Posts Tagged ‘GP300’


My FoxTrak APRS tracker board is now installed in a plastic case, together with 4 x AA NiMH cells which provide near enough 5V to power both the tracker and the GPS. Two mini-DIN sockets on the side of the case allow connection to a PS/2 GPS or PC for configuration, and to the radio. Now I just have to make up interface cables to my radios and install the top half of the case after drilling it and installing the charger socket for the battery.

I purchased a GlobalSat BR-355 PS/2 GPS receiver on eBay and it works very well indeed with the FoxTrak, much better than the GPS in the Yaesu VX-8GR. It gets a fix within a couple of minutes when it is sitting on the shack window sill, unlike the VX-8GR which often never finds its position indoors at all, and the position remains rock steady unlike the Yaesu which tends to wander about.

I wanted to make a cable to use the tracker with my Motorola GP-300 hand-held. However I found that the jack plugs you can buy from component suppliers have too wide a body and can’t plug all the way in to the sockets on the top of the radio, which are a bit recessed. It appears that you need to use a proper moulded plug with the two pins. A cable for the Motorola GP-300 is available on eBay, so I’m waiting for one to arrive.

I was luckier with the old Kenwood TH-205E. The sockets for external mic, PTT and speaker are flush with the top of the case and the cable I made up using separate plugs works fine. Lacking a deviation meter I adjusted the audio output so the braaps sounded as loud as those from other APRS stations.

However, the TH-205E is a bit big and heavy for portable use, especially as it has a high capacity Ni-Cad battery pack (the original being as dead as a dodo.) I had expected the cable to work just as well with the little TH-F7E, because the Kenwood speaker-mic I have works with both radios. But although PTT works on the smaller Kenwood there is virtually no audio. I have to turn the audio up to maximum on the FoxTrak to get enough signal to be decoded by my gateway, and the deviation is still too low.

I am completely foxed by this problem. The only thing I can think of is that it is something to do with using two separate plugs and not the proper moulded two-pin connector used by the speaker-mic. Perhaps, as with the Motorola, the wide body of the plugs is preventing them from going far enough in to disconnect the internal microphone, which is shorting out the audio. Unfortunately the only way to prove this hypothesis would be to buy a cheap Kenwood speaker-mic or programming cable on eBay and cut the cable off. It’s a bit of a gamble, as I don’t know for sure if that’s the solution, and the cables in some of those cheap mics from China are very poorly screened so I could end up with an RF-induced problem.

Out on the fells with Murphy

This morning there was a lot of Sporadic-E about. I spotted – and was spotted by – several stations on 10 metres. I didn’t hear any normal activity on 10, but there was some on 6m and I made a couple of contacts. However the weather was gorgeous, too good to be indoors whatever the propagation, so I took some coffee, a sandwich, the Motorola GP300 and the Intek H-520 Plus and set off to do a couple of Wainwrights.

I parked in a lane between Mockerkin and Lamplugh and walked along the track above Hudson Place. You are high above Loweswater here and can enjoy some wonderful views for no climbing effort at all. Then it was up over the grassy fellside to Blake Fell (WOTA LDW-140.)

There was a strong, cold south westerly wind so I hunkered down in the stone wind break on the summit to have my lunch. A retired couple over from Newcastle joined me and wanted to chat, so it was not until they had gone that I was able to get the radios out. I put the telescopic 5/8 antenna on the GP300 but the wind was so strong it was blowing it almost horizontal so I switched to the helical. I was using the speaker mic, but no-one replied to my calls and I realized that the rig was not going to transmit. That was the first of my troubles.

Dispensing with the speaker mic I called CQ and made contact with Keith G0EMM in Workington. After we moved down to 145.450MHz we were joined by Colin 2E0XSD and Derek 2E0MIX.

The guys knew I had recently acquired a 10m FM H-520 hand held and anticipated that I would want to try using it. I decided it was too windy to try the 4 foot antenna so I used instead the short one that came with the rig. As soon as I pressed the PTT the rig shut down and re-started. Keith suggested there might be something wrong with the batteries, and that seemed to be the case as when I reduced power to 1 watt the rig didn’t shut down but the battery state indicator went from all bars to no bars. So that was the second of my troubles.

As per usual, I had my digital camera with me to try to take a picture, using the self timer, of me at the summit. But either I got only my legs, or only my head, or the wind moved the camera so the picture was blurred. After that, every picture I took with the timer was grossly over-exposed (although if I took a picture manually it was alright.) That was the third of my troubles, as a consequence of which you are spared a picture of G4ILO this post.

After that I set off for what I thought was Burnbank Fell (WOTA LDW-183). My target was a prominent summit with a large stone summit cairn, about 100m lower than Blake Fell. I reached it in about 20 minutes, put out another CQ call and was contacted by Keith and Colin. They had been tracking my position using APRS and informed me that it looked as if I was on Carling Knott. I was sure I wasn’t, as there is no other Wainwright summit in the area. Carling Knott isn’t a Wainwright, and the one I was on looked like a pretty important top that I’m sure Wainwright would have given a page in his Guide to the Western Fells.

I had hoped to descend from there down to the lake but I couldn’t find the path – the fourth of my troubles – so I ended up re-tracing my steps, though avoiding the actual summits to save a bit of climbing. As I walked back over the grassy hill over which I had walked a couple of hours earlier I put out another call on 2m and was answered by Keith and Colin again, who both confirmed that my APRS position now put me on Burnbank Fell! So this featureless grassy hillock that I had barely noticed on the way up is actually a Wainwright, while the higher Carling Knott with its impressive summit cairn isn’t. I’m sure AW had his reasons…

Back at the shack I found there was nothing wrong with the H-520’s batteries, but it doesn’t seem to like the short whip antenna, which of course I never tested it with before I went out. If I had been able to use the four footer it would probably have been fine. The GP300 worked perfectly with the speaker mic, and I couldn’t reproduce the problem with the camera self-timer either. As for activating the wrong fell – I guess I should look at the map a bit more closely.

But it was still a gorgeous day and a wonderful walk, even if it was a bit windy and Murphy was my invisible companion.

Quiet day

Not much happening today. I have been WSPRing on 10m with 5W but heard nothing and have been spotted just once – by OY1OF on the Faroe Islands.

Yesterday evening I was receiving EA4SG in Spain but he was running 20W. I upped my power to a similar level, and was spotted by G0HNW and M1AVV in the early evening. I left the system running all evening but after it was dark I noticed my neighbour’s security lights were coming on at the start of my WSPR transmissions. Not good when you are trying to maintain a “stealth” station!

Before I started with WSPR today I got out the old DOS laptop and the Motorola programming software to make a few changes to my GP300 configuration. I reduced the squelch threshold slightly, reduced the power from 6W to 5W which should help the battery endurance more than it will affect reception of my signals, and I programmed the radio for 16 channels.

Now there are 16 channels it’s difficult to remember what they all are so I made a paper scale to go under the tuning knob which shows the 2m channel numbers or repeater calls. I had to use the magnifying headset to do the very small lettering and I can only read the scale with my reading glasses on – which I don’t when I’m out and about. But I couldn’t read the channel numbers on the original dial scale either so I’m not actually any worse off. I used to have great eyesight – this is what happens after spending most of your life in front of a computer!

The battery charger that wasn’t

I’ve bought loads of radio and electronic stuff from Hong Kong and China on eBay and most of it has been okay. But I’ve had the occasional duff purchase, like the stubby dual band antenna allegedly made by Diamond which I’m pretty sure was a fake.

I bought a Motorola GP300 radio body at the Blackpool rally a couple of weeks ago but I needed accessories like a battery pack, charger and speaker mic. Ebay was the obvious place to look for them. The 1800mAH NiMH battery pack was fine, and a good price. The speaker mic is obviously a clone of the original Motorola design but a lot less solidly made, but I have received good audio reports using it so no complaints there. However I was a bit suspicious about the “overnight charger” purchased from RadioFactory because after 6 hours of charging the battery pack was really hot.

The GP300 battery ran out while I was on Watch Hill this afternoon so I need to charge it back up, but before I do I thought I would take a look inside. The case is conveniently designed so that you can pull it apart after pushing back four flexible plastic clips. The circuit board then just lifts out. I got quite a surprise after I did!

The top of the circuit board is printed with component outlines but most of the components marked are not present, and many of the components that are there don’t correspond with the outlines. In the middle of the board is an unidentified component that looks as if it has overheated.

On the underside of the board, again, most of the components that are supposed to be there are missing. Some of the tracks are bridged together with solder blobs or a wire link. I haven’t got the time or, more importantly, the clarity of mind to work out exactly what the circuit on the board actually is, but it doesn’t look much like something capable of charging a 7.2V battery pack from a 12V wall wart.

I’m not quite sure what to do about this. I have the plastic case and the charger contacts, which as I know from the charger I made for the TH-205E are the hardest parts of a battery charger to make. So I could simply make up another constant current charger circuit on Veroboard and put it into the existing case. Or I could simply cut my losses and buy another Motorola charger from a reputable source. I’m sure that one of my readers will know of one.

Watch Hill

It was a fine sunny morning. I remembered – having worked a couple of activators yesterday – that it was the Summits On The Air (SOTA) Activity Weekend, so I thought we would go to Watch Hill, G/LD-054, and see what I could work from there.

Compared to all the people who have slogged up thousands of feet to get to their summits Watch Hill is a bit of a cheat. It’s a 15 minute stroll from the nearest car park, with only the last couple of hundred metres being a bit steep. But as it is a less than 10 minute drive from home it’s a popular walk for Olga and I and we often take a picnic lunch up there.

I took with me the Motorola GP300 and the Kenwood TH-205E with the 5/8 telescopic whip. Getting the 4 contacts required for a SOTA activation can be a challenge from there, as it is a fairly low hill and there isn’t a huge amount of 2m FM activity round here. Many have tried and gone away disappointed. However on Sunday morning the Workington Radio Club has a 2m FM net. I broke into that and soon had 5 contacts logged. Future would-be activators of Watch Hill please note.

I also made a summit to summit with 2M0NCM/P on Lamachan Hill SS-061 in Dumfries and Galloway, and then caught Geoff G4WHA/P who was just stopping for lunch on Wether Hill, WOTA summit LDW-103. I wouldn’t have heard him from home, so that was a nice WOTA chaser point for me.

The Motorola produced great, loud audio which is ideal for listening on a windy hill-top, and I got an unsolicited report of “BBC quality” audio on my transmissions, so it seems to be working well. However I noticed that some stations seemed to chop up a bit. I’m not sure if they were weak and the squelch is very sharp or whether their deviation is a bit wide for the Motorola IF filters. I will need to investigate this further.

The TH-205E came in handy after the Motorola gave a few beeps to warn, I think, that the battery was exhausted. There is no visual indication of battery state on the Motorola so I had no advance warning. The station I was working said that he could hear a carrier but no audio after the battery went. Still, it does seem to be a nice radio and rugged enough for this type of use.

GP300 success

Two more items for the Motorola GP300 arrived from Hong Kong today, an 1800mAH NiMH battery pack and a charger. I’m a bit dubious about the charger. I put the battery pack on the radio and started charging it, and when I checked six hours or so later the battery pack and radio were really hot. I would have thought the charger should have shut off by that point. So I’ll have to watch the charge times.

I wanted to have another try at programming the radio using a newer version of the software from the hampedia site but when I started up the Toshiba Satellite 1800 and tried to go into the Bios to re-enable the cache (which I disabled yesterday to slow the computer in the hope of overcoming the programming problem) it asked for a password. Somehow when I disabled the cache I must have accidentally enabled a Bios password, but of course as I didn’t do it intentionally I have no idea what the password is. I tried to start Windows 98SE but it took 20 minutes to load and was unusable once it eventually did. So that’s that.

But in the end another solution was found. I registered with the forum at the curiously named Batwing Laboratories website, which apparently is the fount of all knowledge for all things Motorola, and posted about my problem there. Tom in D.C. (W2NJS) replied that the DOS in Windows 98SE wouldn’t do, I must use MS-DOS 6.22.

Now I was programming micros since before IBM invented the PC. I’ve read Ray Duncan’s “Programming MS-DOS” from cover to cover several times so I was pretty much an expert on the subject at one time (though I’ve forgotten just about all of it now) and I would never have thought that there were any differences between the two versions affecting the use of the serial port. But Tom was firm enough in his advice that I downloaded an MS-DOS 6.22 boot CD image and made myself a boot disk. It wouldn’t recognize my Windows 98SE partition so I had to vape that, reformat under MS-DOS 6.22 and set everything up from scratch. Fortunately I still remembered enough about things like config.sys and autoexec.bat to get it to work.

I reinstalled the programming software, connected the interface, and this time I got “Radio Communication OK!” Tom in D.C. probably heard my cheers from there. So I was finally able to program eight 2m frequencies into the radio – five simplex channels plus the three local repeaters – and have just completed two QSOs on the GB3LA repeater from inside the house using a quarter wave telescopic whip, so it works!

The Motorola GP300 seems to work a bit differently to ham radios. For example, there are three power levels but the power level is fixed for each channel, so if I set High power in order to access a repeater from home I can’t reduce the power to Low to save batteries when I’m in line of sight of it from a hilltop. And if you want a Scan function you have to dedicate a channel to that.

Possibly there are some tips for setting up these radios for ham band use that I’m not aware of yet. But even if there aren’t, it’s still a nice radio for £1. Even if by the time you add in the cost of the programming interface, the battery pack, the charger and the adapter that converts the Motorola proprietary antenna socket into a BNC it ended up costing more like £40.

Motorola programming frustration

The renovation of the G4ILO shack is about half completed. The wood for the new shelf module needs another coat of paint, then it can be built and everything put back in again. Unfortunately old age is catching up with me and I am just sooooo tired and have so many aches and pains from all the work so far that progress is (literally) painfully slow. I missed the talk on SOTA at the radio club on Monday evening because I would probably have just fallen asleep!

After the flying hiatus some items I ordered from China and Hong Kong are starting to filter through including the programming interface for the Motorola GP300 radio. It is a Maxton RPC-M300, pictured on the right, and it came with a CD containing the necessary programming software. (The software can also be found on the hampedia website, so please don’t ask me for a copy.)

The software runs under real MS-DOS, not a DOS window. My researches had already established that it doesn’t run properly on newer, faster computers, so I installed it on the oldest PC I had available, a 2002 vintage Toshiba Satellite 1800, which happens to have both a floppy drive and a serial port. It doesn’t have network access, so getting anything on and off it is a bit of a headache, but I still have a copy of a Windows 98SE install CD and the required boot disk, so I was able to use that to provide the MS-DOS access.

No instructions came with the interface. It’s obvious that it clips on the back of the radio, and the red and black wires are used to provide power, but there is no indication of what voltage to use. Some DIY interfaces that have been published use a 9V battery so I set the variable power supply to 9V. The other two plugs – one like a telephone plug and the other a 3.5mm stereo jack – are presumably for other radios that the interface can be used with, so I left them dangling free.

I applied power and the red light on the interface came on. I then tested communication between the software and the radio, and the green light flashed for a few seconds, then I got an error #2 “No acknowledgement.” I tried again, this time after switching the radio on with the volume control, but then I got an error #7 “Invalid opcode.”

I had read that the programming software may not run properly on any Pentium computer at all, due to its use of timing loops. One of the suggestions to slow a faster computer down is to disable the CPU cache, so I went into the Bios and did this. This didn’t make any difference to my inability to program the radio, but it did make Windows 98 take 20 minutes to load and be unusable once it has done so. Unfortunately I discovered this morning that I had somehow managed to set a password on the Bios which of course I don’t know, so now I can’t get back in to the Bios to re-enable the cache. 🙁

It seems as if I will have to give up on the idea of programming this radio myself. My only hope now is that someone at my radio club is able to help with this. Unless anyone has any other suggestions?

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