Decrease BER %

MMDVM_HS Hat hardware
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kc7wsu
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Joined: Tue Apr 24, 2018 2:00 pm

Decrease BER %

Post by kc7wsu » Fri Mar 29, 2019 2:41 pm

I have an MMDVM_HS and am getting a 1.0-1.5% BER with a -475 offset. This is a JumboSPOT that I purchased to play with. I already have 2x DVMega.

Has anybody tried swapping the TXCO for a higher quality one to remove the offset and decrease the BER?

Regards,

Chris Andrist, KC7WSU

M1DNS
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Re: Decrease BER %

Post by M1DNS » Fri Mar 29, 2019 5:31 pm

What you have is a relatively good BER already. I wouldn't bother.
Try a little fine tuning, changes in steps of 2 or 5 might bring it down a little more. Anything 1.0 or below is fine for home use.



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dh3ybe
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Location: Germany

Re: Decrease BER %

Post by dh3ybe » Thu Apr 04, 2019 9:27 pm

Hi Chris,

or the tx power could be high, if your work with the hotspot in the same room. HF is disturbing eletronic devices a little bit.

Best regards
Kai
dh3ybe

RC3C
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Re: Decrease BER %

Post by RC3C » Thu May 02, 2019 1:27 pm

Hi

I have during 0,2% to 0,4% in BER (green color) with RXOffset/TXOffset -300. Try to use this value.
73s! Anton (aka Tony) RC3C
in Moscow, RU

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KE0FHS
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Re: Decrease BER %

Post by KE0FHS » Thu May 02, 2019 3:42 pm

Each individual hotspot can require a different offset. If you're experiencing high (greater than 1%) Bit Error Rate (BER) with your radio, you can try reducing it by adjusting the RX Offset:
  1. Set up Pi-Star with the MMDVMHost Configuration Mode you want to use. Be sure to apply changes.
  2. The best way to work on this is to have Pi-Star open in two browsers:
    1. Set up the first to view the Expert Editor, where you'll do the adjustments:
      1. Enter Expert Editor: pi-star.local/admin/expert.
      2. Click MMDVMHost.
      3. Scroll down to the Modem section and find the RXOffset setting.
    2. Set up the second to view the dashboard so you can view the resulting BER readings.
  3. The easiest thing to do is to make calls lasting a few seconds to a Parrot talkgroup or reflector.
  4. In the Expert Editor, adjust the RXOffset setting, make a parrot call, and observe the readings. You're aiming for a BER of less than 1%, preferably less the 0.5%.
    1. Begin with +/-100 offsets, and see how that affects the BER.
    2. Once you find the lowest BER with the +/-100-step offsets, repeat the process with +/-50-step offsets, and finally +/-10-step offsets until you find the lowest BER.
  5. Repeat this process in each MMDVMHost Configuration Mode in which you're experiencing high BER, until you achieve the optimal BER in each one. If you can't find a good balance for the BER between the different modes, it may be better to use different hotspots for each different mode.
Alternative and more exact method to calculate offsets: Daniel, K9NPX, has a good article on using MMDVMCAL to get more exact RXOffset (and TXOffset) settings for a DMR radio: Hotspot Offset Calibration: http://www.k9npx.com/2019/02/hotspot-of ... n.html?m=1
73, Toshen, KE0FHS
Playing with Pi-Star (unofficial notes about setting up and using Pi-Star):
https://amateurradionotes.com/pi-star.htm

M1DNS
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Re: Decrease BER %

Post by M1DNS » Thu May 02, 2019 4:59 pm

admin/expert/edit_mmdvmhost.php



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RC3C
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Re: Decrease BER %

Post by RC3C » Sat May 04, 2019 9:43 am

KE0FHS wrote:
Thu May 02, 2019 3:42 pm
Each individual hotspot can require a different offset.
Yes, it does. I have TYT MD380UV at home with nano hotspot MMDVM_HS_hat. It has (as I wrote b4) in max 0,4% BER

in maximum
rxtxoffset-300.PNG
rxtxoffset-300.PNG (20.13 KiB) Viewed 862 times
in minimum
rxtxoffset-300 min.PNG
rxtxoffset-300 min.PNG (13.15 KiB) Viewed 861 times
73s! Anton (aka Tony) RC3C
in Moscow, RU

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