Batboard

I am currently programming a UHF XTS3000 initially using conventional analog.

The radio has the following features:

Firmware 07.14.00.00
DSP N08.03.01
Flashcode 580001-00200-8

RX sensitivity is EXCELLENT. Better than my UHF Jedi and Waris radios!!! The XTS3000 is better than my "best" UHF MTS2000..and much better than all my other UHF Jedi's and better than my "best" HT1250. I've read various comments about deaf XTS3000's but this XTS3000 is very sensitive...maybe its just the luck of the draw...like with all the UHF Jedi's..some are deaf and other hot but they are all within the "worthless" pessimistic spec !!

The RX audio is OK but I am finding that it sounds a bit narrow and processed?

I need to experiment with the various settings ...RX emphasis , Ultra Narrow IF 5.76 vs 7.8 KHz filters etc

The XTS3000 currently has RX emphasis enabled and 5.76 KHz IF filters enabled.

What are the best settings for RX analog audio especially when receving weak signals??

At the moment, when I open the squelch (with no signal), I get a nice sounding "bright" white noise but as soon as you RX a very weak signal, its like a narrow filter is automatically enabled. Its a bit like switching from a 6KHz to a 3KHz filter on AM.
On other Moto radios, if you open the squelch (ie. listen to white noise) and then RX a weak signal, the weak signal sort of mixes with the white noise...with the XTS3000, the weak signal caused the "tone" of the white noise to change from a wide bright noise to a narrow processed noise...if you know what I mean!!

Any thoughts?

On any Astro radio, the white noise you hear is artificially generated, because the radio is still using the DSP, even in analog. The noise you hear on a weak signal is the true noise. The MTS radios only make true noise, as they are analog radios w/o any DSP. GARY

OK on the DSP and artificial white noise in analog mode!

What's the artificial white noise for? Maybe to set volume levels?

I'm thinking that the audio sounds narrow because of the 5.76KHz IF filters? I will try switching to 7.8KHz filters. From the Help Pages, it seems that the narrow 5.76 KHz filter is only used on "narrow" 12.5KHz spaced, 2.5KHz dev systems...so I guess it has no effect if you use 20KHz spacing 4 KHz dev?? I'm not sure why they don't have a narrow option for 20kHz/25KHz spaced systems?

UPDATE: I switched from the 5.76 KHz to 7.8 KHz IF filter and noticed a drop in the XTS3000 RX sensitivity but better audio.

I guess this is to be expected. In theory, if you switch from a 15KHz IF filter (25KHz spacing, 5KHz dev) to a 7.5 KHz IF filter (12.5KHz spacing 2.5KHz dev), there is usually around a 3dB improvement in sensitivity...which is significant from a weak signal point of view.

A 5.76KHz filter is very narrow...I have a few FM receivers which have switchable 6KHz or 15KHz IF filters and the 6KHz filter makes a significant difference to sensitivity...basically the radios are using the AM 6KHz filter on FM...a 7.5KHz filter is normally used for narrow band FM.

If an XTS3000 is set to 20KHz spacing (approx 12.5KHz IF filter) , a switch to the 5.76KHz filter will result in a big improvement in sensitivity although the high dev could result in poor audio...I think.

Using the XTS3000 7.8KHz IF filter (slightly wider than the "usual" 7.5KHz IF filter), the UHF XTS3000 was still more sensitive than all my Jedi radios and about the same as my best HT1250

Food for thought: a guy sent me a 800 MHz XTS3k once that worked in conventional but would flash OUT OF RANGE in trunking, even with all of the trunking parameters verified and the alignment checked. Flipping the Ultra-Narrow IF filter from 5.76 to 7.8 fixed it.

Was the trunking network a narrow spaced 12.5KHz system?

I was thinking that the Ultra Narrow IF filter only worked if the XTS3000 is set to 12.5KHz spacing 2.5KHz dev?

Maybe the trunking TX base station was a bit off frequency and widening the filter helped with receiving a slightly off frequency signal. Or maybe the base dev was a bit too high so again the wider filter helped?

I have found that in analog mode the XTS3000 does NOT like a slightly overdeviated signal which results in "filter rattle" and causes the SQ to close on speech peaks. I guess this is due to the DSP filtering. My other analog only Motorola radios (CDM/ HT1250) will RX a 4/5KHz dev signal using the narrow 12.5khz filter setting with no problem at all...no filter rattle or speech peak issues.

g8tzl2004 wrote:Was the trunking network a narrow spaced 12.5KHz system?

I was thinking that the Ultra Narrow IF filter only worked if the XTS3000 is set to 12.5KHz spacing 2.5KHz dev?

Maybe the trunking TX base station was a bit off frequency and widening the filter helped with receiving a slightly off frequency signal. Or maybe the base dev was a bit too high so again the wider filter helped?

It killed all trunking reception, not just on his target system.