Duplex Hotspot Anomalies (N5BOC)

MMDVM_HS Hat hardware
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k2dls
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Duplex Hotspot Anomalies (N5BOC)

Post by k2dls » Sun Aug 25, 2019 1:54 pm

I have an N5BOC duplex HAT running on a Pi Zero W. So do several local radio friends. We have all noticed the following issues in DMR mode:

1) Sometimes a PTT results in a "not found" message. Sometimes it takes several keyups to negotiate.
2) Sometimes a transmission gets completely thrown away and not sent out the network. There are times when I have talked for 2 minutes and then figured out the transmission did not get repeated.
3) Sometimes a transmission is not sent out the network but the last few words (several seconds) echo back.

The hotspot and radio offsets from one another have been accounted for with tools such as MMCDMCal and otherwise minimize BER rate to 1% or under. The issues occur whether using an MD-380, Alico (MD-DJ5, similiar to the Anytone 878), a CS 700/750 or a Motorola XPR. We've all implemented a suggestion to set the preamble to 960 ms.

Are these issues unique to the N5BOC boards or are folks seeing similiar issues with other duplex HATs? I'm hoping that this is something that will eventually be cured in hotspot firmware, but thought I'd throw the issue out here to see what the community experience has been thus far.

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KE0FHS
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Re: Duplex Hotspot Anomalies (N5BOC)

Post by KE0FHS » Sun Aug 25, 2019 4:27 pm

This isn't an issue unique to the LoneStar duplex hotspots by N5BOC. If anything, his boards are better quality than some alternatives.

A few things to consider:
  • There is a known DMR timing synchronization issue with some duplex hotspots and radio combinations. Bud, W0RMT, has a good post on the Pi-Star User Forum about adjustments that can be tried to address the issue: viewtopic.php?f=30&t=1207#p4960
  • There's a detailed article "focused on the MMDVM board with dual (duplex) radios and the DMR protocol, operating on the Brandmeister network," which includes sections on using pistar-mmdvmcal for calibration, and on performance tuning: https://www.commswg.site/_amateur_radio ... plex.shtml
  • DMR Configuration: DMR EmbeddedLCOnly (Embedded Link Control Only) option – The default is off. Turning it on disables the Talker Alias data that is sent by MMDVMHost. If you are experiencing audio drop-outs from some stations, you might want to try turning this option on. If you do turn it on, you can go ahead and turn DMR DumpTAData off. (The default is on. This option controls whether Talker Alias data is logged in the /var/log/pi-star/MMDVM-YYYY-MM-DD file.If you're not using Talker Alias, you can turn this option off.)
73, Toshen, KE0FHS
Playing with Pi-Star (unofficial notes about setting up and using Pi-Star):
https://amateurradionotes.com/pi-star.htm

KD8DVR
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Re: Duplex Hotspot Anomalies (N5BOC)

Post by KD8DVR » Sun Aug 25, 2019 9:48 pm

I am experiencing the same exact issues with my 2 duplex hotspots. Each is a different design, also. They are both generic chinaboards. So I'd say it is across all duplex designs.

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KE0FHS
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Re: Duplex Hotspot Anomalies (N5BOC)

Post by KE0FHS » Sun Aug 25, 2019 9:53 pm

KD8DVR wrote:
Sun Aug 25, 2019 9:48 pm
I am experiencing the same exact issues with my 2 duplex hotspots. Each is a different design, also. They are both generic chinaboards. So I'd say it is across all duplex designs.

Sent from my SAMSUNG-SM-G920A using Tapatalk
You might want to read the article I mentioned above before jumping to that conclusion, especially the note at the beginning with the heading, "MMDVM Buyers":
https://www.commswg.site/_amateur_radio ... plex.shtml
73, Toshen, KE0FHS
Playing with Pi-Star (unofficial notes about setting up and using Pi-Star):
https://amateurradionotes.com/pi-star.htm

k2dls
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Joined: Mon Aug 20, 2018 5:24 pm

Re: Duplex Hotspot Anomalies (N5BOC)

Post by k2dls » Tue Aug 27, 2019 10:15 pm

After some experimentation, the thing that really seems to fix it is to set the DMR preamble duration on my Alinco DJ-MD5 (similar to Anytone 878) to 100. My duplex hotspot now seems to respond to all PTT requests properly. A friend tried it on a Motorola XPR where he was having issues and the setting also seemed to help.

Bridgecom recommends this preamable duration setting for use with the Anytone 878.

73
Last edited by k2dls on Fri Aug 30, 2019 7:58 pm, edited 2 times in total.

KD8DVR
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Re: Duplex Hotspot Anomalies (N5BOC)

Post by KD8DVR » Tue Aug 27, 2019 10:24 pm

Ok. Where is this setting? I don't recollect seeing any preamble.

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KD8DVR
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Re: Duplex Hotspot Anomalies (N5BOC)

Post by KD8DVR » Tue Aug 27, 2019 10:27 pm

Never mind. I found it. It defaults to 100. Didn't help my problem any.

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