Batboard

I have noticed a VERY ANNOYING buzz on high volume receive audio on the HT1250 when MDC receive is active. I have noticed that changing channel spacing to a wider setting (from 12.5 to 25khz) in each personality makes a difference in the wider the spacing the less the buzz. I have also noticed less buzz when using MDC System II as the receive system. I have played around with all the MDC settings (I.D.'s, etc) and they don't seem to make a difference nor does the specific PL/DPL make a difference in this problem, but minus decoding a PL/DPL the problem goes away too. It seems that if the MDC I.D. decode display is set, you get this buzz at high volume regardless of freq, PL, etc. Is there anything I can do to clean up receive audio when decoding MDC I.D's? Thanks

<font size=-1>[ This Message was edited by: KD6MHO on 2001-12-27 01:29 ]</font>

I should also add that the buzz is heard whenever carrier is present and MDC receive is selected, whether or not the received signal has a MDC packet with it or not.

I experience the same thing with the HT1250, no solution though.

You can make it better with companding, but then you have to deal with the sound quality issue of companding.

Chris

There is a legitimate bug with the receive buzz on the Professional Series radios when using MDC and TPL signalling systems simultaneously, due to the default values for baseband offset frequencies. (My dealer swears that I was the first user to discover this when the radios first came out- My little claim to fame )

To eliminate the problem, the baseband offsets have to be reset to different values using Global Tuner.

I'm on the road right now, but when I get back into my office in a couple of days, I can look up the values that I found that eliminate the problem.

I also have a service bulletin from // on the issue somewhere. I'll see if I can dig it up too.

Very cool! I am glad that there is a way around it and I am sure I won't be the only one glad to hear that there is a fix for it! Looking forward to hearing how it's done. And I am also glad to hear that I am not alone with this problem!

I am having a similar problem, if possible can you send that information my way when you get it! I would greatly appreciate it!

Adam
[email protected]

Sorry I've been away so long, but why go back to the office any earlier than you absolutely need to....

Anyhow, the Professional Series radios are prone to buzzing on received audio under the following conditions:
1) When receiving TPL on a channel set for MDC or QCII signalling
2) When receiving a signal with TPL on a channel set for CSQ
3) (Rarely) When receiving DPL on a mode programmed for DPL

To fix these situations, you need to go into the Utilities menu in Global Tuner, and choose "Baseband Offset Update".

The Baseband Offset Update window will present offset values for CSQ, DPL/MDC/QCII, and TPL ranges 1-4, as well as "radio buttons" for the three channel spacing ranges.

When updating values, you should update all three spacing ranges, and you must click the "Update" button before switching ranges in order to save the values to the radio.

That being said, the best (and / or Motorola recommended)solutions that I have found for the three cases above are as follows:

1) TPL buzz on a mode with MDC or QCII- Change the DPL/MDC/QCII offset from the default of 646Hz to one of the default TPL offsets such as 57Hz, 86Hz, or 115Hz. I personally have had good results using 57Hz.

2) CSQ Offset- If you're having trouble with TPL buzz on a CSQ channel, choose a new value that is at least 20Hz off from any TPL tone that the radio will likely be receiving on that channel.

3) DPL buzz on a DPL channel- It's trial and error time with the DPL offset value. Motorola suggests 86Hz as a good starting point.

Hopefully this will help all of you out. For those of you who requested it, I have private messaged you with more detailed information. Otherwise, if you want more detail drop me a private message and I'll get back to you.

Good luck!

<font size=-1>[ This Message was edited by: HumHead on 2002-01-03 14:17 ]</font>

Thanks..

Just changed the MDC offset to 57 Hz and it worked like a charm.

Chris

Very interesting stuff, anybody who works with the professional series radios should copy & paste the info into a text file for future reference.
I had a similar problem using HT1250s on a GR1225 repeater system. Same idea, using MDC & TPL. Horrendous sounding buzz on all the HTs, but GP300s & Kenwoods sounded great! Also, the HTs sounded just fine going through their MSR2000 repeater with the same set-up. Scratched my head for a few hours on this one. I don't know if changing the tuning values as posted here would have worked, I didn't try them. A solution was stumbled upon after trying many different things. Turns out, the GR1225 set to strip the PL on receive, and regenerate it on transmit. Once it was set to CSQ on both RX & TX, and the repeat audio filtering was changed from "EIA" to "FLAT" (to allow the PL to go through), the problem thankfully went away. Just in case anyone else was having a similar problem!

Todd

If you only set it on the 12.5 spacing should it work for those channels with 12.5 spacing set? Or do you still have to change the DPL/MDC/QCII setting for all 3 spacings for it to work?

I am having quite a bit of trouble with this. Any help would be greatly appreciated.

Thanks...

In theory, you would only have to change the tuning values for the affected spacing. However, as long as you are in there, I cannot imagine why one would not just take the extra couple of seconds to fix all three spacings.

I was being stupid. I changed all the spacings to 57Hz and it worked like a charm. Will that effect anything else in the radio. What is the theory behind the baseband offset? Just curious...

The actual theory gets a little complex, and I'm not 100% sure I could present it coherently. Here is /\/\'s attempt at a concise summary:

Motorola wrote:The baseband-offset frequency is the amount of offset necessary to keep the RF carrier out of the second order notch frequency generated by the Baseband AC coupling.

Reviving an old, but very valuable thread.

I tried 57 Hz, and got zero results/problems as before, it seems that 86 Hz is the best setting for everything. It fixed Loud DPL on channels set for MDC, loud PL on other w or w/o MDC, and also LTR data noise- which was an especially big problem on 12.5Khz.

Pain in the butt. idk why Motorola doesn't just make the default something usable as-is. I don't think anyone really wants to hear the LTR/DPL rumbling!