|I have 3, each working simultaneously on YSF, D*, and DMR.
||Time Owned: 0 to 3 months.
|I bought my first mmdvm, as a finished device, from an Amazon seller. It came up very easily on FUSION and D-Star. Try as I might, though, with adjusting the RXOFFSET/TXOFFSET to something other than the recommended zero frequency shift, I could not get DMR to work. The mmdvm just would not respond any of my 3 DMR handhelds.|
I bought two more "kits" off of eBay to which I added the Pi-Zero/W's, with the goal of having all 3 working wirelessly with my home network (and later tethered to my cellphone for mobile operation). The plan was to operate each mode on widely enough seperated RF frequencies such that desense would not be a problem between them or my radios.
The kits took about a month to arrive from China. Header parts were wrong (single row instead of double row) and some were missing (I had to add some of my own parts to finish the builds). The included instructions recommended a +500 setting for the TX and RXOFFSET's.
I downloaded the correct Pi-Star image for the Pi-Zero/W and configured the 16GB TF (SDHC) chips one each for YSF, D-Star, and DMR...saving the original 8GB TF from the first one as archived software and setup info.
YSF came up on one of the kits with no issues, nor OFFSET changes, nor any other tweaks needed. It runs that way today.
D-Star needed to be configured differently than the way I had it set up for my SharkRF openSPOT. DV mode still worked (didn't need DR mode), but the DIRECT repeater settings for channel info on my ID-31A no longer worked. I had to put in B & then G for the originating and gateway settings. This may seem obvious to those with long time experience with D-Star, but with my Shark working fine without such settings for nearly 2 years, I had a devil of a time figuring out what simple setting was missing or wrong. I found it in a D-Star Setup YouTube video. I saw what was missing on the presenter's screenshot. He never mentioned it, but I saw it. After that, D-Star worked great. Reflectors can be changed from my radio, and now I use the radio on one channel and spin thru the menus to change the YourCallsign setting back and forth between that to which I want to link and back to CQCQCQ. So, I learned something valuable about how D-Star operates via my struggle and am using my ID-31A in Icom's intended, streamlined way. D-Star is now dedicated to the Amazon pre-built unit.
DMR...sheesh...what a pain to get it working.
I knew my hardware in the 3rd mmdvm (2nd kit) was working, as swapping TF chips from the other two units got FUSION and D-Star working fine in the 3rd mmdvm.
I could get the 3rd mmdvm to receive DMR by going to the Brandmeister site and setting one or more TG's to static mode. The DMR mode appeared in the OLED display of the mmdvm and all 3 or my DMR handhelds came to life on receive.
It wasn't until I accidentally diddled the RX and TXDCOFFSET settings that the mmdvm began to recognize and respond to my handheld (UHF MD-380). (I thought I was playing with the frequency adjust TX and RXOFFSET controls only.) I then tweaked for best BER with the MD-380. (It was horridly high at first.) DMR now worked great...with that radio.
The SharkRF openSPOT1 as an auto-calibration routine one can run to tweak modulation type and mode in DMR for best BER. I don't see this in Pi-Star. So when I used my 2nd handheld, a Radioddity GD-77, with the DMR mmdvm, it's BER was higher. I got both radios to work with low BER's with RX/TXOFFSET set to +150 (and not the recommended +500) and RX/TXDCOFFSETs of +500.
I surmise this DC offset to be a +500 mV "centering" of the data stream in the vocoder's decoder circuit. But...that's just a guess, as no one seems to have information available on what all of the diddle settings do and how much they can be varied until hitting a limit or getting into trouble. I wish I had a list for this !!! I don't like "shooting in the dark" when trying to align something.
Then I brought my Baofeng/Radioddity RD-5R into play. It received TG audio fine, but the DMR mmdvm totally ignored this radio when it would transmit. So, I wrote down my original settings and began to blindly diddle again with the same two pairs of mmdvm OFFSET adjustments. I also turned off Dual-Standby and turned on the sending of the radio's DMR ID at the beginning and end of each transmission in the RD-5R's CPS software's menu settings. The radio worked well this way and remain configured as such.
Thus, I finally got all 3 radios to reasonably "play" with the DC offsets back to zero and the frequency ones set to -150. Go figure...why did this mmdvm not work for the first two radios until I tweaked the DC offsets by accident?
Now all 3 DMR radios work reasonably on T&R. The GD-77 and RD-5R have BER's near zero to as high as 0.3%. The MD-380 has the worse BER of the 3, running about 0.7% to 1%...still respectable enough for good communications quality. So I "declared success". I now had reached my goal of having all 3 mmdvm's working simultaneously across my 3 favorite digital modes.
It was a real odyssey with many twists and turns to get to this final endpoint.
The moral of the story is one has to be willing to diligently work at getting the configurations "happy" if the default settings don't work "right out of the box" for you.
Maybe you'll get lucky and maybe you won't. I didn't get lucky...I pounded on the DMR issue with mmdvm-3 for several weeks until my fortuitously accidental, lucky breakthrough.
There's little documentation on these black-boxes, other than the quite good instructions for the Pi-Star software itself. But Pi-Star doesn't delve deeply into tweak-troubleshooting for the RF modem board. This lack of documentation, no test points on the mmdvm boards, nor oscilloscope trace examples of proper operation makes troubleshooting a blind endeavor. This is NOT the way to work for the easily frustrated or weak of heart !!!
The "parrot" function on YSF and DMR still both work lousy. There is always a lot of garble on my return audio streams for these modes. Yet, the D-Star echo function always returns audio that is clear as a bell. Plus, I have never had anyone complain about my audio being garbled during normal qso's on all 3 modes. So, I cannot truly guess what's going on with parrot on YSF and DMR. Perhaps it's the way the mmdvm decodes the returned Internet audio only for these modes. The SharkRF openSPOT1 always did a credible job on echo-parrot return audio for all 3 modes.
So, would I do this irritating configuration job again? The simple answer is YES. They work well enough for me to make me very happy with the outcome. The rating is not a 5 of 5 because of the many roadblocks with which I had to grapple. So, 4 out of 5 is a fair rating, IMHO.
My two SharkRF openSPOT1's (non-WiFi versions) cost me $230 and $199 respectively. The first mmdvm was $105 off of Amazon. My two kits wer $38 apiece. 16GB SDHC TF chips were $2 each. Raspberry Pi-Zero/W's were $5 for the first and $3.14 for the one I bought on March 14th (Pi-day). Any future mmdvm's will be kits, now that I'm "dangerous enough" to know what I'm doing. So figure $45 each shipped, versus $230 for a SharkRF openSPOT2 direct from Estonia.
I like puzzles. I like to learn new things. If I were in a hurry, I would have traded the additional "bucks for time and convenience" to get the more easily configured WiFi enabled openSPOT2. But, gee...with the $185 difference per unit, I got one pre-built and tested mmdvm plus two kits for less than one openSPOT2.
Going for 3 kits "right off the bat" would have cost me only $135 (but I wanted to remove the "build up" and "pi-star image burning" variables for at least the first unit). For me, these economics and the remaining learning experiences outweighed the hassle and convenience of going fully-SharkRF once again.
Your own situation and tolerance for roadblocks, irritations, and delays may be different than my own. I hope my experiences may be helpful in assisting you on how you may want to proceed...
|Quality Control Issues
||Time Owned: 0 to 3 months.
| Bought mine from California seller on EBay about 2 months ago.|
All was fine for the first month then the screen started going out. Is acting like a cold solder joint.
Still trying to dial in the offset for 0 BER, box stated -200 but I am much closer at -525.
Works ok at connecting to modes but next time I will spend a little more on a better model.
|No factory QA
||Time Owned: 0 to 3 months.
|Mine is a Chinese one from eBay. There are lots advertised, every one that purported to be shipped from a UK address had a legal address in China and the seller listed everything from toilet brushes to garden chairs... buyer beware!|
On the face of it, mine appeared to work OK. However, upon checking the RF output level with a spectrum analyser it was only -35 dBm at maximum (should reach +10dBm). Others have reported the same problem, which turns out to be incorrect, or faulty, components in the filter between the SMA socket and the ADF7021 I/C. It’s not easy to remove the OLED display (if fitted) and equally difficult to bypass the filter as the SMD parts are tiny and the tracks are thin.
Ignoring the poor RF performance of some of these, the other problem is the generic “500” offset sticker on most of them (mine included). The real offset turned out to be -10, not the value on the sticker...
The firmware version was quite old, fortunately the built in Pi-Star upgrade facility worked 1st time to upgrade the board.
Having fixed the low RF problem and worked out the correct offset, the board works fine and the OLED display is good too.
||Time Owned: 6 to 12 months.
|The MMDVM or "Hot Spot" allows the user to operate their amateur radio equipment on one or more of several digital modes without the use of a repeater. The MMDVM for all practical purposes becomes your private repeater. |
I found configuring the hotspot to be easy. I got mine off Ebay. I actually have two. They do require computer literacy and some moderate technical aptitude. Instructions provided may vary from seller to seller. I found on both my purchases the instructions to be useless. I did, however do my homework once purchased. There are numerous tutorials online and i suggest you read/view them BEFORE purchase. There are system tweaks that require adjustment to use the device to its full potential.
The hotspots, once configured, are a "set them and forget them" type deal, unless you like to play around and use different servers and modes from time to time.
Their range with the provided antenna is sufficient to cover most standard properties, and certainly any house. I took a VX-7R antenna and now get a quarter mile range or more. I can make it from my apartment to the swimming pool easily.
Hotspot firmware updates are easy; but it is recommended you know what you are doing. Updates to the operating system, pi-star are even easier. If you don't want to update the operating system yourself, don't worry. Every night the hotspot "phones home" and downloads the latest version and/or support files.*
* NOTE: As of this writing, pi-star is at version 4, which requires a manual install of the operating system to the SD card of the hotspot. Once manually installed, future updates will be handled automatically.
The hotspot also includes a CW ID, which identifys after a set period of time. This makes the device compliant with amateur radio regulations. (I've heard some models don't have this capability, but mine do). It is required, if you have the capability, to enable the CWID. It is NOT enabled by default.
Audio quality is dependent on your internet quality and other factors. It passes the datastream to and from the internet.
I love mine and being an apartment dweller, consider them to be a Godsend. Highly recommended.
|Other models available
||Time Owned: 0 to 3 months.
|Agree with K9OJ's review. I also got mine from AliExpress. Took about 6 weeks from order to arrival. Mine needed to have the antenna connector, header pins and OLED soldered to the board. Easy with the right tools. Added it to my RPiZeroW, configured Pi-Star and we were off and running on DMR. Have since ordered another board less the case and OLED for another project. Now that the ZumSpots are no longer available, this is a cost effective alternative. RX & TX offsets are now labeled on the boards for easier configuration on Pi-Star. Set mine as labeled and worked fine. For the cost, these can't be beat!|
|Fantastic Value in Multi-Mode Hotspot
||Time Owned: 0 to 3 months.
|The Jumbo Spot RTQ comes ready to run with Pi-Star preloaded on an 8GB MicroSD card. I added the pistar.uk wifi file to the SD card and the Jumbo Spot fired up and joined my wifi network.|
The Jumbo Spot can do Yaesu System Fusion (YSF), YSF-to-DMR, DMR, D-STAR, P25 and NXDN. it came with MMDVM version 1.3.3 and Linux kernel 4.9.35+ installed.
I'm using the Jumbo Spot for D-STAR and DMR. It uses the very easy to use but powerful Pi-Star software for configuration and control. I got the Jumbo Sport RTQ from aliexpress.com for $115 but it took about three weeks for delivery. Although it runs off a Pi Zero W it performs just as well as my $299 Nano-Spot with its more powerful four core processor. The Nano-Spot comes in a nice case and has an external WiFi antenna but the two hotspots are functionally almost identical.
I found my Jumbo Spot likes an RXOffset and TXOffset of 400.
I'm very happy with this little hotspot. 73 de K9OJ