Re: Phase or frequency modulation?

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Sujet : Re: Phase or frequency modulation?
De : pcdhSpamMeSenseless (at) *nospam* electrooptical.net (Phil Hobbs)
Groupes : sci.electronics.design
Date : 07. Jul 2025, 15:00:44
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Don <g@crcomp.net> wrote:
Correction. <https://www.sigidwiki.com/wiki/Database> includes one
PM zombie satellite: <https://www.sigidwiki.com/wiki/Transit_5B-5>
 
Liz Tuddenham wrote:
I have been checking the performance of a variable-reactance type of
frequency modulator which 'pulls' a crystal oscillator.  After
multiplication and mixing, the signal appears at 145 Mc/s.
 
Listening to this signal on an Icom 706 MkII transceiver I found it was
barely intelligible, with severe high frequency cut.  At first I
suspected my modulator but I checked the audio output of the Icom with a
good-quality signal generator and found the response was:
 
200c/s : -3dB
400c/s :  0dB
750c/s : -3dB
1 Kc/s : -6dB
1k5    : -10dB
2k0    : -13dB
2k5    : -16dB
3k0    : -18dB
 
(Using the wideband FM setting of the Icom produced similar results, so
the limitation was in the detector/A.F. stages, not in the I.F. filter)
This looks as though EITHER a 6dB per octave response is being imposed
on the output of the FM detector OR the detector is expecting phase
modulation.
 
The handbook for the Icom refers throughout to frequency modulation and
does not mention phase modulation.  Most references to modulation in the
2-metre band (144-146 Mc/s in the U.K.) mention frequency modulation and
the use of phase modulation would cause 'splash' into adjacent channels
at higher audio frequencies because of the rising characteristic.
 
Has my Icom been designed for a market where phase modulation is the
norm or is there another explantion?
 
Good question. It's a shame the All Identified Signals database
<https://www.sigidwiki.com/wiki/Database> lacks a filter for PM mode.
Otherwise it might indicate countries where PM is popular.
 
Danke,
 

Probably nowhere. Analog PM stinks—it’s no better than AM at low modulation
index, and atrociously wasteful of bandwidth at high index.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics

Date Sujet#  Auteur
7 Jul08:44 * Phase or frequency modulation?33Liz Tuddenham
7 Jul14:14 +* Re: Phase or frequency modulation?24john larkin
7 Jul15:04 i`* Re: Phase or frequency modulation?23Liz Tuddenham
7 Jul16:07 i `* Re: Phase or frequency modulation?22john larkin
7 Jul16:11 i  +* Re: Phase or frequency modulation?20john larkin
7 Jul18:28 i  i`* Re: Phase or frequency modulation?19Liz Tuddenham
7 Jul18:48 i  i `* Re: Phase or frequency modulation?18john larkin
7 Jul19:06 i  i  +* Re: Phase or frequency modulation?15Liz Tuddenham
7 Jul22:54 i  i  i+* Re: Phase or frequency modulation?3john larkin
8 Jul08:50 i  i  ii`* Re: Phase or frequency modulation?2Liz Tuddenham
8 Jul16:16 i  i  ii `- Re: Phase or frequency modulation?1john larkin
8 Jul12:19 i  i  i`* Re: Phase or frequency modulation?11Phil Hobbs
8 Jul12:30 i  i  i +- Re: Phase or frequency modulation?1Liz Tuddenham
8 Jul13:45 i  i  i +* Re: Phase or frequency modulation?7piglet
8 Jul15:23 i  i  i i`* Re: Phase or frequency modulation?6Phil Hobbs
8 Jul16:55 i  i  i i +* Re: Phase or frequency modulation?4Liz Tuddenham
8 Jul18:34 i  i  i i i`* Re: Phase or frequency modulation?3Phil Hobbs
9 Jul12:29 i  i  i i i `* Re: Phase or frequency modulation?2Liz Tuddenham
9 Jul13:20 i  i  i i i  `- Re: Phase or frequency modulation?1Phil Hobbs
8 Jul20:00 i  i  i i `- Re: Phase or frequency modulation?1piglet
8 Jul18:39 i  i  i `* Re: Phase or frequency modulation?2john larkin
8 Jul20:00 i  i  i  `- Re: Phase or frequency modulation?1Phil Hobbs
8 Jul23:20 i  i  `* Re: Phase or frequency modulation?2Ralph Mowery
9 Jul00:45 i  i   `- Re: Phase or frequency modulation?1Phil Hobbs
7 Jul18:28 i  `- Re: Phase or frequency modulation?1Liz Tuddenham
7 Jul14:41 +* Re: Phase or frequency modulation?2Don
7 Jul15:00 i`- Re: Phase or frequency modulation?1Phil Hobbs
7 Jul18:28 +* Re: Phase or frequency modulation?2Liz Tuddenham
9 Jul09:08 i`- Re: Phase or frequency modulation?1Liz Tuddenham
8 Jul22:25 `* Re: Phase or frequency modulation?4Ralph Mowery
9 Jul09:08  `* Re: Phase or frequency modulation?3Liz Tuddenham
9 Jul15:59   `* Re: Phase or frequency modulation?2Don
9 Jul16:42    `- Re: Phase or frequency modulation?1Liz Tuddenham

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