Posts Tagged ‘10 FM’
This afternoon I made my first DX contact using a hand-held radio. It was a fine, warm day, so after lunch I left Olga doing things in the garden and went for a stroll with the H-520 10m FM radio. I took a footpath through fields to the north of the town that led up to the Carlisle road. It’s quite high up there, with great views down into the town and to the mountains beyond. However I was only carrying what would fit in my pockets, so the camera got left behind.
I used to take a 2m radio up there but I don’t think I ever made a contact so I lost interest. The other problem with that path is that you sometimes have to run the gauntlet of a herd of cattle. In the UK it’s illegal to put a bull into a field through which is a public right of way. However there is no such restriction on cows. They can be quite inquisitive, and there have been a few cases recently of people being knocked down and injured while walking through a field of cattle. It is quite frightening being followed across a field at less than the safe stopping distance by a couple of hundred tons of beefburgers in the making, as happened to Olga and I a couple of years ago. Shouting “horseradish sauce” at them has no effect at all!
Today, fortunately, the bovine creatures kept out of my way. I found a suitable operating spot, put the whip antenna on the Intek and started calling CQ. After a few minutes I had a call from Zdenek OK1AQW, coincidentally the same station that got away from me yesterday. Today he was strength 9 on the S meter, the same as Roger G0MWE had been from just a few miles away. We moved off the calling frequency and completed a solid 5 minute QSO, kept short only because Zdenek was receiving a lot of interference from other stations on the same frequency.
My report was initially 57, but was amended to 59 dropping to 51. At one point Zdenek informed me that I was coming over another British station that was calling on the frequency. He was running 100W to a quarter wave vertical and I think he was a bit surprised to hear I was running only 2.5W to a 140cm telescopic whip!
Incidentally it turns out OK1AQW doesn’t live near Prague at all as I wrote yesterday. His QRZ.com page is wrong. He is actually more than 100km east of Prague, about 10km from the Polish border, in locator JO80eb. I calculate that to be a distance of 888 miles or 1,430km. Not bad for a voice contact using a battery powered hand-held radio and whip antenna. Don’t you just love Sporadic E?
I didn’t manage any other contacts. I heard DO5DGH calling CQ repeatedly but he didn’t hear me. But this was a nice taste of what is possible. Some people might wonder why someone who owns nice radios like a K3 and even an FT-817 should put so much effort into trying to make contacts using a modified hand-held CB but I think to talk to someone direct using a battery powered self contained hand-held radio, without the aid of a satellite, a repeater or internet linking, is the ultimate challenge and far more exciting than anything I could achieve even if I had the full legal power, a tower and a beam!
I came a little closer to my objective of trying to make a DX contact using only a hand-held radio this afternoon. After dropping Olga off in town for a hair appointment I went up to my usual haunt Watch Hill accompanied my my 2m and 10m hand-helds. I had just stopped on the top when I heard Geoff G4WHA/P calling CQ WOTA from Kidsty Pike on the GP300 which was on my belt. He was a bit noisy as the radio only had the rubber duck on it so I foolishly decided to swap it for the 5/8 telescopic before calling him. Unfortunately in the minute or so it took to swap over the antennas I lost him and didn’t hear him call again.
Colin 2E0XSD called me and we had a brief chat, then I made several other calls hoping to catch Geoff or anyone else who happened to be listening. After about five minutes Colin called again to say that he was hearing activity on 10m FM. I got out the Intek with the 4 foot whip and started listening around. I did hear some activity, including what sounded like a French station down in the noise on 29.600 who was not clearing the FM calling channel. I also heard what sounded like Russian on 29.620.
After numerous calls on 29.600 I heard a CQ from OK1AQW near Prague in the Czech Republic, loud and clear. I called him but he replied that I was too weak to copy. A couple of minutes later I started calling again and OK1AQW came back to me with my full callsign! I replied “OK1AQW this is G4ILO/P you are 55 in IO84 QSL?” but got no response from him. I repeated his report several times but heard nothing. I don’t know if a full 4W would have made a difference, but a couple of days ago I adjusted the full power level of the H-520 back to 2.5W to try to mitigate the problem of high current draw when the SWR is less than perfect. So that was a gotaway, unfortunately.
I didn’t hear any more DX on 10m, but I did have a QSO with Roger G0MWE from Dearham who was using a new FT-897D and pleased to hear some activity on 10m. Roger suggested I should use a better antenna which would certainly be possible to erect up there but that would defeat the object of using the hand-held. But I’m sure with perseverance I will eventually achieve my objective.
On my first outing with the Intek H-520 Plus handheld transceiver a week ago I found that the batteries died as soon as I pressed the PTT. It turns out that this is a very common problem with this transceiver. M3XEM has even made a video about it which he has posted on YouTube.
After trying some different NiMH cells, freshly charged, my H-520 seemed to be happy using my longer whip antennas, though it still wouldn’t work with the supplied mini-whip. But after only a little use of the batteries it began cutting out again when using a 2ft centre-loaded whip. The only antenna it would still accept was the 4ft whip with counterpoise. I felt that something wasn’t right, so I decided to investigate.
I measured the battery voltage and current. The batteries were not freshly charged but had been used on Sunday to make numerous calls though no contacts. With the radio turned on and receiving the current drain is 90mA and the battery voltage was 7.71V. This is substantially above the 7.2V nominal voltage which suggests that there should be plenty of life still left in the batteries. This was confirmed by the battery state indicator.
I then transmitted into a dummy load. On the 1W setting (with slightly under 1W output) the current drawn was 750mA. On the 4W setting (with about 3.5W measured output) the current drawn was 1.3A. The voltage across the batteries whilst full power was being transmitted dropped to 6.75V, significantly less than the 7.2V nominal voltage. The current consumption is not excessive in comparison to an FT-817 which is specified to draw up to 2.0A at 5W output. One factor contributing to the voltage drop is the use of separate AA cells. Most handheld radios use battery packs in which the cells are welded together to minimize resistive losses.
The radio still worked fine at 6.75V, but this was transmitting into a dummy load. On most of my 10m antennas – and as observed by M3XEM – the battery voltage would fall away after a couple of seconds and the radio would cut out and restart. I tried to measure the voltage across the batteries when using the two short whips and it fell right away to 3 or 4 volts! This explained why the radio cut out and restarted. It must be drawing a lot of current to cause such a large drop, but I was unable to measure exactly how much as the radio’s voltage sensor cut the power to the TX too quickly for my meter to catch the reading.
My conclusion is that when presented with a load that is something other than 50 ohms, the PA of the H-520 draws an increased current. This effect is significant enough that the radio cuts out even on the 1W setting using the mini-whip antenna. This current draw may be more than rechargeable AA cells are designed to sustain, quickly pulling the voltage below the “low voltage” sensor level.
The transceiver isn’t really “eating the batteries” as some users have claimed, as the cells quickly recover their original voltage when the load is removed. The problem is purely and simply poor design which causes the PA to behave in this way and draw too much current when presented with a mismatch. As can be seen from the schematic (which is included in the manual) there is no SWR protection to back off the power.
It is very unlikely for a whip antenna on a hand held radio to present a perfect match, so the H-520’s performance in this respect is lamentable. As I noted in an earlier post, the supplied whip antenna was found to give its best match at 28.5MHz. It would present a high SWR on the UK and EU CB frequencies that most buyers of this radio would use and I doubt if any buyer of this particular radio would have found it possible to use the highest power setting with this antenna.
Another glorious day and Olga and I took a picnic lunch up to Watch Hill. We go there not because it is a SOTA summit but because it is near home, a nice walk, not a steep climb (so Olga is happy to come with me) and one of the easiest operating sites for me to reach when I want to get away from all the electronic QRN I’m plagued with at home. Unfortunately there isn’t a picnic table up there and I haven’t yet found a way to support the MP-1 antenna on a bare hilltop. Using a right-angled PL-259 adapter and a 259 to 3/8 adapter on the back of the FT-817 only works if you have a level surface to put the radio on and no breeze. So despite taking them with me I wasn’t able to get any use out of them. No doubt a photo tripod would do the job but that is too much ironmongery for me.
I did also take the Intek H-520 Plus and a couple of BNC mounted whip antennas but although there clearly was propagation on 10m I didn’t manage to work anything. I did hear something puzzling though. After one call on 29.600 I heard what I’m sure was a native English speaking voice announced something on the lines that this was the EA????? repeater. Unfortunately I’m getting increasingly slow witted these days so I don’t remember the exact announcement nor the full call and I didn’t hear it again. 29.600 is supposed to be the 10m FM calling frequency and not a repeater output so what could it possibly have been?
Back home later in the afternoon and VHFDX.net showed that there was a big Sporadic-E opening on 6m and even 2m in Eastern Europe. I decided to try 10m which seems to be the neglected band and managed to make several contacts including a new country for me, OD5NH in Beirut, Lebanon.
My reason for getting the Intek H-520 Plus hand-held was to try to work some Sporadic-E DX from the great outdoors. I didn’t think the supplied 18cm whip would be much good for that so I looked for the longest 10m BNC whip antenna possible. The best I could find was the AT-10 with a 4 foot telescopic whip which I believe is made by Sandpiper Antennas in Wales. It is sold by Waters and Stanton. I ordered one yesterday and it arrived in the post this morning – nice to see they can get it right sometimes.
The first thing I did with the antenna was put it on my AA-200 antenna analyzer. I was dismayed to find that the SWR on 10m was more than 10:1 and the best match was around 38MHz. I anticipated that this would be going straight back. However the instruction sheet “Getting the best out of your antenna” recommends using it with a counterpoise. I had expected to use one for best performance anyway, so I decided to try this before writing the antenna off completely.
The instruction sheet recommends a length of 6ft 5in for 10 metres, but I found that was too short as the best match was still well above 30MHz. By trial and error I eventually found a length of 7ft 6in was about right. The best SWR was still only 2:1 so I think the antenna is capable of improvement, but there is nothing else available to the best of my knowledge.
If a counterpoise is required you might think it would be a good idea for the manufacturers to provide somewhere to attach one. I tried using an alligator clip but it tended to slip off the BNC connector. In the end I managed to solder to the outer sleeve of the BNC connector using my biggest soldering iron turned up to maximum temperature so the counterpoise is now permanently attached to the antenna (until the wire breaks off, which it will probably do in the middle of a field just at the start of a massive band opening.)
Now I just need some Sporadic-E to see how far it is possible to work with a hand held radio.
As some of you know, I’m a bit of a sucker for hand-held radios. Whilst browsing eBay I’d often come across the Intek H-520 Plus CB hand-held and thought what a nice looking rig it was and wouldn’t it be nice if it could be converted to amateur 10m usage. A couple of days ago I stumbled across a site that gave the details of how to convert it for amateur 10m use so I decided to order one. It arrived this morning.
Never has a radio been taken apart so soon after its arrival. (Real hams don’t care about warranties!) Unfortunately, no matter how hard I tried, I couldn’t find again the site that had the modification information, but I vaguely remembered the details. Beneath the battery compartment there is a loop of wire. Snip it and push the ends apart. I’m not sure what that does. Now put the batteries back in and turn on the radio whilst depressing the Menu button. You can then select the option “Po” by pressing the down arrow button. Press Menu again, then press and hold the up arrow button until the frequencies displayed are in the 29MHz region. You now have a 10m FM / AM hand held.
Whilst I was doing this I was WSPRing on 10m and I saw some very strong traces from stations in Germany indicating that there was short-skip Sporadic-E on 10m. Were conditions such that I would actually be able to make some contacts with the new radio today?
The antenna supplied with the Intek H-520 Plus is about 15cm long so I suspect it will be less than useless for making any DX contacts. Clearly what I need in order to use this as a portable radio is some kind of long BNC 10m antenna, but at the moment I don’t have one. The H-520 comes with a “car kit” which screws to the bottom of the radio and allows you to power it from an external supply and connect an antenna with a PL-259 plug. So I hooked it up to the shack supply and the attic dipole.
I tuned around and there seemed to be things going on, so I found a clear frequency, 29.520MHz, and called CQ. After a few seconds jack PE1JRP called CQ on the same frequency. I called him and we made contact. He found my signal was up and down, as I did his, but he gave me a 53 report. He said that Leo PA3ELQ was waiting on the frequency and he then called, for my second contact. My report in this case was 57. They were both pretty impressed with my signal running – as I thought – 4W output.
I decided to check the H-520 Plus on my power meter and found that, far from putting out the advertised 4 watts, it was only radiating a whisker over 2. I took it down to the CB channels and even there it was giving barely 3W output. I also recalled that the web page that I could no longer find mentioned the need to turn up the deviation for 10 FM use.
I managed to locate and download a service manual for the H-520 Pro and this gave a procedure for adjusting the power. I had to turn the power control pot all the way up and I still only got about 3.6W on battery power (and just about 4W when running from the car adapter.) That’s good enough, though. From the block diagram I also was able to identify the FM modulation pot and turned that up a bit, though neither of the Dutch stations had complained about my audio. In the picture above, the red circle shows the wire loop that you cut, the green circle shows the power out pot and the blue circle the modulation control.
With the radio back together I hooked it up to the dipole again and worked Oliver DH5PK, receiving a 53 report. I am quite happy with my three contacts considering that I only opened the box after lunch and the radio spent much of the time disassembled. I saw from VHFDX.info that there was a great opening on 6 metres at the same time, but making contacts with less than 4W of FM is more challenging.
What I’m hoping, of course, is that I can make some contacts like this using the H-520 Plus as a hand held radio with a whip antenna!