dm1701 harmonics?

[dj9zza]

hello
i bought the baofeng dm 1701 directly from china now i ask how it looks like with the harmonics of this device. has anyone already measured the device does it manage the 60db?

[VK3KYY]

hello
i bought the baofeng dm 1701 directly from china now i ask how it looks like with the harmonics of this device. has anyone already measured the device does it manage the 60db?

I don't think anyone posted any spectrum analyser data for this radio

[KZ4DT]

Measurements taken using a tinySA Ultra -- not a lab-grade spectrum analyzer. Conducted measurements with a 40dB external attenuator and 20dB internal attenuation set on the tinySA Ultra.

It is surprisingly clean. It meets all the specs (harmonics less than 25uW) except for 2m 3f0 and 4f0 which are close. All 3f0 frequencies in 2m fall in the 70cm band so you are unlikely to get any complaints there for putting 79uW into your antenna. 4f0 @ 586MHz is only 56uW spurious into the antenna -- how much of that is radiated and detectable?

Now my $25 FM radios and $50 GMRS radios are a different story.

[VK3KYY]

Measurements taken using a tinySA Ultra -- not a lab-grade spectrum analyzer. Conducted measurements with a 40dB external attenuator and 20dB internal attenuation set on the tinySA Ultra.

It is surprisingly clean. It meets all the specs (harmonics less than 25uW) except for 2m 3f0 and 4f0 which are close. All 3f0 frequencies in 2m fall in the 70cm band so you are unlikely to get any complaints there for putting 79uW into your antenna. 4f0 @ 586MHz is only 56uW spurious into the antenna -- how much of that is radiated and detectable?

Now my $25 FM radios and $50 GMRS radios are a different story.

Thanks for sharing.

I have a TinySA but no attenuators


BTW. What power level did you test with?

[KZ4DT]

All tests were 5W commanded by OpenGD77, so 3.2W / 35dBm is a bit short.

https://www.amazon.com/gp/aw/d/B07MZLVY9T

[VK3KYY]

All tests were 5W commanded by OpenGD77, so 3.2W / 35dBm is a bit short.

https://www.amazon.com/gp/aw/d/B07MZLVY9T

OK.

Thanks

I wondered in case higher powers produced more harmonics

BTW.

You can calibrate the power using the Options->Calibration menu

Power calibration is stored in approx 10MHz ranges

We didn't choose the ranges, its part of the official calibration data, but neither TYT nor Baofeng actually seem to bother to calibrate the power output of their radios

Also, power output varies a bit depending on battery voltage. We don't attempt to compensate for this, becuase the compensatation would probably be different for each radio, and its unliklely that anyone would go to the effort of calibratiung at both max and min battery voltage

I normally calibrate with a fully changed battery and know that as the battery voltage decreases the output power will decrease

Also, on UHF someradios can barely make the advertised 5W power, but on VHF they can normally manage between 6 and 7W when the PA is driven to its maximum

[KZ4DT]

We didn't choose the ranges, its part of the official calibration data, but neither TYT nor Baofeng actually seem to bother to calibrate the power output of their radios

Also, on UHF someradios can barely make the advertised 5W power, but on VHF they can normally manage between 6 and 7W when the PA is driven to its maximum

A couple of follow up points. I measured the attenuation of my 40dB pad with my nanoVNA-H4 and it measures 41.8dB, so the output power of my radios is a little higher than what is shown in those plots.

I have two DM-1701s and looked at both power calibrations. They are pretty different from each other, so the factory must have some algorithm to set those. Neither table was close to correct, however. I was able to get the curves to match pretty well until the 4W point. VHF at max power is about 5.5W and UHF is 3-4W depending on actual frequency and radio. The 50mW setting is now usable for my DMR hot spots -- one radio was only putting out 90mW on the 250mW setting in UHF.

I am still learning how to use the tinySA and have changed the default "Calc:AVER4" to "Calc:MaxH" to speed up the harmonics measurement considerably -- the default averaging takes up to 120 seconds sometimes to settle out. For the power calibration I set the center frequency to match the Tx and then the span to 500kHz which makes that measurement very fast too.

[VK3KYY]

We didn't choose the ranges, its part of the official calibration data, but neither TYT nor Baofeng actually seem to bother to calibrate the power output of their radios

Also, on UHF someradios can barely make the advertised 5W power, but on VHF they can normally manage between 6 and 7W when the PA is driven to its maximum

A couple of follow up points. I measured the attenuation of my 40dB pad with my nanoVNA-H4 and it measures 41.8dB, so the output power of my radios is a little higher than what is shown in those plots.

I have two DM-1701s and looked at both power calibrations. They are pretty different from each other, so the factory must have some algorithm to set those. Neither table was close to correct, however. I was able to get the curves to match pretty well until the 4W point. VHF at max power is about 5.5W and UHF is 3-4W depending on actual frequency and radio. The 50mW setting is now usable for my DMR hot spots -- one radio was only putting out 90mW on the 250mW setting in UHF.

I am still learning how to use the tinySA and have changed the default "Calc:AVER4" to "Calc:MaxH" to speed up the harmonics measurement considerably -- the default averaging takes up to 120 seconds sometimes to settle out. For the power calibration I set the center frequency to match the Tx and then the span to 500kHz which makes that measurement very fast too.

While looking at the power calibration for the 10W UV380 Plus, I noticed the problem with the maximum power on all radios not being correct, because the calibration point is 4W not 5W.
I think is a legacy problem caused because the UV380 , and hence DM1701 calibration process , is based on the MD9600 calibration process.

I am in the process of changing this, to allow calibration at 5W, 1W and 250mW.