cdm wiring question

[brin831]

hey guys i'm trying to find some info on how to wire this setup and if its possible??

i have a couple cdm 750's

i want to set them up where i can inject audio into the tx side actually a director's hot mic, so it will always be transmitting, and then have the same radio recieve from a hand held, and have that audio come back out.

i know to tie the ground to the ptt to have the radio transmit the tx audio source, but can i then have another radio interrupt the transmit and where do i pull the audio from ? the speaker pins on the accessory connector or the rx audio?

is it in the programing of the radio ?? where can i do this ??

i have all necessary cables and we have done this in a half duplex manner with 2 radios, one constant tx and the other for rx but we don't always need to have the audio repeat and plus that uses 2 frequencies ...

any thoughts??

 

[fineshot1]

hey guys i'm trying to find some info on how to wire this setup and if its possible??

i have a couple cdm 750's

i want to set them up where i can inject audio into the tx side actually a director's hot mic, so it will always be transmitting, and then have the same radio recieve from a hand held, and have that audio come back out.

i know to tie the ground to the ptt to have the radio transmit the tx audio source, but can i then have another radio interrupt the transmit and where do i pull the audio from ? the speaker pins on the accessory connector or the rx audio?

is it in the programing of the radio ?? where can i do this ??

i have all necessary cables and we have done this in a half duplex manner with 2 radios, one constant tx and the other for rx but we don't always need to have the audio repeat and plus that uses 2 frequencies ...

any thoughts??

This is a disaster waiting to happen. Wiring up a mobile to tx all the time is gonna burn it up
sooner or later. Mobiles are not made to tx full time. Besides - its also a legal thing as you
are supposed to be in control of any transmitter and if you wire it up to tx full time then you
are not in control of it.

 

[brin831]

ok ...

well not to try and be a prick but have you ever head of or been to a race, they broadcast the radio coverage via a mobile on 454.000 tv uses the same thing for wireless coms the pit reporters with head sets buncha mobile radios ... golf same thing ... mobiles.

we have an xpr8300 repeater ... which is really just two mobiles inside ... yes they have a fan and larger heat sink, but its rated for continuous duty to 45 or 50 watts ...

we have large fans blowing across the mobiles we use currently and i would venture to say they stay just as cool as the radios that only rx.

and besides this is only getting used couple hours a day its not 24/7 365 ... so yeah inthe long run the life cycle of the transmitter may be shorter but we have not had and issue yet with one sooo i don't know ... i haven't talked to any of the other groups i mentioned to see what life they get out of theirs but i would venture to say they do quite well ...

as far as the legality, we have a license for the frequencies we are transmitting at a fairly low wattage 10 and have already spoken with fcc officials at events in the past about our setup most find it quite interesting that radios are used in this manner but there is no better way to get a large area of coverage ...

pro and consumer gear that is only allowed to 50mw like wireless mic's etc just don't have any real distance 300 ft?!?

 

[fineshot1]

ok ... well not to try and be a prick but have you ever head of or been to a race, they broadcast the radio coverage via a mobile on 454.000 tv uses the same thing for wireless coms the pit reporters with head sets buncha mobile radios ... golf same thing ... mobiles.

Yes, it would have helped my understanding of your application if you had mentioned this before.

we have an xpr8300 repeater ... which is really just two mobiles inside ... yes they have a fan and larger heat sink, but its rated for continuous duty to 45 or 50 watts ...

Yes - and these are designed and built to be 100% duty cycle repeaters unlike the mobile conversions.
Most mobile conversions have the TX radio with the power turned down to about the 50 or 60% point in
order to try and stay cooler along with having fans installed.

we have large fans blowing across the mobiles we use currently and i would venture to say they stay just as cool as the radios that only rx.

I would not go as far as saying that but the fans are a major plus. There are many that come on this web
site seeking wiring info to use two mobiles as a repeater and never put any thought into cooling of the
TX radio and when suggesting this to them they don't seem to realize the significance of this and usually
blow it off only later to post something to the effect of why did the radio burn up.

and besides this is only getting used couple hours a day its not 24/7 365 ... so yeah inthe long run the life cycle of the transmitter may be shorter but we have not had and issue yet with one sooo i don't know ... i haven't talked to any of the other groups i mentioned to see what life they get out of theirs but i would venture to say they do quite well ...

See my response above - many come back on this or the batlabs website and wonder why the tx radio
burned up or didn't last too long.

as far as the legality, we have a license for the frequencies we are transmitting at a fairly low wattage 10 and have already spoken with fcc officials at events in the past about our setup most find it quite interesting that radios are used in this manner but there is no better way to get a large area of coverage ...

I was not questioning any licensing you may have - just providing input on control responsibilities as far
as the repeater transmitter is concerned. If someone is going to be present at all times during the operation of this then you probably don't need to be worried about that in case it malfunctions and someone needs to shut it off.

pro and consumer gear that is only allowed to 50mw like wireless mic's etc just don't have any real distance 300 ft?!?

Yes - that would be totally inadaquate for the purpose.

 

[Skypilot007]

i want to set them up where i can inject audio into the tx side actually a director's hot mic, so it will always be transmitting, and then have the same radio recieve from a hand held, and have that audio come back out.

From what I can gather from this it almost sounds like you want the same radio to transmit and receive at the same time. Am I missing something?

 

[fineshot1]

i want to set them up where i can inject audio into the tx side actually a director's hot mic, so it will always be transmitting, and then have the same radio recieve from a hand held, and have that audio come back out.

From what I can gather from this it almost sounds like you want the same radio to transmit and receive at the same time. Am I missing something?

Yes - you are missing something. He is referring to TWO mobiles. One for RX and one for TX
and inquiring about wiring them together as a repeater.

 

[ramal121]

"so it will always be transmitting, and then have the same radio recieve from a hand held"
Sounds to me like he wants to have a radio transmit and receive at the same time. No way.
You can have a second radio receive and pipe that over to the first radio that is transmitting, but then he states "one constant tx and the other for rx but we don't always need to have the audio repeat and plus that uses 2 frequencies ...". OK, yes you can use two radios, but you will have to use two different frequencies. You cannot have a full duplex device on a single frequency.

So if I read this right, there will be a transmit radio in constant transmit (broadcast mode if that is kosher). What he wants transmitted is audio from handhelds (via a seperate receive radio) and a directors hot mic (whatever that is). This could be done with a mixer. If the mixer has ducking, then priority could be assigned to an audio source.

The CDM can provide audio via pin 11. Not sure what level a directors mic is.

 

[brin831]

hey guys me see i f i can clarify this a bit more what we have now is two radios one that is always transmitting

what i wanted to know is if i can make the radio do both, basically when the mic is hot, when she hits a button to talk on it can i make the radio transmit, for however long she leaves it hot, and then have it receive when not transmitting ... a talk back from the talent.

what i don't know is how to make the radio transmit just when the mic is hot, now we have the ground tied to ptt, and use flat audio tx as input yes through a mixer where we adjust levels.

and have used both speaker +- and rx audio as sources of the receive audio

i know a radio can't do both at same time but how could make it transmit the audio i want all be it most of the time .... then when the mic is not hot in the com system the radio doesn't need to tx and can then be used for talk back ...

 

[EMTLJB]

Are you looking to have a VOX (voice activated transmit) set-up?

 

[brin831]

Yes I guess that would work how would I go about that because the tx audio would most likely come off either a mixer or directly from the 2 wire to 4 wire interface to the com system.

 

[wv8mat]

VOX or Remote PTT button on a mic?, the Remote PTT would be easier then a VOX for most mobiles. like a foot switch or something like that