XTS5000 - UHF sensitivity variation - why?

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g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

XTS5000 - UHF sensitivity variation - why?

Post by g8tzl2004 »

I've been reading a Motorola spec sheet on the XTS5000.

380-470 MHz XTS5000's have a quoted analog sensitivity of 0.25uV for 12dB SINAD while the 450-512 Mhz radios have a quoted sensitivity of 0.20uV.

Likewise, P25 sensitivity at 5% BER is also 0.25uV for 380-470 MHz radios, while 450-512MHz radios have a quoted sensitivity of 0.20uV.

Why are 450-512MHz radios more sensitive?

Maybe its something to do with the greater band coverage of the 380-470MHz radios (90MHz split) vs 450-512MHz (62MHz split)? Maybe sensitivity in the middle of each band is the same..its just the band edges which are deafer in the 380-470MHz radios?

Any ideas?
N4KVE
Posts: 1647
Joined: Wed Apr 02, 2003 10:35 am
What radios do you own?: APX XTS XTL TRBO 900MHZ

Re: XTS5000 - UHF sensitivity variation - why?

Post by N4KVE »

I too noticed saw this spec sheet a year or so ago, & thought maybe that's why my 5000 didn't seem quite as sensitive in analog as my MTS2000's. No test equipment, just my ear. This only seemed to happen trying to hear repeaters 60 miles away & the 5000 was hearing the repeater as mostly noise, & the MTS radios were only slightly better. Never a difference on local repeaters. I asked, the same question, but never got a response. I did have the 5000 aligned, but now the difference is hardly noticeable. But I do want to know why it's spec'd that way. Maybe now someone will have an answer. GARY N4KVE
g8tzl2004
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Joined: Wed Sep 08, 2004 10:13 am

Re: XTS5000 - UHF sensitivity variation - why?

Post by g8tzl2004 »

I find my VHF MTS radios have excellent sensitivity..each VHF MTS seems to have basically the same consistent sensitivity from set to set.

My UHF MTS radios have very very variable sensitivity. They range from around 0.18uv (122dBm) to 0.28uv (118dBm) ie 4dB difference. Careful realignment brings no real improvement. Its the luck of the draw whether you get a good one!!! I guess its due to component tolerance differences. All radios are still within spec ...but the spec is very pessimistic. Motorola make some of the most sensitive radios you can buy... often a quoted spec of 0.3uV turns out to be an actual spec as good as 0.14uv...BUT not for UHF MTS Jedi's!!!! I only have 1 sensitive UHF MTS, about 5 average and 3 deaf ones!!

With the CDM range, Motorola quote a "typical" sensitivity as well as the official spec ie. 0.3uV but 0.22uV "typical". I think my UHF CDM is around 0.18uV which is about the same as my UHF MCS2000 ...although I do also have a deaf UHF MCS2000.

Any idea why your XTS needed to be realigned? Had it been reflashed so the softpots were out? You would think that Motorola would carefully align a top end radio in the factory. I have found that UHF MTS front end alignment is very broad..so the softpots have to be really well off to make much difference.

I've read that XTS3000's (3000 NOT 5000) are deafer than MTS2000's BUT I'm not sure whether this is for VHF or UHF. I think it will be difficult to outperform a VHF MTS2000...but to equal a VHF MTS2000l will be fantastic anyway. I just hope UHF XTS5000's are not as variable as UHF MTS2000's!!

Last night I progged a mint VHF MT2000. It still had its original factory codeplug and was last programmed EXACTLY 19 years ago on the 25 Aug 1993 at 16.03. The radio was still on frequency and sensitivity is excellent. The 19 year old battery is taking a 10 minute charge...so I will do some zapping and see if I can improve it!!!
N4KVE
Posts: 1647
Joined: Wed Apr 02, 2003 10:35 am
What radios do you own?: APX XTS XTL TRBO 900MHZ

Re: XTS5000 - UHF sensitivity variation - why?

Post by N4KVE »

g8tzl2004 wrote:
Any idea why your XTS needed to be realigned?
I have a XTS 3000, [Nick radio] & a XTS5000, & the 5000 could not hear the 3000 in IMBE. But all my Astro Sabers could hear the 3000, so I sent the 3000 & 5000 to a well known member here. I figured if he did both radios, the problem would go away. Sure enough, the 3000 had bad dev settings. He aligned it, but told me the 5000 was on the money. Even though it was slightly deafer, it was "in spec". Funny thing, but since day 1, the 3000 has had the hottest receive of all my UHF radios. But I too wondered if the low split 5000 was slightly deafer than the hi split because the coverage is broader. 380-470, vs 450-520. But right now, there's a tropical storm going through town. GARY N4KVE
g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

Re: XTS5000 - UHF sensitivity variation - why?

Post by g8tzl2004 »

All my MTS's are "in spec" BUT I think the front end sensitivity rated spec is a worse case condition...all radios should be significantly better. Hence why the CDM's have a stated "typical" (0.22uV) as well as rated spec (0.3uV).

The real world difference between a radio which just mets spec (ie 0.3uV or 117dBm) and a hot receiver (0.14uV or 124dBm) is 7dB..which is enormous!!! You would need to connect the "in spec" deaf radio to a 5 element yagi to get the same sensitivity performance as a sensitive radio using the set top 1/4 wave!!!

When I searched the archives there are lots of comments about deaf XTS3000's vs XTS5000's...so its interesting that you have a reverse situation!! There are also some comments about deaf XTS5000's due to using Impres batteries..maybe you get excess processor noise from the Impres battery which "blocks" weak signals. I have processor noise issues with many of my radios when Rxing really weak signals..it seems to come from the LCD and is made worse by poor grounding. All problems disappear when you use an external antenna.
N4KVE
Posts: 1647
Joined: Wed Apr 02, 2003 10:35 am
What radios do you own?: APX XTS XTL TRBO 900MHZ

Re: XTS5000 - UHF sensitivity variation - why?

Post by N4KVE »

I just tried it again. Keyed up a repeater 60 miles to the south from the base. 2 3000's heard it, 95% noise, but the signal was able to break through the squelch. Same with a MTS 2000. Grabbed my 5000, & I hear nothing. Even when holding the monitor button, so the squelch is wide open. No impress batteries on anything. I tried the same thing on a repeater 30 miles away, & the 5000 kept up with the other radios. I don't know if it makes a difference, but my 5000 has the older RAM processor board. I wish I had a signal generator so I could see exact numbers. GARY N4KVE
g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

Re: XTS5000 - UHF sensitivity variation - why?

Post by g8tzl2004 »

Maybe the XTS5000 has an internal sproggie on the 60 mile repeater frequency? My Saber III has a sproggie on my local repeater which becomes much worse when I switch on the LCD display light!!! I guess its processor noise again.

I often search for really really weak signals with the squelch open (although I always set my SQ level at the lowest possible threshold so the SQ usually opens anyway on super weak signals). I then use the same identical base antenna connected to each radio and compare signal intelligibility and noise levels between different radios. There is very little difference between VHF MTS's but UHF's MTS's are very variable. Maybe the UHF XTS5000's also vary from set to set ..they will all be "in spec" but some will still be a bit deaf? I really hope this is not the case!!
g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

Re: XTS5000 - UHF sensitivity variation - why?

Post by g8tzl2004 »

With regard to processor noise, I have just been programming my MT2000 and found that if I have the carrier SQ set to open (ie. white noise when no signal present), I get a low level "tick tick" noise when receiving a weak signal. If I close the SQ, the tick tick noise disappears and all I hear is the real signal. I guess this is more processor noise again!!!

I also found that if I held my hand over the keypad and LCD, I get "crackling noise" QRM on a weak signal which disappeared if I held the radio with just 2 fingers at the base. I guess the processor noise is radiating from my hand into the set top antenna. Using an external antenna resulted in 100% clean signals.
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