getting audio from an XTS 5000R

[JoeyD714]

I represent the EMS union in a major american city. due to a problem with deeply entrenched corruption & incompetence in the city mgt. we need to be able to record all radio traffic on the EMS channel 24/7 with time stamp.

ok TMI, but it's background. We have the computer & we're pretty sure we have the software we need.
Problem is getting the audio from the radio.

I bought an adaptor off of ebay (NEW Motorola BDN6676 Audio Adaptor Connector XTS HT MTX) that supports a shoulder mounted speaker/mic and has a PTT button on it. When I plug my stereo headphones into it as a test, it keys the transmitter. a definite no-no.

I took a stereo headphone extension cord that I had in stock that's been cut so I could open the "left" & "right" wires and try them one at a time to see which one keys the Xmiter and not use it - assuming the other one would be the speaker audio.

Finding: It aint that simple. The (left) tip wire will key the Xmiter if grounded or connected thru the HP speaker to gnd.
the (right) shank wire MAY have the RX audio on it but is VERY quiet. certainly not enough to drive a shoulder speaker.

I just need access to the audio signal so I can feed it to the line in on the computer to record the rx. I can build my own attenuator or impedance matching ckt as needed, But 1st I need the audio.

I don't have access to the intended speaker/mic to tear it apart and see what I need to know, or the money to buy one. We are on a tight budget and I already told my boss that this adaptor is what I needed.... if it's designed to bring speaker level audio to a shoulder mounted speaker, how can it not be what I need?

What would be great is if someone could send me a schematic of what's going on a) inside this adaptor and/or b) what's going on inside the speaker mic so I can figure out what it wants or order to get what I want.

Any help in getting to the bottom of this would begreatly appreciated, Thanks in advance.

Dox can be emailed to me at joeyd714y@yahoo.com

Thanx again.

[fineshot1]

Not sure if this can help you but it is a lot of good info on the XTS series - good luck

Batdude s Guide for the XTS XTS and Astro Digital

[Devilz311]

So this is a portable radio going to be solely used for recording audio? If it's not encrypted, you might be better off using a scanner, or if it is, a mobile radio.

And your dispatch agency doesn't already tape the channel? I thought that was pretty much standard...

[greenthumb]

Go to Radio shack and purchase a cable with a 3.5 mm mono (not stereo) male plug on the XTS adapter end of the cable and the correct gender and size of plug for whatever recording device you are using on the other end of the cable and that should solve the problem.

I do find it odd that the radio can be keyed from the audio output of that adapter.

[Josh]

Originally Posted by greenthumb

I do find it odd that the radio can be keyed from the audio output of that adapter.

I agree. I'll have to check mine to see if it exhibits the same thing. The purpose of the PTT button on the adapter is so the radio doesn't key when something is in the jack alone.

[JoeyD714]

Devil, you missed that part about our city being corrupt., In a perfect world you think you can trust "the authorities", but we have found out rather rudely that this is not a perfect world.

Greenthumb and josh... remember a shoulder mounted speaker mic with its own PTT switch is s'posed to plug into it, so the ability for it to key should be there, but so should the ability to HEAR Audio and NOT key.

Thanx for everyones prompt responses, I do appreciate your input. Fineshot1; I'm looking at that now thank you very much. I will let yall know if I find the answer in there. In the mean time anyone who knows that they know the answer please feel free to lets us know.

I've been working on electronics since I was 7 years old and I'm 49 now. I can figure anything out given access to enough information, or a test subject to dissect and study.

I was thinking about opening it up and either, 1) soldering a pair of wires to the speaker 2) installing a 3.5 mm speaker only jack or 3) examining the accessory interface for answers, but then I read about this thing being pressure sealed for submergibility & decided to preserve that integrity.

Again thanks to anyone who an provide the info needed.

[JoeyD714]

Originally Posted by greenthumb

Go to Radio shack and purchase a cable with a 3.5 mm mono (not stereo) male plug on the XTS adapter end of the cable.

Tried that it keys the transmitter when you plug that in. it shorts the shank conductor to ground and makes the unit key.

because this adaptor is designed to support a shoulder mounted speaker/mic with a PTT switch, it MUST support keying the transmitter thru the 3.5 mm plug.

[JoeyD714]

Originally Posted by Josh

I agree. I'll have to check mine to see if it exhibits the same thing. The purpose of the PTT button on the adapter is so the radio doesn't key when something is in the jack alone.

Actually my experiments prove the opposite.
the PTT switch on the adapter will NOT key the transmitter UNLESS something IS plugged into the 3.5 mm jack.

Interestingly, I also tried connecting my headphones across the tip and ring wires and leaving the ground wire out and I get strong audio, but it's distorted.

I measured 8.9 V. DC between the tip and gnd, and 2.6 V DC between the ring wire & Gnd. Maybe I should try a capacitor in series?

[Josh]

In my experiences, plugging a mono headphone plug directly into the top of the radio doesn't cause the radio to key. It does allow the basic function of RX audio to be passed to an external device, ie speaker.

The XTS5000 will power a speaker and a bunch of other accessories. You will find however that basic headphones will be distorted at volumes that are much higher than its lowest setting, depending on how the radio is set up, lowest allowable volume level could be pretty high.

In order to get a good line level by this method, you will want to get an attenuated cable, such as sold at radio shack and mentioned before which will lower the levels to usable ones to plug into your recording device.

Looking at my accessories, the PTT accessory port adapter will not work unless something is plugged into it. I have an earphone accessory that not only plugs into, but screws into the jack on the radio. It is a stereo type plug, but again it terminates at a single earbud- no microphone.

As another tip, Motorola recommends that the accessories be attached while the radio is OFF to avoid any unwanted operation.

If when you do have a speaker connected and the audio is too low, it is probably the result of a high impedance of the speaker. I don't know what the radio is specifically looking for, but matching it is highly desirable to avoid wrecking the audio electronics. You may want to find a speaker/mic and use pinouts for the connector found on batlabs.com along with a multimeter to see what the impedance is and then try a speaker that matches it. It may be only 3.2ohms.

[robertpearsall]

make sure the adapter pinout is correct here is a link to the pin out info http://www.batlabs.com/images/mtsxacc.gif i have made a audio adaptor using this for my xts 2500 if you unplug the mic cable from tne mic you can get what you need to do it at any radio shack with out braking the mic if you need help you can pm me

[MattSR]

Hi,


You need to use an AC coupling capacitor inline with the Tip and sleeve connections. This will block the DC component that is used to key up the radio (the PTT switch) Since the BDN6676 is a surveillance adaptor the audio level will be significantly lower than the normal, balanced speaker mike outputs - but if you're feeding this into a recorder or a OC line input, this is what you need anyway - the lower level will be much better for your application.

Batlabs has a diagram that shows how the 3.5mm surveillance headsets are wired - and a picture speaks a thousand words so here it is:-

[MattSR]

Please note - using pins 2 and 3 from the Jedi connector directly is a *bad* thing as the audio output stages are a *BRIDGING* amplifier. Earthing one side will result in bad things happening to the audio output stages of the radio

Regards,
Matt

[JoeyD714]

Originally Posted by MattSR

Hi,


You need to use an AC coupling capacitor inline with the Tip and sleeve connections. This will block the DC component that is used to key up the radio (the PTT switch)
Batlabs has a diagram that shows how the 3.5mm surveillance headsets are wired - and a picture speaks a thousand words so here it is:-

Thank you Matt I Love you... This explains everything. I was just fixin to try a capacitor once I noticed all that DC on the tip.

But still little confused.. the diagram shows the spkr between the tip and Gnd via cap., but I was getting the strongest audio between tip & ring... (that might explain the distortion.) But if this is how batman says it is then this is what I'll try.

Thank you to everyone for you information and encouragement.

[MattSR]

The audio adapter has a bunch of circuitry in there that does things - it doesn't surprise me that theres some degree of signal on the Mic line but no doubt that audio goes away when you close the PTT switch. The mic line will then be configured as an input by the adapters internal circuitry.

Anyways, thats about as much help as I can give. let me know how it goes!

[JoeyD714]

Originally Posted by MattSR

Anyways, thats about as much help as I can give. let me know how it goes!

Great News, The schematic of the speaker/mic posted above was great help.

It basically told me that for rec audio I need to have a capacitor in series with the speaker between the tip and gnd connections. it said to use a 4.7u but a 10u jumped right in my hand while looking for caps, and my experience with audio electronics tells me that 10 u is a decent value for audio., I used it, works great, kinda quiet in the head phones, but great for feeding into the line input to the PC. I'm listening to it now. perfect.

Once i get all the service packs and firewall stuff installed on the PC I can start playing with the few recording softwares that I have saved on my flash drive to see which one does what we need best.

Once we settle on the desired recording software and the web masters here Authorize us to feed and send the software, we'll be able to put up the Detroit EMS dispatch channel feed

Thanx for the help.

[MattSR]

No worries! glad to be of service