I have been having all kinds of problems trying to recieve Wichita police here in Park City(lot of posts about it) heres the deal,I brought the scanner to work today which is on the south side of Wichita,turned it on driving home north to Park City and sounded GREAT,it worked flawlessly,lots of calls and clear as a bell,as I got about 3 miles north of downtown on the interstate the signals started to chop and then when I got into Park City,it was almost nothing again,can the signals be that weak?
That is exactly the problem of simulcast distortion. The Sedgwick simulcast system uses ten transmitting sites. All of these sites are transmitting on the same frequencies.
When your scanner is receiving transmissions from multiple towers, it has trouble decoding the signals because the same packet of data may be out of perfect sync - data from transmitter "A" is microseconds off from the data coming from transmitter "B". The scanner is thus being confused and cannot produce clear audio.
("Regular system radios" - those used by responders cost $3,500 compared to the $400-500 for a scanner. The "brains" of the system radios are a lot more effective on dealing with signals coming from more than one site. That's because of the cost.)
Only when you receive transmission data (the 1's and 0's associated with digital readio signals) from one transmitter, will you get that clear audio.
To help illustrate this, look at the graphic below, which shows a hypothetical three site simulcast system. The three rings show the coverage of each transmitting site. The green areas is where the audio is clear. Orange will be poor audio (garbled/broken) and the red you may not hear anything at all.
This is not an issue of weak signals - just the opposite: too many signals. If you notice the signal strength meter when you hear that garble, it probably shows all bars. Thus this is a case of the scanner having difficulty decoding all the signals it is being bombarded with.
Things to try: Turn site attenuation on. Change the P25 Adjust Mode and P25 Adjust Levels to see if improvements are made. You won't achieve perfection, just some degree of improvement.
I struggled with this same predicament with our local simulcast system and its 13 sites. I had a 996XT in my fire department vehicle, which also had a "real system radio". I knew there was traffic on the system, as I heard it on the real radio, but nothing or garble on the scanner. But I could go 1/4 mile away and the scanner was perfectly clear.
As far as actual coverage area goes, it's a whole new concept these days due to frequency availability. Instead of one big transmitter with lots of power on a big antenna, metropolitan areas are using simulcast systems. Simulcast systems have several transmitters on lower power to achieve the coverage area. For our system in Louisville KY, the design parameters were to cover the geographical boundary, plus three miles beyond.
Simulcast systems are great things if you are an emergency responder, but just the opposite for a scanner listener. When we went from a conventional analog system to a digital simulcast system, it was like day and night. Most everywhere had a good, clear signal with few dead spots. In my nearly 40 years in public safety, I believe our new radio system was probably one of the best things that happened.
I've also had a great number of scanners over those years. The x96 series scanners had their difficulty in receiving simulcast systems. However the newest models, the x36 series, are much better. I can take a 396XT (the portable version of the 996XT) in my vehicle which has a 536 scanner. The 396XT will have garbled/no audio, where the 536 is clear.
