Different digital modes

n9upc · Post by **n9upc** » Thu Jul 20, 2006 8:08 pm

Well I have made the jump into VHF conv digital now and have a question for all:

When programming the astro tx formats in an xts5000 there are three modes listed:

C4FM
CQPSK
WIDE

What are the differences between the digital modulation modes and can a digital scanner decode all these formats???

I know a lot of PS I believe use the C4FM modulation but what are the differences between all three and which one should be used???

Please feel free to either post her or e-mail me directly at: [email protected]

Thanks in advance.

Post by Pj » Thu Jul 20, 2006 8:16 pm

Wide is used in wide area/simucast systems. I forget what the other is typically used for.

All should be decodeable(sp??) by an apco scanner.

Post by **VE9MP** » Thu Jul 20, 2006 8:21 pm

C4FM uses 12.5 KHz of bandwidth and CQPSK uses 6.25 KHz.

judoka · Post by **judoka** » Sun Jul 23, 2006 1:29 pm

I think that CQPSK requires a linear transmitter so it is usually only set as Tx modulation in the repeater and Rx modulation in the Terminal. It is supposed to be indistinguishable from C4FM at the receiver, Scanner may have difficulty with Wide if it doesn't know about it because it will try to receive a wide band signal with a narrow band front end and will throw away some useful signal.