Batboard

ok, i am going to try to explain this as simple as possible...

we have a customer who just swapped 6 msr2000's for 6 new mtr's....

soon after the swap we start getting service calls from field units saying "dispatch is front-end clipping" themselves and that there is obviously some sort of delay.

with my very own eyes i witnessed dispatchers speaking before the base station even had time to key, but giving them the benefit of doubt i investigated...and personally i think the msr's were a little more quick on the draw when it came to tx'ing, but not by much...

this system is vhf simplex, so i told the dispatchers to wait to see call lights from other sites before speaking, but still they say that the problem still exists....which i dont believe...

anyways, their centracom 2 console sends a function and a guard tone via microwave...

the customer wanted me to look at some rss parameters to see if there was any way to bring the delay time down...

so i look at the antenna relay delay...its set at 30ms which is the lowest it can go (in a range of 30-900ms)..

then the customer asked me to change the tone remote command from its current programming:

1950 hz - command 1 : select channel 1
command 2 : tx when llgt is rx'ed

to just transmit when low level guard tone is recieved and just do away with the function tone... but regardless, the console is still going to send that function tone, so that wont make a difference right?

ok, then the last thing we pondered on was the tx idle. they are simplex at 159.075, so the tx idle calculates to 159.025...

i warned the customer that changing this value to match the tx and rx freq will eventually cause some interference issues...but we tried it in 4 out of 6 of the stations with no problems...but guess what??? they still are complaining of delay...

is there any parameters or something i am missing, or does the dispatchers just need to get used to waiting a second before speaking? the boss makes it seem like its impossible to change human behavior...but in my opinion if the call lights are lit on other stations at the console, then the trucks should be receiveing it as well, and they should just consider those lights to be "go-ahead" lights before they talk...

i am just trying to think of anything else before we tell the customer that we cant do a thing about it...

Your trying to change the law of physics here. It takes
a finite amount of time for a tone control system to
function. There is no way around that. The time
between mic PTT at the base and the remote TX being
on the air could go out to better than a second under
the right conditions.

Next don't forget that it takes time for the RX PL
decode on the mobiles to decode and open up the
squelch. This is a minimim of 200 to 400 miliseconds.
Add this to the TX kep up time and what do you have.
A good period of time before the guys in the field are
going to hear the dispatcher.

If they want to be machine gun speakers, then they
had better get use to repeating their transmissions.
It is much simpler to train them to at least count to 3
before they try speaking.

Sometimes it takes trying to explain to them that just
because you have a water hose, the water doesn't
always come out the far end the instant you turn the water on.

Jim

Were the MSR2000 Base Stations directly (as in hard) wired to the Microwave equipment or DC Keyed remotely opposed to TRC Keying?

In my city the tone delays are not acceptable. For all of our Public Safety channels we use e&m (direct) keying. ( 12 channels )

We do use tone keying on the local gov channels where a delay can be tolerated.

these stations (as well as the msr's were) are trc controlled off of the microwave.

i understand the delay is there. but for a rural ambulance company operating on a simplex base, i think a second isnt too much to ask for...

i would hate to overhaul this system to use e&m keying...mostly because two of the sites have 2 remote bases that are operated by channel changing function & keying tones

Assuming they really want it fixed, you could use this in the audio path between the mic, and the console.

http://www.ah6le.net/arcom/rc210/rad.html

You might need to find a way to keep it keyed until the buffer is empty if you go for a really long delay.

yeh that may be sorta tricky keeping the base station keyed while delayed audio is going out since the llgt wont be present for all of the transmission...

now the dispatchers will be "end-clipping" themselves....

they are just going to have to get used to waiting a second or so before they speak, or they wont be heard...and thats the only real thing i can think to tell them...

now, coming up in a few months, they are going to a new zetron console...i havent messed with the programming on those much, but can you add a go-ahead beep for dispatch?

What Zetron are they going to, the 4020 has audio delay. It buffers and holds off the audio for up to 3 seconds (adjustable) giving the station time to key and the rx pl to decode before passing audio and keeps the station keyed till the buffer is empty..

I use it on my bases that are on control stations, I never could get the dispatchers to wait 2 seconds before talking. I even have 1 that gets the first word out before the PTT is pressed most times, no audio delay can help that one.

You could go to guard tone keying but that only handles 1 of the delays. It's a training issue I could never solve so I went with the delay (cant beat um, join um)

i know its going to be a 4000 series, and i am pretty sure they will be doing a 4020...where is the option for this delay?

also, if anyone knows...what is "mic delay eliminator" in the 4010 software under audio options?

I think it is standard with what Zetron calls the Universal Channel card that goes in the remote rack. We have a 12 channel system so our rack has 2 system control cards (1 working, 1 hot standby) 3 console interface cards (1 for each console) and 6 Universal channel cards (2 channels per card)

We do all tone remote control but I think the cards can do DC and E&M also.

Channel Card options are set on a per channel basis via an rs232 connection on the front of the card, uses any terminal program (procom works fine). The button consoles program with Zetrons CPS that runs in DOS, Touch screen console has it's own Windows programing software installed on the P.C. that it runs on.

As I said, I have a few channels that are on control station and the delay totaly cut out the front end clip. I can almost get a 1 to 5 count out before I hear it in a receiver.

It's been runing about 8 months now with no problems with the exception of finding the Touch screen needs to be rebooted every couple of weeks to keep the license manager from reporting no license found. The button consoles are flawless, guess it takes windows to create problems with the touch screen.

Remember Bill Gates said "it's not a bug, it's an undocumented feature"