Nomad wrote:
Actually the Collins designed R-388/51J series of receivers was a
predecessor design to the Collins designed R390A. See:

http://www.r-390a.net/


I had a 51J-3 & sold it because it was not in the same league as my
R390A. IMHO, my HRO's, Hammarlund Super Pro & Drakes all outperformed
the 51J by considerable margins.

The 51J is a good looking radio though. But IMO the performance doesn't
live up to the looks & the mistique.


I am curious what you found lacking in the 51J compared to the
other receivers?
--
Richard Knoppow
Los Angeles

Chuck Harris wrote:

What you could do, is put some of your favorite diodes in a metal can,
and install them after your radio has died from EMP. Something which
will never happen anyway.

Probably not due to nuclear effects, but I have sadly seen lots of radio
gear destroyed by RF on grounds from nearby transmitters when antenna lines
failed. Not to mention my personal favorite, the radar that wasn't supposed
to be pointed toward the radio shack. The R-390 wouldn't be damaged by
that... hell, the front end probably wouldn't even overload....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Richard Knoppow wrote:

I am curious what you found lacking in the 51J compared to the
other receivers?

Selectivity. The crystal filter really stinks, compared with the Collins
mechanical filters.

I had a 51J for a few years and traded it up for an R-390. Ergonomically
I liked the sliderule tuning on the 51J more, and the audio quality was
better, but the mechanical filters on the R-390 were a lifesaver.
--scott

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

On 1/9/07 6:58 AM, in article , "Scott Dorsey"
wrote:

Richard Knoppow wrote:

I am curious what you found lacking in the 51J compared to the
other receivers?

I had the experience of using a new 51J4 along side a new TMC GPR90 in the
late 50's. I loved them both, but I always had better ability to pull out a
readable signal with the GPR90. For specific meet schedules I always
started with the 51J4, because of it's freq accuracy. These were used for
both the ham bands, and for commercial service. We also had the best of
test equipment, so I did run s/n tests on them. I don't recall the numbers,
but the GPR90 was better. Just as I love the SX28 for it's looks and
warmth, I loved the GPR90 for it's. With room lights turned down, it was a
beauty. The 51J4 is cold.

Just FYI, I also had full-time use of a new TMC GPT750 transmitter. There
was nothing not to love about it, either. My little CE 10B could easily
drive it to the max, but I preferred to run it barefoot.

Don


Selectivity. The crystal filter really stinks, compared with the Collins
mechanical filters.

I had a 51J for a few years and traded it up for an R-390. Ergonomically
I liked the sliderule tuning on the 51J more, and the audio quality was
better, but the mechanical filters on the R-390 were a lifesaver.
--scott

On 8 Jan 2007 15:28:36 -0500, Scott Dorsey wrote:
Stan Barr wrote:

Yeah, true. I regularly transmit on, say, 3.5MHz while one of the receivers
is tuned to Shanwick AT control on 5.599 without any problem, but then
that's a bigger separation and I'm only running a few watts normally.

That brings to mind... I have been listening to Shanwick weather recently,
just below 80M. Do they welcome reception reports?

I don't know, but I imagine they get a few. They probably have a
website.



--
Cheers,
Stan Barr stanb .at. dial .dot. pipex .dot. com
(Remove any digits from the addresses when mailing me.)

The future was never like this!

On Mon, 08 Jan 2007 17:10:25 -0500, Chuck Harris
wrote:
Scott Dorsey wrote:
In article ,

Any reason why a 1N4007 wouldn't be happy in there?

Well, yes. When functioning as a demodulator, the diodes take the
IF frequency (455KHz), and the BFO frequency (453.65/456.35KHz), and
make audio. When functioning as a modulator, the diodes take the
audio, and the BFO frequency, and make modulated IF.

A 1N4007 cannot switch at even audio rates, let alone at 455KHz.

You could always try a "vaccuum state" diode such as a 6AL5...

--
Cheers,
Stan Barr stanb .at. dial .dot. pipex .dot. com
(Remove any digits from the addresses when mailing me.)

The future was never like this!

Stan Barr ) writes:
On Mon, 08 Jan 2007 17:10:25 -0500, Chuck Harris
wrote:
Scott Dorsey wrote:
In article ,

Any reason why a 1N4007 wouldn't be happy in there?

Well, yes. When functioning as a demodulator, the diodes take the
IF frequency (455KHz), and the BFO frequency (453.65/456.35KHz), and
make audio. When functioning as a modulator, the diodes take the
audio, and the BFO frequency, and make modulated IF.

A 1N4007 cannot switch at even audio rates, let alone at 455KHz.

You could always try a "vaccuum state" diode such as a 6AL5...

Of course, Collins likely had a good reason for using solid state
diodes there.

Far lower current consumption would be one thing.

The semiconductor diodes also make it smaller.

But also balance. I'm sure it's far easier to keep a balanced modulator
balanced when using semiconductor diodes than two tubes each supplying
two diodes.

Michael VE2BVW

On 1/9/07 10:32 AM, in article
l, "Stan Barr"
wrote:

On Mon, 08 Jan 2007 17:10:25 -0500, Chuck Harris
wrote:
Scott Dorsey wrote:
In article ,

Any reason why a 1N4007 wouldn't be happy in there?

Well, yes. When functioning as a demodulator, the diodes take the

Splitting hairs, if the diodes were in a ckt such as a "ring modulator"
where they functioned as a product detector, then they *were* a demodulator,
but most diode detectors were just envelope detectors.


IF frequency (455KHz), and the BFO frequency (453.65/456.35KHz), and
make audio. When functioning as a modulator, the diodes take the
audio, and the BFO frequency, and make modulated IF.

A 1N4007 cannot switch at even audio rates, let alone at 455KHz.

You could always try a "vaccuum state" diode such as a 6AL5...

On 1/9/07 10:44 AM, in article , "Michael Black"
wrote:

Stan Barr ) writes:
On Mon, 08 Jan 2007 17:10:25 -0500, Chuck Harris

wrote:
Scott Dorsey wrote:
In article ,

Any reason why a 1N4007 wouldn't be happy in there?

Well, yes. When functioning as a demodulator, the diodes take the
IF frequency (455KHz), and the BFO frequency (453.65/456.35KHz), and
make audio. When functioning as a modulator, the diodes take the
audio, and the BFO frequency, and make modulated IF.

A 1N4007 cannot switch at even audio rates, let alone at 455KHz.

You could always try a "vaccuum state" diode such as a 6AL5...

Of course, Collins likely had a good reason for using solid state
diodes there.

Far lower current consumption would be one thing.

The semiconductor diodes also make it smaller.

But also balance. I'm sure it's far easier to keep a balanced modulator
balanced when using semiconductor diodes than two tubes each supplying
two diodes.

Michael VE2BVW



If you were to use any tubes at all, it would be best to use one tube akin
to the 6be6, hang the oscillator and the product detector ckts on it, and
have the advantage of getting conversion gain instead of loss.

Don

Don Bowey wrote:
On 1/9/07 10:32 AM, in article
l, "Stan Barr"
wrote:

On Mon, 08 Jan 2007 17:10:25 -0500, Chuck Harris
wrote:
Scott Dorsey wrote:
In article ,
Any reason why a 1N4007 wouldn't be happy in there?
Well, yes. When functioning as a demodulator, the diodes take the

Splitting hairs, if the diodes were in a ckt such as a "ring modulator"
where they functioned as a product detector, then they *were* a demodulator,
but most diode detectors were just envelope detectors.

How so? The diodes in a KWM2/2A are used as a ring modulator, and
work just as I described below. A 1N4007 would not be capable of
working that way at 455KHz.



IF frequency (455KHz), and the BFO frequency (453.65/456.35KHz), and
make audio. When functioning as a modulator, the diodes take the
audio, and the BFO frequency, and make modulated IF.

A 1N4007 cannot switch at even audio rates, let alone at 455KHz.
You could always try a "vaccuum state" diode such as a 6AL5...