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Antennas

Dual Band Antennas

This section is dedicated to dual-band, VHF and UHF, antennas. This are the ones that can be used with the VUHFRadio or HAM Radios. I bought an assortment of dual-band antennas from AliExpress to use with the VUHRadio for field tests and to make it usable as an actual transceiver and not just some debugging device in the lab.

The antennas I bought are shown in the figure on the right. From left to right: Nagoya NA-771 Clone, Nagoya NA-771 Original, UT-106UV Clone, UT-108UV Clone. They are all 1/4 wavelength monopole antennas for VHF and 1/2 wavelength for UHF, and integrate an inductor to adapt for each band.

A resumed table with the antennas working bands, based on S11 results, is shown bellow (frequencies are in MHz):

Antenna VHF 6dBm VHF 10dBm UHF 6dBm UHF 10dBm
NA-771 Clone 138.8 - 149.2 140.6 - 146.4 402.0 - 484.2 421.2 - 436.8
NA-771 Original 148.0 - 163.0 150.8 - 155.8 432.0 - 531.0 442.8 - 465.6
UT-106UV Clone 138.8 - 149.0 141.0 - 145.8 419.4 - 442.8
475.2 - 510.0
897.4 - 986.7
924.0 - 971.5
UT-108UV Clone 139.2 - 150.0 141.2 - 146.6 426.6 - 435.6
711.2 - 764.4
982.9 - NA
996.2 - NA

Both the NA-771 antennas are very good for both bands I’m using in the VUHFRadio project. The UT-106UV and UT-108UV are only very good in VHF and in higher UHF bands, 868/915 MHz, but are still usable in my desired UHF band, 433MHz.

NA-771 Antenna

This Section shows a more detailed view of the S11 parameter for both the NA-771 antennas and comparing them. The NA-771 antenna is a very popular direct connect antenna for handheld HAM Radios like the UV-5R and are available with different connectors like SMA Male, SMA Female, BNC, …

The test was performed with the antenna standing free on a tripod away from any grounding metal or housings. The R&S VNA used was calibrated at the end of the cable that connects to the antennas.

The results for these antennas is shown in the figure bellow with the corresponding S11 results file for download underneath it.

These results show that the Original Nagoya antenna is better then the clone which is expected. The clone antenna is still very good though with the original having a better overall performance, worse matching in VHF but better in all other bands.

UT-106UV and UT-108UV Antenna

This Section shows a more detailed view of the S11 parameter for both the UT-106UV and UT-108UV antennas and comparing them. These are antennas with a magnetic stand and come with a 3 meter long connection cable which had to be modified for the input matching (S11) test.

The test was performed with the antenna standing free on a tripod away from any grounding metal or housings. The stand of the antennas had to be modified to a much shorter cable so that the VNA could be calibrated as close as possible to the actual antennas. First I used a stand with the original 3 meter cable but the results where not usable due to inadequate calibration. Unluckily, or for this case luckily, one of the bases had a shorted cable so for that base the cable had to be exchanged anyways. The modified stand is visible in the group photo at the begging of this section, the stand of the UT-108UV antenna (the most right one).

The results for these antennas is shown in the figure bellow with the corresponding S11 results file for download underneath it.

Both these antennas work well in VHF but are not great for UHF, at least in my desired band of 433MHz. They both also seem to be worse then either of the NA-771 antennas, I will verify if this holds true in the field tests with the VUHFRadio.

UT-102UV Clone Antenna

For fun I also tested a smaller dual-band antenna that was laying around at my workplace. This is also a magnetic stand antenna like the UT-106UV or UT-108UV and was tested the same way as those, with the shortened connection cable stand.

The results for this antenna are shown bellow and like with all the previous results the corresponding S11 files are available for download underneath the figures.

This antenna has a much worse VHF performance than any of the above dual-band antennas, it is actually so bad that it can’t really be called dual-band… It seems to be a good antenna for the UHF band though with better characteristics then the other two magnetic base antennas tested.