Saturday, April 23, 2011

2m HT antenna shootout

I've been wanting to do this for a long time. I wanted to try to compare the difference between various antennas for 2 metre band handhelds so as to see how much you lose using a small inconspicuous antenna or how much you gain by using an extra long one. The results were broadly as expected. The longer the better. But there were a couple of surprises.

The efficiency of the antennas was compared using my Yaege FC-1 frequency counter, which has a relative dBm scale. I transmitted into each of the antennas in turn, noting the dBm reading on the FC-1 which was positioned a couple of metres away. This is hardly an antenna test range. However, the results were validated in on-air tests where various local amateurs were asked to report on my signal strength as I swapped antennas. The on-air results were in agreement with the measurements, which allow me to believe that they are a fair representation of the performance of these antennas in the real world.

As an aid to comparison, the performance is given as effective power out relative to a manufacturer supplied antenna driven with 5 watts. The antenna provided with the Yaesu VX-8GR is used as the reference antenna. Choosing a manufacturer supplied antenna turned out to be rather a poor reference, as although the Yaesu standard antenna performs very well, the antenna supplied with the Kenwood TH-D72 performed very poorly. It was 5dB down on the Yaesu antenna, putting it in the same range as the short stubby antennas. This is probably because the Kenwood antenna's resonant frequency, as checked on my antenna analyzer, is around 158MHz. Although it would be reasonable to suspect a fault with the antenna supplied with my TH-D72, the one supplied with my Kenwood TH-F7E (which I have since sold) was identical. If you are using a Kenwood radio then you have even more reason to throw away the supplied antenna and buy a better one.

The antennas in the picture from left to right are:
  • A dummy load. This is just my little joke! Many "experts" like to say that the short stubby antennas are no better than dummy loads. In fact, my results suggest that they perform quite well for their size and are much better than dummy loads. However, as with all of these antennas, the best results depend on the antenna being resonant (having a good SWR) at 145MHz. All these antennas have quite a narrow bandwidth and if they are off-frequency it has a significant effect on their performance.
  • A 2in. 144MHz stubby bought on eBay. This antenna is 5dB down on the reference Yaesu dual-band whip and would be the equivalent of reducing power on the handheld from 5W to 1.5W.
  • An A-137 dual band stubby bought on eBay. I have two of these. The first one was tuned spot on 145.5MHz so I got a second one which was resonant just above 146MHz. Performance is slightly better than the single band stubby, being the same as reducing power to 2W.
  • A 2m Stubby Duck from Smiley Antenna. I got this because I thought it would deliver better performance than the small stubbies while still being small enough to sit comfortably in a pocket. This proved correct. Performance is just 2dB down on the reference stock antenna, the equivalent of running 3W instead of 5W.
  • A 6in. 2m helical antenna. This antenna came with the old TH-205E handheld and as far as I know is the original antenna supplied with the radio. Checked on an antenna analyzer it was resonant a few MHz high in frequency but I brought it down to 145MHz by dropping a ferrite tuning core down inside the helical and securing it with Blu-Tack. This enabled me to open a repeater I could not open before the modification, illustrating the importance of tuning these antennas to get best performance. This antenna is just 1dB down on the reference antenna, like using 4W instead of 5W - hardly noticeable.
  • A Nagoya NA-701 dual band BNC antenna. I purchased this antenna as a replacement for the manufacturer supplied antenna due to my converting all my handheld radios over to BNC sockets by permanently fitting adapters. It is almsot exactly the same size as the supplied antenna and its performance is identical to it.
  • An 8in. 2m helical antenna. This antenna was bought as an untuned helical which required cutting to frequency. I got it from Waters and Stanton and it is of extremely poor quality. However, the RF isn't bothered by the shoddy manufacture. It performs exactly the same as the supplied VX-8GR antenna.
  • The antenna supplied with the Yaesu VX-8GR. This is the reference antenna for this comparison. As mentioned above, the antennas supplied with other radios (notably Kenwood) may not be as carefully tuned and may perform more poorly than this.
  • The antenna supplied with the Yaesu FT-817ND. This is slightly bigger than the one supplied with the VX-8GR and has a BNC mount not an SMA. It performs about 1dB better, equivalent to running 6.3W. Adding the tip which makes the antenna work on 6m has no effect on 2m performance. As I have come to expect from Yaesu, this antenna is resonant precisely on 145MHz, as was the one with the original FT-817 that I had many years ago.
  • A quarter wave telescopic BNC whip. These 19in telescopic antennas are available from a variety of sources. I think this one came originally from Maplin. It gives your signal a 3dB boost, equivalent to doubling your output power (and doubles the received signal strength also.) At a cost of £8, it is a cheap way to double your effective power and not too long to be cumbersome in use.
  • A Nagoya NA-767 bought on eBay. This is a dual band telescopic antenna which is 38 inches (97cm) long when extended. It has a heavy metal base which presumably contains a loading coil. The BNC connector is made mostly of plastic, but the base is sprung which should take some strain off it. The telescopic sections are quite stiff. The build quality of the antenna is not great but it is quite cheap. The performance gain is substantial, giving a 4 times power boost over the quarter wave antenna, equivalent to running 40 watts output.
  • A Sharman RH-770 dual band antenna bought from Capital Stores. This appears to be a clone of the Diamond RH-770 which is sold at the usual rip-off prices by certain ham radio dealers. The Sharman version is half the price. It is a dual band antenna with centre loading and is 93cm (36 inches) long when extended. It looks and feels a better quality antenna than the NA-767. It also performs slightly better on 2m, giving your handheld a full ten times gain on transmit and receive compared to the supplied rubber duck. It's the equivalent of running 50 watts from a handheld!
  • Not shown in the picture is the 45.5inch Black Whip from jeepbangkok on eBay. This is a 5/8 wave single band (2m) antenna and was the best performing handheld 2m antenna of all, giving 11dB of gain over the manufacturer supplied whip, the equivalent of running 63 watts of power! Sadly the telescopic whip was of poor quality and pulled apart during a recent WOTA activation.
Clearly one should not use such long antennas as the last three on a typical modern handheld radio with SMA antenna socket unless you are using a stout SMA to BNC adapter that tightens down to rest on the body of the radio so that no twisting moment is applied to the SMA socket. Even then, you may rightly be wary of using such a long antenna in the windy conditions often encountered on Lake District summits, which often bent the sprung base of the Black Whip into a 45 degree angle. Because of this I have made up a rucksack mount with a BNC socket and a 19in. quarter wave counterpoise so these high gain antennas can be used off the radio.

I was unable to test the free standing WOTA Pole (ribbon cable Slim Jim inside a plastic tube) under the same conditions but on-air reports suggest that it may give even more gain than the Black Whip. However, it isn't always convenient to set up a guyed antenna on a summit, so one of these telescopic high gain antennas could be the answer to improving your signal when using a handheld radio.

These test results have related exclusively to the 2m band. I do not have test equipment that works up to 440MHz, nor is there any activity on 70cm in this part of the world so I have no plans to compare the performance of these antennas on UHF.


Richard G3CWI said...

Hi Julian

A graphical display of the results would help the readability of your article.

Thanks for an interesting read.


Ben said...

It's a shame, I also has an antenna from jeepbangkok which broke very easily.

Gorayski said...

Hi there, very insightfull your comparison. Have you ever heardor tested the DIAMOND RH901S?
Thanks and regards,

Unknown said...

No I'm afraid I haven't.

Julian, G4ILO