RD-5R won't talk to hotspot, what have I done wrong?

[KA1CM]

Hi Everyone. I've encountered a weird problem, please have a look at the video.

I have two RD-5R. The hotspot refuse to listen to the one on the left. I've check frequency, color code, and DMRID on the left radio, everything seems correct. I don't know what to do next.

73, Charlie.

P.S. the synchronize of the two video is not perfect. I click start screen recording before I click start on my phone camera.


youtu.be/MemxYX_RS7k

[G4EML]

It may be that your two radios are on very slightly different frequencies. Most hotspots are excessively fussy about frequency.

Do you have a means of comparing the transmit frequency of the two radios? A radio or SDR with a spectrum display would show the difference. You could then use the OpenGD77 calibration menu to adjust the non-working radio to the same frequency as the working one.

Colin G4EML

[KA1CM]

It may be that your two radios are on very slightly different frequencies. Most hotspots are excessively fussy about frequency.

Do you have a means of comparing the transmit frequency of the two radios? A radio or SDR with a spectrum display would show the difference. You could then use the OpenGD77 calibration menu to adjust the non-working radio to the same frequency as the working one.

Colin G4EML

I do have SDRPlay, but, according to the manual on GitHub. The calibration is not working or the Rd-5R?

[SA0BUX]

It may be that your two radios are on very slightly different frequencies. Most hotspots are excessively fussy about frequency.

Do you have a means of comparing the transmit frequency of the two radios? A radio or SDR with a spectrum display would show the difference. You could then use the OpenGD77 calibration menu to adjust the non-working radio to the same frequency as the working one.

Colin G4EML

I do have SDRPlay, but, according to the manual on GitHub. The calibration is not working or the Rd-5R?

You can still compare the carrier frequencies on all three devices and see if you can adjust the hotspot somewhere in between.
You can use pistar-mmdvmcal to find out more.

[F1RMB]

It may be that your two radios are on very slightly different frequencies. Most hotspots are excessively fussy about frequency.

Do you have a means of comparing the transmit frequency of the two radios? A radio or SDR with a spectrum display would show the difference. You could then use the OpenGD77 calibration menu to adjust the non-working radio to the same frequency as the working one.

Colin G4EML

I do have SDRPlay, but, according to the manual on GitHub. The calibration is not working or the Rd-5R?

The Calibration section in the user guide is outdated. You have the calibration screen on every supported radio.

Cheers.
---
Daniel

[KA1CM]

Thank you Colin, Daniel, and Lars.

It is working now. however, all of my radio are about 300Hz to the right of the center (+300Hz) and the RD-5R in the problem was 150Hz to the left (-150Hz). I calibrated the -150Hz one to +250 for now to make everything work.

Now, I’m up on a new quest. I don’t know what is wrong, maybe my SdrPlay is not centered. I’m diving into how to calibrate the SDR, so I can have a good reference. I’ve seen some good discussions on the topic of finding a good reliable true frequency reference on the air, which is very interesting topic and seems fun to do. I will update my progress later.

Thank you again for great advice.

[SA0BUX]

Thank you Colin, Daniel, and Lars.

It is working now. however, all of my radio are about 300Hz to the right of the center (+300Hz) and the RD-5R in the problem was 150Hz to the left (-150Hz). I calibrated the -150Hz one to +250 for now to make everything work.

Now, I’m up on a new quest. I don’t know what is wrong, maybe my SdrPlay is not centered. I’m diving into how to calibrate the SDR, so I can have a good reference. I’ve seen some good discussions on the topic of finding a good reliable true frequency reference on the air, which is very interesting topic and seems fun to do. I will update my progress later.

Thank you again for great advice.

Can you receive WWV ?

On RTL-SDR V3 I have used kalibrate-rtl ( https://pysselilivet.blogspot.com/2019/ ... e-rtl.html ) which use GSM base stations for calibration.
It could be possible to use LTE too but I haven't tried that.
https://www.reddit.com/r/RTLSDR/comment ... ate_a_sdr/

But SDRplay doesn't interface the same way as RTL-SDR so maybe WWV is the simplest way.

[G4EML]

Those sort of frequency errors are not unusual and a proper DMR repeater would have no problem with them. Unfortunately most Hotspots use a receiver chip that is not really designed for TDMA and consequently is very critical on frequency.

The SDR play doesn't have a very accurate frequency reference but it can still be used to compare two transmitters.

I don't know how you are set for beacons in your part of the world but many amateur beacons are now GPS locked and would provide a good reference.

Colin G4EML