Woohoo! Billy Boy finally gets to touch Trbo. One of my customers went from a Kenwood conventional UHF repeater with a mix of portables to a MTR3K repeater with XPR7550 portables. Frankly, I was amazed at the improvement. So, I sat down with a bunch of their old portables, some Moto UHF portables I have, and a couple XPR7550's to compare performance. All had direct sensitivity in the -114 to -118db range which is pretty normal. Where the XPR7550 shined was receiving radiated signal. They were always 10db or more better than the others.
I put a UHF rubber ducky on the generator, and turn the gen down until a portable with it's antenna parallel to the ducky squelches. I've done this a thousand times over the years as part of my PM's because I've found a number of broken portables that way. Their direct sense is good, but their sense off the air with an antenna is horrible because the antenna port is broken. Generally, with a ducky on my IFR1200, portables squelch around -108db. The Kenwoods with the stubby antennas the customer insisted on using came in around -105db. Not horrible. Totally expected degradation. But,the XPR7550's stay open down to almost -120db with this method.
That's almost as low as the gen will go. I checked for leakage by throwing a 20db pad on the gen port, and put the ducky after that. Still got the same results after doing the math. I even ran the line out a 20ft BNC jumper with the ducky on the end. The XPR's are not getting an extra kick of stray energy from the gen. They just receive better off the air than Kenwoods, and several Moto portables on the same freq.
Has anyone else experienced this yet?
XPR7550 rx sense better than most radios?
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Re: XPR7550 rx sense better than most radios?
I often do this test as well. I also check TX to confirm I can couple 0.5 to 1.0 watts of power to the service monitor. As you say, a good way to check the complete package.
Curios on what you're using for your values? Squelch opening, 12 dB SINAD, just going by ear for a reasonable audio signal?
Curios on what you're using for your values? Squelch opening, 12 dB SINAD, just going by ear for a reasonable audio signal?
Re: XPR7550 rx sense better than most radios?
I'm working with whatever the radios are set to for squelch. I didn't break out the tuner on any of them. They all landed in the -114 to -118 direct depending on the model. The earball said it was a reasonable setting - not quite 12db sinad. I did not check whether they were OR or AND squelch.
Re: XPR7550 rx sense better than most radios?
It turns out that -
Yes! The 7550's are more sensitive than most other radios, and by a significant amount. I did the direct sensitivity wrong. You don't screw in an adapter into the antenna port like previous models. Our Trbo dude had a fancy jig to do that. You peel off the plastic escutcheon above the battery which reveals a waterproof plug covering an sma connector. Fancy jig has an sma extension sleeve so you can mate a cable to check pwr and sense. Done that way, the customer's radios came in at -128db / .11uV which is amazing. Even though the published spec is a normal .3uV / .22uV typical analog, it looks like they can be 10db better than that.
Apparently this "improvement" has already caused problems with customer's adding to an existing system with older 6000 series radios that don't do quite as well. Customers perceive the older radios are broken, or the system is broken. OR because of the increased sensitivity, co-channel interference becomes a more serious problem, and the new radios appear to not work as well as the older ones. Oy vey!
Break out your dog bone underwear.
But, if you start off with 7550's be ready to be amazed especially with in-building coverage. You get a free 10db or so that can really open up some of the dark spaces in the bowels of concrete and steel.
Yes! The 7550's are more sensitive than most other radios, and by a significant amount. I did the direct sensitivity wrong. You don't screw in an adapter into the antenna port like previous models. Our Trbo dude had a fancy jig to do that. You peel off the plastic escutcheon above the battery which reveals a waterproof plug covering an sma connector. Fancy jig has an sma extension sleeve so you can mate a cable to check pwr and sense. Done that way, the customer's radios came in at -128db / .11uV which is amazing. Even though the published spec is a normal .3uV / .22uV typical analog, it looks like they can be 10db better than that.
Apparently this "improvement" has already caused problems with customer's adding to an existing system with older 6000 series radios that don't do quite as well. Customers perceive the older radios are broken, or the system is broken. OR because of the increased sensitivity, co-channel interference becomes a more serious problem, and the new radios appear to not work as well as the older ones. Oy vey!
Break out your dog bone underwear.
But, if you start off with 7550's be ready to be amazed especially with in-building coverage. You get a free 10db or so that can really open up some of the dark spaces in the bowels of concrete and steel.
Re: XPR7550 rx sense better than most radios?
I tested some UHF 3500's yesterday. They came in around -120 to -122db. So, a little hotter than the average UHF portable of the past, but definitely not as hot at the 7550's.
Re: XPR7550 rx sense better than most radios?
Bill - any idea how the mobile XPR4550 compares to the newer XPR5550 for RX sensitivity?
The 10dB improvement in the 7550 RX is exceptionally good - I need to do the exact math but on the TX side, power could be reduced from 5w to 0.5w for identical coverage results compared to the older 6550's!!!
The 10dB improvement in the 7550 RX is exceptionally good - I need to do the exact math but on the TX side, power could be reduced from 5w to 0.5w for identical coverage results compared to the older 6550's!!!
Re: XPR7550 rx sense better than most radios?
Bill - are your sensitivity figures based on the signal required to open the squelch or are they based on 12dB SINAD?
Maybe some radios have the squelch set high so you need a stronger signal to open the squelch?
I have just acquired a UHF XPR7350 and analog RX performance is excellent - it just beat my "best ever" UHF portable (which is not a Moto) for RX sensitivity - a big improvement over my UHF XTS5000 , HT1250 and MTS2000.
I also found the "default" squelch was set to open on just copyable signals which is great for DX!! All my other Motorola radios generally have the default squelch levels set too high so signals which are actually copyable are missed. I always use the Tuner software to set the SQ at a much lower level...but the XPR7350 already came with the SQ set at much lower level.
In general, I have found that my older VHF Motorola radios have excellent sensitivity and beat just about every other radio manufacturer for RX sensitivity. But with my older UHF Motorola radios I have found that sensitivity is good but NOT the best and tends to be variable from radio to radio. However, with the UHF XPR7000 series, Motorola now takes top place in my list of my most sensitive UHF portable radio....its just a pity you need a special cable to connect an external antenna!!
Maybe some radios have the squelch set high so you need a stronger signal to open the squelch?
I have just acquired a UHF XPR7350 and analog RX performance is excellent - it just beat my "best ever" UHF portable (which is not a Moto) for RX sensitivity - a big improvement over my UHF XTS5000 , HT1250 and MTS2000.
I also found the "default" squelch was set to open on just copyable signals which is great for DX!! All my other Motorola radios generally have the default squelch levels set too high so signals which are actually copyable are missed. I always use the Tuner software to set the SQ at a much lower level...but the XPR7350 already came with the SQ set at much lower level.
In general, I have found that my older VHF Motorola radios have excellent sensitivity and beat just about every other radio manufacturer for RX sensitivity. But with my older UHF Motorola radios I have found that sensitivity is good but NOT the best and tends to be variable from radio to radio. However, with the UHF XPR7000 series, Motorola now takes top place in my list of my most sensitive UHF portable radio....its just a pity you need a special cable to connect an external antenna!!
Re: XPR7550 rx sense better than most radios?
Sorry I missed your earlier post.
Earball 12db sinad. Rx qualified, speaker on, hearing a tone with reasonable clarity but not perfect. I definitely did not get precise about measuring, but I could drop carrier another db or two before sq would close. That's not a lot of headroom, but that's generally all you get at the bottom of performance. Still beat the previous portables they had by 10db.
Earball 12db sinad. Rx qualified, speaker on, hearing a tone with reasonable clarity but not perfect. I definitely did not get precise about measuring, but I could drop carrier another db or two before sq would close. That's not a lot of headroom, but that's generally all you get at the bottom of performance. Still beat the previous portables they had by 10db.
Re: XPR7550 rx sense better than most radios?
Thanks Bill.
Have you done any RX comparisons with any VHF (rather than UHF) XPR7550's? Most of my older Motorola analog VHF radios already have hot RX front ends so it will be interesting to see how the VHF XPR7550 compares.
Also have you done any RX comparisons with the 1st generation XPR4550 mobile vs the 2nd generation XPR5550 mobile. I have received conflicting reports. Some say that both mobiles are identical while others say the later XPR5550 is hotter. Maybe the VHF versions are identical but the UHF XPR5550 has a hotter RX front end.
It shows how useless Motorola's official spec is for the UHF XPR7550 ie. 0.3uv for 12dB SINAD / typical 0.22uV for 12dB SINAD. More like 0.12uV for 12dB SINAD.
Have you done any RX comparisons with any VHF (rather than UHF) XPR7550's? Most of my older Motorola analog VHF radios already have hot RX front ends so it will be interesting to see how the VHF XPR7550 compares.
Also have you done any RX comparisons with the 1st generation XPR4550 mobile vs the 2nd generation XPR5550 mobile. I have received conflicting reports. Some say that both mobiles are identical while others say the later XPR5550 is hotter. Maybe the VHF versions are identical but the UHF XPR5550 has a hotter RX front end.
It shows how useless Motorola's official spec is for the UHF XPR7550 ie. 0.3uv for 12dB SINAD / typical 0.22uV for 12dB SINAD. More like 0.12uV for 12dB SINAD.
Re: XPR7550 rx sense better than most radios?
Nope. Only customer I have with Trbo. Everyone else is P25 or analog.
Re: XPR7550 rx sense better than most radios?
The squelch on the XPR7350/7550 is so "good" for weak signal working that I'm worried that commercial users will "demand" that Motorola provides a firmware update which increases the threshold so that long distance co-channel interference problems are resolved!!!
However, I guess commercial users can just switch in the "tight" squelch setting.
I'm still trying to figure out if you can actually adjust the SQ threshold using either CPS or Tuner software. I don't think you can so there appears to be just 2 factory set SQ levels - normal and tight. Thankfully "normal" is set at the absolute threshold which is great for DX.
Come to think of it, why is the default SQ level on many of my older Motorola radios set so high. Although its easy to adjust using Tuner software, I guess it often just gets left at the factory default level. What is the disadvantage of hearing a weak noisy signal? Other than issues with co-channel interference, surely its better to hear a weak noisy signal rather than nothing at all? Is it not better to hear a noisy "cry for help" rather than nothing?
However, I guess commercial users can just switch in the "tight" squelch setting.
I'm still trying to figure out if you can actually adjust the SQ threshold using either CPS or Tuner software. I don't think you can so there appears to be just 2 factory set SQ levels - normal and tight. Thankfully "normal" is set at the absolute threshold which is great for DX.
Come to think of it, why is the default SQ level on many of my older Motorola radios set so high. Although its easy to adjust using Tuner software, I guess it often just gets left at the factory default level. What is the disadvantage of hearing a weak noisy signal? Other than issues with co-channel interference, surely its better to hear a weak noisy signal rather than nothing at all? Is it not better to hear a noisy "cry for help" rather than nothing?