OpenGD77

VK3KYY wrote: ↑

Fri May 15, 2020 1:24 am

Did you calibrate the power output on both radios.. Otherwise they won't be producing the same power.
Even if you have calibrated the power on both radios, the 50mW power setting varies a lot between each radio, because the Voltage vs Power output response on the PA FET in each radio won't be the same, as the calibration points are only at 1W and 5W

If you calibrate both radios for 1W and 5W and run both radios on 1W they are likely to have the same range in both directions, but even then, they may not be both equally well calibrated for their 4FSK deviation, and you need specialized test equipment if you want to calibrate that as well.

I don't have any way to measure power here at all, I have a fairly junky SWR meter but wouldn't be useful for this at all. I've eyeballed a few SWR/Power/Frequency counter doodads from places and all of them say no DMR.

I actually only have one GD77, although I'm seriously considering getting a second one because this works so well. My mmdvm works fine, but it feels like the GD77 works better, less distortion. Around the house, RF performance is all the same.

Ok.

I have a cheap digital SWR / Power meter. I it just has one big red button on the front and a LCD display. I don’t know how accurate it is, but it’s good enough for the use it put it to.

BTW.

The MMDVM Jumbospot hotspots are extremely insensitive.
I investigated the cause of the insensitivity a while ago, and it seems to be related to the RF design where the RF chip has separate pins for the Tx and Rx antennas, but both pins are connected together , albeit via a LC network.

I have an RF module from Aliexpress which uses the same RF chip, but has a silicon RF relay switch chip on it, and the sensitivity of that module is about 10 x better than my Jumbospot.

So my conclusion was the RF design and cost saving on the Jumbospot to not use an antenna switch cause these hotspots to be quite deaf

I don't know if a DMR power meter actually exists.

I discussed this with a technician who repairs Motorola DMR radios, and the radios have a special "Test" mode where they transmit a carrier with no DMR pulses etc, so that the technician can test the power output

It would be possible to build a meter which automatically synchronises with the DMR signal, but it seems pointless unless its absolutely impossible for the radio to transmit just a carrier, or FM etc

sfoto wrote: ↑

Sat May 16, 2020 1:49 am

the only case where you'll NEED a DMR-specific power meter is one particular Motorola radio that has no analog mode, otherwise you just do it on analog 12.5kHz channel.

Ah duh, of course. I don't know why I didn't consider that. I think I'll get one of those as my next toy. SW-102 is what I was looking at, any of you used that meter?

I ended up buying one of these off Ebay a few years ago. It's a Agilent / Keysight VSA Transmitter Tester.

https://www.keysight.com/en/pd-10000027 ... =US&lc=eng

It's got routines to do power measurement on TDMA and several digital mode signals.

It can also be controlled externally through HPIB and there is open software for doing this.

I think this instrument ran about $500 (it's considered obsolete now that 4G and beyond is the "sweet spot" in development labs).

Hi,

kd2lh wrote: ↑

Sat May 16, 2020 2:32 pm

I ended up buying one of these off Ebay a few years ago. It's a Agilent / Keysight VSA Transmitter Tester.

https://www.keysight.com/en/pd-10000027 ... =US&lc=eng

It's got routines to do power measurement on TDMA and several digital mode signals.

It can also be controlled externally through HPIB and there is open software for doing this.

I think this instrument ran about $500 (it's considered obsolete now that 4G and beyond is the "sweet spot" in development labs).

That's a nice tool !


Cheers.
---
Daniel

Yes - it's based on Agilent's PSA Spectrum Analyzer frame, and has much of the same firmware and precision standards in it. The tools are about 12 years old, and already considered out of date.

http://literature.cdn.keysight.com/litw ... 2389EN.pdf

It went out of favor with labs, and a bunch started showing up on the used marked for little prices.

In particular, they can do I/Q phase power measurements.

Hello together!

How can a MMDVM_HS_HAT (DB9MAT & DF2ET) for PI (GPIO) so many Watts? I know it has only 10 mW. The standard is in the modemsection 100, so
I mean it has ful Power of 10mW.

Greetings Daniel. I have configured the power output at 5w, I use it with the mmdvmhost for windows, but after a while it restarts, which did not happen when it was at 50mW. Turn the power down to 2W and it looks like it's stabilized. Could it be that 5W cannot be used? How much is the maximum power that can be configured?

Greetings.