ARLA/CLUSTER: Você está em FM Estreito ou Largo..?

[Pedro Ribeiro (CR7ABP)]

Esses termos "Wide" e "Narrow" usados nessa explicação diria estarem um 
pouco desactualizados para a nossa situação actual.

O 20K0F3E não tenho ideia de que se use actualmente no contexto do 
radio-amadorismo nacional, grande parte dos repetidores de 70cm e 
comunicações directas feitas nesta banda usam o modo 16K0F3E que é o que 
consideramos actualmente como "Wide", o 11K2F3E é o usado pelos 
repetidores de 2m e recomendado pela IARU-R1 para uso em comunicações 
directas nos 2m e creio que até nos 70cm!

Tecnicamente considera-se "Wide" ou "Narrow" dependente do rácio entre a 
banda do sinal modulante e o desvio máximo instantâneo da portadora.
O chamado "índice de modulação"

Já agora, a vantagem do aumento do índice de modulação é a melhoria da 
relação sinal/ruído.

Quer o 12K0F3E quer o 16K0F3E são baseados em índices de modulação 
próximos da unidade.

Se o desvio máximo for muito maior que o sinal modulante, é "Wide"

Exemplo:

16K0F3E
Desvio máximo = 5kHz
Banda Sinal Modulante = 3kHz

Bt = 2 * (5000 + 3000) = 16kHz
Não sei se neste caso o conceito de "muito maior" se poderá aplicar ...

Se o desvio máximo for muito menor que o sinal modulante, é "Narrow"

Exemplo:

11K0F3E
Desvio máximo = 2,5kHz
Banda Sinal Modulante = 3kHz

Bt = 2 * (2500 + 3000) = 11kHz
Não sei se neste caso o conceito de "muito menor" se poderá aplicar ...

Já não é tão difícil de classificar o FM Musiqueiro como "Wide"

Desvio máximo = 75kHz
Banda Sinal Modulante = 15kHz

Pela regra de Carson:
Bt = 2 * (75K + 15K) = 180kHz !!!

Referência:
http://en.wikipedia.org/wiki/Frequency_modulation

73!

On 22-10-2010 14:12, João Gonçalves Costa wrote:
>
> Are you narrow or wide?
>
> Recently our local repeater coordinator began asking your emission designator on the application form. A break-down of emission designators can be found in section 2.201 of the telecommunications part of the code of federal regulations.
>
> 20K0F3E - FM Voice 20kHz bandwidth - Wide
> 16K0F3E - FM Voice 16kHz bandwidth - Narrow
> 11K2F3E - FM Voice 11.2kHz bandwidth
> 8K10F1E - P25, phase 1, 12.5kHz Bandwidth
> 5K76G1E - P25, phase 2, 6.25kHz Bandwidth
> 6K00F7W - D-Star, 6kHz bandwidth
>
> The confusion I often see lies whether a system is narrow or wide. 20 KHz bandwidth or 16 KHz. To determine this we must look at Carsons bandwidth rule.
>
> http://en.wikipedia.org/wiki/Carson_bandwidth_rule
>
> As you can see in the analog world, your bandwidth will be determined by transmitter deviation. If you have 5 KHz deviation (now a days considered wide band I guess) you will occupy 20kHz of bandwidth. If your deviation is in the 2-3 KHz area you will occupy 16kHz bandwidth now referred to as narrow FM.
>
> Now a days wide / narrow transmitter deviation is usually a software selectable option. The quote/unquote standard for ham radio has been 5KHz max deviation/20kHz bandwidth.
>
> If you can't determine by software/programming configuration you'll likely need access to a deviation meter/service monitor to determine your deviation.
>
> http://www.repeater-builder.com/rbtip/deviationmeter.html
>
> +/-2.5kHz maximum deviation is also a standard for 800 MHz and above and has been since the mid 90's. This is why you typically see 12.5kHz channel spacing up there. Actually I have never seen any Wide analog FM above 800 MHz except on remote broadcast studio-transmitter links.
>
> So if nothing else use the mid 1990's as a date of determination. If we are talking VHF/UHF commercial equipment manufactured 1997 or more recently you can probably assume it's "narrow FM"/Max 3 KHz deviation - yielding 16kHz bandwidth. Another clue is if it was in commercial service using a 12.5 kHz step/channel spacing scheme, it is likely narrow FM.
>
>
> Here is the history:
>
> A process of "refarming" the informal name of a notice and comment rule-making proceeding (PR Docket No. 92-235) opened in 1992 to develop an overall strategy for using the spectrum in the private land mobile radio (PLMR) allocations more efficiently to meet future communications requirements. The FCC created mandates for the two-way radio equipment manufacturers.
>
> In 1997, all new two-way radio models had to be capable of operation on the "new 12.5 kHz narrowband" channels. This is often called "dual-mode" equipment since the radio can accommodate both narrow- and wide-band channels. The idea was to begin to move gently toward narrowband channel operation over time. At that time, the FCC did not create any mandates to remove older wideband radio units from service or require you to use a new narrowband channel.
>
> The Part 90 LMR narrowbanding mandate was released 12-23-2004 by the FCC for all Part 90 business, educational, industrial, public safety, and local and state government two way radio system licensees currently operating legacy "wideband" (25 KHz) voice or data/SCADA radio systems in the 150-174 MHz (VHF) and 421-512 MHz (UHF) bands. The executive summary of the FCC order  establishes January 1, 2013 deadline for migration to 12.5 KHz technology.
>
>
> (Note many ham HT's are capable of WFM / Wide FM receive, intended for reception of FM radio/ Analog TV audio. Don't confuse this with the two way standard... Broadcast Wide FM is 150 KHz of bandwith.)
>
> Fonte: Steve, KB9MWR
>
>
>
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-- 
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Pedro Ribeiro
Indicativo: CR7ABP
QTH: São Francisco, Alcochete
GRID LOC: IM58MR
** Limitado a RX em Categ. 3 até 31/03/2012 **
( Decreto-Lei 53/2009, Art 8, 2a e Art 5, 3a )
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