AmateurRadio.com

My hopes that the TH-205E I bought on eBay would be fully operational after connecting the fully-charged new battery were dashed last night when I attached the battery, switched the radio on and got … precisely nothing. However I already had a suspicion as to what was wrong. Whilst searching for information about the radio I had found information about a design fault in early models of the TH-205 that was corrected by a modification in later versions.

The original TH-205s had a miniature 4A fuse in line between the battery and the power switch. However if external power was applied using an incorrect type of DC plug, the battery was not disconnected from the supply line. The external power could overheat the battery and blow the 4A fuse. I suspected that the fuse had blown.

In fact, I’m afraid it was probably me that blew the fuse. When I first plugged in external power from my shack GSV3000 power supply I noticed the current meter quickly blip as contact was made before the power jack disconnected the battery from the circuit. I didn’t know at that time about the fault, or that the original battery was a dead short. It probably isn’t a good idea to plug in DC power leads while the power is on, but I expect I had other radios on at the time and didn’t want to turn the power off.

I opened the TH-205E up again. I could see the wires from the battery went to a jack on the RF board which is underneath the IF board, so I had to remove the IF board to get to it. This really is a nicely made radio and it is easy to take apart. The fuse, with a ferrite bead on one of the leads, was in the obvious position next to the red wire from the battery. In the picture you can see its position marked L23 after I had snipped the fuse out (I didn’t want to remove the RF board from the chassis to unsolder it completely, so I will solder the replacement to the lead ends that are left.)

I didn’t have a miniature 4A fuse to replace it with. The official Kenwood modification is to replace the fuse with a blocking diode to prevent DC power reaching the battery pack. But they use not just any old diode, but a Schottky barrier rectifier diode which has a low voltage drop of about 0.4V. (A regular silicon diode would cause a voltage drop of about 0.9V.) Of course, I didn’t have a 2A Schottky barrier rectifier diode in my parts drawer either.

I did consider simply replacing the fuse with a thin strand of wire. Since I only have the low voltage 7.2V battery pack I don’t really want any additional voltage drop. I know about the problem so I could simply avoid it by not hot-plugging external power into the power jack. But there is always the risk I might forget and I don’t want to do the repair again, so I decided to do the proper modification.

I ordered the diode from eBay supplier PIC-Projects. I have to say that eBay has become my main source of electronic components and is a major salvation when you need an odd part like this. There is no minimum order charge or handling fee that makes it uneconomic to order less than £30 worth of stuff, and the prices of both parts and postage are very reasonable. Sometimes you have to order cheaper parts in quantities of 10 or 50, just like the “professional” suppliers like Farnell, but the prices make it worth while and it helps to build up a stock of parts for future projects. I ordered 5 of these Schottky diodes because they were only 35p each, and I’m sure I’ll find a use for the other 4 eventually.

Hopefully the diodes will arrive in tomorrow’s post and I’ll finally be able to put the TH-205E on the air with its new battery!

Cross Country Wireless will be announcing a new product at the Blackpool radio rally this Sunday. It’s an end-fed antenna consisting of matching unit, wire and an insulator, and comes in three versions for 40m, 30m and 20m.

Many users speak highly of the performance of the Par EndFedZ antennas from the USA. It will be convenient to be able to buy such antennas from Europe without the hassle and expense of import charges, and it’s good to see new amateur radio products being made here in the UK.

Sometimes you just get lucky. After I repaired the TH-205E I recently won on eBay, I was looking around for ideas on what to do about the dead battery pack and I found someone selling brand new Kenwood KNB-4 battery packs for £2.40. Well, not brand new, but never used, in the manufacturer’s box, though they would have been manufactured some time around 1993. The seller claimed that, although stored for a long time, after three full charge / discharge cycles they should be capable of holding a reasonable charge.

The KNB-4 was not actually made for the TH-205E. However due to Kenwood keeping the same form factor for its hand-held transceivers for several years the newer battery pack is able to be used in the older radio, as I was able to confirm from the W&W Manufacturing website, which claims it is equivalent to the PB-4 accessory battery for the TH-205. This is the large “high capacity” battery, with 1500mAH capacity as compared to the 500mAH of the one that came with the radio. Unfortunately it is only 7.2V which gives a power out of 1.5W according to the manual. It would have been nice to have had the 12V 1200mAH one which gives 5W out but you can’t have everything.

This is a big battery pack and it turns the already large TH-205E into a veritable giant, as the picture of it next to the TH-F7E shows. This is more than just a radio! You give your biceps a workout every time you use it. The radio will hold down your log sheets on a windy hilltop where lesser rigs would blow away and it also makes a handy weapon to beat off any assailants who might try to mug you whilst you are on the air.

Unlike the supplied battery, the KNB-4 doesn’t have its own charging socket, just contacts for a drop-in charger. So I will need to make a drop-in charger for it. I have already made a start using a piece of Veroboard with contacts made from a paperclip. The battery is charging at 240mA from the shack power supply, so after 10 hours I’ll know if it can hold a charge. If it does then I’ll make up a proper constant current charging circuit and put it in a nice box. Then I’ll have a great little, err, I mean great big 2m radio that will certainly attract a lot of attention wherever it goes!

I just had a reply from the RSGB’s ETCC regarding my NoV application. In a nutshell, applying for an NoV to use a 2m frequency for a personal short-range node is a non-starter as “it would be entirely inappropriate for RSGB to assign one of the scarce channels available within the 2M band for your personal use.” However it is possible to use provisions already in the license for “remote control of your station” to operate on any frequency I choose, without an NoV. So I have asked them to withdraw my application.

As a holder of a full UK amateur radio license, there are apparently no restrictions on frequency or power that I can use for the remote control circuit (other, of course, than those that apply to normal amateur radio operation.) However the link has to be “adequately secure” to prevent unauthorized transmissions. Typically for a legal document, no specific guidance is given as to what “adequately secure” means from a technical point of view. Limiting the power – or, perhaps more importantly, the receiver sensitivity – so that it cannot receive anything other than my own transmissions might be good enough, but I certainly would not consider it adequate security for my WiFi network (though a few years ago, before everyone got WiFi equipment, I certainly used to.)

Using a transceiver that supports DCS like my FT-817 – as I am currently doing – might be considered acceptable, though it wouldn’t take too long for someone to run through all the available codes and find out which one I am using. However I don’t want to use the FT-817 for this forever, I’d prefer to find something cheap that I can dedicate to it, and most of the cheap ex-commercial radios don’t support things like DCS. They also run too much power. So at the moment I’m not sure what the best long-term solution is.

I hate to admit it, but I can see that D-Star has the advantage here. Being digital, it knows who is calling in to the system. I presume that the DVAP Dongle has a facility to limit access to your own specific call, which would solve the security issue once and for all.

Perhaps I’m worrying too much about this. After all, the reason I’m doing this is because there is very little local VHF FM activity receivable from here. Which means the likelihood of anyone accessing my node, even if it was unsecured, is practically zero.

Postscript: I think I may have found the solution.

I went for another stroll up Tallentire Hill this afternoon with the TH-F7E. The FT-817 is tied up running my EchoLink hotspot until I can find something cheap I can dedicate to the task – I have my eye on a pair of PMR446 radios that are modifiable to 70cm.

I took along my DIY 2m rubber duck antenna and a “Black Rod” 2m 5/8 telescopic whip that I recently bought on eBay. In case you are wondering, I use an “HT Saver” SMA to BNC adapter to take the strain of the longer whip. But I am seriously considering using the TH-205E for such outings in future, if I can sort out a battery pack for it, because it has a proper BNC antenna socket and is much better suited to use with a large telescopic whip.

The 2m FM channels were not exactly buzzing with activity but I heard the GB3CS repeater 100 miles away and a GW station (Wales) in QSO. I tried swapping the two antennas for a comparison, but could hear nothing on the rubber duck at all. This surprised me, as the last time I did a comparison there was hardly any difference between it and a quarter wave telescopic, and I didn’t expect the 5/8 to make such a huge difference.

The TH-F7E is multimode on receive, so I took a listen on 2m SSB as well. I heard the GB3NGI Northern Ireland beacon much stronger than I can receive it from here. But I couldn’t hear GB3VHF from South East England at all. I haven’t heard it from home at all recently either, although it is supposed to be back on the air after a move to a new location. I guess the new location isn’t as favourable as the one it has operated from for longer than I have held a ham radio license. GB3VHF was the first amateur 2m signal I ever heard, after building my first 2m receiver, so hearing its call in Morse always causes some nostalgia.

I put out several CQ calls on 145.500 and was eventually called by Bill G3WJH in Seaton, only a few miles away by line of sight. I swapped the antennas again, and he couldn’t hear me at all on the duck. Colin, 2E0XSD then joined us, and then we were called by Richard G0IBE/P on Lord’s Seat (a SOTA and WOTA summit) so we all exchanged reports with him for chaser points. Jim G3ZPD from just south of Cockermouth then called in and worked Richard as well. By that time I was getting a bit chilly as it was a lot colder up there than it was at home, so I came back.

On my return I checked the DIY Duck on my antenna analyzer and found an infinite SWR. I pulled off the whip and the copper wire had fractured just about level with the top of the BNC adapter, which is probably the point that experiences the most bending. I guess 22SWG enamelled copper wire isn’t flexible enough to use for a helical antenna. Back to the drawing board.

If you’re a regular reader of this blog you’ll probably have observed my comments about the lack of activity on VHF hereabouts. Even though I can raise three 2m repeaters there is next to no activity on any of them. And although there are several active amateurs in West Cumbria most are “over the hill” from me so I never hear them.

Some time ago I thought about setting up an EchoLink node to make it possible to have some contacts on VHF. But when I realized how much trouble I would have to go to in order to get permission for this I went off the idea pretty fast.

My interest in this basic idea was rekindled when I read recently about the D-Star Digital Voice Access Point. Personally I’m not going to be interested in D-Star until the prices of compatible radios come down and you can buy them from other manufacturers than Icom. Besides, I like my little TH-F7E with its wideband AM/FM/SSB/CW receiver and don’t want to change it for one that doesn’t have that facility. But why shouldn’t I set up a very low power EchoLink node for my personal use so I could make some contacts using my TH-F7E hand-held from round and about the house?

I put in an online application for a Notice of Variation (NoV) to my license to run an attended simplex node – which so far hasn’t made any progress. However, fellow blogger Tim G4VXE writing about his experience with the DVAP mentioned that he made some quick enquiries via the RSGB’s ETCC as to the legality of using the DVAP without an NoV and they were not concerned about DVAPs or hotspots as long as there is no third party traffic.

I presume that D-Star, being digital, knows who is calling in to the system so you can set it so only you have access. With EchoLink you can really only have security by obscurity, using low power, a poor antenna and an obscure frequency so that it won’t pick up transmissions from anyone else. I’m not sure if this meets the official standards for not allowing third party traffic, but my enquiry to the ETCC has also gone unanswered (so far.) I got fed up with waiting and decided to go ahead.

I first tried EchoLink many years ago when it first was announced. At the time I had no way to access the system except direct from my computer. After making a few contacts that way I found that talking to hams without using any radio wasn’t very interesting, so I didn’t use it again.

Even though I am only using RF to make the link of a few metres to the radio connected to the computer, because I am using an actual radio it really feels like I am making a radio contact. I have set up the G4ILO-L node so that it doesn’t allow connections from computer-connected users. There may be disadvantages to this and perhaps some will consider it a bit unsociable but I still feel that using amateur radio at each end of the link is an important distinction that differentiates EchoLink from internet chat. I can still join EchoLink conferences and conferences may include directly connected users so talking to people who aren’t using a radio isn’t completely ruled out.

I dare say there are some who will still consider that making contacts in this way isn’t amateur radio. But the fact that my RF is not going directly from my radio to his is of no great importance as far as I am concerned. This isn’t meant to be a way to explore propagation or work DX. It really isn’t much different from using a repeater.

If I find that it is worthwhile keeping my EchoLink node running then it will create a couple of new radio projects to work on. I will need to make a new computer/radio interface and either build or modify a radio that I can dedicate to the link so that the equipment I am currently using for it can be released for other uses.

Because I signed up for EchoLink soon after it was announced I have a coveted low node ID number: 3098. I have swapped this number over to use for the link. The G4ILO-L node is running low power to a leaky dummy load so it can only be used to contact me. If you have access to the EchoLink network by radio, please give me a call. It would be great to talk to you.

By the time I had finished repairing the TH-205E the sky had cleared and the sun had come out so after tea I thought I should go for a bit of fresh air and exercise. Olga is still suffering from a chesty cough and didn’t want to come so I decided to drive over to Tallentire village and walk to the top of Tallentire Hill. A couple of weeks ago I had spent a couple of hours parked near the top making some contacts from my HF mobile station. But it isn’t possible to get right to the top by car unless you have a 4 wheel drive vehicle, because the track is rather stony. Even if you had a 4×4, there is nowhere to park off the road right at the top. The actual summit is in a small field and accessible through an unlocked gate from the track, but it is presumably private land so whilst walkers enjoying the view may be welcome, hams setting up a portable station would probably be accused of trespassing.

But on a day like today it is worth going just for the view. The picture above shows the trigonometrical point (a reference point for measuring height used by the Ordnance Survey) looking south east towards the Skiddaw range. On the larger version (click on the small one to see it) you can see snow-covered mountains beyond Keswick in the background.

The next picture shows the view south west and on the large version you can see some of the buildings of Cockermouth nestling in its valley. The big mountain on the left is Grasmoor with its steep drop towards Crummock Water. In the distance you can see the Buttermere fells.

The last picture shows the view north across the Solway to Dumfries and Galloway in Scotland. I don’t know the names of the Scottish mountains.

I would love to own the field containing this summit so I could use it as a portable site whenever I wanted, even if it meant buying a 4×4 vehicle! With the take-offs shown in the pictures the site might be quite good for VHF, so I will have to take the MFD and the FT-817 up there one day when there is a 2m contest in progress.

Today I didn’t manage to raise anyone with the TH-F7E I took with me. But despite the sun it was pretty cold up there with a stiff breeze so after a few calls on 145.500 I headed back down again.