UV-3R RTX bibanda V-UHF

 This nice Subminiature dual band is characterized by definitely interesting performance, especially in relation to its modest cost. It is not my intention to list his features, easily available on the Net, but report the results of measurements made on my copy.
Given that the results are certainly not free from uncertainty and errors of measurement, they are referred to only one specimen, therefore can not be considered significant. Measurements were performed on battery charge.

Antennas

The two supplied antennas were measured and the results charts for VHF and UHF bands are shown down. Some clarification:

• measurements were made using VNWA2 with antennas placed above a ground plane, similar to the top of the UV-3R.
• the antennas are particularly sensitive to their surroundings, thus the resonance changes only moving the RTX nearer or further from the face, the body or the hands. So consider the point of resonance, shown on the graphs, as an ideal.
• the interval between marker 2 and marker 3, includes values of VSWR of between 1:1 and 1:2.

 

• UHF Antenna UHF Antenna
• VHF Antenna VHF Antenna
•  

SMeter

The instrument is made of a bar graph of 12 segments that turn on some segments not individually but in groups. The measure shows to what level of input signal segments, or groups, are activated: the number identifies the set of the segment or groups, considering the number one furthest to the left.

 

RF signal level	Active segment
< -128 dBm	-
-127 dBm	1-2-3-4
- 120 dBm	1-2-3-4-5
-117 dBm	1-2-3-4-5-6
-111 dBm	1-2-3-4-5-6-7
-106 dBm	1-2-3-4-5-6-7-8-9-10
=> -100 dBm	1-2-3-4-5-6-7-8-9-10-11-12

     

Battery Status Indicator

When you turn the device on, the display shows, for about 1 second, the voltage supplied by the battery. In addition, a graphical indicator in 4 states provides information on the state of the battery during use. It consists of a battery icon filled with three notches. With the function SAVE switched to off, the apparatus was powered with a stabilized power. 
The power supply voltage was measured, with hp34401a, as a function of 4 states of graphic indicator, to find the real voltage in comparison to the one that is indicated on the display when the instrument is turned on, and eventually the voltage on which the device turns off. The results follow in the table.

 

 

No. notches indicator	Read voltage	True voltage
3	4,1	4,20
2	4,0	4,11
1	3,7	3,82
0	3,4	3,47
Spegnimento	3,4	3,38

 

 

 

 

 

 

 

Power consumption

The RTX, powered by external power supply, was adjusted to deliver 4 Vdc, with volume at minimum and squelched. The current consumption, measured with HP 34401A, showed the following values.

It confirms a strange behavior reported by some OM, relative to a variable absorption with the SAVE function enabled. Further investigations will follow.

 

RTX State	VHF	UHF
RTX Off	0,4 mA	0,4 mA
RX Led Display Off	68 mA	69 mA
RX Led Display On	84 mA	85 mA
Tx Low Power	380 mA	900 mA
TX Full Hi Power	1100 mA	1130 mA

 

VHF Section

VHF RX

The VHF section was tested at a frequency of 145,500 kHz. In reception is virtually confirmed the sensitivity stated by the manufacturer of 0.2 uV (12 dB SINAD). The measurement was made with a generator Marconi MI-2024 and PC with software of Sinad ComTekk. The extent of MDS, as described in RKE 6/2011 (I4SBX), highlighted the value of -124 dBm (3 dB (S + N) / N), with a measurement made in the Narrow-bandwidth estimated at 5 kHz.

VHF TX

The power was measured with Anritzu MS2601B spectrum analyzer. In high power with 20 dB fixed attenuator, the amplitude of the peak (145,500 kHz) was about 13.1 dBm. Added the 20 dB attenuator come to 33.1 dBm, which is equivalent to 2.04 W.
The switching to low power showed an amplitude of -1.5 dB, 20 dB attenuator adding we arrive at 18.5 dBm, equivalent to 70 mW. On a negative note, the presence of the second harmonic at 290 MHz amplitude of about +5 dBm (3 mW). Curiously, this harmonic is measurable both on high and low power, with approximately the same level. The presence of this harmonic, the cause, and the remedy has already been extensively documented online. Follow screen shot of the spectrum analyzer.

• Full Power Full Power
• Low Power Low Power
• Full Power & II Harmonic Full Power & II Harmonic
• Low Power & II Harmonic Low Power & II Harmonic
•  

UHF Section

UHF RXThe UHF section was tested at a frequency of 433,200 kHz. In reception is virtually confirmed the sensitivity stated by the manufacturer of 0.2 uV (12 dB SINAD). The measurement was made with a generator Marconi MI-2024 and PC with software of Sinad ComTekk. The extent of MDS, as described in RKE 6/2011 (I4SBX), highlighted the value of -122 dBm (3 dB (S + N) / N), with a measurement made in the Narrow-bandwidth estimated at 5 kHz.
UHF TX

As for the VHF section, the power was measured with Anritzu MS2601B spectrum analyzer. In high power with 20 dB fixed attenuator, the amplitude of the peak was about 12.8 dBm. Added the 20 dB attenuator come to 32.8 dBm, which is equivalent to 1.9 W. The extent to low power showed a modest decrease in amplitude of 10.4 dB, 20 dB attenuator adding we arrive at 30.4 dBm, equivalent to 1.1 W. The second harmonic is attenuated and well beyond the ranks - 50 dBc. Follow screen shot of the spectrum analyzer.

• Full Power Full Power
• Low Power Low Power
• Full Power & II Harmonic Full Power & II Harmonic
• Low Power & II Harmonic Low Power & II Harmonic
•  

Conclusions

This small transceiver is definitely a winner in the price performance ratio. Just think that an ordinary duck antenna dual band (144/430) in the domestic market at a price that varies between half and 2 / 3 of the cost of the UV-3R to realize this. Some people consider the poor quality of trims: personally, I disagree. As use has shown, it is intutive and easy.

Positive notes

The very low cost, well-balanced the power of 2W output capacity of the battery. Excellent receiver sensitivity, weight and very compact. Interesting that the presence of VOX allows for hands-free operation, for example in the maintenance / calibration of antennas. Interesting the ability to program via PC memories of the transceivers, with RS-232 or USB.

Negative Notes

VHF low-pass filter section with cut-off frequency too high and consequences modest attenuation of the second harmonic. This excessive width of the filter also allows strong signals out of band to enter. Volume level, even at idle, too. The squelch opens about the same amplitude of input signal regardless of the value set. Unbalanced the difference between high and low power: too much difference in the VHF (2 W / 70 mW), low UHF (1.9 W / 1.1 W). Some menu items are not documented.

In conclusion

Do not be fooled by the length of negative in opposition to positive notes. The verdict is definitely very positive. As Daniel I6AQE, silent key, used to say: " it's only missing a little door that will open, if the transceiver brokes, from where you'll get back the money spent to buy it ".

73s de I6DVX