On Mar 31, 2022, at 7:53 PM, Trevor Clarke via mvus-list mvus-list@lists.febo.com wrote:

Regarding a demonstration for HAMvention...I've still got a couple of
gunnplexers I haven't done anything with them. We had a discussion here a
while back and I believe the consensus is that they are pretty close to
complete, just needs a power supply and mic/speaker circuitry. If someone
else has a 10GHz or 24GHz gunnplexer, we could setup a point to point
station near the booth and on the other side of the convention site and let
people play around with them.

Trevor R.H. Clarke
Computer Science House
Rochester Institute of Technology
retrev@csh.rit.edu
http://www.csh.rit.edu/~retrev/

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Trever… That would be cool! Maybe from my flea market space, although the
direct path is likely blocked. Still worth a try.

From Tom Holmes, N8ZM

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let

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On Mar 31, 2022, at 10:34 PM, Trevor Clarke via mvus-list mvus-list@lists.febo.com wrote:

I wonder if there are any big hunks of steel around we could bounce off of.
Maybe a water tower.

Trevor R.H. Clarke, K8TRC

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Regarding a demonstration for HAMvention...I've still got a couple of
gunnplexers I haven't done anything with them. We had a discussion here a
while back and I believe the consensus is that they are pretty close to
complete, just needs a power supply and mic/speaker circuitry. If someone
else has a 10GHz or 24GHz gunnplexer, we could setup a point to point
station near the booth and on the other side of the convention site and let
people play around with them.

Trevor R.H. Clarke
Computer Science House
Rochester Institute of Technology
retrev@csh.rit.edu
http://www.csh.rit.edu/~retrev/

On Thu, Mar 31, 2022 at 6:57 PM Jim Bacher via mvus-list <
mvus-list@lists.febo.com> wrote:

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Trevor,

The Gunnplexer also needs an FM receiver at the chosen IF frequency.
Unless path loss is too much of a problem, wideband FM with the IF set
on a clear spot in the FM BC band works well, and it's fairly easy to do
high fidelity full duplex voice communications.

But Gunnplexers drift around like crazy with temperature and other factors,
so it is very desirable to include a frequency tracking loop that tunes one
of the Gunnplexers (not the receiver!) so as to maintain a constant IF
frequency at a clear spot in the FM BC band.

It's very nice if you can scare up an old-fashiond FM BC receiver that
has AFC, to provide access to a DC-coupled signal from the FM
discriminator to provide the error signal for the AFC system.

You may actually find that you don't need a mic amplifier, rather that
you'll want to use a mic attenuator (depending on the mic).

I once did a bunch of this kind of stuff circa 1980, including a link
between two cars traveling in "very loose formation" from Ann Arbor
to Dayton.  There an additional complication was that there were a
lot of complete signal dropouts, and I had to make the AFC loop
switch into "hold" mode during such times, else the AFC would
usually fail to re-acquire lock when coming out of the signal drop.

All this was done entirely with analog technology, with the "track
and hold" AFC being hastily cobbled together in the last few days
before Hamvention start after a highway test revealed the need for
it.  Part of this was also a "quieting detector" so that the loop would
know when to go into hold mode.  The FM BC receiver was a kluge
built out of parts bought from Heath Co for their (then) top of the
line Hi-Fi FM tuner, originally built to serve as a "laboratory" receiver
of sorts.

Sadly I no longer have that receiver, else I'd offer it for your use.  But
when I was packing for my move from Puerto Rico, I looked at that
pretty carefully and concluded that the poor thing had been eaten
alive by mold and fungus, so I tossed it out instead of moving it.

No matter what you've got, if you want the link to keep working
without fairly constant attention, you will need to position the
antennas at both ends so that people aren't moving around near
the antennas.  Also, doing so will more or less automatically
assure RF exposure safety.

Dana

On Thu, Mar 31, 2022 at 6:53 PM Trevor Clarke via mvus-list <
mvus-list@lists.febo.com> wrote:

let

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Trevor,

The Gunnplexer also needs an FM receiver at the chosen IF frequency.
Unless path loss is too much of a problem, wideband FM with the IF set
on a clear spot in the FM BC band works well, and it's fairly easy to do
high fidelity full duplex voice communications.

But Gunnplexers drift around like crazy with temperature and other factors,
so it is very desirable to include a frequency tracking loop that tunes one
of the Gunnplexers (not the receiver!) so as to maintain a constant IF
frequency at a clear spot in the FM BC band.

It's very nice if you can scare up an old-fashiond FM BC receiver that
has AFC, to provide access to a DC-coupled signal from the FM
discriminator to provide the error signal for the AFC system.

You may actually find that you don't need a mic amplifier, rather that
you'll want to use a mic attenuator (depending on the mic).

I once did a bunch of this kind of stuff circa 1980, including a link
between two cars traveling in "very loose formation" from Ann Arbor
to Dayton.  There an additional complication was that there were a
lot of complete signal dropouts, and I had to make the AFC loop
switch into "hold" mode during such times, else the AFC would
usually fail to re-acquire lock when coming out of the signal drop.

All this was done entirely with analog technology, with the "track
and hold" AFC being hastily cobbled together in the last few days
before Hamvention start after a highway test revealed the need for
it.  Part of this was also a "quieting detector" so that the loop would
know when to go into hold mode.  The FM BC receiver was a kluge
built out of parts bought from Heath Co for their (then) top of the
line Hi-Fi FM tuner, originally built to serve as a "laboratory" receiver
of sorts.

Sadly I no longer have that receiver, else I'd offer it for your use.  But
when I was packing for my move from Puerto Rico, I looked at that
pretty carefully and concluded that the poor thing had been eaten
alive by mold and fungus, so I tossed it out instead of moving it.

No matter what you've got, if you want the link to keep working
without fairly constant attention, you will need to position the
antennas at both ends so that people aren't moving around near
the antennas.  Also, doing so will more or less automatically
assure RF exposure safety.

Dana

On Thu, Mar 31, 2022 at 6:53 PM Trevor Clarke via mvus-list <
mvus-list@lists.febo.com> wrote:

let

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Trevor,

The Gunnplexer also needs an FM receiver at the chosen IF frequency.
Unless path loss is too much of a problem, wideband FM with the IF set
on a clear spot in the FM BC band works well, and it's fairly easy to do
high fidelity full duplex voice communications.

But Gunnplexers drift around like crazy with temperature and other factors,
so it is very desirable to include a frequency tracking loop that tunes one
of the Gunnplexers (not the receiver!) so as to maintain a constant IF
frequency at a clear spot in the FM BC band.

It's very nice if you can scare up an old-fashiond FM BC receiver that
has AFC, to provide access to a DC-coupled signal from the FM
discriminator to provide the error signal for the AFC system.

You may actually find that you don't need a mic amplifier, rather that
you'll want to use a mic attenuator (depending on the mic).

I once did a bunch of this kind of stuff circa 1980, including a link
between two cars traveling in "very loose formation" from Ann Arbor
to Dayton.  There an additional complication was that there were a
lot of complete signal dropouts, and I had to make the AFC loop
switch into "hold" mode during such times, else the AFC would
usually fail to re-acquire lock when coming out of the signal drop.

All this was done entirely with analog technology, with the "track
and hold" AFC being hastily cobbled together in the last few days
before Hamvention start after a highway test revealed the need for
it.  Part of this was also a "quieting detector" so that the loop would
know when to go into hold mode.  The FM BC receiver was a kluge
built out of parts bought from Heath Co for their (then) top of the
line Hi-Fi FM tuner, originally built to serve as a "laboratory" receiver
of sorts.

Sadly I no longer have that receiver, else I'd offer it for your use.  But
when I was packing for my move from Puerto Rico, I looked at that
pretty carefully and concluded that the poor thing had been eaten
alive by mold and fungus, so I tossed it out instead of moving it.

No matter what you've got, if you want the link to keep working
without fairly constant attention, you will need to position the
antennas at both ends so that people aren't moving around near
the antennas.  Also, doing so will more or less automatically
assure RF exposure safety.

Dana

On Thu, Mar 31, 2022 at 6:53 PM Trevor Clarke via mvus-list <
mvus-list@lists.febo.com> wrote:

let

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Thanks for the info Dana! I need to figure out what IF the devices are
currently tuned to but if it's in the proper range I was going to repurpose
my baofeng HT as a receiver, should do a bit better than an FM broadcast
receiver as far as sensitivity. I've got a scanned copy of Bob Richardson's
Gunnplexer Cookbook. While it's a few decades old, the concepts are the
same, might just need to adjust some of the sample circuits to use newer
parts. It discusses some frequency stabilization techniques including AFC
and ovens.

Trevor R.H. Clarke
Computer Science House
Rochester Institute of Technology
retrev@csh.rit.edu
http://www.csh.rit.edu/~retrev/

On Fri, Apr 1, 2022 at 9:21 AM Dana Whitlow via mvus-list <
mvus-list@lists.febo.com> wrote:

factors,

one

But

here a

someone

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