TRX-1: Improvement suggestions - scan rate and sensitivity

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chris451rr

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iowa
When the TRX-1 is operated in fringe areas, I find it will miss a lot of calls, side by side for example to a bc296xt, where it is a mix of UHF 800 VHF with various squelch modes and trunk modes.

In summary the scan speed or dwell time is too fast for weak signals.
This has been verified by using a signal generator and various scan modes.
I warmed up the signal generator to verify the numbers.
TRX 1 running on battery (no ac adapter noise) coax directly to antenna and signal generator.
Program a test frequency and navigate to that channel and adjust the signal generator to determine squelch open point.
Squelch opens at -115dbm on a fixed test frequency 155.160mhz.
Scan only a few channels 155.15626 and 155.160 and one trunked group.
Will stop near -115 dbm.
Scan a huge scan list (numerous bands and systems and CTCSS but including 155.160 carrier squelch.
Misses this channel until power is turned up to -105 to -100.
Clearly when the scanner is changing bands segments and modes it is not keeping up at 70chans/sec.

For whistler: Set up a signal generator on a fixed carrier access frequency.
Set up a scan list of 2 channels, verify it will stop at -115.
NOw set up a scan set of lots of channels bands and modes.

If it is locked down to just a few channels or one system and wildcard, it will catch all the calls.
Also it does well in strong signal areas.
In the specifications it states 70 channels per second scan rate.
That is quite fast for weaker signals and there is no adjustment for this.

So for a given channel DMR
Fixed radio gets 100%
BC296xt will detect all such signals but there is a delay depending on how many channels
trx-1 will miss quite a few calls.
Trx improves quite a bit if locked down to the trunked system and squelch is backed off.
Open squelch helps a lot.
TRX has no decode issues I've seen with DMR here and gets some DMR formats that a fixed channel (baofeng dm5r plus) is not decoding. (I don't have a TYT).
But will miss calls unless locked down to a single channel
will not decode.(two codecs? Some older Motorola DMR codecs are not in the baofeng)
Squelch Signalbar and Trunk do a lot of flashing on/off.
Open squelch and lockout all carrier squelch channels improves hits.
The time constant in the squelch seems too long compared to the scan speed.
When switching to a trunked talk channel that is weak or marginal or simulcast, it will fail to detect it and move on, but is improved when the squelch control is open.
Then the scanner will stop on a carrier access channel and squelch has to be turned back up.

Workarounds:
Reduce channels scanned to a few.
Place high priority channels in several scan sets
Scan a trunked system with wildcard and lock it down to a few high priority channels.
If a call is heard use the left arrow then lock down on the channel(usually the last one heard)

Other issues:
When turning on it is in menu mode and does not start scanning after it boots up.
Battery charging is hard to predict. There is no spec on charging current nor a flow chart for how the timed battery charging works.
Sometimes it will crash when power drops. Very rarely it requires a pull the battery out reset. There does not seem to be a keyboard combo that will reset it.
If it is running it takes a long time to charge - battery seems to give full run time after a day.
Run time on the current set of batteries (NIMH 2.5ah) about 5 or 6 hours.
Could be much less depending on use.

Things I will eventually measure or do if nobody else has:
Charge current when on/off.
Measure current at batteries.
Source 5v current drawn during charge/run/not charging and running/off.
Look for the local oscillator on a spectrum analyzer
Test band sensitivity for a series of frequencies
Try some remote control commands.
 

SCPD

QRT
Joined
Feb 24, 2001
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Location
Virginia
Thanks for your work, however many do not have the slightest idea what dBm means. Just saying. :wink:

I am with you .. I find that the scanner manufacturers do not do a very good job in initial testing of their scanners to see how they work in the real world. It is fine to test in the middle of who knows where, but to test in the big city ... that is a test where many scanners just plainly fail. This is not a Whistler only issue .. but Uniden as well.

I think that they should have a list of beta people in certain cities who sign non disclosure agreements and will test their scanners before they hit the market. It would save them a lot of grief later.

I live in the 2nd most RF dense city in Canada and my scanners mostly crater here. I know some **** from Ontario is going to tell me to shut up, right about now.

Oh .. I was going to say, that the TRX-1 is not all that bad at all, it is WAY WAY better than the older scanners. But then .. I find that most people have issues when they put an outside antenna on their handheld scanner .. overall a dumb idea.
 
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chris451rr

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Aug 1, 2008
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Location
iowa
It was written for engineers but its easy to explain.
For reference, the very best radio will pick up -120dbm Decibels below a milliwatt and provide a slightly noisy but readable signal..
Its a logarithmic ratio so 10db is a factor of 10 and 120db is a factor of 10^12.
As that negative number approaches -100dbm then the sensitivity is 20 decibels or 100 times less sensitive then the best possible sensitivity. So you could say from my numbers above that it takes approximately 100 times more signal for the scanner to stop than when it is sitting on a channel.
Hope that clears it up for some of the readers. Another way is to rate the senstiivity in microvolts.
So 0.15microvolts is very good, and I have to apply 15 microvolts before the scanner will stop (thats 100 times 0.15) but engineers like logarithms because they cover a wide range with fewer numbers.
There is one other feature request.
When the squelch stays open provide a time-out to allow it to continue scanning. Ability to enable/disable on a per channel basis would be nice.
 
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SCPD

QRT
Joined
Feb 24, 2001
Messages
0
Location
Virginia
I have the dBm to microvolt chart (and s meter values) on my wall .. I get it.
My R7000 goes down to about -127, and yes .. anything near that is pretty hit and miss.

I was just being funny .. but thanks for the lesson. Some learning here is never a bad idea. :)
 
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