Brevard County TRS Updates

batdude

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Batdude, those captures you posted look like something is dreadfully wrong. No way that the sites are so badly tuned that the first harmonic is just 20 dB below carrier. If it were that bad then the FCC would have shut it down. Mastr III repeaters are cleaner than that. But even that doesn't really matter because they're using Mastr Vs in the system now, which most certainly can be assured to be delivering signals of sufficient purity that the first harmonic is easily 60 dB down or better. (Minimum standard for FCC type acceptance.) In fact the spec sheet says -70.


What are you using to capture those spectrums and has it been bench checked lately? Honestly those look like something that'd come out of a cheap SDR with all the selectivity and rejection performance of a bus full of nymphomaniacs.

I have spent MANY hours with a yagi antenna, watching the system sites using a Rohde & Schwarz FSEA 30 spectrum analyzer that met calibration specs, and cross-checked with a Tektronix 494AP, and never seen ANYTHING even remotely like those spectra.

Those spectra....I don't believe them. You've got intermod or receiver overload or a really cheap SDR there. Just flat out not buying it.

Yeah, I looked up the header stamps on those charts and it looks like you're using an SDR. Well, you might want to test that SDR using a good clean signal generator and verify its actual performance. I'm thinking it's kind of garbage-like at the moment. Now, granted, I expect a lot out of test equipment and spectrum analyzers. I've worked with some of the best stuff ever made and worked with it every day for seven straight years. I'm picky and critical. I've had equipment with a zero span noise floor under -160 dBm and signal generators with a 140 dB dynamic range. I will be critical of the perfomance of a cheap SDR.

As for when the Brevard system was installed, I remember clearly that when two Satellite Beach PD officers were killed on A1A by a drunk driver, I was at work that evening in Cocoa Beach and had to detour through the Atlantic Plaza around the scene. And I knew something had happened because I was listening in using a Motorola STX-821 with GPS 1.1 controller, scanning the site frequencies. ( This was before any trunking scanner or any surplus EDACS radios existed yet.) That was 1992. I believe the system became operational in 1989 or 1990.

My point is....don't use a cheap SDR to make a point based on a spectrum capture. If you are looking for a GOOD analyzer on the cheap, for 500 bucks or less get an Agilent 4406A transmitter tester which is a basic 3.5 GHz range spectrum analyzer (plus options) and it has a bandwidth resolution of 0.1 Hz at minimum span and a very clean low noise floor. (I don't recall that spec at the moment.)
 

batdude

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the original pictures are from an Airspy. I don't consider it a cheap SDR. i stand by my picture, as it's been very accurate in the past --- compared to every other signal I see on 800mhz - oddly enough, Brevard is the only one that splatters like this --- of course, they are pretty much the only analog system left on the air that I can hear....

I am not anywhere close to one of their sites, or a broadcast tower, or cell tower. it's not intermod.

Here is a picture from my iCOM 8600 - the spurs are plainly evident in this picture as well. Note that these side-spurs, at least in my experience are associated with the "EDACS Jingle" that used to play to disrupt the scanners (now these are just pulses - not tones). The actual audio channel bandwidth seems to be ok.

85346




As for the FCC shutting Brevard down, I have to disagree with you on this one. The FCC is an inept bureaucracy that is more interested in selling spectrum to make money than any kind of serious enforcement actions. Unless there was actual, documented interference to either a neighboring public safety or US Govt system - they aren't going to do squat. The PSIC sites in Osceola (specifically site 10 listed here on RadioReference) is still operating without a license and transmitting a BSI of "CHANGEME" (obtw, so is the Marion County 700Mhz system - BSI=CHANGEME). I sent a letter/email to the head of the FCC enforcement section regarding PSIC, someone guy from the FCC called me about it - and basically told me that they just don't have the resources to do anything about it -- until there is interference. Shocking.

Understand your comments on the dates - i didn't live down here at that time, so I took a stab. I knew it was the early 90s (or so), but that actually makes it even more insane that the system has been operational for 30 years. I commend the technicians that are forced to find ways to keep this thing active and working for the county.


doug
 

batdude

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sorry for the duplicate reply-post above. here is a really good shot. the first picture is my reception of the Orlando site for the Orange County 800 system (Orange County Trunking System, Orlando, Florida - Scanner Frequencies) 853.9125 -- as you can see -- the red line is their control channel --- it's buried really far down in the weeds --- as expected, since I am nearly 50 miles from their transmitter. The second picture is what I see when 853.900 (Brevard analog EDACS) keys up. Again, I am just making a point of what >I SEE< ... nothing more, nothing less. (these pictures were taken seconds apart)

85349
 

ElroyJetson

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Hmmm.... I've got an IFR spectrum analyzer just sitting here doing nothing at the moment. It has a minor display problem but it's usable.

I'll hook up an antenna to it and see what the local site looks like on it. I THINK I have an 800 antenna around here somewhere...

I also need more information on your screen captures. Hz per division in the frequency axis, levels in the amplitude axis.

What you're showing there would look like spurs if they're out of the modulation bandwidth of the transmitter. But if they're within the modulation bandwidth, then that's just what the modulation looks like due to the way it's captured.

The difference between spurs and modulation is how far out they appear from the carrier.

On a swept analyzer, both sweep rate and resolution bandwidth make a huge difference to what the modulated signal looks like, and the nature of the modulation of course makes a big difference as well.

And, no, I don't believe that an Airspy SDR's RF performance is quite on par with that of a lab grade spectrum analyzer from R&S or HP/Agilent/Keysight. I don't buy into the notion that a 130 dollar gadget can play on the same field with equipment cost hundreds of times more.

Remember, I'm not just a scanner enthusiast, I'm actually an RF technician and, for a time, I had the best equipped lab outside of a major corporation such as Harris, Northrop-Grumman, or Lockheed-Martin. And not once did I ever see the bad transmitter performance you're reporting on the Brevard sites, using excellent equipment. I was experimenting with monitoring the control channels and trying to analyze the data streams using the digital demod options in the R&S analyzers. That was an "off list" application for that demod package but it turned out to be possible. It'd never have made a replacement for Trunker but I could lock to the sync word and see some things.,
 

batdude

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And, no, I don't believe that an Airspy SDR's RF performance is quite on par with that of a lab grade spectrum analyzer from R&S or HP/Agilent/Keysight. I don't buy into the notion that a 130 dollar gadget can play on the same field with equipment cost hundreds of times more.
you would be amazed what a $130 gadget is capable of. no, it's no Agilent SA or $3000 (or $20000) analyzer... but the fact that I see the exact same thing on a top of the line $2000 icom receiver gives me a good sense that what I am seeing on the SDR is indicative of the signal being received at my QTH.

here is a good picture with some scaling to show you what I see, 3 distinct carriers at lowering levels of signal strength, each one about 5khz away from the main carrier, first one about about -55, then the second at -65 and the third at -75 (again, just in reference to the main carrier at -25.5 peak dbFS. Note the prior pics were from FMPA (a simple receiver program w/ SA capability) - and the below is SDR#. these side carriers "pulse" as the carrier modulates RF (no audio) for the "we bring good things to life" anti-scanner crap.

The top line is referred to w/in SDR# as "db full scale = dbFS". That may not equate to a damn thing in real life other than comparing to other signals as I receive them, but this isn't an over-saturation or intermod type problem. I see this on nearly every single channel of their system.

Compliant with FCC? I have no idea. Being a "good neighbor" on 800mhz? absolutely NOT. My thoughts? whatever setting on the (assume?) Master III or system controller that is adding this post-carrier drop "anti-scanner" pulsed modulation crap, needs to be turned OFF.


85351
 
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so what your claiming is that the 800 system of brevard is splattering all over the band. i had a chat with CI they are building the systems out in the install bay. so the switch will be flipped on 2025 as it is going.
 

batdude

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so what your claiming is that the 800 system of brevard is splattering all over the band. i had a chat with CI they are building the systems out in the install bay. so the switch will be flipped on 2025 as it is going.
let me redirect. what I am saying - is that from MY VANTAGE - my antenna, my QTH, my hardware - yes, your statement is correct. I see the same thing on multiple radios, so it's not unique to one particular receiver. There is not a cell site/pager or any other significant RF source in my backyard, and the nearest Brevard antenna is about 5.5 miles away. I would imagine that anyone using a radio "on the system" - isn't going to notice this ..... to them, it probably sounds great/works good. On a spectrum display, it looks like hammered dog poop.

I am not an RF engineer but I'll state that if someone pointed out something like this to something I was in charge of, I would damn sure want to figure out if this was happening. Having dabbled in the two-way industry informally over about 30 years, I can state that not once, ever - did I see any RF technicians look at a site with any kind of spectrum analyzer other than to perhaps sweep a set of duplexers or rudimentary cable fault checks. does that mean much? No. It's just what I have observed, but I do use that as a data point in my thinking. Does CI "site sweep" the Brevard EDACS system? No idea.

I would hope that someone with CI sees this - and at least takes a look at what I see on my end. I'm not asking for a site visit to my house. I'm just hopeful that they would at least have the attitude to "check their gear" - and if I'm wrong, and a magical GE zombie is living in my attic - so be it.

I will also readily admit that..... having come from a strictly Motorola background, my knowledge of legacy GE hardware is minimal - especially from the site infrastructure standpoint and programming/setup. As Elroy pointed out, this system is VERY old. Well past obsolescence - i think Harris pumped out the EDACS end of life / support letter back in 2017.


doug
 

ElroyJetson

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You're seeing modulation sidebands. Note that they're exactly 4800 Hz above and below the carrier.

EDACS Narrowband Simulcast (non encrypted) uses GMSK modulation (Gaussian Minimum Shift Keying).

I'll try to find some information on what would be an expected (And FCC compliant) emission pattern for that format,
but with the sidebands being down over 50 dB I would expect that it's probably within compliance.

You know me. I'm not generally likely to defend anything GE related. I'm traditionally a Motorolan. But honestly, I'm not seeing any big problem here. You're expecting me to believe that a whole bunch of regularly maintained Master V repeaters at sites that have been upgraded, and in many cases BUILT, fairly recently, all have spurious emission problems, while at the same time you seem to have failed to note that the "spurs" are sidebands that are a natural consequence of 4800 baud control channel operation.

Understanding modulation and how it actually works was a subject of special study that I got into. I really wanted to know how it worked, and what is going on in the transmitted signal on a nanosecond by nanosecond basis. How data rate and modulation depth and the number of symbols and how they are encoded all interact, from the most basic two state frequency shift keying all the way to QAM-256 and its representation as a constellation on certain types of analyzers so equippped to handle it.
 

batdude

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Elroy, your explanation is plausible - but I don’t really get how sidebands as you say are part of the signaling portion of the voice call. But hey, I don’t know bupkiss about GE trunking. I wish there was another system close by I could compare with Brevard. The first sideband isn’t down 50db when you make it relative to the carrier peak - more like 25 or so... is that acceptable? No idea.

regardless of it being technically “in spec” or correct - it’s still stomping all over neighboring channels— And that is not good (and kind of my point)


Doug
 

ElroyJetson

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Let me ask you this and forgive me if you may have already answered. If the signal is "stomping all over neighboring channels", who's saying it's doing that? Is there a licenced user on adjacent channels that's having an issue with this?
 

batdude

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I have no idea if a neighboring system is actually experiencing interference from Brevard. I do know for a fact that a certain administrator of a very large system nearby had to go out the other night and disable a few channels on their system... due to.... ? interference. was it Brevard? Don't know - and he doesn't either. 800 is a strange band for propagation.

Like I said before, running a legacy 25khz system in 2020 just doesn't work well for surrounding users. There are several channels on the Brevard system that have a neighbor just 12.5khz and <50 miles away. Legal / Coordinated? Probably. Good idea? Nope.

See my comment above about being a "good neighbor". Brevard isn't being one.
 

ElroyJetson

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You and I both know that certain people in the county, and Harris, and CI, are all deathly afraid of getting into a situation where they are required to bid out a new system and risk the possibility of Motorola winning it. Somehow, this super long timeframe "upgrade" approach seems to be the means by which they are dancing around the issue. Not saying it's legal. Not saying it's NOT legal. But this county has a history of playing fast and loose with contract law when Motorola wins. Motorola actually won the bid for the Port Canaveral Police Department's system. The county's reaction, to cut to the chase, was to decide that PC didn't actually need its own police department and the SO continued to handle law enforcement there.

And to this day, Harris Corporate Security still runs on the system in Palm Bay, even though the security department of Harris does not in any meet the legal definition of a PUBLIC safety services provider, and thus those operations of a corporation's security department on a public safety system operating in the exclusive public safety section of the band, and funded by taxpayer dollars, continue despite being actually illegal.

I have no illusions about this county's apparently very weak desire to be strictly and absolutely honest and compliant with all the laws including contract law and radio system operations laws....and their ethics don't stand up well to close scrutiny, either.
 

APX8000

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A lot of expensive toys but the “I THINK I have an 800 antenna around here somewhere....” would be a cheap way to actually use those high priced toys. My Ferrari does things better than your Yugo....when I can find my gas can. Listening to you two go back and forth is entertaining though lol.
 

TDR-94

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The telecom providers are probably "splattering" more than any PS system in the area.
 

ElroyJetson

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When I left the business a few years back, I sold off the majority of my equipment. The sad reality of the test and measurement equipment market is that any piece of gear depreciates rapidly so by selling it when I didn't need it anymore, I got cash value out of equipment I didn't need anymore, didn't have to store anymore, and didn't have to maintain anymore or repair if it should fail, and is losing more value with every passing week.

If I have enough need to re-equip a test bench, I can do that when the need arises.

Odds are that what I have left still makes for a better test system than most radio hobbyists will ever have.
 

ElroyJetson

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As for the transmitter specs, the Mastr V 800MHz repeaters type acceptance information is found here:

Operating Frequencies

Device operates within approved frequencies overlapping with the following cellular bands: CDMA 10,Sec 800 MHz DOWN |

Frequency RangePower OutputToleranceEmission DesignatorRule PartsGrant NotesApp #
851-869 MHz100 Watts0.3ppm8K00F1D90, 90.21BC1.1
851-869 MHz100 Watts0.3ppm9K80D7W90, 90.21BC1.2
851-869 MHz100 Watts0.3ppm9K70D1W90, 90.21BC1.3
851-869 MHz100 Watts0.3ppm8K00F1D9BC3.1
851-869 MHz100 Watts0.3ppm9K80D7W9BC3.2
851-869 MHz100 Watts0.3ppm9K70D1W9BC3.3
851-869 MHz100 Watts0.3ppm8K00F1D90, 90.21BC2.1
851-869 MHz100 Watts0.3ppm9K80D7W90, 90.21BC2.2
851-869 MHz100 Watts0.3ppm9K70D1W90, 90.21BC2.3



9K80D7W is 2 slot TDMA (Phase II)
9K70D1W is most likely the applicable designator for linear simulcast operation.


Spec sheet is here:

 

ElroyJetson

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Funny? More like "Highly anticipated". Actually I think there should be laws that prevent people who manage large single vendor contracts from working for that vendor within five years of leaving the management position.

In fact I think that general ideal should be applied universalkly to all contracting at every level from local to federal including military contracts. Contractors should not be in a position where they can manipulate a political environment by hiring them at a later point in time...if you help us get the contract. That kind of thing should be absolutely forbidden.
 
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