2025-06-06 — Raspberry Pi 5 Porch Ops, Minor Scoop About FlexRadio’s Impressive Engineering, Thorough Explanation of Single Frequency Digital Mobile Radio Repeater, N8GNJ Seminar at SEA-PAC 2025
"The processor system in the FlexRadio 8000 series, and the new Aurora series (and other FlexRadio products) is a Raspberry Pi Compute Module 4 (CM4)." - Steve
Readers should keep in mind that just because it is using a CM4 doesn't mean it is running Raspbain. It is most likely running VxWorks or Yocto Linux. These are real time operating systems (RTOS) that are optimized for performance and stability. While I'm certain in the longer timeline someone will swap out the installed CM4 with one that has a more hacker friendly OS installed, imbedded Linux isn't for the casual user. There's not going to be a package manager, for example. Things will be locked down.
But it is a huge step in the right direction. Kudos to Flex Radio for letting us know what's under the hood!
Eric - Thanks for that. I didn't intend to convey that the FlexRadio units using the CM4 should be considered "hackable" - only that the use of the CM4 was what I consider to be elegant and cost-effective engineering, with a clear expansion path to >potentially< upgrade to a CM5 if that is eventually warranted.
John - Yes, I had seen that and consider it significant. It was in my bookmarks, but had not previously been mentioned in ZR. It's the first (that I'm aware of) use of Polar Modulation and a significant achievement. And more evidence of this extraordinary era of abundance of technology that Amateur Radio can take advantage of... and we're starting to do. I'll feature this in the next issue of ZR. Thanks for the pointer!
Oh that's a great tip on the Single Frequency Repeater. It makes sense that would be possible with a TDMA system. Makes me want to get a DMR radio and play with it. For basic (ham) voice use I tend to think they have very little benefit over FM but I'd certainly count SFR as an advantage!
Justin - We've had "Single Frequency Repeaters" for a very long time... but previously they were listen, record, and then replay and transmit - very inefficient compared to dual frequency repeaters. I remember reading in 73 of how it was done with tape recorders. I'll talk more about this in the next issue of ZR.
"The processor system in the FlexRadio 8000 series, and the new Aurora series (and other FlexRadio products) is a Raspberry Pi Compute Module 4 (CM4)." - Steve
Readers should keep in mind that just because it is using a CM4 doesn't mean it is running Raspbain. It is most likely running VxWorks or Yocto Linux. These are real time operating systems (RTOS) that are optimized for performance and stability. While I'm certain in the longer timeline someone will swap out the installed CM4 with one that has a more hacker friendly OS installed, imbedded Linux isn't for the casual user. There's not going to be a package manager, for example. Things will be locked down.
But it is a huge step in the right direction. Kudos to Flex Radio for letting us know what's under the hood!
Eric - Thanks for that. I didn't intend to convey that the FlexRadio units using the CM4 should be considered "hackable" - only that the use of the CM4 was what I consider to be elegant and cost-effective engineering, with a clear expansion path to >potentially< upgrade to a CM5 if that is eventually warranted.
Are you aware QRP Labs was selling the QMX+ at Hamvention that is NOW RUNNING POLAR MODULATION? Hans developed his own code. -de NI0K
Linky, please?
John - Yes, I had seen that and consider it significant. It was in my bookmarks, but had not previously been mentioned in ZR. It's the first (that I'm aware of) use of Polar Modulation and a significant achievement. And more evidence of this extraordinary era of abundance of technology that Amateur Radio can take advantage of... and we're starting to do. I'll feature this in the next issue of ZR. Thanks for the pointer!
Radio: https://qrp-labs.com/qmxp.html
SSB Polar modulation: https://qrp-labs.com/qmxp/ssbbeta.html
Oh that's a great tip on the Single Frequency Repeater. It makes sense that would be possible with a TDMA system. Makes me want to get a DMR radio and play with it. For basic (ham) voice use I tend to think they have very little benefit over FM but I'd certainly count SFR as an advantage!
Justin - We've had "Single Frequency Repeaters" for a very long time... but previously they were listen, record, and then replay and transmit - very inefficient compared to dual frequency repeaters. I remember reading in 73 of how it was done with tape recorders. I'll talk more about this in the next issue of ZR.
Hah yep! I have the modern version of the tape recorder method:
https://www.argentdata.com/catalog/product_info.php?products_id=98
SFR is great because it's "duplex" just like normal repeaters - no waiting! Well, 30ms of waiting I guess...