How quickly can an antenna be switched?

[tweiss3]

Hi all,
I've just had a thought !

When transmitting, then on the switcher will be only switched to transmission, on this radio.

When receiving, in order to relay, it will need to capture, a 50% section of the received voice, then transmit it in 50% time, then back to receive.

Less than 50% of the voice relayed isn't perhaps good enough.
C.

DMR does this, but its natively designed that way. Analog would have to issue a time delay that shifts just as long as the "record" increment. The down side to this is it would then create an "echo", or even something that sound like multipath propagation to those already in range of the initial transmitter. It's going to be an expensive venture without desired results.

The other thing besides switching speed, is how fast can the transmitter power up to relay the message, as you will loose time in that warm up as well. I would also question how fast you will burn out the radio, even if it was only 4 cycles a second, that's a lot of on/off switching and potentially a lot of wear on the electronics.

It really sounds like you need to either get on a real repeater, or continue relaying traffic between each other. You could also look to using echolink or other internet connectivity protocols, but to keep it simplex, and reach all involved, you all need your antennas higher to maintain a true line of site. Even 10' higher for each of you would significantly increase the range.

 

[Camerart]

DMR does this, but its natively designed that way. Analog would have to issue a time delay that shifts just as long as the "record" increment. The down side to this is it would then create an "echo", or even something that sound like multipath propagation to those already in range of the initial transmitter. It's going to be an expensive venture without desired results.

The other thing besides switching speed, is how fast can the transmitter power up to relay the message, as you will loose time in that warm up as well. I would also question how fast you will burn out the radio, even if it was only 4 cycles a second, that's a lot of on/off switching and potentially a lot of wear on the electronics.

It really sounds like you need to either get on a real repeater, or continue relaying traffic between each other. You could also look to using echolink or other internet connectivity protocols, but to keep it simplex, and reach all involved, you all need your antennas higher to maintain a true line of site. Even 10' higher for each of you would significantly increase the range.

Hi T,
No DMR.

The transmitter won't power up as it doesn't power down.

More than 20K/second switchng.

No repeater.

C.

 

[mmckenna]

Less than 50% of the voice relayed isn't perhaps good enough.
C.

No, it wouldn't be. And it would be annoying as hell.

The sound would be way worse than a commercial/public safety radio running in priority scan mode where the receiver jumps back to check the priority channel every second for a very brief period. Way less than 50%, more like 2%, and it's not uncommon at all to have users complain about 'missing traffic' because of that little short interruption.

 

[a417]

Hi T,
No DMR.

<snip>

You basically want what DMR is providing, but without DMR...on an Analog frequency...in simplex?

@tweiss3 basically tells you what you are trying to accomplish is done, in DMR form.

The sound would be way worse than a commercial/public safety radio running in priority scan mode where the receiver jumps back to check the priority channel every second for a very brief period. Way less than 50%, more like 2%, and it's not uncommon at all to have users complain about 'missing traffic' because of that little short interruption.

As a user this is frustrating as hell. As the administrator who has told the chiefs that this is an AWFUL idea, and that programming radios like this will lead to redundant transmissions and missed calls....its "throwing stuff around the office,thoughts of resignation in rage" when they say "why don't our radios work correctly?"

 

[Camerart]

No, it wouldn't be. And it would be annoying as hell.

The sound would be way worse than a commercial/public safety radio running in priority scan mode where the receiver jumps back to check the priority channel every second for a very brief period. Way less than 50%, more like 2%, and it's not uncommon at all to have users complain about 'missing traffic' because of that little short interruption.

Hi M,
There still seems to be missunderstanding.

When you say the receiver jumps back every secondm where did that come from. The receiver will be receiving all of the time, and the antenna will switch back to the receiver 20K/second.
C

 

[Camerart]

You basically want what DMR is providing, but without DMR...on an Analog frequency...in simplex?

@tweiss3 basically tells you what you are trying to accomplish is done, in DMR form.



As a user this is frustrating as hell. As the administrator who has told the chiefs that this is an AWFUL idea, and that programming radios like this will lead to redundant transmissions and missed calls....its "throwing stuff around the office,thoughts of resignation in rage" when they say "why don't our radios work correctly?"

Hi A,
The radios won't be programmed at all, only the antenna switcher.
C.

 

[mmckenna]

When you say the receiver jumps back every secondm where did that come from. The receiver will be receiving all of the time, and the antenna will switch back to the receiver 20K/second.

Your example of connecting/disconnecting the antenna at 20,000 times a second is going to impact audio quality.

The example I was giving was the "priority scan" function that public safety/LMR radios have, where the audio is interrupted at programmable intervals. While not the same as what you are proposing, the impact on audio quality would be similar: It would suck if you were doing this with analog radios.

With digital radios, where audio can be compressed into packets and sent with interruptions, it wouldn't be an issue if done correctly.

 

[Camerart]

Hi all,
Sorry for the confusion. Perhaps I'll leave it there, and test to see what this sounds like with only a receiver, and an antenna switcher.

From what I gather from some of the replies, it does seem as if it isn't viable. If anyone is still interested, I can let you know how I get on, but it will be quite a while, as this is only an idea, so far.

Thanks for all the replies.
C.

 

[Camerart]

Your example of connecting/disconnecting the antenna at 20,000 times a second is going to impact audio quality.

The example I was giving was the "priority scan" function that public safety/LMR radios have, where the audio is interrupted at programmable intervals. While not the same as what you are proposing, the impact on audio quality would be similar: It would suck if you were doing this with analog radios.

With digital radios, where audio can be compressed into packets and sent with interruptions, it wouldn't be an issue if done correctly.

Hi M,
Ok, I haven't investigated compression yet, just the antenna switching.
Cheers, C.

 

[mmckenna]

Hi M,
Ok, I haven't investigated compression yet, just the antenna switching.
Cheers, C.

Got it.

To compress audio in the way we think you are talking about, it's going to need to be digitized and sent as packets. That is why the DMR subject keeps coming up.

 

[tweiss3]

Here is the long and short of your issue. There isn't equipment commercially available to do what you want. You are going to have to design the switch, find a way to make it physically oscillate between the two inputs, build a dummy load to ground it out, design and time an analog audio buffer that will dump the audio in time with the opening in switch, and CONSTRUCT IT ALL FROM SCRATCH.

To summarize it:
1) designing your own is going to cost you anywhere from $500 + time and up, who knows how much you could waste chasing this idea.
2) Raising everyone's antenna 10' is likely to help, and be relatively inexpensive. (just a few bucks)
3) Put up a crossband repeat on the edge of reception and someone just has to switch bands if they can't hear ($350)
4) Everyone goes digital and you setup DMR Single Frequency Repeater for a short time ($400-$500 each person)
5) Get on a local repeater that isn't being used (free)
6) Put up a real repeater (not hard but $3000+, requires coordination)

 

[a417]

Hi A,
The radios won't be programmed at all, only the antenna switcher.
C.

My issue had nothing to do with functional programming of the radio, but was correctly explained by @mmckenna in his post.

as to this...

The receiver will be receiving all of the time, and the antenna will switch back to the receiver 20K/second.

The reciever will not be recieving all the time, it will be having its signal path interrupted 20k/sec. This wil decimate the audio quality.

 

[FKimble]

Actually your receive will be less than 50% and then your transmit will be off approx 50% +. Audio just went from terrible to much worse.

Unlike digital which stores and then transmits packets, Analog is continuous. So when ant is in RX it passes voice to TX side, who has no ant connection at that time. Ant switches to TX side but RX is now not able to receive anything so nothing is transmitted, ever!

Frank

 

[Camerart]

Got it.

To compress audio in the way we think you are talking about, it's going to need to be digitized and sent as packets. That is why the DMR subject keeps coming up.

Hi M,
No DMR, as this will only work with existing radiosor it's not worth persuing.
c

 

[Camerart]

Here is the long and short of your issue. There isn't equipment commercially available to do what you want. You are going to have to design the switch, find a way to make it physically oscillate between the two inputs, build a dummy load to ground it out, design and time an analog audio buffer that will dump the audio in time with the opening in switch, and CONSTRUCT IT ALL FROM SCRATCH.

To summarize it:
1) designing your own is going to cost you anywhere from $500 + time and up, who knows how much you could waste chasing this idea.
2) Raising everyone's antenna 10' is likely to help, and be relatively inexpensive. (just a few bucks)
3) Put up a crossband repeat on the edge of reception and someone just has to switch bands if they can't hear ($350)
4) Everyone goes digital and you setup DMR Single Frequency Repeater for a short time ($400-$500 each person)
5) Get on a local repeater that isn't being used (free)
6) Put up a real repeater (not hard but $3000+, requires coordination)

Hi T,
All good points.

I was hoping that it may make a web similar to the internet.

We had a repeater, but it is now in a garage (covid related)

I'm only thinking about the idea, not particularly the consruction.

I won't go into details, but I've had a ideas in the past, with the same feel as this one, given up only to find it being used now.

As for designing, I'm not bad at electronics, and you may be surprised at what can be done, in a shed

C.

 

[mmckenna]

Hi M,
No DMR, as this will only work with existing radiosor it's not worth persuing.
c

Well, if you can figure it out, you'll be on to something. Single frequency repeat like this, if it worked, would have been a huge thing in the industry before digital came along.

good luck.

 

[Camerart]

Hi, the others concerned with chopping the signal and it's quality and compression.

I always try to get round problems. (having said that I know I can talk nonsense sometimes)

How about the transmitter, transmitting FM as normal----the antenna box gets the signal, chops it every 20KHz, speeds up x2 each section------transits them as 50% chopped----------the next NODE box receives these 50% sections-----opens them up and joins them for listening pleasure.

I won't go any farther.
C

 

[Camerart]

Well, if you can figure it out, you'll be on to something. Single frequency repeat like this, if it worked, would have been a huge thing in the industry before digital came along.

good luck.

Hi M,
Another good point, most things have been thought of.

Anyway?
C

 

[mmckenna]

Hi, the others concerned with chopping the signal and it's quality and compression.

I always try to get round problems. (having said that I know I can talk nonsense sometimes)

How about the transmitter, transmitting FM as normal----the antenna box gets the signal, chops it every 20KHz, speeds up x2 each section------transits them as 50% chopped----------the next NODE box receives these 50% sections-----opens them up and joins them for listening pleasure.

I won't go any farther.
C

Synchronization may be an issue. Compressing analog will be an issue. That won't be something that's handled just by antenna switching, that's going to take something to unpack the audio. This is where digital shines.
Again, if this was a viable solution, it would have been developed. While I can certainly appreciate the desire to make it work just for the challenge, there are probably very good reasons it wasn't done in the past. Remember, hams are usually a resourceful bunch and a lot of development has happened in the hobby. Maybe not so much anymore, but it does still happen. Your particular challenge isn't anything new, not on the ham side, not on the LMR side.

You say you want to do this with existing radios, but I don't see a way to do that without some heavy modifications.

I can certainly understand the desire to come up with a unique solution that hasn't been tried before. That's what the hobby is about. But I think you may not be fully understanding the challenges of making this work. If you can make it work, it's not going to be easy or cheap, and it's going to take more than just antenna switching.

 

[popnokick]

Camerart- Something I missed or didn't understand earlier in this thread: You made references to someone/thing being "100" and used the word "deaf". Were those references to signal strength and inability to receive a station strong enough to copy it? Or is there some need for some sort of speech-to-text display and displayed text-to-speech translation via an assistive device?