Batboard

Hi,

I'm looking to find a radio that can support 6.25KHz channel spacing & offer baseband (flat) TX/RX audio via the accessory port (like the old GM300's used to provide via the 16 pin connector. Can someone tell me (or point me to the right model/direction) if the XPR4350 supports this via the accessory connector?

What I'm trying to do:
use the radio as an RF deck for a D-Star hotspot on 145.600MHz (6.25KHz channel width for maximum efficiency and performance).
The audio access needs to not have any emphasis or de-emphasis (flat) like the GM300's provided.

If the XPR4350 is not the right radio, can someone please help me by specifying an alternative model that offers the above, but also offers it with 6.25KHz channel width? I'd appreciate the assistance.

Best Regards,

John, K1WIZ

I wouldn't use a digital radio for this. The DSP in it may distort or cause problems with reproducing the digital information.

If you are injecting flat audio into the unit, and the modulated signal is only 6.25kHz, even a GM300 should be able to accurately reproduce the signal. The IF would be wider than normal, but it shouldn't affect the ability to use it in low-noise sites.

That's not a 6.25kHz frequency you've mentioned, so as I said, even a GM300 should do the job.

Remember - it's only going to be as wide as what you put into it.

Take a look - folks making these hotspots are doing this with Maxtracs, etc.

There is no Motorola that officially offers a 6.25KHz bandwidth as that is almost by definition going to be a digital modulation and obviously not one that Motorola offers as TRBO is essentially 12.5KHz (Ok not quite but close enough for this conversation). I'd say call Icom, I hear their support for D-Star is top notch. El oh el

escomm wrote:There is no Motorola that officially offers a 6.25KHz bandwidth as that is almost by definition going to be a digital modulation and obviously not one that Motorola offers as TRBO is essentially 12.5KHz (Ok not quite but close enough for this conversation). I'd say call Icom, I hear their support for D-Star is top notch. El oh el

I can't help it - ehehehehhehehehehhee *snicker*

here is a better idea

go on http://www.dmr-marc.net/ get your ID and program up the DMR repeaters in Mass and use that radio what it was built for.

You would get some distortion and ISI (inter symbol interference) if you used a real 6.25 kHz IF filter as the typical VHF amateur +/- 1 ppm stability already introduces up to 0.3 kHz uncertainty and D* is wider than 6 kHz.

At UHF you're looking at a kHz and that's even before the arguments begin over the format's GFSK emmision bandwidth.

I'd just use a 12.5 kHz IF but if you do want to go narrow, look for some of the 8 kHz wide ceramic 450 or 455 kHz AM Murata filters for the second IF and retro fit them to a 12.5 kHz receiver. You might need to work on the filter matching to reduce the in-band ripple.