Why does digital seem to break up about 20% of the time I listen to it?

[Monoxide16]

My area is digital, it uses apco 25. I hate it. On so many transmissions it comes in all broken up and all gargoly. 3 towns in my county have switched back to conventional because of how bad digital is. When it works, its sounds good. But so many times it's all gargoly and distorted and I can't make anything out. Why can't digital work good like conventional always has and still does?

[K8TEK]

packet loss...

[Jay911]

Digital either works or it don't. This becomes painfully evident when an agency tries to cover the same area with digital that they used to with analog, over the same towers. Example: If you hear the audio equivalent of "Di--atch, this is --mper Twen--y--ven, --n sc--ne", the odds are that you can tell that Pump 27 is on scene. The same signal in digital just doesn't get through, period.

Thus the misconception that digital has shorter range. The truth is, analog can operate much further into the fringes than digital can, and in analog, your brain is able to fill in the gaps most of the time. Digital just gives up.

[JungleJim]

Originally Posted by Monoxide16

My area is digital, it uses apco 25. I hate it. On so many transmissions it comes in all broken up and all gargoly. 3 towns in my county have switched back to conventional because of how bad digital is. When it works, its sounds good. But so many times it's all gargoly and distorted and I can't make anything out. Why can't digital work good like conventional always has and still does?

That badly garbled audio is due to a high bit error rate. The error correction is working over time trying to correct but there is only so much it can do. Typically it is assumed that the errors are due to a weak signal over the RF link where the background noise, static, begins to cause errors. This is common and a typical source of the problem but if the system is not set up correctly it can introduce its own errors or magnify those coming in from a base station receiver.

[Raccon]

Originally Posted by Monoxide16

My area is digital, it uses apco 25. I hate it. On so many transmissions it comes in all broken up and all gargoly. 3 towns in my county have switched back to conventional because of how bad digital is. When it works, its sounds good. But so many times it's all gargoly and distorted and I can't make anything out. Why can't digital work good like conventional always has and still does?

This has probably nothing to do with the system being digital but rather a poor system design, e.g. the up- and downlink may not be balanced. I use a GSM phone and a PMR system and have no such problems, even though both are digital. On occassion of course I may experience some problem, but it's rare and certainly nowhere close to 20%.

Jay911, the statement that 'Digital either works or it don't.' is false, Bit Error Rate being one area where you can have audible distortion but still understand the message. Applies to GSM and digital PMR systems for example.

[Wyandotte]

It's a little bit of what everyone mentioned.

First off, digital does has better range than analog, if it's VHF and flatland. I've done personal testing of this, with multi-mode radios at 153 mhz. The range of understanding the same radio in APCO25 mode was over double the range of the same radio on FM. But this was like I said VHF.

But most digital systems are up near microwave frequencies. And ALL communications at 800 mhz, analog and digital, can get flaky. Unlike VHF, objects such as trees, hills, and buildings will reflect, refract and absorb the RF signal at 800 mhz. That's why an entity that wants to go 800 mhz has to put up a half dozen towers to cover the same area that the ol' VHF system did with one tower.

So what happens is that just a flutter of the signal on APCO25 knocks out a data packet. If it was analog, the human ear could ascertain the weak signal enough to tell what was said.

Of course, like I have said many times in many posts, if the munincipality would just change the base coax and antenna every ten years or so, the radio saleman wouldd't be selling a whole new radio system because the old one won't transmit over a mile.
Of course the old radios don't have any range, the coax has been up there 40 years and leaks RF like a sprinkler system.

[Jay911]

Originally Posted by Wyandotte

Of course, like I have said many times in many posts, if the munincipality would just change the base coax and antenna every ten years or so, the radio saleman wouldd't be selling a whole new radio system because the old one won't transmit over a mile.
Of course the old radios don't have any range, the coax has been up there 40 years and leaks RF like a sprinkler system.

Ain't that the truth - sometimes more literally than you think! A local system was just overhauled. One site is co-located on a main, master site for the county, which was erected in ~1996. They were assessing the lack of good signal on the system being overhauled. Disconnecting the heliax on the master site, they encountered some 'moisture'. It took half an hour for the water to drain from these cable runs.

[scanrfan]

Originally Posted by Jay911

Ain't that the truth - sometimes more literally than you think! A local system was just overhauled. One site is co-located on a main, master site for the county, which was erected in ~1996. They were assessing the lack of good signal on the system being overhauled. Disconnecting the heliax on the master site, they encountered some 'moisture'. It took half an hour for the water to drain from these cable runs.

Sound like that system was "ALL WET" and just about "WASHED UP"!!!