Some of your radios not talking to Pi-Star? Try this
Posted: Thu Apr 04, 2024 6:04 pm
I own a few radios, TYT MD380, Anytone 878, Anytone 578UVIII, Motorola XPR4550, Motorola XPR7550, ICOM ID51A+
Some would talk to my hot spot and some wouldn't, I suspected a frequency issue with my hot spot.
I built my hot spot seven years ago using a Raspberry Pi and a DVMega Raspberry Pi-Hat (GPIO) Dual band board running Pi-Star V4.1.4 Feb
This particular radio board would not work with the embedded SSH Access calibration tool in Pi-Star so I had to come up with a different plan.
Not owning a frequency counter that would accurately resolve down to 100hz I went a different route.
I set up a digital VFO in my Anytone 578 and dithered the frequency +/- until I saw what appeared to be a -450hz offset before showing up in Pi-Star.
Going further, I built 10 private channel talk groups in my Motorola XPR7550 and labeled them +500hz down to +100hz and -100hz up to -500hz and offset my hot spot radio frequency in each talk group by the same amount.
I then moved away from my hot spot several hundred feet and opened up the Pi-Star dashboard on my smartphone which is connected to the home WiFi.
then selecting each offset and keying them up while watching the RF activity on the Pi-Star dashboard screen I came to a similar conclusion of -450hz.
I then went into "Expert" mode in Pi-Star and went to the Modem menu and put +450 into the RX and the TX offset fields respectively and now all of my radios are reliably connecting into Pi-Star.
I then loaded a previous version of my XPR7550 software back in which removed the experimental talk groups.
What I have learned:
Apparently the threshold for reliable communication between radios and the hot spot is +/- 500hz
Always suspect the hot spot first, why? Because most higher end radios use TCXO and most hot spots do not, so they drift.
Some would talk to my hot spot and some wouldn't, I suspected a frequency issue with my hot spot.
I built my hot spot seven years ago using a Raspberry Pi and a DVMega Raspberry Pi-Hat (GPIO) Dual band board running Pi-Star V4.1.4 Feb
This particular radio board would not work with the embedded SSH Access calibration tool in Pi-Star so I had to come up with a different plan.
Not owning a frequency counter that would accurately resolve down to 100hz I went a different route.
I set up a digital VFO in my Anytone 578 and dithered the frequency +/- until I saw what appeared to be a -450hz offset before showing up in Pi-Star.
Going further, I built 10 private channel talk groups in my Motorola XPR7550 and labeled them +500hz down to +100hz and -100hz up to -500hz and offset my hot spot radio frequency in each talk group by the same amount.
I then moved away from my hot spot several hundred feet and opened up the Pi-Star dashboard on my smartphone which is connected to the home WiFi.
then selecting each offset and keying them up while watching the RF activity on the Pi-Star dashboard screen I came to a similar conclusion of -450hz.
I then went into "Expert" mode in Pi-Star and went to the Modem menu and put +450 into the RX and the TX offset fields respectively and now all of my radios are reliably connecting into Pi-Star.
I then loaded a previous version of my XPR7550 software back in which removed the experimental talk groups.
What I have learned:
Apparently the threshold for reliable communication between radios and the hot spot is +/- 500hz
Always suspect the hot spot first, why? Because most higher end radios use TCXO and most hot spots do not, so they drift.