C4FM or CQPSK?

[SKYNET156]

I am programing an Astro Saber, and i am wondering when programing a P25 conventional channel, which do i select on the CPS for type?

 

[SCPD]

You may want to try this in the Motorola forum?

 

[N_Jay]

I am programing an Astro Saber, and i am wondering when programing a P25 conventional channel, which do i select on the CPS for type?

If it is a single site system or simplex, it is most likely C4FM

If it is a simulcast system it is most likely CQPSK.

 

[SKYNET156]

well...it's a conventional channel, so does this still need to be used?

 

[wlmr]

well...it's a conventional channel, so does this still need to be used?

Yes it does.

 

[N_Jay]

well...it's a conventional channel, so does this still need to be used?

"Conventional" does not specify if it is simplex or repeated, or if it is or is not simulcast.


My guess is probably not, so program it one way and then the other and see which works best.

 

[SKYNET156]

Well it's receive only, so there would be no TX, so what is the best to choose?

 

[W2SJW]

C4FM.

From my best recollection, CQPSK is only used on multi-site simulcast P25 trunk systems (9600 baud).

 

[SKYNET156]

and my next question is this with the CPS, I am programming Kentucky State Police Scanner Frequencies and Radio Frequency Reference site 3, now when programming this with the CPS, the network ID comes up as 293, do i change this for the nac? is the network id the nac? and it give me the option also to do C4FM, CQPSK or Wide, what is the best option to RX only a P25 Conventional Channel like KSP?

 

[W2SJW]

A network ID is used in reference to discussing a trunk system. Seeing that what you want to program is conventional, you need to use the NAC codes listed there in the database. If you leave the radio set at the Motorola default of 293, you won't hear anything on those channels!

NAC is the equivalent of PL/DPL on digital voice. You should stick with standard C4FM, especially now that I see that the agency you want to monitor is not trunked...

 

[N_Jay]

delete

 

[N_Jay]

Well it's receive only, so there would be no TX, so what is the best to choose?

It should only affect RX.

The right one is best and the other is somewhat sub-optimum.

I don't know how sub-optimum.

 

[N_Jay]

. . . You should stick with standard C4FM, especially now that I see that the agency you want to monitor is not trunked...

The determining factor would be whether it is SIMULCAST or not.

Trunking has nothing to do with the issue.

 

[W2SJW]

I know, and I concede that point! :wink:

I just spent the last half-hour texting a few friends that either still do/once did work for /\/\, and they all believe that the KSP would be using C4FM.

CQPSK is normally used on P25 TRS's that have sites transmitting multiple signals on multiple frequencies simultaneously.

KSP is using multiple sites to transmit the same signal. I'm gonna keep digging on this one, because I was never able to set my 5000's to CQPSK on a conventional personality & have it stick (I wanted to see if C4FM & CQPSK 'sound' different 'in the raw').

 

[W2GLD]

C4FM is the standard for all conventional (simplex or repeater use) in the U.S. today.

CPQSK is used only for "Large Networked, TRUE Project-25 Trunking" systems such as the Michigan MPSCS.

KSP uses a series of conventional Motorola Quantar Project-25 repeaters that are networked on the back end for statewide coverage using both wireline and microwave links.

All of there radios are programmed for C4FM as the standard audio!

On a side note, I saw that the three formats were mentioned somewhere in this article.

C4FM is the standard used for standard Motorola Smartnet/Smartzone and Conventional Radio Systems with digital audio (Project-25). These systems would include the NJSP systems, Burlington County New Jersey, Atlantic City New Jersey, Philadelphia and so on. Basically if it's not a "TRUE Project-25 Trunking System (9600 Baud Control Channel) then it uses the C4FM format with few exceptions. For example, the Bucks County Pennsylvania system is a standard Motorola Smartzone system but still uses the "WIDE" format as does the State of Delaware currently. These will eventually change to the C4FM format as upgrades take place. As of 01-2009 these systems were still using these formats. The C4FM format can be either 25.0KHz channel spacing with 5.0KHz. maximum deviation or 20.0KHz. channel spacing with 4.0KHz. maximum deviation, or 12.5KHz. channel spacing with 2.5KHz. maximum deviation. Most 800MHz. systems operate within the 20.0KHz. range, however there are exceptions. UHF is generally 25.0KHz. or 12.5KHz for the most part with the 12.5Khz. becoming the normal, at least until the 6.25KHz. Phase II starts to become more of a reality.

CPQSK is the standard used for "Large Area, Networked, TRUE Project-25 (9600 Baud Control Channel) systems. Systems such as the Michigan MPSCS, Virginia STARS, etc.
This format assumes narrowband compliance at 12.5KHz channel spacing with maximum deviation at 2.5KHz.

I hope this information helps. I would go ahead and setup the conventional channels for "C4FM" and call it a day...

Good luck and happy monitoring!

Regards,

Jerry - W2GLD

 

[W2SJW]

Thanks Jerry, couldn't have said it better myself!

 

[obijohn]

The determining factor would be whether it is SIMULCAST or not.

Trunking has nothing to do with the issue.

The correct answer is C4FM. Your radio should always transmit in C4FM. The fact that what it receives is CQPSK or C4FM is moot. The receiver doesn't care. CQPSK is only used by simulcast base stations at this time. (Linear simulcast modulation is CQPSK format).

If it is a receive only conventional personality, just ignore the setting, because the choice in question (CQPSK vs C4FM) only applies to what
mode the radio TRANSMITS.

 

[obijohn]

I'm gonna keep digging on this one, because I was never able to set my 5000's to CQPSK on a conventional personality & have it stick (I wanted to see if C4FM & CQPSK 'sound' different 'in the raw').

I'm not sure that even with version 13.00.01 firmware that subscriber radios will even transmit in CQPSK.
I think it is a hardware dependent selection, probably years down the road.

I believe that if you choose "CQPSK" it defaults to "C4FM', just like you found.

 

[N_Jay]

The correct answer is C4FM. Your radio should always transmit in C4FM. The fact that what it receives is CQPSK or C4FM is moot. The receiver doesn't care. CQPSK is only used by simulcast base stations at this time. (Linear simulcast modulation is CQPSK format).

If it is a receive only conventional personality, just ignore the setting, because the choice in question (CQPSK vs C4FM) only applies to what
mode the radio TRANSMITS.

Since a subscriber unit ALWAYS transmits C4FM, and this is a subscriber unit setting, I would have to surmise that the setting is used to adjust some RECEIVE parameter.

While a well designed C4FM receiver will receive CQPSK fairly well, and a properly designed CQPSK receiver should receive C4FM nearly perfectly, in the real world there may be some RX parameters that are shifted slightly one way or another to optimize for one modulation or the other,

Interesting that it is only good in trunking, since it is possible to build a P25 conventional simulcast system, but then again, Motorola tends to be so trunking centric, they the CPS development team may not know much about conventional operation.

 

[MattSR]

Does anyone know the technical details of how LSM is different from CF4M or CQPSK?