Is this the best that I can expect?

[MTS2000des]

I'm done with trying to make wine out of water

Bottom line is the current P25 scanners cannot properly receive LSM simulcast transmissions, anything else is just like duck taping a bumper on a car. Until the manufacturer's get off their behinds and either write some DSP code that makes their current radios act right or introduce new models, I'm done with it. I'll use my work radio when I'm at work to listen to what I am authorized to listen to, and at home, my conventional only/RX only XTS5000 does the job. I'd much rather listen to the occasional bus driver (nuisance delete on top button!) or water works crew and reliably hear the signals without having to put up elaborate antenna arrays (impractical for a portable anyway) or play find a hot spot.

I'm lucky to be able to listen anyway outside of work as the two IMBE systems (Cobb and Atlanta) don't run encryption on but a handful of talkgroups.

 

[MOGA]

MTS2000, while undertaking a quick study of Linear Simulcast Modulation in light of your last post to discover the reasons for the difficulty of wide band receivers in demodulating that type of transmission, l discovered this little nugget of information in the product documentation of a communication analyzer:

How do you Measure Frequency Error of a CQPSK Signal?

With digital modulation, seemingly easy measurements like frequency error become difficult. This is due to the fact that with the phase shifts occurring on the RFcarrier, a stable frequency measurement is difficult obtain. To determine the actual frequency of the signal, a mathematical rendering of the RF signal must be calculated as a separate computation and then compared against a mathematically derived "ideal" signal. Only then can we determine accurate frequency error measurements....

then a little later on...

...The ability of the modulator to produce as close as possible to an ideal waveform is critical to the receiving radio's ability to decode the digital data being sent over the air.

This snip gave me the idea of adjusting the Noise Thresh expert setting of the radio to its lowest value. My thinking is that it would force the radio's DSP to perform more frequent error corrections while decoding the LSM channel. I noticed an immediate improvement afterward. It has not entirely eliminated the little bit of choppiness that I still experience but the transmissions are noticeably more stable. YMMV. I just heard nearly every word of the response to a running gunfight in progress, the transmission of which lasted for over ten minutes. Very satisfying. In the past, it is the more exciting transmissions that seem to become completely unintelligible as the call goes on.

One other question. What type of coax should I use for a 25' run at 800 MHz? I was going to use LMR 400 until I saw a recommendation on the interwebz that suggests LMR 195 for runs 25' and under. Does this sound like good advice? I want to keep as much signal as I can so if the signal loss is anything more than negligible between the two types of cable for that freq/length then I'll stay with the 400. I've checked technical resources for each type of cable to assist in a decision but all that I can find are loss rates per 100 feet, which aren't of any help given my intended application.

Thanks.

 

[rmiller818]

This link was given to me in another thread:

Coax Calculator

Still trying to figure out the best way to mount my yagi as well.

If the noise threashold thing works for you great (I am going to give it a go as well) but my impression is that is not what would affect it.

 

[MOGA]

I haven't stopped monitoring since my earlier post. The setting change has made an improvement for me beyond a doubt. Whether the change has affected the DSP as I theorized is anyone's guess but I'll take the reception improvement any way that I can

rmiller, thanks for the coax calculator. It's clear that there's no contest between the 200 & 400 spec LMR cables as far as signal loss. Once I've gotten some good cable, the real fun begins: testing the various antennas. Even if the Yagis don't perform on the APD system as well as I'd like, they'll still be useful for monitoring other 800 systems in the area. I've got a 2m base antenna to put up too so I have my hands full with mounting/testing antenna projects for a while. Cable first, though.

 

[rmiller818]

The 400 better I guess?

I got to figure out what to do with mine, want to split it to feed 4 scanners.

 

[MOGA]

Well it's been three months, and I've been all around the mulberry bush with monitoring Atlanta TRS.

I firmly believe in the wisdom of MTS2000s words. Without a dedicated radio, there are ok days, and then there are monitoring days that are a little better for us guys in simulcast environments. If I can get an hour without multicast, I'm a happy camper.

My best setup is a 800 yagi affixed to a retractable PA speaker stand that I can move around inside the house, depending on the room that I'm in. Pointing the antenna at one tower while rejecting the others that come in from the sides and back helps eliminate the choppiness a lot. Being on the second floor while using this antenna is when I get some of my best sessions. Too bad that my wife hates seeing it, and usually I have to confine my activities to my office when she's home, which is in the extreme section of the house that has the poorest reception. Connecting the antenna and the radio is 10m of LMR400. Heavens is that stuff stiff. I've yet to get it rolled out into anything that resembles a straight line. I think I probably would have opted for something else if I had known how unwieldy it really is.

I also have a GRE 800 whip (RS 800 Scanner Whip Antenna) and a Diamond SH77CA that are used in conjunction by way of a dual headed BNC adapter that work wonders with each other. The combination of the two performs better than any two antennas that I have, whether the same or different designs, and I have about a dozen or more whips of various makes and sizes. I was using two GRE 800s together that pull in a solid signal any time that I couldn't or didn't want to pull out the yagi-uda. Yet they don't eliminate the voice drop out the way that these two do. It's weird, because the SH77CA sucks ass on 800 by itself. I use it for VHF/UHF monitoring primarily. I actually wonder if it's acting in the capacity of a parasitic element on 800?

I just priced a XTS5000 Motorola. My wife would freak the frick out if I bucked up that kinda $$$ on another radio. I'll just have to make do with what I have, I guess. The first $1500 I get free and clear is definitely going toward a SA58, AR10, or M1A anyway.

2m base is up. No problems there. Put the base antenna up in the attic, run some quality coax between the walls, and viola. I've got reception from Dallas to Monroe, Kennesaw to Hampton. I only wish my scanning reception could be so wide.

 

[MOGA]

Having had a recent all-together different experience decoding simulcast P25 from home, I thought it due to briefly revisit and update this old thread.

For starters, my PSR 500 was stolen and I recently replaced it with a 600.

Using just the stock telescoping whip, I've had NONE of the experiences I had with my 500.

Either something has changed in the RF environment with respect to the Atlanta system, the circuitry of the 600 has the benefit of some new design, or the 500 I used to own was defective. Either way, I haven't monitored one call in thirty six hours that was garbled in the beginning of the transmission. I am finally satisfied with the investment I've made in P25 scanning.

There IS hope for monitoring Atlanta simulcast radio after all.

 

[ButchGone]

hmmm, the 500 and 600 should work about the same. Anybody else with the psr 500 can chime in about their reception? Maybe the 600 has more shielding or just works better?
BG..

 

[ChattScan]

Bottom line is the current P25 scanners cannot properly receive LSM simulcast transmissions, anything else is just like duck taping a bumper on a car. Until the manufacturer's get off their behinds and either write some DSP code that makes their current radios act right or introduce new models, I'm done with it.
....

If you were running for some elective office, I would vote for you!!!

 

[RickS31]

Having a RS 106, and not having the 197 or 600 to compare to, I can attest to the sensitivity of the 106/500. I get great reception on the Atlanta system pretty far up here in Cobb Cty and do a reasonable job on the Dobbins 400 Mhz TRS as well. Of course Cobb booms in. This is all with just either the stock antenna for non-800 Mhz systems and the RS 800 Mhz rubber ducky for 800 systems.

I can just imagine what I could hear with appropriate outside antennas. I'm totally sold on the scanner.

Rick

 

[rmiller818]

Could be a few things. The 500 and 600 are the same radio internally.

Perhaps you had changed some settings on one radio but not the other?
Maybe it is because of the antenna, the whip may be more or less sensitive than the antenna you were using on the 500? Sometimes a less sensitive antenna is better.
I have also heard because of its case the 600 (or any base scanner for that matter) should perform slightly better. (Larger ground plain?)

I personally haven't noted much difference in my 106 and 197, both hooked to my yagi or otherwise.

 

[Oldglide]

Performance differences in PSR-500 vs. 600 etc.

Seen the schematics for both, absolutely identical. My best guess would be component layout differences due to different PCB sizes but with all things being equal, same settings etc. I believe the biggest difference is the metal case on the 600. It is much better at attenuated or rejecting un-wanted junk. Most important, we're dealing with the laws of physics here,:roll: nothing is for sure.

 

[MOGA]

I just priced a XTS5000 Motorola. My wife would freak the frick out if I bucked up that kinda $$$ on another radio. I'll just have to make do with what I have, I guess. The first $1500 I get free and clear is definitely going toward a SA58, AR10, or M1A anyway.

LOL. That DI was spent on a quad-band Yaesu, the replacement for the PSR 500 that was stolen, and putting an upper on an AR build. Just couldn't get over how much 308 ball is commanding these days to invest in a 30cal setup. Maybe next year.

The 500 wasn't new, so perhaps its circuitry was shoddy or damaged before it came into my possession? Either way, glad I don't have to live with it anymore.

 

[N8IAA]

The 500 wasn't new, so perhaps its circuitry was shoddy or damaged before it came into my possession? Either way, glad I don't have to live with it anymore.

I don't have a bit of difference between my 106, or 197. The 500 had to be not functioning properly in the first place. Most likely why it was sold. Will be buying either another 197 or 600 in the near future. Was looking at the 310, but, don't need another analog scanner.
Larry