XPost: rec.radio.amateur.moderated, aus.radio.amateur.misc
VK2KFJ Blog
///////////////////////////////////////////
(red) MMDVM board failures
Posted: 15 Aug 2021 05:10 PM PDT
http://vk2kfj.blogspot.com/2021/08/red-mmdvm-board-failures.html
I have bought a few different MMDVM boards to run with Raspberry Pi, such
as JumboSpot, the dual HAT boards and some red colour S56AL clones.
These red boards I found to be best for P25, as the other boards typically
have too much frequency drift, which makes the other boards like JumpSpot
work fine for DMR usage, but for P25 usage it is much more critical,
otherwise you get lots of artifacts in the voice transmissions.
Anyway, the first board I bought, was working great for P25, after 6 months
it suddenly stopped receiving transmissions from the RF modem receiver, it
just ignores any transmission, the Receive light no longer lights up, I
spent considerable time looking for solder faults under magnifying glass, comparing the circuit diagram to the board, followed the path, but could
not fix it. So I bought another two of the red boards, tested them, they were working, great I put them both to work, so I could run two different frequency P25 hotspots, about a month or so, one of them dies, no receive
from the radio modem side, then after 4 months the second board dies,
again, same fault, receiver stops decoding signals.
All three boards transmit perfectly. I also configured and tested these
boards for DMR operation and it is the same deal, receiver does not work, transmits ok in DMR mode. I know it is not the mode. All three boards are
using the onboard ceramic antenna, so it is not a case of RF overload, as
it is same IC's and circuit used on my JumboSpot boards.
These boards are marked as S56AL v2.1 and coloured red. These are NOT
boards from Alex S56AL, this red board is a chinese clone board based on S56AL's circuit design.
As it stands, I still running these boards in Tx mode, I can monitor 3 different P25 TG's at once now, as none of the boards can receive, so they won't be talking to each other. In the meantime, I am now looking for
another MMDVM board that is stable enough for P25 usage and won't fail
after a few months.
Here are the pics of the "Red" board. Note: JP1 to external SMA socket
antenna is not bridged.
Also Note I added the 4 pin IDC sockets to my boards so I can plugin a OLED display
///////////////////////////////////////////
160metre Net
Posted: 15 Aug 2021 04:21 PM PDT
http://vk2kfj.blogspot.com/2021/08/160metre-net.html
news that Steve VK2STG from south of Cooma runs a daily 160metre SSB net
on 1860kHz LSB at 8pm eastern
--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)