TRBO DELAY ON AUDIO

[efc]

Hi all,

Got a weird problem.

1. XPR 6300 VHF

2. DC line comes from a Spectra Tac voter, to a CPI DTP interface.

3. Output from CPI is PTT,MIC HI, MIC LO, to the back of the access. plug on the Trbo.

4.What happens is a slight delay between the radio Rx and when the radio transmits, I would say about half a second. When the trbo is in repeat mode, no delay.

5. Now I am thinking it is because of the added interface,although when the radio receives, the PTT seems instant.The delay appears to be with the Trbo.Checked ant. relay delay, it is 0 since the Trbo is in "base" mode and not "repeat" mode. Of course the cust. notices this and says it sounds like the nextel digital delay.Although I cannot really here it. Any thoughts?

Thanks

[Bill_G]

I think you mean the XPR8300 repeater, and not the XPR6300 portable.

You don't say whether you are using digital or analog mode, and I haven't played with the series enough to confirm there is a delay using the accessory port, or a difference in mode performance. I suspect there might be. Internal repeat is probably faster since the radio never has to drop the payload down to audio. It merely passes it through with low latentcy. But, as soon as you require it to do external audio output/input processing, you add time to the turn around to the voter, and that number may be as high as a half second, though more realistically around 300mS. I would say what you are experiencing is normal, and to be expected.

[efc]

Sorry, XPR 8300 I had 6300s on the brain.The base is in Analog mode.Yes I am thinking this may be normal.This is new territory for me so I am learning the quirks The thing that gets me is that the cust. says it seems as though the base is "holding" on to the audio like the type of digital delay you get with Nextel. Personally, I cannot really here it. He says it occurs when 2 radios are next to each other and otherwise the system works good.

[alex]

I would expect that this is due to the DSP. Although you are not doing digital, the audio is processed through the DSP even if it is just everyday analog audio. It's similar to using an Astro/Astro25 series radio for analog... always a really slight delay compared to your good 'ol HT1000 or analog radio.

-Alex

[escomm]

What Alex said. The DSP cannot process the signal in real time, so you will have the noticeable delay even when running in analog mode. It's also the reason that you don't get the same kind of feedback when you have one radio transmitting and it hears its own transmission out of a nearby radio. And it still sounds like you have a sock in your mouth when talking

[alex]

I wonder if there is a way to just bypass the DSP all together... unless they are using it to provide some other functionality...

[efc]

Alex, another guy and I were wondering the same thing about bypassing the DSP.And yea you are right,when you mentioned that it dawned on me, which according to the big M is true.So while I had them on line, I asked about jumpering or whatever to bypass the DSP. They say no you cannot do that. That is just the way it is. Gee....can't wait to tell the cust.

[Tom in D.C.]

"Delayed" audio is a fact of life when using a digital radio to receive communications. Many of us have been living with it for
years on our XTS and similar radios. The TRBO exhibits the same exact behavior even though it uses a different digital platform.

[alex]

Alex, another guy and I were wondering the same thing about bypassing the DSP.And yea you are right,when you mentioned that it dawned on me, which according to the big M is true.So while I had them on line, I asked about jumpering or whatever to bypass the DSP. They say no you cannot do that. That is just the way it is. Gee....can't wait to tell the cust.

Well -

Think of it this way... If your going to bypass the DSP you are probably also going to have to bypass the trbo repeater controller since that is what the audio probably passes through.

At that point, you might as well not buy the XPR repeater...

You would want to find the flat tx audio / flat rx audio test points and probably use those to go to an external controller....

I'm shooting from the cuff here, so if I'm off a bit - someone correct me. If your not using trbo, and you need something that is a good 50% duty cycle system (I don't know off hand what the rated duty cycle is in analog for trbo) then maybe looking at using a CDR or other repeater you can just hook off the shelf stuff up to?

-Alex

[Bill_G]

If they can't stand this delay, how do they put up with cellphones?

[resqguy911]

How do they hear the delay anyway? Are they talking to someone that is within earshot? If so, why not just shout instead of using a radio?

[escomm]

If they can't stand this delay, how do they put up with cellphones?

Back, back, back, back ****BANG**** That's too far

[Bill_G]

If they can't stand this delay, how do they put up with cellphones?

Back, back, back, back ****BANG**** That's too far

Well, hopefully they are not trying to switch railcars with this product. Most applications can deal with delay.

[escomm]

No, they would be using NexEdge/IDAS or w/e if they were switching railcars, right?

The delay is quite annoying, not a huge deal, just another reason to go analog or go home

[MattSR]

I wonder if there is a way to just bypass the DSP all together... unless they are using it to provide some other functionality...

If its anything like the P25 gear (99.9% probable), then that part of the repeater is I/Q based SDR stuff. So its has to have a DSP since all the IF processing is done in software anyway.