Full featured duplex board in a Pi Zero form factor. [ Back in stock 3/21/21 ]Designed by N5BOC Store ( LoneStar Semiconductor Designs ) in United States of America
UPDATE ( 2/17/2021 ) Back in stock on 3/21/21 What is it? This is a Duplex Multiple Mode Digital Voice Modem in a Raspberry Pi Zero HAT form factor. While there are other versions of this type of ...Read More…
Back in stock on 3/21/21
This is a Duplex Multiple Mode Digital Voice Modem in a Raspberry Pi Zero HAT form factor. 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. This will enable you to keep the portability of the MMDVM_HS_HAT while at the same time allows you to enjoy the benefits of a DUPLEX board. For DMR this means it can have QSO's happening on both time slots.
I found the DUPLEX boards to have many advantages but all the boards that seemed to be available were made for the full size Raspberry Pi. While this is fine for use at home it was not the cool, compact form factor of the Pi Zero that is easy to travel with or easy to throw in a back pack.
While it is a lot of electronics to pack into a small space I knew if I had enough tenacity I could find a way to pack it all in. And here it is!
This board was designed by myself and all boards are fully assembled domestically and delivered here and fully tested by myself in the great state of Texas. Each board is built using only the highest quality components. This can make a big difference to you. For example this board uses an ECS brand TCXO purchased from Mouser in Mansfield Texas. ECS is known for their quality of oscillators and this one is no exception. They are consistently on frequency with a very low drift over temperature. What this means to you is you will not be hunting for hours trying to find the correct offset that enables the board to hear your radio. These usually require an offset of less than 200 counts and most require an offset of 0. Each board includes documentation of the offset used during final test.
Much care was taken during the design and layout of this board. This board is built on a 4 layer Gold Plated PCB which is 1.6mm thick. ( 0.0625 inches ) The gold plating gives the best solder adhesion ( no pesky cold solder joints ) and makes the board more resistant to oxidation for the absolute highest possible reliability. The inner layers are solid POWER and GROUND planes. This is important because it makes the receiver more immune to noise and therefore more sensitive. This also allows every component on the board to have a very low impedance path to either the +3.3V rail or GND which also improves the noise immunity. Lastly the plane layers being the inner layers act as one VERY LARGE decoupling capacitor which makes this board much more immune to voltage glitches on the power supply.
This board is compatible with both the very popular 1.X" OLED display or the Nextion LCD display. And the best feature of all is this board also implements pads for 2 u.FL connectors which you can install if you want to implement that type of connection. These small RF connectors open up lots of antenna mounting options. Very short u.FL to SMA pigtails are available. With these you can mount the SMA connector anywhere on your case.
Available with or without Dual ANTENNAs: My previous simplex board included a 432 MHz ceramic antenna on the board. But that is not possible to implement on this duplex board. An off-board antenna is a requirement. So I felt I needed to source an external antenna for this board. I wanted to make this easy for my customers and not send them off searching the WEB and Ebay for an antenna that may arrive 1 month after their board. However sourcing a low cost antenna has proven to be somewhat difficult. It is harder than I thought. What was available last month is not always available this month. So since this may change from month to month and also the cost to me may change, I decided to break this out. This option reflects the cost of these components to me. I am passing these on to you at my cost. ( I'm not in the antenna business ) This is the only option on this board.
U.FL connectors The PCB comes with u.FL connectors installed to give you more options for mounting in a case.
I worked closely with C4Labs to help them produce one of their excellent cases.
It can be found here... C4LABS cases
Also cases are being made for this board by Paul Lamhut (WB2HHH) PLA BASED CASE for DUPLEX BOARD
For pricing and to order contact Paul at WB2HHH@arrl.net
While the board is completely compatible with a full size PI, there are no cases that I know of that are made specifically to fit the duplex board when mounted on a full size PI. I could be wrong or this may change. I would recommend checking with C4LABs on this.
note : See USING A FULL SIZE PI in the TEXT below.
I'm sad to say the Turn Key option seems to have evaporated. There was a gentleman in Cali that was using my boards and offering the complete built up hotspot, but he has become a ghost. So at the present time I don't have anywhere I can direct you.
Because the PCB is so packed there is not room to label the LEDs. So you can follow this link to PDF that illustrates what each LED is indicating. Dual Board with LEDs Labeled
I've noticed myself this PDF is a little hard to read. If you are looking at it within your browser, you can use the scaling feature of the browser to zoom in and make it a little more readable.
The most common question I get is which modem do I select from inside of Pi-Star. You should pick... LoneStar - MMDVM_HS_DUAL_HAT for Pi (GPIO)
Much more detailed instructions can be found here... DUPLEX Board setup instructions
Yes, this board will work with a full size PI as in Pi3B+ or Pi4. However there is a mechanical interference between the right hand SMA connector and the USB connector on these full size boards. There is a work around of using what is called a "stacking header". This will elevate the board about 1cm and get it above the USB connector.
Here is an example. Stacking header on Amazon
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 check it out on the bench. If there is a hardware problem I will either repair the board or replace it. If you think you've received a defective board you must contact me about it within 14 days. Anything that arrives DOA I will just replace as long as I have stock of that board. However out of over 1000 boards shipped only 1 was truly DOA. ( Not sure what happened as it was working when it left Texas. ) The board itself has a 6 month warranty on it. If it fails within 6 months I will first try to repair it, and if I can't do that I will replace the board. Please contact me for an RMA # before returning a board. I mostly want people to be happy so I will admit I'm very lenient on returns.
This is to clarify, the TINDIE waiting list is really a "Notify me when back in stock" list. It does not put you in a queue nor does it reserve a board for you. There is a lot of misunderstanding about this TINDIE feature. So I mention it here to help clear up any misunderstanding.
I will try to help anyone that contacts me. Please however it is best to contact me through Tindie because the system is setup to help me track who has been answered and keeps a record of the conversation. A few have used the email address on QRZ. I usually answer that too but it may be a few days before I see that. Also it is much harder to follow a conversation through Email. So your results will be better if you use the Tindie system to contact me. THANKS
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