Canford Walkie-talkie Interface

[alan1180]

Okay so I'm a complete noob with comms and radio systems but I'm looking for a cheap way to connect motorola two way radios to our simple comms system. If I brought a Canford Tecpro AD913 would this be the correct bit of kit and how would I cable the system up?

 

Any help would be amazing!

 

Alan

 

(PS I've looked at over posts where people are saying they need to wire resistors and stuff in but surely it can't be that complicated?)

[boatman]

Okay so I'm a complete noob with comms and radio systems but I'm looking for a cheap way to connect motorola two way radios to our simple comms system. If I brought a Canford Tecpro AD913 would this be the correct bit of kit and how would I cable the system up?

 

Any help would be amazing!

 

Alan

 

(PS I've looked at over posts where people are saying they need to wire resistors and stuff in but surely it can't be that complicated?)

 

YES the AD913 is the box you need; and NO resistors aren't complicated. The AD913 provides a relay contact which closes to simulate the PTT button on the radio. The relay closure happens when the "Call" button on the TecPro beltpack (or master station) is pressed. You will need to investigate how that interfaces to the Motorola radios. I have interfaced an AD913 with a variety of PMR446 radios and they all need different resistor configurations, so there's no standard solution.

[AdrianW]

+1 for the Canford box. Ive used it to interface to the Motorola GP340 radios with no problems (and no resistors either :-)

 

Adrian

[BlueShift]

Yes, this will work fine. But remember that the call button on the wired station will have to be pressed and held for the duration of the transmission to the simplex radio. This can be annoying if you also have flashers on the circuit. Another alternative is to interface it with a radio that supports VOX (auto PTT on audio signal). GP340s do support vox...

[timsabre]

Yes, this will work fine. But remember that the call button on the wired station will have to be pressed and held for the duration of the transmission to the simplex radio. This can be annoying if you also have flashers on the circuit. Another alternative is to interface it with a radio that supports VOX (auto PTT on audio signal). GP340s do support vox...

 

Vox mode only works if the radio-linked person(s) are listen only. As soon as anyone on the wired comms speaks it puts the radio into transmit, so the radio person(s) cannot talk back unless everyone on wired comms is silent.

[BlueShift]

Correct.

 

As I mentioned, this is really only an issue if you cant be pressing call all the time. If thats a viable option, go that route.

[paulears]

I went to a venue with a Wood and Douglas duplex radio link that was linked to a pile of Motorola walkie-talkies for the first time. In the past, I'd simply wired my IEM tx to a spare pack, and had listen only comms - which was fine most of the time, however I tried their system. It worked fine BUT the bandwidth limited audio centred on 3K or so is really, really tiring on the ears - especially when you have to turn it up a bit when things are noisy. In the end, I went back to my IEM, because it was so much nicer to listen to, but kept the walkie talkie on my belt, turned off. My role is mainly listening - but when the DSM wanted me to do something urgently, he'd call, and I'd respond with a short "on it" response, then a followup "done" when I'd sorted the problem - just muttered into the walkie talkie. Pressing a call button to put a walkie talkie into transmit means that for most time, the radio link is silent. Vox, I hate with a passion beause of the first clipped syllable, and the pause while it drops out at the end - sometimes line noise from an open mic can keep it transmitting preventing a response. If you really need to do regular radio comms, then a proper duplex system with continuous transmit is important, or better - a proper digital system. On the cheap - an IEM system works well, but I'm lucky in that I have quite a few.

[BlueShift]

Absolutely.

 

Normally though, Half-duplex is all thats actually required (constant listen with keyed talkback). And this can be achieved very well with Motorolas. Part of the issue is getting a radio base with good quality Audio I/O (like my current favorite, the Tait TB7100) and then being able to EQ the signal to improve audio quality.

Also, don't forget the importance of good headsets. Most radio earpieces are designed to be intelligible at all costs, which means lots of 1-3k and not a lot of LF response. This is great for occasional communication, but not something you want to have to listen to for very long.

 

That said though, If you wan't the best audio quality, don't go with digital systems. All of them sound pretty poor. Perfect for communication purposes, but nothing like full bandwidth. Even digital radios suffer from this problem compared to their analogue counterparts. Its probably the main reason that Telex BTR700 is still so popular.

 

Half of my work these days is large matrix comms systems. In fact, as I type this I'm sitting at my control position at the UK Athletics Championships with an RTS matrix, a couple of radio links and some BTR. Here, the radio comms sounds really good. But only because of some EQ and stuff being done on the return from the tait base. Thats the key really

[dbuckley]

... like my current favorite, the Tait TB7100

 

For those who are less well wallet-endowed then those who use big matrix comms rigs, there's a lot of Tait gear on the second hand marketplace these days, as the big radio users (like the Police) are moving to digital. Thus if you want to put a wireless link in your comms, the kit to do it is readily and cheaply available.

 

Tait gear is cracking kit, designed and made in New Zealand by a company named after the founder, the late, great Sir Angus Tait, a Kiwi of Scottish decent. A bloke who got it right.