I love Tindie for the interesting electronic products that surface there such as 70cm Power Amplifier (PA) for New Packet Radio:
What makes it special?
It has high power RF switches, a VOX trigger and digital input switch. For the lowest packet error rate you should use the digital 3-5V line connected from the NPR and auto switch the PA.
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As any experienced Amauteur Radio data communications geek knows, the transmit / receive turnaround time is a critical factor in the overall data rate of a data communications system. If you have to waste time waiting for the transmitter to be up to power, settled on frequency, you are wasting valuable channel time. Ditto for an external amplifier, unless you can signal it just as fast as the native transmitter, which is the "digital 3-5V line" the builder refers to.
New Packet Radio is a very interesting area of experimentation for me (I have several but haven't yet started experimenting). From their page:
NPR (New Packet Radio) is a custom radio protocol, designed to transport bidirectional IP trafic over 430MHz radio links (ham radio frequencies 420-450MHz). This protocol is optimized for "point to multipoint" topology, with the help of managed-TDMA.
Bitrate is 50 to 500kbps (net, effective bitrate), depending on the RF bandwidth chosen.
The radio modem is cheap (~80$) and home-made, with a 433MHz ISM module inside (flexible enough to be tuned over the whole 420-450MHz band). The modem is connected locally with Ethernet, therefore no specific software is needed on PC.
The modem is easy to build and reproduce.
You can add a DMR radio amplifier in order to achieve 20W radio power or more.
The main usage is an extension of HSMM - Hamnet - AREDN networks.
All the project is open-source : hardware, software, protocol specification.
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Slightly bad news about this new amplifier - its power output of 38 dBm is 6.3 watts.
Worse news - apparently the builder has no plans to ship to the US.
More on New Packet Radio in the coming months, including my personal experimentation at N8GNJ.org.
Thanks for reading!
Steve Stroh N8GNJ
Bellingham, Washington, USA
2021-03-23