AmateurRadio.com

Ever since my outing on to Ling Fell yesterday I have been bugged by not knowing for sure whether the problems I experienced with the VX-8GR were really caused by receiver overload or blocking. I like the construction and features of the Yaesu. But a radio that makes you miss some of the contacts you have laboriously sweated up a summit to make is about as much use as a chocolate teapot. I wondered if I could devise a test to give me an idea of the relative strengths of the different 2m radios. I did, and the candidates are lined up in order of merit below, the worst on the left and the best on the right.

The test methodology was crude. I connected each radio to my dual band vertical and tuned in a weakish station: the GB3AS repeater on 145.600MHz, which is normally an S3 signal – fully readable but with some background noise on the audio. I then transmitted a carrier on 144.025MHz using another radio on a helical antenna a few metres from the vertical. I tried two power levels of the interfering signal, 3.5W (“high power”) and 0.5W (“low power”), these being the available power levels of the test radio. This 8dB difference in the interfering signal level had different effects on the ability to receive the repeater signal.

I am well aware of the limitations of the test I carried out. In real life SOTA or WOTA use a radio may be subjected to strong in-band signals from activators on other summits but they will not be as strong as the signal from a radio a few metres away from the antenna. A radio is likely to be subjected to strong signals from outside the amateur band such as pagers and other commercial signals, which the bandpass filters in modern radios due to the marketing-driven necessity of providing wideband receive coverage will do nothing to attenuate. Many strong signals may mix together to cause intermodulation effects if not blocking. However, a receiver that can handle a strong in-band interfering signal is likely also to be better at coping with many strong signals being received over a range of frequencies. So I think my test results have some validity.

Beginning with the worst receiver, the results are as follows.

• VX-8GR. This receiver was the worst affected by blocking. Noticeable desensing of the repeater signal occurred when the in-band carrier was on low power, while a weak noisy “4 by 1” signal was killed completely. The repeater signal cut out completely when the in-band carrier was keyed on high power. Engaging the RX ATT (menu option 1) caused the repeater signal to drop below the squelch threshold so it was not much help though it did reduce the desensing effect on stronger signals.
• JMT-228. The VX-8 was slightly worse than the Jin Ma Tong JT-228, a £30 Chinese handheld bought on eBay. In fairness, the JT-228 is slightly less sensitive than the Japanese ham radios (judging by the signal to noise ratio on weak signals) which may have helped it a bit. Desensing was noticed when the in-band carrier was on low power, and the repeater signal cut out when it was on high power.
• TH-D72. The Kenwood TH-D72 may only be third worst (or third best) but in fact it was a whole lot better. No detectable desensing occurred when the in-band carrier was on low power. Some desensing occurred, in the form of a drop in S-meter reading and increased noise on the audio, when the carrier was on high power.
• GP-300. Excellent performance was given by the Motorola GP-300. No desensing was noticed when the in-band carrier was on low power. There was a very slight but hardly noticeable increase in background noise level when the carrier was keyed on high power.
• TH-205E. I bought this old boat anchor as a “spares or repair” radio for £6 on eBay for the fun of seeing if I could get it going. With the high capacity battery pack it is about the weight and bulk of an FT-817 and not something I would particularly want to haul up a summit. But no desensing of the repeater signal was observed even when the in-band carrier was keyed on high power, making this the best performing receiver of all.

Out of interest I also carried out the test on my FT-817ND and the Kenwood TM-D710 I use as my 2m base station. The FT-817ND was slightly better than the TH-D72: there was no effect with the low power carrier but the high power one brought a noticeable background hiss on the signal. The TM-D710 performed close to the TH-205E. There was barely any noticeable effect from the high power in-band carrier.

I think the results of these tests, crude though they are, are interesting. The bigger the radio, the more likely it is to have a receiver able to handle adjacent strong signals. Paying lots of money for the latest technology is no guarantee of getting a better receiver. In fact, just the opposite. An ex-commercial handheld or a ham band one from the days when wide band receive coverage was not considered important will work better than the latest marvels.

Were it not that I find the full APRS functionality of the VX-8GR and TH-D72 useful, I’d be tempted to sell both those radios and just use a dumb tracker plugged into the mic socket of one of the others tuned to 144.800. Either I use the VX-8GR for APRS only and carry another radio for making contacts or I must try harder to love the TH-D72. Decisions, decisions. But at least I now have a bit more information to base them on.

Ever since my outing on to Ling Fell yesterday I have been bugged by not knowing for sure whether the problems I experienced with the VX-8GR were really caused by receiver overload or blocking. I like the construction and features of the Yaesu. But a radio that makes you miss some of the contacts you have laboriously sweated up a summit to make is about as much use as a chocolate teapot. I wondered if I could devise a test to give me an idea of the relative strengths of the different 2m radios. I did, and the candidates are lined up in order of merit below, the worst on the left and the best on the right.

The test methodology was crude. I connected each radio to my dual band vertical and tuned in a weakish station: the GB3AS repeater on 145.600MHz, which is normally an S3 signal – fully readable but with some background noise on the audio. I then transmitted a carrier on 144.025MHz using another radio on a helical antenna a few metres from the vertical. I tried two power levels of the interfering signal, 3.5W (“high power”) and 0.5W (“low power”), these being the available power levels of the test radio. This 8dB difference in the interfering signal level had different effects on the ability to receive the repeater signal.

I am well aware of the limitations of the test I carried out. In real life SOTA or WOTA use a radio may be subjected to strong in-band signals from activators on other summits but they will not be as strong as the signal from a radio a few metres away from the antenna. A radio is likely to be subjected to strong signals from outside the amateur band such as pagers and other commercial signals, which the bandpass filters in modern radios due to the marketing-driven necessity of providing wideband receive coverage will do nothing to attenuate. Many strong signals may mix together to cause intermodulation effects if not blocking. However, a receiver that can handle a strong in-band interfering signal is likely also to be better at coping with many strong signals being received over a range of frequencies. So I think my test results have some validity.

Beginning with the worst receiver, the results are as follows.

• VX-8GR. This receiver was the worst affected by blocking. Noticeable desensing of the repeater signal occurred when the in-band carrier was on low power, while a weak noisy “4 by 1” signal was killed completely. The repeater signal cut out completely when the in-band carrier was keyed on high power. Engaging the RX ATT (menu option 1) caused the repeater signal to drop below the squelch threshold so it was not much help though it did reduce the desensing effect on stronger signals.
• JMT-228. The VX-8 was slightly worse than the Jin Ma Tong JT-228, a £30 Chinese handheld bought on eBay. In fairness, the JT-228 is slightly less sensitive than the Japanese ham radios (judging by the signal to noise ratio on weak signals) which may have helped it a bit. Desensing was noticed when the in-band carrier was on low power, and the repeater signal cut out when it was on high power.
• TH-D72. The Kenwood TH-D72 may only be third worst (or third best) but in fact it was a whole lot better. No detectable desensing occurred when the in-band carrier was on low power. Some desensing occurred, in the form of a drop in S-meter reading and increased noise on the audio, when the carrier was on high power.
• GP-300. Excellent performance was given by the Motorola GP-300. No desensing was noticed when the in-band carrier was on low power. There was a very slight but hardly noticeable increase in background noise level when the carrier was keyed on high power.
• TH-205E. I bought this old boat anchor as a “spares or repair” radio for £6 on eBay for the fun of seeing if I could get it going. With the high capacity battery pack it is about the weight and bulk of an FT-817 and not something I would particularly want to haul up a summit. But no desensing of the repeater signal was observed even when the in-band carrier was keyed on high power, making this the best performing receiver of all.

Out of interest I also carried out the test on my FT-817ND and the Kenwood TM-D710 I use as my 2m base station. The FT-817ND was slightly better than the TH-D72: there was no effect with the low power carrier but the high power one brought a noticeable background hiss on the signal. The TM-D710 performed close to the TH-205E. There was barely any noticeable effect from the high power in-band carrier.

I think the results of these tests, crude though they are, are interesting. The bigger the radio, the more likely it is to have a receiver able to handle adjacent strong signals. Paying lots of money for the latest technology is no guarantee of getting a better receiver. In fact, just the opposite. An ex-commercial handheld or a ham band one from the days when wide band receive coverage was not considered important will work better than the latest marvels.

Were it not that I find the full APRS functionality of the VX-8GR and TH-D72 useful, I’d be tempted to sell both those radios and just use a dumb tracker plugged into the mic socket of one of the others tuned to 144.800. Either I use the VX-8GR for APRS only and carry another radio for making contacts or I must try harder to love the TH-D72. Decisions, decisions. But at least I now have a bit more information to base them on.

This afternoon I went for a stroll up Ling Fell, LDW-205. It was a fine afternoon and I wanted a bit of exercise. I took the VX-8GR so I could test the new QRU feature of Lynn KJ4ERJ’s APRSISCE/32 software that allows an APRS user to receive information about nearby objects on request. I have created a QRU server for Wainwright summits so that an APRS user in the fells could receive information about the nearest summits, to aid identification or navigation.

I put a 2m helical antenna on the rucksack support for the walk up, so the VX-8GR could send my position. The other channel was monitoring 145.500MHz (S20) the FM calling channel. As I gained height I started to hear some loud bursts of interference, a combination of a whine and a buzz, on S20. When I got to the top I switched antennas to the RH-770 dual band telescopic. My first call was answered by Colin, 2E0XSD. His signal was moving the meter on the VX-8GR to an S3 or 4 but there was intermittently a lot of crackly interference over his audio. I tried engaging the RX Attenuator option in the VX-8GR menu and it did seem to improve things a bit, but not completely.

A bit later, when I was testing the QRU server, I could hear the APRS packets coming back from my gateway (which is line of sight from Ling Fell, just behind me in the distance in the picture) but they sounded distorted and the VX-8GR didn’t decode them.

I wondered if there was a fault with the cable to the rucksack mount so I put the antenna directly on the radio. My next call was answered by Geoff G4WHA from his car in the car park in Penrith. He was 5 by 1 but his signal was cutting out intermittently. I got the feeling the problem wasn’t Geoff’s, but was my receiver cutting out due to overload from some nearby transmitter. There is a commercial mast a couple of miles away on the other side of the valley, though I have no idea what is on it.

I am starting to get a feeling that the receiver in the VX-8GR is not much good on summits when connected to a decent antenna. I first noticed odd things with the original VX-8R I had when I tried it out with a SOTA Beams MFD. There have also been several occasions when other people using VX-8 series rigs on summits have failed to hear me, even though I could hear them clearly and in some cases was running much more power than they were. This is quite disappointing. I really like the VX-8GR and much prefer it over the Kenwood TH-D72 which I have been thinking about selling. But perhaps it would be better to keep the Kenwood.

I wish that I had the test equipment to try to compare the strong signal performance of my various hand held radios. HF radios have their receiver performance exhaustively tested and the results of tests by the likes of Sherwood Labs are endlessly debated on various reflectors despite the fact that the only difference it is likely to make is whether you can copy a very weak station right next door to an extremely strong one. But the reviews of VHF radios focus only on matters like the ease of use of the menu system, how many memories it has or how the scanning works.

I think the receive performance of VHF/UHF hand helds is just as important as for HF receivers. If a receiver can’t cope on a hilltop on the middle of nowhere how will it fare with the signal levels in a busy urban environment? Heck, you might be missing vital emcomms messages and not know it! It’s about time the ham radio magazines started publishing blocking dynamic range and cross-mod figures for hand held radios.

This afternoon I went for a stroll up Ling Fell, LDW-205. It was a fine afternoon and I wanted a bit of exercise. I took the VX-8GR so I could test the new QRU feature of Lynn KJ4ERJ’s APRSISCE/32 software that allows an APRS user to receive information about nearby objects on request. I have created a QRU server for Wainwright summits so that an APRS user in the fells could receive information about the nearest summits, to aid identification or navigation.

I put a 2m helical antenna on the rucksack support for the walk up, so the VX-8GR could send my position. The other channel was monitoring 145.500MHz (S20) the FM calling channel. As I gained height I started to hear some loud bursts of interference, a combination of a whine and a buzz, on S20. When I got to the top I switched antennas to the RH-770 dual band telescopic. My first call was answered by Colin, 2E0XSD. His signal was moving the meter on the VX-8GR to an S3 or 4 but there was intermittently a lot of crackly interference over his audio. I tried engaging the RX Attenuator option in the VX-8GR menu and it did seem to improve things a bit, but not completely.

A bit later, when I was testing the QRU server, I could hear the APRS packets coming back from my gateway (which is line of sight from Ling Fell, just behind me in the distance in the picture) but they sounded distorted and the VX-8GR didn’t decode them.

I wondered if there was a fault with the cable to the rucksack mount so I put the antenna directly on the radio. My next call was answered by Geoff G4WHA from his car in the car park in Penrith. He was 5 by 1 but his signal was cutting out intermittently. I got the feeling the problem wasn’t Geoff’s, but was my receiver cutting out due to overload from some nearby transmitter. There is a commercial mast a couple of miles away on the other side of the valley, though I have no idea what is on it.

I am starting to get a feeling that the receiver in the VX-8GR is not much good on summits when connected to a decent antenna. I first noticed odd things with the original VX-8R I had when I tried it out with a SOTA Beams MFD. There have also been several occasions when other people using VX-8 series rigs on summits have failed to hear me, even though I could hear them clearly and in some cases was running much more power than they were. This is quite disappointing. I really like the VX-8GR and much prefer it over the Kenwood TH-D72 which I have been thinking about selling. But perhaps it would be better to keep the Kenwood.

I wish that I had the test equipment to try to compare the strong signal performance of my various hand held radios. HF radios have their receiver performance exhaustively tested and the results of tests by the likes of Sherwood Labs are endlessly debated on various reflectors despite the fact that the only difference it is likely to make is whether you can copy a very weak station right next door to an extremely strong one. But the reviews of VHF radios focus only on matters like the ease of use of the menu system, how many memories it has or how the scanning works.

I think the receive performance of VHF/UHF hand helds is just as important as for HF receivers. If a receiver can’t cope on a hilltop on the middle of nowhere how will it fare with the signal levels in a busy urban environment? Heck, you might be missing vital emcomms messages and not know it! It’s about time the ham radio magazines started publishing blocking dynamic range and cross-mod figures for hand held radios.

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.

A few years ago I read about a program called Radio Mobile which was supposed to be able to plot maps showing your VHF or UHF station coverage using actual terrain data. I downloaded it but couldn’t figure out how to get it to work so I gave up. A few days ago someone mentioned that it is possible to hook the program into an APRS server so I thought that I would try again. I was given a hint that for UK users the G3TVU Quick Start package was the easiest way to get Radio Mobile going.

The default setup is for a location in the Derbyshire Peak District so I followed the instructions on Changing Location to try to create maps centered on G4ILO. I got as far as producing an elevation map but was then baffled by the sentence: “Which can then be ‘Merged/Copy’ with a road map and ‘Kept in new picture’ to produce.”

James VE6SRV came to my assistance with an explanation in English: “On the menu select EDIT then in the drop down menu select MERGE PICTURES… F7. You’ll get a dialog box opened up. It will have a list of various sources on the left, detailed choices about the source in the middle and operation controls on the right.Try picking OSM, and then clicking DRAW. After the merge is complete, you’ll be asked how you want to keep the resulting image, or to discard it. The four options equate to SAVE, SAVE AS, LET ME LOOK AT IT FOR NOW, and TOSS IT. If you chose copy, the OSM tiles will overwrite the relief map. ADD, MULTIPLY, and BITWISE are 3 different methods of merging the shaded relief map with the OSM tiles. Depending upon the colours, and the type of output you want, you’ll need to play a bit with the choices to see how it looks for you. You can also play with contrast and brightness sliders to try and get the output just how you like it.” This was just what I needed, and after a bit of experimentation I soon had a road map of my area merged with the relief map showing the mountains.

The next step was to try to plot the coverage of my station on the map. I believe the default setup had a dummy base, mobile and hand-held station predefined but they were now outside my area and in any case I must have deleted them. Creating a “unit” for my own station was simple enough, but when I selected one of the tools to plot coverage the Draw button was disabled. Eventually I worked out that you have to have at least two stations (“units”) defined and they must both be members of the same network. The program will then plot the coverage for your station as received by a station of the same type as the other one.

I thought the coverage plots were rather optimistic judging by experience so I had to change some of the parameters and choose the “worst case” to get a plot that looked reasonable. This being VHF, it’s possible that the fact of my antenna being located in the attic could result in some degradation of the signal. I felt the default colouring of green for 3dB over noise or better and yellow for 3dB below noise to 3dB above didn’t give a realistic picture so I changed the colouring so that green depicts 10dB or more over noise and yellow shows between 0 and 10dB.

The first plot shows a wide area view:

Click to see the map full-sized. I did a second plot at a larger scale to show the local coverage in more detail:

The plot shows really clearly how my VHF range is limited by the surrounding hills.

Connecting Radio Mobile to an APRS server has limited use. The program doesn’t seem to handle objects very well so for example the GB3CA object put out by MM1MPB shows as MM1MPB and moves that station’s position. But it is a useful way to get other local stations into the system instead of manually entering their details.

The objects sent out by WOTA to show the position of a Wainwrights On The Air activation are shown as WOTA not the name of the object. The Radio Link option can be used to plot the path between two stations and estimate the received signal strength, as in this example showing the path between me and Phil G4OBK/P on the summit of Seatallan.

The estimated S9 signal strength is somewhat more than I actually received from Phil and I was running 50W not 10W. As mentioned earlier my antenna gain is also downrated over reality to try to get a more realistic picture.

Radio Mobile is a clever piece of software and it was interesting to play with it. It was quite hard work to get going, but it was useful to see how the nearby hills affect my VHF coverage.

Chinese-made VHF and UHF hand-held radios are no longer the novelty they were a few years ago when I discovered the Jingtong JT-208 and got one to try. They are no longer the shoddily made bits of junk the Jingtong was, either. Some Chinese makes like Wouxun are now directly imported into the UK and USA so unadventurous buyers don’t have to take chances on eBay. But there are better bargains and more choices to be had if you use the auction site. When I saw a smartly styled compact VHF handheld radio transceiver 136-174MHz being sold for only £40 it looked like just the job for keeping downstairs to monitor my Echolink node and acting as a backup radio for WOTA activations so I decided to order one. Shipping from Hong Kong took one week.

The radio is a model JMT-228 and is made made by Jin Ma Tong Electronics, which is not a company Google has much information about. Whilst tearing off the wrapping I experienced a heart-sinking feeling as the box was revealed together with the description “400-470MHz.” I was afraid the seller had sent the wrong model! Inspection of the manual revealed the radio comes in VHF and UHF versions, and when I looked at the back of the radio the label showed “136.000-174.000MHz.” What a relief!

Together with the radio and manual, the box contains a short helical antenna, a metal belt clip, a carrying strap, a 1500mAhH 3.7V Li-Ion battery pack similar to those used in mobile phones and digital cameras, a 100 – 240V AC charger with fold-out US-style mains plug, a USB cable (presumably used only for charging as there is no mention in the manual of programming software) and a hands-free style speaker microphone terminated in a 2.5mm stereo jack.

Here is an “unboxing” video (not made by me) from YouTube:

The JMT-228 is very light (the manual amusingly gives the weight as 200kg including the battery!) and looks rather similar to the early Yaesu VX models. It’s a bit smaller than the compact VX-8GR as you can see from the photograph below. The build quality seems very good. The radio is built on a die cast chassis as you can see when you put in the battery. It doesn’t have quite the same solid feel as a Yaesu but the light weight is a bonus. The belt clip is metal but a bit flimsy and it is fixed to the radio using one screw. There is no retaining lug (although the clip has a hole for one) so unless you tighten the screw so hard you risk stripping the threads it could rotate allowing the radio to fall off the belt.

The glass in front of the display is actually plastic which scratches rather easily – there are a couple of dings in it already that I don’t remember doing. A small thing perhaps and forgiveable at the price but something many hams won’t think about as we take the high quality of ham radio products for granted.

No claims are made that the radio is waterproof. Indeed, the manual warns: “Never expose the transceiver to rain, wet areas or any liquids, or it may be damaged. However, the speaker/mic and USB/charger sockets have stout rubber covers and another page in the manual states: “The transceiver is not fully water-resistant while using the speaker/microphone” which implies that it could be. The JMT-228 certainly doesn’t look any less waterproof than the Yaesu VX-8GR so it could probably withstand the odd rain shower, but don’t quote me on that as I haven’t tried getting it wet just to see what happens.

The manual is in Chinese and English. The English part is well written for a Chinese radio, though the most important part, describing the “Auxiliary Fuctions” (sic) is squashed into two pages and less well written so you need to do some guesswork to determine some of the functions. RC sets the CTS or DCS tones for receive, TC sets them for transmit. TOT sets a time-out timer. OFFS sets the direction of offset for repeater use, a different menu OST sets the amount of the offset.

There are 99 memories and they store the offset and tone settings in force at the time of programming. It took only a few minutes to enter in the 2m simplex channels, the three local repeaters and my Echolink node settings. Memory mode is clearly the way to use this radio on the amateur bands as it does not have automatic repeater shift as found on dedicated ham radios.

There is a scan mode, which simply scans all the memories. There is also an FM Radio mode that lets you listen to Band 2 FM radio frequencies. The sound quality isn’t the greatest for listening to Classic FM or BBC Radio 3, but it’s usable.

The antenna socket is an SMA type. Surprisingly for a Chinese made radio it is an SMA female, the same as that used on radios from Yaesu, Icom and Kenwood, so you can use the same SMA-M accessory antennas you could use on those radios. I can even use my SMA to BNC adapters! The supplied antenna is 4 inches long, presumably a helical whip, and fairly broadband with the best match, a 1.6:1 SWR, at 156 MHz. This isn’t going to be optimum (tests I have carried out in the past have showed that a noticeable benefit is gained by tuning short helical antennas to match the frequency of use) but it is no worse than the antennas supplied with Kenwood handhelds and only to be expected in a radio designed to operate over such a wide band.

The receiver sensitivity seems on a par with other handheld radios I own. Output power is claimed to be less than or equal to 5W. Frankly, I would not expect to get 5W out of a radio powered by a 3.7V battery pack. If you did, it would get very hot very quickly and the battery would soon run out. I measured the output power at 3W which I think is very good for a radio of this size. I had no trouble opening the GB3LA repeater more than 50 miles away using a 7 inch long helical (but not with the supplied antenna.)

There is no low power setting, which is a bit of a disappointment and will not help battery conservation. On receive, however, the radio seems to run forever, helped no doubt by a quite severe power saver mode. This does not appear to be user configurable nor can it be disabled so you could not use this radio to receive packet or APRS.

The modulation using the internal microphone is OK, but a bit on the low side. Using the included speaker/mic it is a bit better. Note that although this speaker/mic is similar to a hands-free mobile phone kit, the JMT-228 transceiver does not have VOX, so it is necessary to key the transmitter by pressing the button on the back of the mic. Here are some audio recordings of the JMT-228, with a couple of other hand-held radios for comparison purposes.

• JMT-228 using internal microphone
• JMT-228 using provided external speaker-mic
• Old Trio/Kenwood TH-205E with internal mic
• Motorola GP300 with internal mic

As you can hear, the audio level is similar to the Motorola GP300, another radio designed for use on the professional high bands. Amateur band radios tend to have a higher modulation similar to the TH-205E.

When using the speaker/mic I found that the transceiver tended to lock in transmit – presumably due to RF getting into the speaker/mic cable which is right next to the antenna. This is a bit of an annoyance, which could possibly be cured using a really small snap-on ferrite if I had one.

Despite a few niggles I think the Jin Ma Tong JMT-228 transceiver is a nice little radio and would be a good buy for anyone wanting an inexpensive and compact transceiver for use in the amateur 2m band. I think the Chinese are going to own the market for basic single or dual band handhelds very shortly and people will only buy from the specialist manufacturers if they need specialist functionality such as APRS, wide band scanning, a short wave receiver or even, dare I say it, D-Star.