SSB FM [DSP]

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From: Jerry Avins on 21 Sep 2009 09:13

HardySpicer wrote:
> On Sep 20, 8:01 pm, Jerry Avins <j...(a)ieee.org> wrote:
>> HardySpicer wrote:
>>> On Sep 21, 12:57 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>>> PalapaGuy wrote:
>>>>> Single-sideband FM was a popular topic several years ago but I haven't seen
>>>>> any articles on it since then. It looks attractive as a way to transmit
>>>>> narrowband FM efficiently at VHF over short distances. Does anyone know of
>>>>> current uses for this technology?
>>>> Narrow-band FM (NBFM) is the same as low-modulation-percentage AM with
>>>> the carrier shifted 90 degrees. If the modulation index is low enough,
>>>> what you mention is identical to the SSB-SC that is standard on ham and
>>>> CB bands. I suppose people eventually realized that. Or is there some
>>>> other meaning to what you write?
>>>> Jerry
>>>> --
>>>> Engineering is the art of making what you want from things you can get.
>>>> ��
>>> Not sure it behaves the same. FM thresholds but AM doesn't. AM (SSB)
>>> has problems demodulating it I suppose whereas with FM you can easily
>>> use a PLL.
>> NBFM doesn't threshold. You confuse the properties of FM with those of
>> SSB NBFM. As far as I know,n SSB version of high-modulation-index FM
>> doesn't exist.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>> ��
>
> NBFM must threshold. In fact it thresholds worse than wide-band since
> the beta is lower. That anoying sound on every police radio in the UK
> (as it was of course).

By that criterion, AM thresholds too. With enough carrier power, QRM is
negligible.

Jerry
--
Engineering is the art of making what you want from things you can get.
��

From: Jerry Avins on 21 Sep 2009 09:15

HardySpicer wrote:
> On Sep 20, 8:01 pm, Jerry Avins <j...(a)ieee.org> wrote:
>> HardySpicer wrote:
>>> On Sep 21, 12:57 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>>> PalapaGuy wrote:
>>>>> Single-sideband FM was a popular topic several years ago but I haven't seen
>>>>> any articles on it since then. It looks attractive as a way to transmit
>>>>> narrowband FM efficiently at VHF over short distances. Does anyone know of
>>>>> current uses for this technology?
>>>> Narrow-band FM (NBFM) is the same as low-modulation-percentage AM with
>>>> the carrier shifted 90 degrees. If the modulation index is low enough,
>>>> what you mention is identical to the SSB-SC that is standard on ham and
>>>> CB bands. I suppose people eventually realized that. Or is there some
>>>> other meaning to what you write?
>>>> Jerry
>>>> --
>>>> Engineering is the art of making what you want from things you can get.
>>>> ��
>>> Not sure it behaves the same. FM thresholds but AM doesn't. AM (SSB)
>>> has problems demodulating it I suppose whereas with FM you can easily
>>> use a PLL.
>> NBFM doesn't threshold. You confuse the properties of FM with those of
>> SSB NBFM. As far as I know,n SSB version of high-modulation-index FM
>> doesn't exist.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>> ��
>
> NBFM must threshold. In fact it thresholds worse than wide-band since
> the beta is lower. That anoying sound on every police radio in the UK
> (as it was of course).

P.S. The quieting that FM provides above threshold can be thought of as
trading bandwidth for SNR, With NBFM, there is nothing to trade.

Jerry
--
Engineering is the art of making what you want from things you can get.
��

From: Randy Yates on 21 Sep 2009 11:47

HardySpicer <gyansorova(a)gmail.com> writes:

> On Sep 20, 8:01 pm, Jerry Avins <j...(a)ieee.org> wrote:
>> HardySpicer wrote:
>> > On Sep 21, 12:57 pm, Jerry Avins <j...(a)ieee.org> wrote:
>> >> PalapaGuy wrote:
>> >>> Single-sideband FM was a popular topic several years ago but I haven't seen
>> >>> any articles on it since then. It looks attractive as a way to transmit
>> >>> narrowband FM efficiently at VHF over short distances. Does anyone know of
>> >>> current uses for this technology?
>> >> Narrow-band FM (NBFM) is the same as low-modulation-percentage AM with
>> >> the carrier shifted 90 degrees. If the modulation index is low enough,
>> >> what you mention is identical to the SSB-SC that is standard on ham and
>> >> CB bands. I suppose people eventually realized that. Or is there some
>> >> other meaning to what you write?
>>
>> >> Jerry
>> >> --
>> >> Engineering is the art of making what you want from things you can get.
>> >> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>>
>> > Not sure it behaves the same. FM thresholds but AM doesn't. AM (SSB)
>> > has problems demodulating it I suppose whereas with FM you can easily
>> > use a PLL.
>>
>> NBFM doesn't threshold. You confuse the properties of FM with those of
>> SSB NBFM. As far as I know,n SSB version of high-modulation-index FM
>> doesn't exist.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>
> NBFM must threshold. In fact it thresholds worse than wide-band since
> the beta is lower. That anoying sound on every police radio in the UK
> (as it was of course).
>
> Hardy

Mischa Schwartz et al. discuss the FM threshold effect in quite a bit of
analytical detail (a quad integration is performed at one point on
four-dimensional probability distribution!) in section 3.6, p134.

--Randy

@book{schwartzcommtechniques,
title = "Communication Systems and Techniques",
author = "{Mischa Schwartz and William R. Bennett and Seymour Stein}",
publisher = "IEEE Press (reissue, originally New York: McGraw-Hill 1966)",
year = "1996"}

--
Randy Yates % "And all you had to say
Digital Signal Labs % was that you were
mailto://yates(a)ieee.org % gonna stay."
http://www.digitalsignallabs.com % Getting To The Point', *Balance of Power*, ELO

From: Jerry Avins on 21 Sep 2009 13:04

Randy Yates wrote:
> HardySpicer <gyansorova(a)gmail.com> writes:
>
>> On Sep 20, 8:01 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>> HardySpicer wrote:
>>>> On Sep 21, 12:57 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>>>> PalapaGuy wrote:
>>>>>> Single-sideband FM was a popular topic several years ago but I haven't seen
>>>>>> any articles on it since then. It looks attractive as a way to transmit
>>>>>> narrowband FM efficiently at VHF over short distances. Does anyone know of
>>>>>> current uses for this technology?
>>>>> Narrow-band FM (NBFM) is the same as low-modulation-percentage AM with
>>>>> the carrier shifted 90 degrees. If the modulation index is low enough,
>>>>> what you mention is identical to the SSB-SC that is standard on ham and
>>>>> CB bands. I suppose people eventually realized that. Or is there some
>>>>> other meaning to what you write?
>>>>> Jerry
>>>>> --
>>>>> Engineering is the art of making what you want from things you can get.
>>>>> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>>>> Not sure it behaves the same. FM thresholds but AM doesn't. AM (SSB)
>>>> has problems demodulating it I suppose whereas with FM you can easily
>>>> use a PLL.
>>> NBFM doesn't threshold. You confuse the properties of FM with those of
>>> SSB NBFM. As far as I know,n SSB version of high-modulation-index FM
>>> doesn't exist.
>>>
>>> Jerry
>>> --
>>> Engineering is the art of making what you want from things you can get.
>>> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>> NBFM must threshold. In fact it thresholds worse than wide-band since
>> the beta is lower. That anoying sound on every police radio in the UK
>> (as it was of course).
>>
>> Hardy
>
> Mischa Schwartz et al. discuss the FM threshold effect in quite a bit of
> analytical detail (a quad integration is performed at one point on
> four-dimensional probability distribution!) in section 3.6, p134.
>
> --Randy
>
> @book{schwartzcommtechniques,
> title = "Communication Systems and Techniques",
> author = "{Mischa Schwartz and William R. Bennett and Seymour Stein}",
> publisher = "IEEE Press (reissue, originally New York: McGraw-Hill 1966)",
> year = "1996"}

My Schwartz, "Information Transmission, Modulation and Noise", 1st
Edition, 1959; $10.34, says in italics* on p.304, section 6.3,
/"Narrowband FM thus provides no S/N improvement over AM."/

Jerry
_______________________
* Thus anticipating Hardy's misconception by several decades.
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

From: Tauno Voipio on 21 Sep 2009 15:43

Jerry Avins wrote:
> Randy Yates wrote:
>> HardySpicer <gyansorova(a)gmail.com> writes:
>>
>>> On Sep 20, 8:01 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>>> HardySpicer wrote:
>>>>> On Sep 21, 12:57 pm, Jerry Avins <j...(a)ieee.org> wrote:
>>>>>> PalapaGuy wrote:
>>>>>>> Single-sideband FM was a popular topic several years ago but I
>>>>>>> haven't seen
>>>>>>> any articles on it since then. It looks attractive as a way to
>>>>>>> transmit
>>>>>>> narrowband FM efficiently at VHF over short distances. Does
>>>>>>> anyone know of
>>>>>>> current uses for this technology?
>>>>>> Narrow-band FM (NBFM) is the same as low-modulation-percentage AM
>>>>>> with
>>>>>> the carrier shifted 90 degrees. If the modulation index is low
>>>>>> enough,
>>>>>> what you mention is identical to the SSB-SC that is standard on
>>>>>> ham and
>>>>>> CB bands. I suppose people eventually realized that. Or is there some
>>>>>> other meaning to what you write?
>>>>>> Jerry
>>>>>> --
>>>>>> Engineering is the art of making what you want from things you can
>>>>>> get.
>>>>>> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>>>>>>
>>>>> Not sure it behaves the same. FM thresholds but AM doesn't. AM (SSB)
>>>>> has problems demodulating it I suppose whereas with FM you can easily
>>>>> use a PLL.
>>>> NBFM doesn't threshold. You confuse the properties of FM with those of
>>>> SSB NBFM. As far as I know,n SSB version of high-modulation-index FM
>>>> doesn't exist.
>>>>
>>>> Jerry
>>>> --
>>>> Engineering is the art of making what you want from things you can get.
>>>> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>>> NBFM must threshold. In fact it thresholds worse than wide-band since
>>> the beta is lower. That anoying sound on every police radio in the UK
>>> (as it was of course).
>>>
>>> Hardy
>>
>> Mischa Schwartz et al. discuss the FM threshold effect in quite a bit of
>> analytical detail (a quad integration is performed at one point on
>> four-dimensional probability distribution!) in section 3.6, p134.
>>
>> --Randy
>>
>> @book{schwartzcommtechniques,
>> title = "Communication Systems and Techniques",
>> author = "{Mischa Schwartz and William R. Bennett and Seymour Stein}",
>> publisher = "IEEE Press (reissue, originally New York: McGraw-Hill
>> 1966)",
>> year = "1996"}
>
> My Schwartz, "Information Transmission, Modulation and Noise", 1st
> Edition, 1959; $10.34, says in italics* on p.304, section 6.3,
> /"Narrowband FM thus provides no S/N improvement over AM."/
>
> Jerry
> _______________________
> * Thus anticipating Hardy's misconception by several decades.

Probably the main reasons for using NBFM instead of AM in land
mobile service is twofold: A FM transmitter is easier to modulate
and lighter than an AM transmitter; and with sufficient signal
level, the recovered modulating signal fluctuations are smaller
and easier to manage with limiters in FM IF chain.

In aviation, the communication radios are using AM, probably due
to historical reasons and hefty inertia of the huge instlled base.
Besides, there are less signal level fluctuations in an air-land
or air-air link than on a land-land link.

--

Tauno Voipio

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