Stationary vs. Roam question...

[GrumpyAeroGuy]

I am still a little confused as to the particulars of this functionality. I enjoy monitoring a local P25 simulcast system. It has one control channel active at any given time, and is a simulcast system with, I believe, many sites.

I use a PSR500 in the house, pretty much exclusively. I notice, while monitoring, that when I have it set to "Roam" with Hi and Lo set to 85 and 50 (per the easier to read scanner manual recommendation), the reception is down-right abysmal. If I switch to "Stationary", ALL OTHER THINGS BEING/REMAINING EQUAL, it is unbelievably better... one might say almost flawless.

Am I complaining? Absolutely not. DO I understand the whys? No. Can some one help explain it a little better?

If I am understanding this correctly (and I may NOT be), ROAM assumes that you are moving, and it compares reception from, say, several sites, and tries to choose, by virtue of the threshold settings, which of those "site signals" to process and "interpret".

Stationary does what? Just picks the strongest one, or.... (???).....

One thing is for sure. In my house, Stationary gives flawless listening... Roam provides as good as NO listening, chopping in and out, transmissions cutting out, fish bowl, etc, etc..

I have a setting that allows me to enjoy monitoring. This is good.

I am trying to understand what it is between these two settings that gives such a difference in reception. I just want to understand a little better.

 

[mtindor]

As you noted, the system you monitor is one system with multiple simulcast cells. For all intents and purposes, to your scanner this is a single "site".

Here in Ohio I listen to the State of Ohio MARCS system. This system has numerous completely separate sites [non-multicast] in my area with [obviously] different control channels for each.

If I set up a TSYS object for the MARCS system and I list the primary/alt control channel of, for instance, the 5 closest sites, and then I set the TSYS object to MultiSite Stat, it will poll each active control channel for activity. It will check the control channels in a row as I have them programmed in. It doesn't matter if the site is in good range for reliable decode or not. It will poll every control channel sequentially and will attempt to play the audio for any talkgroups I have programmed in for that particular site.

With Multisite Roam, it's going to try and pick the most reliably copied site by sampling the control channels. Don Starr will likely correct me if I'm wrong, but I believe that with Roam it will lock onto a specific control channel and will only monitor that control channel until the signal quality drops below the threshold. Then and only then will it attempt to poll the control channels again for one wiht better signal quality.

ROAM is much better when you are traveling and you want the scanner to [supposedly] lock onto the site with the best signal, which would usually be the one closest to you. Picture travelling along the interstate while you are monitoring a statewide system wiht multiple sites. As you progress down the interstate, the site your monitoring gets weaker, the signal goes below threshold, and the scanner attempts to pick up whatever site is now the strongest [presumably closer to you and the one you'd want to monitor].

STAT is much better if you want to program the control channels of multiple sites into a single TSYS [so you don't have to have duplicate talkgroups] but you want the scanner to scan for activity on EACH site regularly.

In your case, it's not multiple separate sites but a single "site" in the scanner's eyes -- just one set of control channels. You should disable multisite altogether -- just set it to OFF. But if you do set it to STAT [versus ROAM], it probably provides you with better performance because the scanner isn't constantly trying to compare signal quality and then find a new control channel.

If you're monitoring a simulcast site and set it to ROAM, if you go through a bad spot in your house and it goes below the threshold it will have to take time to check for a better control channel [which it wont find because there is only one]. I suppose the extra things it has to do in ROAM for a multicast site end up making it perform poorly compared to STAT or OFF.

Additionally with Multisite STAT, you have the option to scan all control channels in a single pass. Unless I am ONLY monitoring that one system, I don't like to do this. For instance, if I have my local trunked system programmed in, a conventional bank active, and am scanning the one TSYS object for MARCS that has the control channels in it for five sites and I have it set to Multisite STAT, when it goes to scan the MARCS TSYS it will take many seconds to go through all of the control channels before it scans the conventional bank or my local trunked system. If I disable "all CCs in single pass", then the scanner will check a control channel on MARCS, then it'll check my conventional, then it'll check my local system, then it'll go back to the MARCS TSYS and check the next control channel, then my conventional, then my local, then back to the MARCS TSYS to check the next control channel.... repeat ad nauseum. It's a tradeoff. If I scan all CCs in single pass, I give higher priority to traffic on the MARCS TSYS [by virtue of scanning all CCs sequentially]. If I do NOT scan all CCs in single pass on my MARCS TSYS, it provides more opportunities for it to pick up traffic on the conventional and local trunked systems.

Mike

 

[rhaasjr]

Your understanding of the ROAM option is correct. The scanner will search for the first control channel that falls within the set threshold values and use it.

Stationary will do two things, it either checks every control channel on every pass (if using the Scan All Control Channels option) or it will scan only one control channel on each pass through.

The problem you encountered with the ROAM option could be that instead of listening to the strongest or closest site to you, it could have been monitoring a site further away because of the threshold values being used. If the threshold values were set to say 95 high and 75 low, you may have had different results.

Anyway if you are not using the scanner as a mobile unit, i would just use the stationary setting.

 

[GrumpyAeroGuy]

Thanks for the detailed response(s)...

I was referring to the Hamilton COunty Ohio P25 system. I generally have great results monitoring Ohio MARCS.

Just tryin to understand better/more.

I really appreciate the input. Thank you.

 

[KB7MIB]

Wirelessly posted (Mozilla/5.0 (X11; Linux i686; U; en-US) Gecko/20081217 Vision-Browser/8.1 301x200 LG VN530)

I have my 500 set to Roam with Threshold settings of 90 (Lo) & 99 (Hi) on the Phoenix, AZ RWC simulcast. This appears to limit the amount of multi-path interference from more distant sites, resulting in a better quality signal. Your results may vary.