IC-F3400DT with NXDN/MMDVM Hotspot

[alecmesa96]

Hello all,

I have a small amount of experience with digital voice in the ham world, mostly DMR and YSF. However I am completely new to NXDN. I'm looking to get some info regarding the use of a commercial radio that I picked up a few years ago. I have an ICOM IC-F3400DT VHF commercial HT that claims to feature NXDN and dPMR. I also have an MMDVM hotspot running WPSD that also claims to support NXDN. For this reason, I have been interested in seeing if the two can work together for amateur use. I'm well aware that this is a commercial radio and not designed for amateur use, but I have had success getting it to work with my local 2M repeaters, so I would like to see if I can do a bit of digital with it as well. If I'm not posting this in the correct forum, I do apologize.

On the hotspot side, the only thing that I have done is set the frequency to a suitable spot on 2M and enable NXDN operation. I have requested and received an NXDN ID and have set it both on the radio and in the hotspot. I am using an AURSINC Chinese MMDVM duplex hat with my Raspberry Pi 4. I have verified that the modem does indeed support VHF. I tried it with my DMR and Yaesu radios and was able to make it through to my networks just fine using 2M.

I am not used to ICOM programming software, but I have set the hotspot frequency, RAN and the worldwide talkgroup 65000 in what I assume to be the correct way just to test functionality. Digital type is set to NXDN conventional, with the other choices being NXDN single-site trunked, and NXDN multi-site trunked. When I key the radio for any length of time, nothing appears on the hotspot dashboard screen. I have verified that it is actually transmitting on the correct frequency a digital signal (using another radio), but for some reason the hotpot does not react to it whatsoever. I am running the lowest power setting as I am only about 10 feet away from the hotspot. I am thinking that there is an issue on the radio side/something with my settings. Like I said I am not used to ICOM programming software, nevermind their commercial versions.

I'm hoping there is someone out there who is more experienced than me in this department and may be able to lend a hand. I'm not really expecting this to work at all since it may not be compatible to begin with, but I wanted to at lest try to get some guidance if at all possible.

Thank you for any information that you can provide!

 

[tweiss3]

You should use the alignment procedure on the hotspot to adjust the frequency for you radio. NXDN doesn't like anything that is slightly "off frequency". You are in the right direction. It's been a while since I played with NXDN on my hotspot, but I remember having to hold PTT for 3 seconds for it to register a change/talkgroup. After that, it worked a bit quicker, but changes were slow on the hotspot.

 

[alecmesa96]

You should use the alignment procedure on the hotspot to adjust the frequency for you radio. NXDN doesn't like anything that is slightly "off frequency". You are in the right direction. It's been a while since I played with NXDN on my hotspot, but I remember having to hold PTT for 3 seconds for it to register a change/talkgroup. After that, it worked a bit quicker, but changes were slow on the hotspot.

Hi, and thanks for your reply. This makes sense to me due to NXDN very narrow bandwidth of 6.25kHz. I read in a similar post of someone using a Kenwood 900mHz radio for NXDN and he needed a "massive" offset in the calibration tool in order to get the two to work together. The radio that I am using is monoband VHF, but I would imagine this would still apply. I currently use two other radios for this hotspot and needed to run the modem calibration utility for both of them. Well, the DMR radio didn't really need it as it already played nice, but wanted to see the BER come down a little more. My Yaesu HT was barely getting in at all with over 60-80 percent of my transmissions dropping off and a BER or 2-3. In both cases, I found myself running somewhere between -250 and -350hz offset for the calibration utility. I am assuming that this is because my hotspot is off frequency in the positive direction a bit.

I won't be able to take another stab at this until Wednesday evening, so I will be sure to give it a try and post some results. Thanks again.

 

[tweiss3]

I forgot about very narrow, but I think the MMDVM will only do narrow NXDN (12.5). Try setting that and see if it works.