On 2/2/2015 6:44 AM, gareth wrote:
I wonder if there had been any articles published for taking the
100kHz IF output of the EA12 RX and creating an FM discriminator
for it, possibly a pulse-counting discriminator at such a low frequency?



I recall when I was in college, The teacher showed us an old movie
produced by the US-Army on FM radio, it eatured SLOPE detection of an FM
signal... I will not say more but you could tell who in the class had a
ham license and/or experience with FM radio right quick when that hit.
(All the students ROFL in case nobody here is old enough to recall Slope
Detection).

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Home, is where I park it.

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"John Davis" wrote in message
...
On 2/2/2015 6:44 AM, gareth wrote:

I recall when I was in college, The teacher showed us an old movie
produced by the US-Army on FM radio, it eatured SLOPE detection of an FM
signal... I will not say more but you could tell who in the class had a
ham license and/or experience with FM radio right quick when that hit.
(All the students ROFL in case nobody here is old enough to recall Slope
Detection).

I know about the slope detectiion and am 65.

I don't have any of the very old gear, but every so often I listen to the
hams around 3.85 MHz. that use the old military and AM gear. While I don't
think it is really legal (and don't really care) some of those AM
transmitters sound beter if I switch to FM on my Icom 746 pro. I think when
they were made they seem to put out about as much FM as AM.

On Thu, 5 Feb 2015, Ralph Mowery wrote:


"John Davis" wrote in message
...
On 2/2/2015 6:44 AM, gareth wrote:

I recall when I was in college, The teacher showed us an old movie
produced by the US-Army on FM radio, it eatured SLOPE detection of an FM
signal... I will not say more but you could tell who in the class had a
ham license and/or experience with FM radio right quick when that hit.
(All the students ROFL in case nobody here is old enough to recall Slope
Detection).

I know about the slope detectiion and am 65.

I think it might be more the younger crowd. There was that period, in the
late forties or early fifties were very narrow FM was promoted, no need
for the big modulation transformer, and no being detected by input stages
to audio amplifiers. But slope detection was the usual mode, since
virtually no shortwave receivers had FM detectors. Except one could get
an external FM adapter for a late model HRO (I think, there was an
accessory socket for that, but I'm not sure if there was an FM detector;
people used the socket to add an external product detector).

And then of course, when 2m FM took off, lots of people converted their
existing AM rigs to FM by modulating the oscillator in some way, and using
slope detection for reception. Or there was a project in QST in the
summer of 1971, add a converter to an AM broadcast portable, and use slope
detection, then the next month add an FM IF strip.

I used to use my SP-600 with a converter to listen to 2M FM circa 1972,
and I had to use slope detection.

I don't have any of the very old gear, but every so often I listen to the
hams around 3.85 MHz. that use the old military and AM gear. While I don't
think it is really legal (and don't really care) some of those AM
transmitters sound beter if I switch to FM on my Icom 746 pro. I think when
they were made they seem to put out about as much FM as AM.

That's weird. I thought those hardcore AMers wanted purity, and took
effort to ensure they were putting out a good signal. They sure aren't
using modulated oscillators, and I don't think anything where the
modulation would get back to the oscillator.

When I got my Hallicrafter's S-120A (that's the transistorized model)
shortwave receiver in 1971, that AM bunch was the only voice modulation I
could receive on the ham bands, since the receiver had way too weak a BFO.
(Only later did I learn enough to put a potentiometer between the antenna
and the receiver's antenna terminals to work as an attenuator, at which
point I could receive SSB, but only signals strong enough to overcome the
attentuation.). I gathered at the time that they were youngish, I'm not
sure why, maybe what they were talking about. And they probably are the
same bunch now, 44 years later. But at the time it was great, since I
could listen to hams talk.

Michael

"Michael Black" wrote in message
news:alpine.LNX.2.02.1502051950290.19867@darkstar. example.org...
On Thu, 5 Feb 2015, Ralph Mowery wrote:


I don't have any of the very old gear, but every so often I listen to the
hams around 3.85 MHz. that use the old military and AM gear. While I
don't
think it is really legal (and don't really care) some of those AM
transmitters sound beter if I switch to FM on my Icom 746 pro. I think
when
they were made they seem to put out about as much FM as AM.

That's weird. I thought those hardcore AMers wanted purity, and took
effort to ensure they were putting out a good signal. They sure aren't
using modulated oscillators, and I don't think anything where the
modulation would get back to the oscillator.


There may be two kinds of people using AM. One for 'good quality AM' ,but
the other is using mainly the military gear from around the WW2 era or so.
Maybe even before that if they can find it. That is the stuff that can
contain about as much FM as it does AM. The power supplies are often
feeding the oscillator as well as the final stages and not regulated very
well if at all. That probably helps modulate the transmitter to have a lot
of FM in the signal.

"Ralph Mowery" wrote in message
...
"Michael Black" wrote in message
news:alpine.LNX.2.02.1502051950290.19867@darkstar. example.org...
On Thu, 5 Feb 2015, Ralph Mowery wrote:
I don't have any of the very old gear, but every so often I listen to
the
hams around 3.85 MHz. that use the old military and AM gear. While I
don't think it is really legal (and don't really care) some of those AM
transmitters sound beter if I switch to FM on my Icom 746 pro. I think
when they were made they seem to put out about as much FM as AM.

That's weird. I thought those hardcore AMers wanted purity, and took
effort to ensure they were putting out a good signal. They sure aren't
using modulated oscillators, and I don't think anything where the
modulation would get back to the oscillator.

There may be two kinds of people using AM. One for 'good quality AM' ,but
the other is using mainly the military gear from around the WW2 era or so.
Maybe even before that if they can find it. That is the stuff that can
contain about as much FM as it does AM. The power supplies are often
feeding the oscillator as well as the final stages and not regulated very
well if at all. That probably helps modulate the transmitter to have a
lot of FM in the signal.

FM has always been a legal mode for 80m in the UK, it's just that nobody
normally uses it intentionally.
Provided you're using no more bandwidth than normal AM I can't see a
problem.
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk

FM has always been a legal mode for 80m in the UK, it's just that nobody
normally uses it intentionally.
Provided you're using no more bandwidth than normal AM I can't see a
problem.

Well perhaps not 'always'. FM was not allowed prior to about 1952.

Jeff

"FranK Turner-Smith G3VKI" wrote in message
news
FM has always been a legal mode for 80m in the UK, it's just that nobody
normally uses it intentionally.
Provided you're using no more bandwidth than normal AM I can't see a
problem.

I am sure every country has slightly differant rules. As I don't operate FM
below the 10 meter band I am not up on the current regulations in the US
where most of the stations I was hearing are at. At onetime in the US we
could use something like around 2 to 3 khz deviation on 80 meters I think .
That used to be called somethink like sliver band. Maybe still can.
However some of those on 3.85 MHz were way wider than that. I think that
below 30 MHz it is only on some portions of 10 meters that deviations as
wide as 5 KHz can be used in the US.

As I was saying above, I am not sure those AM / FM signals are legal in the
US, but don't really care. It is good that the hams have decided on a
frequency to meet and have fun with the old sets.

de KU4PT

On Fri, 6 Feb 2015, FranK Turner-Smith G3VKI wrote:

"Ralph Mowery" wrote in message
...
"Michael Black" wrote in message
news:alpine.LNX.2.02.1502051950290.19867@darkstar. example.org...
On Thu, 5 Feb 2015, Ralph Mowery wrote:
I don't have any of the very old gear, but every so often I listen to the
hams around 3.85 MHz. that use the old military and AM gear. While I
don't think it is really legal (and don't really care) some of those AM
transmitters sound beter if I switch to FM on my Icom 746 pro. I think
when they were made they seem to put out about as much FM as AM.

That's weird. I thought those hardcore AMers wanted purity, and took
effort to ensure they were putting out a good signal. They sure aren't
using modulated oscillators, and I don't think anything where the
modulation would get back to the oscillator.

There may be two kinds of people using AM. One for 'good quality AM' ,but
the other is using mainly the military gear from around the WW2 era or so.
Maybe even before that if they can find it. That is the stuff that can
contain about as much FM as it does AM. The power supplies are often
feeding the oscillator as well as the final stages and not regulated very
well if at all. That probably helps modulate the transmitter to have a lot
of FM in the signal.

FM has always been a legal mode for 80m in the UK, it's just that nobody
normally uses it intentionally.
Provided you're using no more bandwidth than normal AM I can't see a problem.

But Ralph is complaining about a signal that is both AM and FM.

INtentional FM is different from incidental FM.

Certainly in the US (and I assume Canada), rules were in effect quite a
few decades ago about the stability of a signal. There was a point where
a signal had to be as stable as a crystal controlled signal on the HF
bands, which caused a shift to crystal control, I think that was even
before WWII. So incidental FM would seem to be out of the question after
that. It was only after WWII when things got crowded and better
techniques came along that VFOs made a comeback, obviously much better
built and stable than the variable oscillators of the old days. (And the
same sort of rule followed as the move up to higher frequencies.
Modulated oscillators would work the higher frequencies initially, then
the rule for better stability would come in, and the modulated oscillators
would move to the next higher band, and so forth).

If a signal is putting out both FM and AM, it is either doing it by
accident, and needs fixing, or is some weird form or modulation, that the
rules would either have a separate classification for, or a rule against
it.

Michael