certainly are
striking similarities as one might expect. Tye worst of the lot is/was the
synthesized ADT-T12D. It is an abomination. We took the "D" out of our
aircraft and re-installed a "C" model.

de K3HVG
also: N95JP