N2EY:

First, you can run duplex, simply use two modems and a separate
transmitter and receiver. The second modem can be a USR internal if
you don't have two serial ports for externals.

To run duplex with one modem, there is some kind of patch device they
used to keep the receiver output from getting on the mic input of the
transmitter (but the modem had simultaneous access to both)--and for
the life of me, I can't remember what it was called, first time I had
ever seen one. When I get a chance, I will ask about it. You might
know what it is/was?

Second, it works, build one--or--draw it on paper and decide it does
not work.

I am on to other things, I got tired of webcams years ago. Don't even
video chat on irc, MSN Messenger, ICQ messenger or yahoo messenger
much anymore. And that is much easier than "Mac Amateur IM."

I can tell, this argument will shortly switch to rules and
regulations, it always does, and I have no interest in having such
recited to me. Expect only my bad nature in return.

I didn't do the hardware or even know the "true nature" of the signal
which comes out of that modem and hits the phone line or a mike in. I
just toyed with the software and watched it work--it "lived" in my
garage for a year or so.

I am into my "universal translator" these days and trying to set up to
chat fluently with the russians...

I think the russian girls are kind of cute... grin

John

wrote in message
oups.com...

John Smith wrote:
Dee:

Will you agree that a 56K phone modem, does indeed, transmit this
data
rate with an audio bandwidth of ~300Hz to ~5000K, and if you do so
agree, how can you argue this cannot fit in a HF AM RF signal which
only goes 2.5K each side of center frequency??????????

Of course it can.

The question is whether the RF path will have characteristics
comparable to those of the telephone line.

Are you NOT imposing an audio frequency of AT LEAST a 5K bandwidth
on
the rf carrier with normal speech?

No. Typical ham transceivers only need about 2.5 kHz of audio
bandwidth.

(actually, most quality
transceivers have a wider audio bandwidth than this which can be
set
+/-) and if you agree you are indeed, how can you argue that 5K
bandwidth can carry a 56K data rate over a phone line--and NOT a hf
rf
signal???? That looks insane to me?

It's a question of the characteristics of the RF path. Certainly
there
are some paths that will support the amplitude- and phase- stable
requirements of the 56K modem - and some paths that won't.

On top of that is the fact that most RF paths aren't full duplex.
How
fast is the 56K modem in half-duplex with transmit-receive
switching?

The modem is NOT using the whole 5K bandwidth--necessarily, there
is
compression into a narrower bandwidth which can and is generally
software controlled--if necessary (the modems software is a LOT
smarter than most give it credit for, especially in the case of the
old "onboard processor" and "hardware logic" USRobotics external
modems.

You need to explain to me why it even begins to look difficult to
you
for me to be able to understand what you are asking?

As, I have to be missing something here...

You are. Do you think HF offers the same transmission
characteristics
as a telephone line?

You know, I have not even looked to see on the web, but aren't tons
of
people doing this right now as we newsgroup?

On telephone wires or HF radio?

I suppose you could actually use the rf signal as data carrier
itself
and modulate it directly through on/off switching, as opposed to
modulating the rf carrier with the audio data carrier... but that
would take some heavy duty equip mods/revamps, if it didn't wipe
out
the neighbors cable tv! grin

Think about this:
at 100 mhz if you can precisely control the EXACT amplitude of each
and every cycle of rf out the back end of the xmitter, you have a
virtual 100mbs data carrier... most are working here... 450 MHz?
1Ghz? 12Ghz?

Think about the stability of the RF path at HF.

... and of course, the receiver has to be able to decipher the
amplitudes of each cycle back to a data stream for the video
card...

... this is the land where dreamers are...

John

"Dee Flint" wrote in message
...

"John Smith" wrote in message
...
Mike:

300 baud is ridiculous, in Dee's first post mentioning 300 baud
I
tossed it out the window--that was fine up to about 1985, then
only
the mentally challenged continued to run 300 baud modems!


Please show me and everyone else how we can run more than 300
baud
on HF without exceeding reasonable band widths. There are a
whole
lot of things, not just video, that would be nice to do.

How can we do it? Bandwidth is directly related to baud rate.

Dee D. Flint, N8UZE