C. J. Clegg wrote:
I need something that can be used on certain military HF networks outside
the amateur bands. I have been told that (for some goofball reason) I'm
not allowed to say exactly which networks, but it isn't anything that
would be particularly hard to guess if anyone cared to give it a few
minutes of thought. :-)

Skip the receiver and get a KWM-2. Receive performance is not as good
as the R-390, but it will work fine out of band (they used to be the standard
State Department issue rigs at foreign embassies) and they are a lot easier
to work on. Also, it's a lot more convenient to use.

When that happens, much of the solid state gear (radios, computers, cell
phones, the Internet, packet BBSs, etc.) within a fairly large radius of
ground zero will be reduced to doorstops and paperweights.

Note that a lot of the newer solid-state military gear was designed with
EMP-hardening in mind. You can look for something like the Trans-World
sets (which replaced the KWM-2 at embassies) for example.

Of course, that begs the question of how I'm going to power the damn thing
if commercial power is down, but I guess I'll have to, as they say, jump
off of that bridge when I come to it.

I would worry more about long-term maintenance. The R-390A is a wonderful
rig and a great performer but I would not want to have to work on one.
--scott

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

Scott Dorsey wrote:
C. J. Clegg wrote:
I need something that can be used on certain military HF networks outside
the amateur bands. I have been told that (for some goofball reason) I'm
not allowed to say exactly which networks, but it isn't anything that
would be particularly hard to guess if anyone cared to give it a few
minutes of thought. :-)

Skip the receiver and get a KWM-2. Receive performance is not as good
as the R-390, but it will work fine out of band (they used to be the standard
State Department issue rigs at foreign embassies) and they are a lot easier
to work on. Also, it's a lot more convenient to use.

Yes, it is, but it has a point contact diode balanced modulator/demodulator.
EMP would kill one in a heartbeat.

-Chuck

In article ,
Chuck Harris wrote:
Scott Dorsey wrote:
C. J. Clegg wrote:
I need something that can be used on certain military HF networks outside
the amateur bands. I have been told that (for some goofball reason) I'm
not allowed to say exactly which networks, but it isn't anything that
would be particularly hard to guess if anyone cared to give it a few
minutes of thought. :-)

Skip the receiver and get a KWM-2. Receive performance is not as good
as the R-390, but it will work fine out of band (they used to be the standard
State Department issue rigs at foreign embassies) and they are a lot easier
to work on. Also, it's a lot more convenient to use.

Yes, it is, but it has a point contact diode balanced modulator/demodulator.
EMP would kill one in a heartbeat.

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

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

Scott Dorsey wrote:
In article ,
Chuck Harris wrote:
Scott Dorsey wrote:
C. J. Clegg wrote:
I need something that can be used on certain military HF networks outside
the amateur bands. I have been told that (for some goofball reason) I'm
not allowed to say exactly which networks, but it isn't anything that
would be particularly hard to guess if anyone cared to give it a few
minutes of thought. :-)
Skip the receiver and get a KWM-2. Receive performance is not as good
as the R-390, but it will work fine out of band (they used to be the standard
State Department issue rigs at foreign embassies) and they are a lot easier
to work on. Also, it's a lot more convenient to use.
Yes, it is, but it has a point contact diode balanced modulator/demodulator.
EMP would kill one in a heartbeat.

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.

-Chuck

Chuck Harris wrote:

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.

Okay, so we need a fast Schottky diode, with outrageously high breakdown
voltage. Something like that has to be out there, right?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
Chuck Harris wrote:
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.

Okay, so we need a fast Schottky diode, with outrageously high breakdown
voltage. Something like that has to be out there, right?
--scott

Shottky, and outrageously high breakdown voltage don't go together.

What you think of as a normal diode is a slab of P, and a slab of N
semiconductor bonded together to form a junction. A shottky diode
is a slab of N semiconductor fused to a piece of metal. 100V is a
really high voltage for a shottky diode.

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.

-Chuck

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."

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 10:44 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