Mmdvm duplex hotspot setup

Mmdvm duplex hotspot setup

Disclaimer: These are my personal notes and opinions based on my experience playing around with hotspots, as well as by learning from what others are sharing.

I'm not affiliated with any hotspot projects, except as an enthusiastic user. If anything needs correcting, please let me know. A personal, low-power hotspot is a combination of hardware, firmware, and software that enables an amateur radio enthusiast with internet connectivity to link directly to digital voice DV systems around the world. Basically, hotspots are your own personal digital voice repeater and gateway, which can be really fun.

Here's a simplified diagram of what it looks like when you connect via your hotspot to a BrandMeister-hosted multiprotocol talkgroup, which enables people using different modes to talk with each other:.

mmdvm duplex hotspot setup

Note: Some multi-mode hotspots are themselves capable of directly communicating to different modes. For someone like me who doesn't live within range of a digital voice repeater, a hotspot goes beyond being fun to being a critical key to accessing digital voice systems, a gift that opens doors to the whole wide world. Overall, this is an exciting area of amateur radio that is evolving and progressing rapidly with some excellent work being done by some very innovative hams there's a shoutout to some of these folks at the end of this article.

This is an article about personal, low-power hotspots, also known as personal access points 1not repeaters. I've been playing around with personal, low-power hotspots since I discuss my experiences with all of these in this article. A great way to make use of hotspots is to join some of the many digital radio nets that are run every day by hams throughout the U.

They also have a Telegram group: Colorado Digital Multiprotocol. It has a quite comprehensive list of active DMR nets. The regulations and best practices that apply to amateur radio—including use of frequencies, control of our stations, and on-air courtesy—also apply to our use of personal, low-power hotspots. It's our responsibility to understand and adhere to these regulations and best practices.

My personal practice is that I power on my personal, low-power hotspots only when I'm monitoring and in control of them, adhere to my local band and frequency use plans, and leave adequate pauses between transmissions.

For more about this, see Hotspot best practices. All that said, there are other hotspots available and included in the following list that also are worth considering.The good news is this is actually already getting better as companies figure out hot to mange in this enviroment. I will update this section as that date gets closer. Please head over to that page on the site to place your order there. Thanks so much for your support during this time that is difficult for all of us.

While there are other versions of this type of Duplex board on the market this is the ONLY one which keeps the Pi Zero form factor that has become so popular.

Note: The photos show the board with u. These are a user installed option. The pads are there but it is up to the customer to install these connectors. All the features of a duplex board without having to sacrifice the convenience of the Pi Zero form factor. I'm very lenient on returns. If you have an issue please contact me and I will do my best to resolve your issue by Email.

If after a few exchanges the problem is still not resolved I will ask you to return the board to me where I will either repair the board or replace it. If you feel your board is DOA then you must contact me within 14 days. More technical details and setup information can be found here Documentation More technical details and setup information can be found here Out of Stock.They both use the very easy to use but powerful Pi-Star software for configuration and control. The Nano-Spot comes in a nice case and has an external Wi-Fi antenna but it's functionally almost identical to the Jumbo Spot.

The duplex HAT works great and it's what I currently recommend everyone get. It has dual radios with dual antennas for simultaneous UHF transmit and receive.

I had a heck of a time getting my digital radios to communicate with my hotspots so I created this webpage to hopefully help new hotspot users get up-and-running easier and quicker than I did. See my Nano-Spot Pi-Star settings. The Jumbo Spot transmitter is rated at 20 milliwatts. See my Jumbo Spot Pi-Star settings.

Dual radios allow simultaneous reception and transmission. Its dual radio chips are rated at 20 milliwatts each.

For me setting up the radios to work with a hotspot was much more difficult than setting up the hotspot and Pi-Star software. Here's a rundown on what I had to do to get each radio setup:.

For general troubleshooting I recommend you monitor your radio and hotspot transmissions on an SDR or analog radio so you can verify the hotspot is transmitting and your radio is transmitting in digital mode.

If you have an SDR with computer output use it to monitor your radio and hotspot to compare their exact frequency. Nano-Spot Pi-Star Settings. Jumbo Spot Pi-Star Settings.

mmdvm duplex hotspot setup

Open Source Hardware License. Just program your hotspot frequency as simplex into the "A" VFO and hit the "Dx" button until "DN" digital narrow is displayed and you're all set.

The hotspot frequency is in row 1. A simplex frequency is all that's needed. If you don't:. Use an analog radio to monitor the hotspot and radio's transmissions.

DMR MMDVM duplex hotspot

YSF has a white noise static sound to it. It does not sound "digital". Verify you're using VFO 1.

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Verify the radio transmit mode is showing "DN" digital narrow on the display. Check the radio and hotspot frequencies are the same. Make sure your radio is in simplex mode when using a hotspot. If you put your hotspot frequency in a repeater band your radio may automatically switch into repeater mode and transmit on the wrong frequency.Even when my MD manages to connect, the board seems to occasionally confuse which TimeSlot the MD is transmitting on, with the result that no audio is received by anyone who is listening.

I discussed this with Andy CA6JAU who writes the firmware, and he said there are general problems with the MD connecting even to the simplex versions e. The other possible cause of the problem is time delay though the board, between when the MD sending the connect wake-up message and when the MD receives the response. When leaving a pause break before pressing the PTT in response to the last incoming over, the GD seems to occasionally not connect — but does not give any notification that its not connected.

But in this case it continues to transmit, and the Pi-Star dashboard indicates that the hotspot is not receiving the transmission. This could be an issue with the way Pi-Star displays the status, however I think that the duplex hotspot board is not signalling to MMDVM Host that it has an incoming signal, but is still sending data back to the GD hence it thinks that everything is working fine.

I need to do more tests to attempt to confirm whether this problem is exacerbated by leaving a pause, or whether it happens at random, and to also determine where in the hierarchy the problem lies. Operating in duplex mode, the board is unable to support DMR and other modes at the same time i. Hence board listens for each type of modulation for a short time, in its scan loop. The problem is that for duplex DMR operation, where the transmit and receive frequencies are different, the transceiver e.

The transceiver should make multiple probably 3 connect attempts, with a small gap between each I think around mS between attemptbut its possible that the duplex hotspot would not be listening for a DMR signal during any of the connection requests. The firmware already listens for DMR signals for something like 10 times longer than it listens for the other modes, but this is not long enough to guarantee it listening at the correct time.

There may be a partial workaround for this, to change the duplex firmware, to listen for DMR signals for at least the as long as the time required to hear two connection requests, and to not listen for other modes, for longer than the gap between connection requests. This would probably mean that the scan loop would need to be changed from for example.

mmdvm duplex hotspot setup

It could also potentially result in the loss of the first second or two of audio for other modes. Even with the fix that Andy wrote; my board still has a timeout of around 4 minutes. Its possible that some boards have a worse timeout, as the value seems related to the difference in clock frequency in the transmitter e.

GD and the hotspot. My understanding of this problem is that there is no way to synchronize the data packets arriving from the transceiver e. GD and the data being sent back to from the hotspot. I think there may be some hardware and firmware changes which may be able to fix this in the long term, but there is no simple fix for this without modifying the hardware. I suspect there may be other problems that I am not aware of, so please feel free to comment if you have another problem with these boards.

But it is very new technology and you may potentially have to run it in Simplex mode, either permanently or until specific problems are fixed.

How to Set Up Amateur Radio Digital Voice Hotspot With Pi-Star and mmdvm

While I have not been as methodical in my testing as you have I did notice almost every item you noted with the Duplex Hat. Each one has a different nuance and a different symptom repeatability. All my duplex boards and radios run perfectly in simplex.

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Some of the work-arounds dramatically improve duplex performance. One is not to scan the other modes when using DMR. The Hat firmware, now on 1. I find it amusing that the cheapest radio I own, the GD, has the most consistent access to the duplex hotspots. Since the 1. However, I have seen symptoms disappear in the past only to magically reappear later. I should,note I am using Nextion screens with the Nextion Helper driver.

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Right now my duplex hotspots are usable. Every so often they miss an incoming transmission. As you noted, it all has to do with how quickly or slowly you being transmitting after the other party is done.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. This software is intended to be run on STM32F microcontroller. Also, Arduino with 3. This firmware software is intended to be use into personal hotspots hardware, with a few mili-watts of RF power and short ranges indoor.


This software is licenced under the GPL v2 and is intended for amateur and educational use only. Use of this software for commercial purposes is strictly forbidden. You could use also Any other TCXO frequency is not supported. Please note that a bad quality TCXO not only affects the frequency offset, also affects clock data rate, which is not possible to fix and will cause BER issues.

You could modify this value and other TXLevel paramenters to change deviation levels. If you have trouble with USB, please check this link. If you don't have test equipment, the procedure is trial and error. In some cases TXOffset adjustment is also required for proper radio decoding. You could get the source code of a dfu tool here. Please check the latest firmware here. In general, there are two possible compilation ways:. Those boards need to have the USB bootloader installed.

For example:. You can optionally install a firmware without bootloader, with USB support. Be aware you will need always a ST-Link or serial interface in order to install or update the firmware.

For this reason, you should use USB bootloader, unless you have trouble with the bootloader. No USB bootloader needed. Please visit Mathis Schmieder GitHub here for detailed instructions. Note: The Pi-Star image contains an executable for stm32flash. The next five steps can be skipped! Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

Sign up.So I adjusted the TX offset to and retested the transmit frequency. It appears to be getting closer, showing a frequency of about I set the RX offset equal to the TX offset and that brought the bit error rate down to 0.

I need to work on this a little bit more to solve that problem.

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I was testing with a layout from another ham that displays a lot of information and I think the screen has trouble keeping up with the amount of data.

I will detail this process in my next post. Follow the steps below to do that. What I purchased is a cheaper clone, but it should work about the same as it uses the same firmware. Essentially it is a tiny low-powered repeater on a single circuit board.

It is designed to be a personal duplex hotspot. The board should produce about 10mW of RF power output. The other piece of this project that I decided to add, was a screen.

It has not arrived yet. This will solve the problem of not knowing the IP address of the Pi to connect to the dashboard. I opted for the touch screen which will give me more options for controlling the device. I opted for a slightly smaller 3. This is an enhanced version with more flash memory and more RAM than the basic models.

This display is a Human Machine Interface that is programmed using a piece of software called Nextion Editor. The coding to make the screen work seems pretty simple, however I have not looked at the code in the Pi-Star software that actually sends the information to the screen. The interface is designed, saved to an HMI file, and then compiled into a TFT file, which is then uploaded to the screen.

mmdvm duplex hotspot setup

Here is an example interface from the second guide that another ham has created. Start by going to your PiStar dashboard in your web browser. The hangtime is the amount of time the MMDVM will stay in that mode before allowing other digital mode signals a chance to reach the repeater. Net Hangtime is the amount of time the MMDVM waits after the end of an incoming network transmission from a distant station.

Digital Hotspots for DMR, D-Star, and C4FM (#141)

Default Reflector — This is the default reflector that the repeater will connect to. A reflector is like a group chat or conference server for many repeaters to connect to.There appear to be 2 different types of duplex boards available on eBay.

One which seems to be a direct copy an open source design, and the version of board I ordered; which looks looks like the one I received. After applying these settings, I was able to enter a separate transmit and receive frequency. I chose two frequencies 6 MHz apart on the 70cms band, which is used by a repeater about km from me, but not used for any local repeaters.

The board was supplied with two small, cheep looking antennas, which I presume are designed for the MHz ISM band, and using these directly screwed into the SMA connectors, I found was the hotspot did not seem to work very well.

Using at least one external antenna resolved the desensitization problem, and the added benefit of connecting the Tx connector to an external antenna, is that the range of the hotspot should be increased so that it can be accessed from the garden, and up to around m down the street!

In some cases the audio would make a sort of squawk sound as it cut out. I came to the conclusion that perhaps there was a problem in the firmware which perhaps has a 1 minute timeout for these duplex boards. By coincidence, around this time, I spoke to Steve K2GOG, who told me that he encountered similar issues on his duplex hotspots, but had fixed the problem by using passive cooling on the TCXO, and on the processor on his Raspberry Pi.

At this point I decided to raise an issue on the firmware GitHub repository, of Andy CA6JAU in the hope that he could shed some light on the problem, and after a few days, Andy confirmed that there was some sort of problem with the firmware, as he could reproduce the problem on his duplex hotspot, but was surprised that on one had noticed the bug before now.

The reason that the hotspot cuts out, is related to differences between master clock frequency in the hotspot and in the radio. Over time, while the radio is transmitting and the hotspot is receiving and re-transmitting, the hotspot Tx gets far enough out of sync with the radio until a point where the connection is dropped. Andy had managed to modify his firmware, to attempt to detect if there was an offset in the incoming and outgoing data, and cope with some miss-alignment, but all this did is delay the inevitable time when the radio and hotspot were so out of sync the connection gets dropped.

The good news however, is that the time before the hotspot cuts out, has been extended from 1 minute to around 4 minutes on most radiosand since a lot of DMR repeaters and servers have a 3 minute timeout, the server timeout will occur before the hotspot timeout.

And as this timeout is effectively reset at the start of each over, the problem has effectively been solved. Andy released firmware version 1. Now, just when you thought this article was complete, I have to report yet another, unresolved problem with these duplex hotspots….

Discussing the problem with Andy, he initially thought the problem was the overall latency between the signal being received from the MD to when the hotspot responded transmitted back to the MD In an attempt to resolve this problem, I downloaded the source code for the firmware and the compiler toolchain, onto my Raspberry Pi, and modified the Make file, to use maximum code opimisation using the -O3 optionas this normally yields a reasonable increase in speed — but can sometimes stop code working completely.

Normally this is set to 50 and needs to be increased to around 55 to allow the MD to connect. I made this change and instantly found the MD would connect, however I noticed that every so often that the PiStar dashboard indicated that the MD was on Timeslot 1 when it was actually transmitting on Timeslot 2.

So its best to keep an eye on PiStar when you are transmitting, to make sure that you are on the TS you expect. Because if the hotspot is looking on TS1 and you are transmitting the audio on TS2, then the network gets no audio at all. So far I also saw that problem. If I switch to TG9 nothing is being decoded.

Thats not what I meant Roger. I can select that group i.

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