SDS100 - my observtions

[JoeyC]

My observations with the SDS100 using the Remtronix 800 antenna in various locations around my house located south of 8 and near the 15.

It has a hell of a time capturing the cc of the NextGen West site (45) sometimes taking MINUTES to lock on to it, and then when it does, it is hit or miss whether it maintains a hold. When it does lock on, I get 4-5 signal strength bars, an RSSI of between -55 to -65 using the W-INV filter and NOISE all over the place usually varying between 4000 and 48000, mainly 5 digit numbers and it will SOMETIMES hold that for minutes at a time and then sometimes it drops and reacquires the cc every few seconds. Then there is the legacy RCS site, where I can lock onto the North cell just fine and maintain a NOISE level averaging 100-500 with crackly and staticy analog reception with a -60 RSSI reading. with the W-Norm filter. The digital sounding audio is acceptable with occasional digital blurbs.

On the NextGen South site (41) I am getting an RSSI of -48 to -60 on average with NOISE mainly 2000-9000 with occasional spikes to 25000 with the Inv filter. Audio is much better consistently than from site 45 with fewer digital decode messups.

On the legacy RCS South site I get an RSSI of -60 to -88 with average NOISE 200-700 with occasional spikes into the 5 digit ranges using the Norm filter. More often than not, the RSSI is rock steady at -60 and on occasion will fluctuate. There does not appear to be any NOISE difference when the RSSI changes compared to when it is steady at -60.

I don't understand why my NOISE levels on the NextGen would be so much higher than on the old RCS.

I have chosen the filters I use for each site based on the one that gives the best RSSI value and fewer Errors. Perhaps I should be looking at NOISE levels also? Instead of?

I love the way this thing decodes and sounds in comparison with that 536HP and the 996 that I have in the car which doesn't work worth a damn on the newer systems but it sure doesn't make any sense to me when I compare the values I get from the display when comparing the two.

 

[Anderegg]

The old RCS simply puts more RF in the air to scanners, wit much better signal integrity. I hang on Adams near the 15 sometimes, and I get the same poor NextGen West receive issues. Something to look at is watching talkgroups blink on momentarily, wiht the contro channel and the voice channel rapidly blinking back and forth. This is the issue I have with West down south, and it seems to be mostly due to cell phone tower interference on specific frequencies. I was able to clean the freq lock by about 50% by adding the problem West frequencies to my IFX list in sentinal edit profile option. Below is my list of good and bad West site frequencies...I took a video of the screen for 10 minutes so I could pause to see the frequencies it was not able to lock on, they blink on/off too quickly to see otherwise. I then assigned them to the IFX list, as well as the West control channel. It improved things by 50% or so comapred to not adding them to IFX. Try adding the bad ones from below and see if you get an improvement..adding them will not negatively effect the scanner since they are not working as is. Also, try entering the bandplan into sentinel, so as to not have to rely on the scanner getting a solid read on the CC data of the bandplan, since the control channel may be too noisy to do this quickly.

Good
856.3875
854.3375
855.3625
855.3125

Bad add to IFX list
853.8875
855.8125
854.8875
855.6625

 

[JoeyC]

Good information. I'll do a freq by freq analysis for noise and levels next and see if applying IFX to the bad ones helps out. There is just a never ending amount of variables to try with software filters, hardware filters, IFX, etc. I just wish things would work. Looking forward to that G4 coming if only Ray would ship it. 8 days and counting...

 

[JoeyC]

Also, try entering the bandplan into sentinel, so as to not have to rely on the scanner getting a solid read on the CC data of the bandplan, since the control channel may be too noisy to do this quickly.

Where does one get information on manually entering the bandplan?

 

[Anderegg]

From Scandiego

#Format: Table ID,Base Freq,Spacing,Input Offset,Assumed/Confirmed,BandWidth,Slots
00,851.00625,0.00625,-45.00000,"Confirmed",0.01250,1
01,762.00625,0.00625,30.00000,"Confirmed",0.01250,1
02,851.01250,0.01250,-45.00000,"Confirmed",0.01250,2
03,762.00625,0.01250,30.00000,"Confirmed",0.01250,2
04,935.01250,0.01250,-39.00000,"Confirmed",0.01250,1
05,935.01250,0.01250,-39.00000,"Confirmed",0.01250,2

From my Sentinel, see attached pic


Just use the first 4 for SD City 700MHz. The P25 bandplan is pretty standard off the shelf.

 

[JoeyC]

Yeah, I didn't think setting any of that was necessary with a P25 system.

 

[Anderegg]

Yeah, I didn't think setting any of that was necessary with a P25 system.

The radio can read it off air...my 996's would have the data filled if I went into the menu later, that's how you could tell if the system ever received well, the bandplan areas would be filled!

My thought is better safe than sorry, so I just fill them in on everything, give the scanner less to do.

Paul

 

[JoeyC]

Haven't yet gotten to adding to an IFX list, but monitoring site 45 more in depth today, it appears as if my RSSI guestimation earlier was inaccurate. I am still stumped as to why the reading will on occasion show full bars and an RSSI of -60 locked onto 852.575 and then most of the time the RSSI is what I think is a more accurate depiction fluctuating between -90 and -115ish locked onto the same control and with the scanner in the same or similar places around the house.

 

[jonwienke]

RSSI is more accurate than bars. -110dBm is a weak signal, and roughly the point where the scanner will have trouble picking up the signal.

I have chosen the filters I use for each site based on the one that gives the best RSSI value and fewer Errors. Perhaps I should be looking at NOISE levels also? Instead of?

RSSI shows overall signal strength, NOISE gives you an indication of the quality of the signal. High NOISE indicates a weak signal, RFI from cell towers or something, or some combination of the two.

 

[Anderegg]

The RSSI is useless for monitoring West from the South area...like I said, ym station has a yagi pointed at the Woodson West site, -35dBm (you know how strong that is on the SDS), and still get cell phone phading frequencies and lots of 40-80 D error transmissions. Before the Yagi, we were getting the same -50-60dBm on South and West, only the West was basically unlockable, while South was loud and clear...SD City 700MHz ystem BTW is -70-80dBm with the same yagi, and has clear 0 D errors. Note the LCD saying DATA for a lock on the CC...if you have -60dBm but DATA is comng and going, your most likely being phaded by a cell tower.

As for "bad frequencies...my SDS as well as my Whistler scanners have issues with specific freqs...I think it's 770.01875 or 771.01875 that is the worst...it's one that ends in 1875.

Paul

 

[mitbr]

Good information. I'll do a freq by freq analysis for noise and levels next and see if applying IFX to the bad ones helps out. There is just a never ending amount of variables to try with software filters, hardware filters, IFX, etc. I just wish things would work. Looking forward to that G4 coming if only Ray would ship it. 8 days and counting...

Ray stated to me that a new shipment of G4 pagers is coming in this Monday waiting for mine as well!

 

[Anderegg]

I ordered my G5 Thursday from Zip, and it arrived today...even included a free copy of the Minneapolis Gazette for some reason.

Paul

 

[JoeyC]

Ray stated to me that a new shipment of G4 pagers is coming in this Monday waiting for mine as well!

Yeah he told me last thursday that shipment was coming and that it would be shipped THIS WEEK. (Last week now) AND hasn't, from the lack of the promised tracking info...

 

[JoeyC]

RSSI is more accurate than bars. -110dBm is a weak signal, and roughly the point where the scanner will have trouble picking up the signal.

RSSI shows overall signal strength, NOISE gives you an indication of the quality of the signal. High NOISE indicates a weak signal, RFI from cell towers or something, or some combination of the two.

When evaluating each individual frequency for strength and clarity, with the scanner trunking, is the RSSI, noise and D-errors depicted at the time of reception indicative of the individual frequency that is in use at the time, or of the trunking system as a whole? I've made a list of each freq on the site and have started to evaluate each one for RSSI and errors. At first I was on to something when I found the same freqs regularly throwing a lot of errors and weakish signal, but 2 minutes later the same objectionable freqs will do a long-winded EMS report with negligable errors and a -60dBm reading, totally invalidating any of my previous findings.

Question. Does a cell tower always emit RF and does it vary depending on how many calls it may be working or does the RF drop at times when no cell activity occurs on it (if that is even a possibility).
Trying to explain why I get SOLID -60dBm readings that hold sometimes as long as a minute or more then other times it is mess jumping wildly around -115 to -80s or so.

 

[JoeyC]

and as I type, the scanner is cycling through the 3 control channels unable to capture a signal for about a minute, only to reacquire for a brief period, then drop again. Is there some threshold for signal setting that I should screw with?

 

[Anderegg]

My RCS North (old RCS) was getting squaking garbage from the County's MDT transmitters...also it was hearing SD City 800MHz voice traffic bleedover...this was locked into the old RCS North CC and even when listening to old RCS analog voice traffic, you can hear the squaks and the other voices like an old early 90's non triple conversion scanner. That type off of channel cross talk is easy to hear in analog, more difficult when your deceode is in digital.

Thow IFX at the Control Channel frequency, see if that improves your CC lock. And the first things I attacked wioth IFX were the frequencies that were 100% not able to be receved, meaning the CC would throw the scanner to them, but it could not RX on them, and would bounce and flicker between the CC and voice channel without ever stopping on it. I found that from recording the screen for a few minutes and pausing the playback to see the flicker of voice freq it was not able to lock. After a few minutes, it became obvious these were always the same frequencies...threw IFX at them, started getting locks on them, even if high D error, but at least it was an improvement.

Paul

 

[jonwienke]

Question. Does a cell tower always emit RF and does it vary depending on how many calls it may be working or does the RF drop at times when no cell activity occurs on it (if that is even a possibility).
Trying to explain why I get SOLID -60dBm readings that hold sometimes as long as a minute or more then other times it is mess jumping wildly around -115 to -80s or so.

A cell tower broadcasts some signal 100% of the time, although the exact pattern of frequencies varies depending on call volume.

 

[Anderegg]

Verizon (United States of America) Cell Tower Map

CellMapper is a crowd-sourced cellular tower and coverage mapping service.

www.cellmapper.net

 

[inigo88]

Question. Does a cell tower always emit RF and does it vary depending on how many calls it may be working or does the RF drop at times when no cell activity occurs on it (if that is even a possibility).
Trying to explain why I get SOLID -60dBm readings that hold sometimes as long as a minute or more then other times it is mess jumping wildly around -115 to -80s or so.

Yes. Here's a waterfall example of WCDMA (3G AT&T site) and sound sample. The signal covers 4.2 MHz of bandwidth at once.

3G WCDMA - Signal Identification Wiki

WCDMA, known primarily as 3G mobile, is a family of 3G data protocols used to send voice, text and signaling data to smart phones and other wireless devices.

www.sigidwiki.com

Unlike trunking, everybodys digital call data lives in that jumbled CDMA mess simultaneously. I don't think it ever really turns off unless everyone in your cell stopped talking and using data all at the same time, which seems pretty unlikely.

4G LTE looks and sounds similar.

 

[jonwienke]

Even if no devices are connected to the tower, It's still going to broadcast to advertise its presence and let authorized users know how to connect, just like a P25 control channel broadcasts continuously.