Question about CTCSS?

[RadioBob1000]

Hi,

I have a question about police radios used during the 1960's.

Assume the radio system is a duplex repeater system.

Lets pretend I am in a police car and transmitting on the radio. (Someone else is driving)

Also pretend that I am making a very long broadcast, that lasts about 10 minutes.

During that 10 minutes the car is going through downtown of a major city with lots of large buildings.

If at some point my transmitter loses line of sight to a repeater, what happens? I suspect that repeater stops retransmitting my broadcast.

Next assume that 20 seconds later, I am out of that "shadow" and regain the line of sight to the repeater. Will the radio system start to retransmit my broadcast? If so, what would a listener hear? Would they hear my broadcast but with a 20 seconds missing?

The key here is I only pressed the push to talk button once at the beginning, and I held it down for the entire 10 minutes, even while passing through the "shadow" zones.

What I am trying to find out is if I pass through a shadow zone will the repeater start repeating my broadcast as soon as I get out of the shadow zone or is the rest of my broadcast completely lost after the system drops me when I entered the "shadow" zone and I need to push the PTT button again in order to initiate a new broadcast?

Thanks in advance

Bob

 

[doctordialtone]

If at some point my transmitter loses line of sight to a repeater, what happens? I suspect that repeater stops retransmitting my broadcast.

The repeater will drop - then resume transmission when the car comes back into range, as if it's a new transmission

 

[DJ11DLN]

If you're asking whether the PL tones are constant during transmit or if they just occur at the beginning, they are constant. When the repeater lost your signal, it would unkey (after whatever delay was incorporated), and when it again picked up your signal, with the correct PL, it would again transmit and pass your "broadcast" along.

 

[ko6jw_2]

In the 1960's repeaters were not that common nor was PL. Mobile radios of that vintage used tubes and were likely powered using dynamotors. PL tones were generated with reeds.

A ten minute transmission would be extremely bad practice. Most modern repeaters have time out timers set for perhaps 3 minutes. I don't know if 1960's repeaters had them or not. Nevertheless, tying up a repeater for ten minutes, then or now, wouldn't make you any friends.

Your signal would likely get noisy before it dropped out. Then the dispatcher would be trying to get you back which you wouldn't hear because you're still talking. Other units might be trying to call you as well.

I realize that this is all hypothetical and I don't know why it has to be set in the 1960's. The effect would be the same today unless you are suggesting that 1960's radio systems were less sophisticated. They were, but people still used voters to get better coverage. Most systems that I monitored in the days used remote bases and though there might have been only one transmitter, there could have been multiple receivers.

By the way, all repeaters are duplex.

 

[a417]

By the way, all repeaters are duplex.

with the rare exception of the elusive "store & forward"...but I haven't seen an active one in 15 years.

 

[wtp]

Continuous Tone Coded Squelch System... the other name kind of says it all.

 

[RadioBob1000]

Thanks for your replies.
Actually, I know more about the system now. The way it worked, the main transmitter broad cast at 45.66 MHz (not sure if M is 1000 or mega) to a repeater that was listening on that frequency. The repeater transmitted on 45.74 MHz. The mobile units (motorcycles car radios) listened on 45.74 and transmitted on 45.74 (listened and transmitted on same frequency). There were two receivers both listening on 45.74 MHz that were connected by telephone line to the dispatch center.

Assume that the two receivers were on the top of the two tallest buildings in a very large US city and assume that one of the mobile units has a stuck microphone ( the push to transmit button is stuck open) And the mobile unit is traveling throughout the city for 10 minutes in that condition. Can there even be "shadow" zones with radio waves? I know there can be dead zones with microwaves, but can there be dead zones or "shadow" zones using radio waves as your communication medium? Is it possible that the mobile unit could enter a "shadow" zone and the signal to the receiver would be temporarily lost and then regained when the mobile unit got out of the "shadow" zone, or is it very unlikely that there would be any "shadow" zones if using radio waves?

Thanks