"Joel Kolstad" ) writes:
Michael Black wrote:
No, the January 1977 issue of Ham Radio magazine, it was the
cover article.
I could never really make sense of the article. My recollection
is that it didn't do a good job on conveying the theory to
the average ham, or even the purpose of such a mode,

I would think it would be for the same reason as SSB for AM? To achieve
half the bandwidth utilization for a given signal? (But at the expense of
3dB poorer SNR...)

It's been quite a few years since I looked at the article. There was
just something about the article that seemed like I'd been dropped into
something. Maybe the style was different from most articles in the
magazine, maybe because it didn't really seem to be a practical article.
There just seemed to be something missing. Yes, it would take up less
space, but then why not go to some other mode? It's the only time I've
seen something on the subject, and I think it could have better been handled.

Michael VE2BVW

Michael Black wrote:
It's been quite a few years since I looked at the article. There was
There just seemed to be something missing. Yes, it would take up less
space, but then why not go to some other mode? It's the only time I've
seen something on the subject, and I think it could have better been
handled.

Fair enough. If the idea were to conserve bandwidth, you'd probably be
using narrow band FM anyway at which point SSB-NBFM takes no less bandwidth
than convention SSB-AM and... it _might_ even have worse SNR, although I
don't know calculations off-hand. Hence I suspect that SSB-FM is nothing
more than a curiosity... could be fun to implement just for the sake of
experimentation once we're all running software defined radios, though!

From your description it sounds like someone was excited by the novelty of
the idea but ran out of steam before actually implementing the idea!

---Joel Kolstad

Michael Black wrote:
It's been quite a few years since I looked at the article. There was
There just seemed to be something missing. Yes, it would take up less
space, but then why not go to some other mode? It's the only time I've
seen something on the subject, and I think it could have better been
handled.

Fair enough. If the idea were to conserve bandwidth, you'd probably be
using narrow band FM anyway at which point SSB-NBFM takes no less bandwidth
than convention SSB-AM and... it _might_ even have worse SNR, although I
don't know calculations off-hand. Hence I suspect that SSB-FM is nothing
more than a curiosity... could be fun to implement just for the sake of
experimentation once we're all running software defined radios, though!

From your description it sounds like someone was excited by the novelty of
the idea but ran out of steam before actually implementing the idea!

---Joel Kolstad

as i understand, the fm signal, due to its nature of changing rate of
phase change generates a number of sidebands. Filtering these
sidebands would mean that a band-pass filter is being applied to the
fm signal. That would amplitude modulate the signal as well. Amplitude
modualting would create some more sidebands but within the filter's
band-pass.
Finally, we would arrive at a 'least-bandwidth' signal that would
resemble SSB. So you might as well expend five crystals (for a ladder
filter and an oscillator) and get good ol SSB going.
A more intiutive example would be to consider an FM signal being
modulated by a single tone. That would waver the carrier back and
forth around the center frequency of the carrier. Now, if you passed
this through a band-pass filter, you will see the amplitude drop off
at the filter's skirts. This will resemble an amplitude modualted
signal. depending upon the filter bandwidth, you might see either an
AM, or a two-tone (carrier center being one, the modulated tone the
other) SSB signal.
I may be completely missing the point though, i welcome an
explanation.

- farhan

as i understand, the fm signal, due to its nature of changing rate of
phase change generates a number of sidebands. Filtering these
sidebands would mean that a band-pass filter is being applied to the
fm signal. That would amplitude modulate the signal as well. Amplitude
modualting would create some more sidebands but within the filter's
band-pass.
Finally, we would arrive at a 'least-bandwidth' signal that would
resemble SSB. So you might as well expend five crystals (for a ladder
filter and an oscillator) and get good ol SSB going.
A more intiutive example would be to consider an FM signal being
modulated by a single tone. That would waver the carrier back and
forth around the center frequency of the carrier. Now, if you passed
this through a band-pass filter, you will see the amplitude drop off
at the filter's skirts. This will resemble an amplitude modualted
signal. depending upon the filter bandwidth, you might see either an
AM, or a two-tone (carrier center being one, the modulated tone the
other) SSB signal.
I may be completely missing the point though, i welcome an
explanation.

- farhan

as i understand, the fm signal, due to its nature of changing rate of
phase change generates a number of sidebands. Filtering these
sidebands would mean that a band-pass filter is being applied to the
fm signal. That would amplitude modulate the signal as well.

I think you have a point here. Removal of one side of the set of sidebands
turns the FM signal into a sort of AM/SSB signal. During transmission, FM's
robustness to impulse noise will be lost. The presence of a limiter in the
receiver, will turn the signal + noise back into a corrupted DSB FM signal
for demodulation.


Sverre
LA3ZA

as i understand, the fm signal, due to its nature of changing rate of
phase change generates a number of sidebands. Filtering these
sidebands would mean that a band-pass filter is being applied to the
fm signal. That would amplitude modulate the signal as well.

I think you have a point here. Removal of one side of the set of sidebands
turns the FM signal into a sort of AM/SSB signal. During transmission, FM's
robustness to impulse noise will be lost. The presence of a limiter in the
receiver, will turn the signal + noise back into a corrupted DSB FM signal
for demodulation.


Sverre
LA3ZA

Thanks everyone

Sometimes I really get curious and want to know about something.

I haven't seen the Ham Radio article, but I'm thinking if the whole
idea had any merit it would be a popular mode by now.

Bruce kk7zz

www.elmerdude.com

Thanks everyone

Sometimes I really get curious and want to know about something.

I haven't seen the Ham Radio article, but I'm thinking if the whole
idea had any merit it would be a popular mode by now.

Bruce kk7zz

www.elmerdude.com

Sverre Holm wrote:
I think you have a point here. Removal of one side of the set of sidebands
turns the FM signal into a sort of AM/SSB signal. During transmission,
FM's robustness to impulse noise will be lost.

This would appear to depend on how sharp the skirt of our hypothetical SSB
(really VSB, now) filter is? I.e., at low carrier deviations there's some
AM and therefore it's not _quite_ as robus, whereas at higher carrier
deviations the filter would be nice and flat and look just like regular FM
in terms of amplitude.

After all... in the presense of some AM on regular double side band FM, most
receivers still perform just fine, don't they?

---Joel Kolstad