Help me out with this solution, CDM1250 as a pager to xband

[libuff]

ok... heres the background and the solution i am trying to setup... our county ems dispatcher uses QCII to activate our department for calls. ALL our neighboring FD's utilize UHF, so we went to UHF. we have had a special modified Minitor 2 pager base to rebroadcast the QC2 calls over our UHF repeater system via a CDM1550. the pager base is no longer available for one reason or another.

so i am trying to utilize other possibilities to get this going... i would like to hook up a CDM1250 VHF or Maxtrac VHF via the accy port to the CDM1550, and setup the corresponding VHF channel as "AND" signaling for PL & QC2 with an auto reset after x seconds.

the cable is my issue... i am not sure what is needed... this is my idea so far, but im bringing it to you guys to get this perfect the first time... money IS an issue.. and my moto dealer says ricks are no more?

from the VHF CDM1250... Activated Port 4, to PL & CSQ Detect/Talkgroup Detect (Active level low, debounce off)
otherswise im goign to tap the speaker out for audio...

connecting the pin 4 from the VHF1250 to the PTT pin3 on the UHF1550. and audio from the ext mic from the vhf...

anyways im quite confused... also do i need anything in-line (as one person suggested to me already)?

HELP ME! Thanks!

[Jim202]

You seem to be confused on what your asking for. You make the statement that everyone
is on UHF and your base radio that you did use to send out the pages with is no longer
available. So jus go get another UHF base radio and connect up a paging encoder.

Then you start talking about VHF. What does the VHF have to do with the original
issue of UHF paging? Before anyone can provide any suggestions, you may need to
re state you issue.

One word of caution that I will strongly impress upon you when using any repeater
system and paging, the audio through the repeater and the audio being generated
at the radio used for the paging encoding MUST NOT ALLOW THE PAGING TONES TO
GO INTO COMPRESSION. When any paging tones are sent over a radio distortion is
a major cause of the pagers not responding to the tones all the time. If the tones
are allowed to get into compression, it distorts the tones normally by clipping them
and the pagers have a hard time trying to decode the tones. If any DTMF is used
this is even more prone to failure.

Most radio shops don't have a clue how to set up repeaters and the base radios
taht are used for paging. If they just take a few minutes to read the manual that
came with the radio from the MFG, they will see some simple steps that need to be
taken. The bottom line is the repeater needs to be set so that a deviation of 3 KHz
input will only give 3 KHz deviation output. This also reduces the background noise
that you hear on stations when they talk. Like a fire truck has all the engine noise
in the background when the driver is on the radio. If someone is in a car with the
window rolled down, all you hear is the roar from all the road noise. These are the
signs of the repeater adjusted wrong.

Getting back to what your trying to do. Let me make a wild axx guess that what you
were trying to say was take a VHF radio and link it to the UHF system. This could be
done, but again pay very careful attention to the TX audio levels in both of these radios.

Jim

ok... heres the background and the solution i am trying to setup... our county ems dispatcher uses QCII to activate our department for calls. ALL our neighboring FD's utilize UHF, so we went to UHF. we have had a special modified Minitor 2 pager base to rebroadcast the QC2 calls over our UHF repeater system via a CDM1550. the pager base is no longer available for one reason or another.

so i am trying to utilize other possibilities to get this going... i would like to hook up a CDM1250 VHF or Maxtrac VHF via the accy port to the CDM1550, and setup the corresponding VHF channel as "AND" signaling for PL & QC2 with an auto reset after x seconds.

the cable is my issue... i am not sure what is needed... this is my idea so far, but im bringing it to you guys to get this perfect the first time... money IS an issue.. and my moto dealer says ricks are no more?

from the VHF CDM1250... Activated Port 4, to PL & CSQ Detect/Talkgroup Detect (Active level low, debounce off)
otherswise im goign to tap the speaker out for audio...

connecting the pin 4 from the VHF1250 to the PTT pin3 on the UHF1550. and audio from the ext mic from the vhf...

anyways im quite confused... also do i need anything in-line (as one person suggested to me already)?

HELP ME! Thanks!

[libuff]

Jim,

Thanks for the quick reply.. my appologies for the lack of clarity of my original statement...

our county MEDCOM system is VHF... they tone via VHF.... our company's system is UHF... all we need from the VHF side is the audio from the normal toning sequence. we do NOT activate our own pagers on UHF, our pagers are still VHF. We do not encode our own QC2 calls, our countywide dispatcher does.

previously, we had a Minitor 2 pager on some special pager base(it was a custom mod on an amplified charger), which when activated transmitted the "beeping" noise & audio from the dispatcher on the UHF radio system. the interface for this was a UHF CDM-1550LS+ on conventional channels.

we want to do the same thing, but from a MAXTRAC or CDM-1250 either of which on VHF, utilizing the "AND" signaling feature with QC2 available on either radio.

[Jim202]

I guess your still lacking on a few of the details or I am still missing part of the picture here.

Are you planning on obtaining UHF pagers and this is what is starting the questions?

Will you have your own dispatcher?

Will all the pages be done or still originate from the VHF side of the house only on VHF?

Is this a splitting of departments due to poor relations or poor dispatching or re-organization?

Why can't the dispatch do a simulcast on both UHF and VHF when a call is paged OUT?

Is your system a UHF repeater?

Based on a couple of hunches, I would try to suggesting that you see if a UHF radio could
be installed at the dispatch center to allow your system direct access to the dispatch.
This would allow the pages to originate right at the dispatch center on both VHF and UHF.
Adding a radio black box to rebroadcast the paging is not the best choice to solve the
problem if I understand it here as you so far have explained it.

I work for a company that makes radio interoperability gateways and have been in the
radio service and design for over 40 years. Spent most of that time as a member of a
number of different fire departments along the way. Public safety is in my blood and I
hate to see money spent where it doesn't need to be. I also demand the best radio
system that can be had for a reasonable amount of money.

As a result of my years in the field, I tend to tread slowly and try to come up with the
best approach. So try to humor me here and try to make the picture as clear as
you can.

Jim



Thanks for the quick reply.. my appologies for the lack of clarity of my original statement...

our county MEDCOM system is VHF... they tone via VHF.... our company's system is UHF... all we need from the VHF side is the audio from the normal toning sequence. we do NOT activate our own pagers on UHF, our pagers are still VHF. We do not encode our own QC2 calls, our countywide dispatcher does.

previously, we had a Minitor 2 pager on some special pager base(it was a custom mod on an amplified charger), which when activated transmitted the "beeping" noise & audio from the dispatcher on the UHF radio system. the interface for this was a UHF CDM-1550LS+ on conventional channels.

we want to do the same thing, but from a MAXTRAC or CDM-1250 either of which on VHF, utilizing the "AND" signaling feature with QC2 available on either radio.[/quote]

[libuff]

I guess your still lacking on a few of the details or I am still missing part of the picture here.

Are you planning on obtaining UHF pagers and this is what is starting the questions?
no, we are just looking to have our uhf radios "sound like a pager"
Will you have your own dispatcher?
yes, but out dispatcher would just coordinate units, he/she would have no access to activate pagers, that would still be done via the VHF side by the county dispatcher.
Will all the pages be done or still originate from the VHF side of the house only on VHF?
yes, all QC2 originates from VHF
Is this a splitting of departments due to poor relations or poor dispatching or re-organization?
i think poor orgnization on some parts, re-organization on others possibly. long story
Why can't the dispatch do a simulcast on both UHF and VHF when a call is paged OUT?
the county dispatcher doesn't have any access to our UHF system, they will NOT install the equipment to tap directly into our UHF system, as it would also require them to tap into many other individual systems through out my county
Is your system a UHF repeater?
yes

[Mikey]

So what your trying to do is Crossband repeat (VHF to UHF) Only when your company gets toned out right?? You probably can set up a simple crossband repeater setup with the CDM1550 you have and say a CDM 750 VHF setup to alert on QCII decode only this would repeat the alert and audio for a X number of seconds over on too your UHF channel. Do a search on the board here for Will's repeater interface and see if that will help. Also you could probably use a R.I.C.K to interface the 2 radio's together if you have access to one of those.

Am i even close to what you are trying to accomplish?

Mikey

[HumHead]

It sounds like this only needs to be a uni-directional re-broadcast, not a bi-directional repeater. Also, the CDM750 does not support QCII.

What he is trying to do should be relatively simple. Assuming the radios share a common ground, program a pin (usually 4 or 8 ) on the receive radio for PL & CSQ detect, and connect it to a pin (usually pin 3) on the TX radio set for external PTT input. Route the audio into the TX radio External Mic Audio in. Put a small DC blocking capacitor in line with the audio input to block the bias voltage. Also be sure to set an appropriate time out timer on the TX radio in case the RX radio fails.

Now the one tricky part- if you need to have the alert beep sent over the air, I am not certain if the alert beeps are sent over the Pin 11 audio output. If they are, just connect pin 11 on the receive radio to the Ext Mic Audio in pin on the receive radio. If the alert tones are needed, and are not available on pin 11, you will have to connect an 8 ohm to 600 ohm transformer across the RX radio's speaker outputs and use that to source the audio. Whatever you do, do not connect one side of the RX radio's speaker output directly to ground. That will most likely be the end of the receive radio's audio PA. Also note that if you end up using the speaker output, the output level will follow the volume control. You will have to protect that against tampering.

Even if you want to build everything yourself to save money, it will still be worth your while to make sure that you have the final assembly properly aligned by someone with a service monitor.

[libuff]

It sounds like this only needs to be a uni-directional re-broadcast, not a bi-directional repeater. Also, the CDM750 does not support QCII.

What he is trying to do should be relatively simple. Assuming the radios share a common ground, program a pin (usually 4 or 8 ) on the receive radio for PL & CSQ detect, and connect it to a pin (usually pin 3) on the TX radio set for external PTT input. Route the audio into the TX radio External Mic Audio in. Put a small DC blocking capacitor in line with the audio input to block the bias voltage. Also be sure to set an appropriate time out timer on the TX radio in case the RX radio fails.

Now the one tricky part- if you need to have the alert beep sent over the air, I am not certain if the alert beeps are sent over the Pin 11 audio output. If they are, just connect pin 11 on the receive radio to the Ext Mic Audio in pin on the receive radio. If the alert tones are needed, and are not available on pin 11, you will have to connect an 8 ohm to 600 ohm transformer across the RX radio's speaker outputs and use that to source the audio. Whatever you do, do not connect one side of the RX radio's speaker output directly to ground. That will most likely be the end of the receive radio's audio PA. Also note that if you end up using the speaker output, the output level will follow the volume control. You will have to protect that against tampering.

Even if you want to build everything yourself to save money, it will still be worth your while to make sure that you have the final assembly properly aligned by someone with a service monitor.

awesome, exactly what i am looking for... if i setup the pin for csq/pl detect, will that also follow the QC2 setup if i make signaling "AND" ?

[HumHead]

Yes it will but, under the Accessory Configuration tab, you want to set the RX audio type to "filtered audio".