Wanted: UV380/390 , DM-1701/RT-84 power calibration testers

[VK3KYY]

In the power calibration testing, which I have conducted on my UV380 (5W) and my DM-1701, the official power calibration data seems to be not very accurate.

So if anyone has a reasonably accurate power meter which works on both UHF and VHF there are some tests I would like them to do


Firstly you need to install the latest experimental firmware


https://opengd77.com/downloads/MDUV380_ ... dee2485ce4

This firmware has 2 reset modes for the Factory Calibration data

SK2 + Green on the Factory Calibration screen (Options -> Calibration -> Factory reset screen) reads the factory calibration and applies some correction factors

SK2 + SK1 + Green reads the factory data without modification


To do this test you need to use the SK2+SK1+Green method

Then on 145MHz...

Record the "Adjust" values for 1W, 2W and 5W, and also measure the power produced by those Adjust levels

Now change the Adjust values for 250mW,1W,2W and 5W to achieve 250mW, 1W,2W and 5W and record the Adjust values.

Repeat for 430Mhz, 440Mhz and 450MHz

Then post that data here

i.e

145MHz
45,80,120
1.1W, 2.5W,4.3W
22,40,75,150

etc

i.e

Freq
Factory adjust values for 1W,2W and 5W
Power for 1W,2W and 5W
Adjust values needed for 250mW,1W,2W and 5W




The more data I have the more accurate I can make the default calibation, by attempting to use average corrections to the Adjust value when the normal SK2+Green factory reset method is used


Please post questions if you have any confusion about what is required.

[G4EML]

Hi Roger,
Here are the readings from my two radios using the Marconi 2955.

MDUV380

145MHz
103, 121, 162
1.16, 2.21, 5.40
73, 100, 118, 158

430MHz
79, 102, 154
1.51, 2.74, 5.80
44, 69, 89, 141

440MHz
81, 105, 153
1.49, 2.74, 5.60
42, 70, 92, 143

450MHz
84, 107, 156
1.53, 2.65, 5.70
43, 72, 95, 145


MDUV390

145MHz
133, 150, 178
1.3, 1.96, 4.10
109, 128, 151, 188

430MHz
110, 125, 160
0.70, 1.51, 3.80
94, 117, 133, 180

440MHz
107, 125, 164
0.73, 1.71, 4.10
91, 113, 130, 179

450MHz
108, 128, 170
0.92, 2.00, 4.50
87, 110, 128, 179


73
Colin G4EML

[VK3KYY]

Thanks Colin

Just to confirm, When you did the factory reset, did you hold in SK1 and SK2?

Cheers

Roger

PS

It's interesting with the large variation in output power for similar PA drive levels between different radios which use the same hardware design

My RT3S seems to have a very good PA, and a UV390 I tested on Sunday seemed equally good, but your UV390 seems to have a less efficient PA

It also seems to show the factory calibration of the High power data point is unreliable

Actually all the factory power calibration data points seem inaccurate

[G4EML]

Hi Roger,

Yes I did the SK1/SK2 reset on both radios.

Cheap RF devices probably vary greatly in performance between batches. They may even be using whatever transistor is cheapest at the time.

I think it is unlikely you will find a good compromise for the calibration in all radios.

Colin.

[VK3KYY]

OK. Thanks.

I could understand if the PA drive levels were different from radio to radio, but what I don't understand is why TYT seem to have different calibration values in each radio, yet the power output at each data point is not correct.

Looking again at you data, I wondered if perhaps the were calibrating the power at the mid point of each frequency range e.g. 435 rather than 430, but looking at your values for the low power setting (W)

You need PA drive of 117,113 and 110 for 430,440 and 450, and the value of , but even on 440, which needs 113 , the official value was only 107

Looking at the data I have for the 10W radios, the PA band pass filtering, does seem to be optimal at the mid point of VHF and of UHF, i.e max power and max effeciency is achieved at around 150Mhz and 450Mhz, which does make sense.

However, with the 10W radio, there is blantant miss advertising by calling it a 10W radio, and it can barely make 10W on a narrow range of freqs i.e 145 and 450. More realistically its an 8W radio, and surprisingly the normal UV380 delivers 8W across the entire VHF range when set to -W+ / max PA drive

[SA0BUX]

Baofeng DM-1701 after SK1+SK2+Green Cal Factory reset.
I measured the power at 250 mW too.

Seems that the PA already is saturated at 5W setting , increasing the level didn't change the output significantly.

Code: Select all

145 Mhz				
32, 54, 95, 142
0.27,1.07, 2.69,3.80
31, 53, 80, -	
				
430 Mhz				
22, 35, 67, 113
0.16, 0.65, 2.05, 2.82
24, 42, 65, -	
				
440 Mhz				
22, 34,	66, 112
0.22, 0.63, 2.00, 2.82
23, 40, 40, -	
				
450 Mhz				
23, 36, 76, 116
0.28, 0.69, 2.19, 2.75
21, 43, 71, -

[G4EML]

To get 5W output you do need a fully charged battery or an external power supply and a very short good quality connecting cable.


Roger,

Power adjustment is well known for being difficult. It depends so much on the test cables, dummy load match and supply voltage that I doubt they have very tight tolerances in the factory. In practice the difference between 4W and 5W is less than 1dB, that is quite a tight tolerance to achieve and I doubt the power meter calibration would be any better than +-1dB.

Colin.

[SA0BUX]

To get 5W output you do need a fully charged battery or an external power supply and a very short good quality connecting cable.


Roger,

Power adjustment is well known for being difficult. It depends so much on the test cables, dummy load match and supply voltage that I doubt they have very tight tolerances in the factory. In practice the difference between 4W and 5W is less than 1dB, that is quite a tight tolerance to achieve and I doubt the power meter calibration would be any better than +-1dB.

Colin.

I checked the specification on the Marconi 2955 and the RF Power meter had
±10% ±1 digit up to 500 MHz which sounds pretty good.

But as you said , difference between 4 W & 5 W is only 0.97 db
I have to use some power attenuators and the accuracy is around ±0.5 db , but the tinySA I used is more like ±2dB.
Wish I had a proper calibrated HP/R&S RF power meter or so but they are expensive.
Best would be to use a professional testlab with calibrated equipment.


The battery was fully charged on the DM-1701, but I will test some RT3S too for comparison.

[VK3KYY]

The battery was fully charged on the DM-1701, but I will test some RT3S too for comparison.

Thanks

My DM1701 seems to have much lower output power than my RT3S.

The DM1701 only manages just over 5W, unlike the RT3S which can produce 8W+ on 2m!

I think the GD77 can produce around 7W on 2m, from what I can remember of the tests I did several years ago

[SA0BUX]

The battery was fully charged on the DM-1701, but I will test some RT3S too for comparison.

Thanks

My DM1701 seems to have much lower output power than my RT3S.

The DM1701 only manages just over 5W, unlike the RT3S which can produce 8W+ on 2m!

I think the GD77 can produce around 7W on 2m, from what I can remember of the tests I did several years ago

What device do you use when measuring power?

I'm redoing some measurements with my "RF Power Meter V5" which I think could be rather accurate.
Eliminated cables too by using two 30 dB power attenuators in series and using only some SMA-N converters.