Third-party Kenwood accessories

Ebay is a good place to buy accessories like speaker/mics and headsets for your radios. A few years ago I used it to buy a speaker/mic for my Kenwood TH-F7E. After I sold that radio I used the speaker/mic with my TH-D72. When I tried it with my old TH-205E however I found that PTT didn't work. I soon established that the reason was the genuine Kenwood accessories used a monophonic 2.5mm plug with only two contacts, tip and sleeve, for mic audio and PTT. The third-party accessories from eBay used a stereo 2.5mm plug with tip, ring and sleeve, but there was no connection to the ring. It looked as if the plug in the radio was trying to make contact in the area of the ring. This obviously was OK for newer Kenwood radios but with the 205E there was no ground connection for the PTT.

Ring and sleeve of the 2.5mm plug should be connected

My first thought was to open up the speaker mic, find the wire connected to the ring and connect it to ground. However I soon found that the cable of my speaker/mic had no wire connected to the ring at all. My only option was to try to bridge the two contacts together using solder. This I did, and the speaker/mic then worked with the TH-205E.

The Wouxun KG-699E and the Baofeng UV-3R+ also claim to use accessories with a Kenwood-compatible plug but just like the 205E I found that PTT did not work. I have just performed the same modification to the plugs on a "Kenwood-compatible" headset/boom mic and also one of the earpiece/mics that came with the Baofeng and Wouxun so that they would all work with all four radios. It is easy to do, but you need to take care as it's easy to melt the plastic parts of the plug and you could easily ruin it if too much heat is used.

Using a sharp craft knife cut away a small section of the black plastic insulation between the ring and the sleeve of the 2.5mm plug to reveal an inner metal sleeve. Open this up a bit more using the edge of a jeweller's file. Then make a solder bridge between the ring and sleeve. You need to apply heat using the edge of the soldering iron bit to the inner sleeve in order that the solder will bridge the gap. Apply the soldering iron for as short a time as possible to avoid melting the plastic insulation and destroying the plug. I used Blu-Tac to hold the plug in a steady position whilst soldering.

After you have bridged the contacts use a jeweller's file to remove any excess solder from the plug. You should also smooth the plastic insulation between the plug contacts which may have melted and bulged a bit. The plug should be completely smooth between the contacts, the solder bridge and the insulation. It should plug easily into the socket on the radio. If it needs a firm push then try a bit more filing until it goes in easily. You don't want the plug to get stuck in the radio nor for it to damage the socket contacts if force is needed to insert or remove it.

I accept no responsibility for damaged plugs or radios as a result of trying this modification. However I have done three of them now with success each time so it is possible with care. Now my "Kenwood-compatible" accessories will work with old and new Kenwoods as well as the Baofeng and the Wouxun.

Foxed

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.

A stroke of luck

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!

Broken duck

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.

G4ILO-L EchoLink hotspot

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.

Comedy in the woods

As someone who likes a walk in the great outdoors I enjoy reading accounts of people who take their radios out into the countryside for a bit of QRP fun. Today I thought I would try to emulate them. However although I did make a few contacts the attempt was a bit of a disappointment on several counts. Even the photos I took with my camera self-timer were disappointing as the operator completely obscured the radio and a picture of myself sitting on the ground at the foot of a tree apparently talking to my hand is not something I feel should be preserved for posterity on the internet.

As the CQ WW WPX SSB contest was on I thought this would be a good opportunity to make some QRP SSB contacts. The batteries in the FT-817ND seemed to be less than fully charged, and the battery endurance of that radio is poor enough already thanks to its power-hungry receiver. I decided to take my K2 instead, which would give me the benefit of 10W output and really punchy audio. So the local dog walkers witnessed the odd sight of someone setting off up the forestry track into the woods near Watch Hill wearing boots and rucksack and carrying a small Pelican case.

Fifteen minutes later they would have witnessed the even odder sight of the same person trying to throw a stick with a bit of wire attached over a tree branch. Now I know why the MP-1 was invented! After about ten minutes of persevering I managed to get the wire over a branch about 12ft high. The stick hung down the other side tantalizingly out of reach and I spent the next five minutes trying to hook it with the end of my walking stick so that I could pull the wire taut and secure the end of it.

I had previously prepared two lengths of wire for my portable antenna. One is about 22ft long, and has a few feet of nylon cord attached to the end for tying to sticks or rocks to hurl over branches and then secure in position as the radiating element. The other is about 16ft long and is laid out along the ground as a counterpoise. They are fixed to the red and black terminals respectively of a BNC to binding post adapter which is plugged in to one of the antenna sockets of the K2. The reason for the selection of these particular lengths is that I seem to recall them being suggested by Elecraft as good lengths to use with the T1 portable auto-tuner.

There are no picnic benches or tables in the forest so I just sat down on the ground and used the Pelican case as a table. The K2 sat on that, and the antenna ran off directly behind it at about a 45 degree angle, over the tree branch and down a few feet at the other side. The counterpoise ran off at right angles.

I switched on the K2 which was still on 15m from my last mobile outing and immediately heard many strong signals. However signals didn't seem as loud or as plentiful as I would have expected during a major contest. I pressed the Tune button and the K2 ATU whirred away and finally delivered its verdict: 9.9:1! It couldn't match it!

I didn't hear anything on 10m so that wasn't worth trying. I got a usable SWR on 17m but there was hardly any activity on that band. On 20m the best SWR was between 2:1 and 2.5:1, and on 40m I managed to get 1.5:1. Unfortunately the K2 is a bit SWR-sensitive - something I never noticed during the years I used it as my main home station when I could always get a 1.2:1 or better - and it flashed up Hi Cur (high current) when I tried to use 10W on 40m. So I had to back my power down to use that band, which didn't help matters.

I made nine contacts in less than an hour's operating, which included a break to eat my sandwiches:

1130   7.113  ON5SY   59  609  59  001
1131   7.123  PI4Q    59  801  59  002
1133   7.167  PA6Z    59 1022  59  003
1138   7.123  SP4TKR  59 1130  59  004
1143  14.286  YL6W    59 2416  59  005
1212  14.292  HG1S    59 1821  59  006
1215  14.315  OG6N    59 1450  59  007
1217  14.321  SN2B    59 2772  59  008
1218  14.335  SP9LJD  59 1876  59  009

But these were not nice easy contacts like I made using the same radio and the same power from the car using the MP-1 antenna. My thanks, as well as my apologies to the stations that wasted valuable minutes trying to pull my call and serial number out of the ether.

It was getting a bit cold and I felt a few spots of drizzle so I decided to call it a day. I think I'll stick to taking VHF on hikes in future.

DIY helical antenna for 2m

A few weeks ago I made a rubber duck helical antenna for my TH-F7E. I didn't get around to writing about it at the time, plus it took a while to get some reports of its performance.

Well, it works extremely well, and I have just added a description of how to make it to the main G4ILO's Shack website. See A DIY Ducky for 2m.

Charged up

I recently sold my Yaesu VX-8E because the lack of APRS RF infrastructure in this part of the world rendered that part of its functionality fairly useless and I didn't need two FM hand-helds. My Kenwood TH-F7E is a more useful radio to me because of its ability to receive CW and SSB. The only thing I didn't like about the Kenwood was the lack of a drop-in charger base. To charge the radio you have to uncover a charging socket and then plug in a lead from a wall-wart charger. That might seem like a small inconvenience, but having to crawl around on the floor plugging in the charger, then thread the charging cable through to a safe place to stand the radio while it charged was a bit of a chore. Most hand-helds offer a base charger as an option; even the cheap and nasty Chinese Jingtong had one. I think Kenwood missed an opportunity to sell an accessory here.

I was sure I wasn't the only one lamenting the lack of a base charger for this fine little radio so I posted a question about it on QRZ.com and was pointed by Mel KS2G in the direction of W & W Manufacturing Company of Hicksville NY, who make a range of replacement batteries and chargers for two-way radios and other devices. They offer battery packs for most amateur radios, including the Kenwood TH-F6A which is the US version of the TH-F7E and all of them are charged using a drop-in charger.

The company didn't respond to attempts to contact it via the contact form on its website, but Mel very kindly phoned and obtained an email address for a helpful lady named Flossie, with whom I placed my order.

It wasn't exactly cheap. Since the stock Kenwood battery doesn't have contacts for base charging I had to purchase a replacement battery as well as the charger unit. By the time I paid VAT and tax collection tax it came to half as much as the actual radio.

The new battery has a 2000mAH capacity compared to the 1500mAH of the standard version. The charger is a universal unit and takes plug-in "cups" for different radios, so if I ever sold the TH-F7E I could keep the charger and just buy a "cup" for whatever replaces it. I was a bit disappointed to discover that when placed in the charger the radio faces to the side rather than the front. It doesn't really matter, since you can't use the radio while it is in the charger, and perhaps they do that to discourage the temptation to switch it on. But it would look better if it faced the front.

Also supplied with the charger was a European 220V switched mode 24V 1A power adapter. I really didn't need that, and would have liked the option to save some cost by not having it. I haven't checked to see if it makes any of the usual switched mode warbly noises and broadband hash. I generally avoid switched mode power supplies at all cost. For batteries up to 7.2V which the TH-F7E is, the instruction sheet states that the charger will run from 15V so I am actually running it from my Diamond shack supply that powers my K3, which normally runs at about 14.2V. It worked fine, and charged the new battery in a couple of hours.

I am very pleased with this smart if rather expensive accessory, which will help me make the most of the TH-F7E by keeping it nicely charged up.

Remembering the Belcom LS-202E

I'm not really cut out to be an award chaser. You can too easily end up with the tail wagging the dog, staying in the shack on a fine, sunny day just to be near the radio because you know that someone is going to be activating a rare island or whatever.

This weekend I had hoped to catch some activations of Wainwright summits for SOTA and WOTA. But I had to go out. The activator was using 2m SSB, and an FT-817 was too bulky and conspicuous to carry around with me. So I took to wondering, not for the first time, what a shame it is that the Kenwood TH-F7E (TH-F6A to you Americans) cannot transmit SSB as well as receive it.

Back in the 1980s when, despite the lack of sophistication compared to today's technology, ham radios somehow seemed more exciting and innovative, you could buy radios from small manufacturers like Mizuho, Belcom and Shimizu that offered something out of the ordinary compared to the offerings from Yaesu, Icom and Kenwood.

One such product was the Belcom LS-202E, a 2m hand-held transceiver that worked on both FM and SSB. It was slightly larger than a 2m FM hand-held of the time, with 1.5W output (fairly standard for those days.) The frequency was selectable using thumbwheel encoders as in Icom's highly popular FM hand-held, the IC-2E.

I had one of these radios and had quite a lot of fun with it. I was also trying to break into journalism at that time so I wrote a review of it which was published in the short-lived independent ham radio magazine "Amateur Radio". If you are interested, you can see a copy of the review.

Sadly, the LS-202e wasn't a keeper. The output on SSB was quite low and there appeared to be no speech compression or ALC so you couldn't make the best of that 1.5W. Stations who found you weak on SSB often heard you better when you switched to FM.

Another problem - which I didn't discover until after I'd written the review, so it wasn't mentioned - was that the synthesizer tended to go out of lock if the radio was cold. And it usually is cold out of doors in this country, so several trips out to work SSB from the hilltops proved abortive. The radio went back to the importers two or three times to try to make it work right. But they never really succeeded, so in the end I sold it.

I still think the basic concept was a great idea. And I'm surprised that none of the radio manufacturers have tried again to make something like this using today's much improved technology. A multimode hand-held you could slip in a pocket covering VHF and even HF with a couple of watts output would have me plunking down my money faster than you can say "Mastercard." How about it Yaecomwood?

HT Saver

One of my ham radio pet hates are those SMA sockets used to mount the antennas on all modern VHF/UHF handheld radios. They are very fragile, and not designed for the repeated changing of antennas that most of us go in for. I don't see any justification for using them except on those very slim credit card sized handhelds which are pretty fragile devices anyway. But all the manufacturers now use them so we're stuck with them.

With the Kenwood TH-F6A / TH-F7E you really have no choice to switch antennas if you want to make use of the shortwave receive capability because the VHF/UHF antennas are useless on shortwave. Last week I made a shortwave receive antenna for it which I called the Wonder Whip. This antenna works on 2m and 70cm transmit as well, but it is a bit long to leave on the radio when carrying it so I still need to remove it quite frequently.

I made the Wonder Whip on a BNC connector so I needed to use a BNC to SMA adapter to use it on the radio. The trouble with the readily obtainable BNC to SMA adapters is that they do not have a large base that clamps down on to the body of the radio for extra support like the supplied antenna does. This means the SMA adapter takes the full force of any sideways knocks. It is very easy to snap off, as many HT owners have found to their cost. So when I saw some SMA to BNC adapters with a large base being sold very cheaply on eBay by a Hong Kong trader called PartsPipe I ordered a couple of them. The pair cost less than £5 including postage and they arrived in just over a week which is one of the quickest shipments I've had from the Far East.

To my disappointment I found that when screwed on to the TH-F7E as far as it would go there was a gap of about one millimetre between the base of the adapter and the radio. Fortunately I found a steel washer that slips over the SMA antenna connector and fills the gap. I will probably be able to get a matching brass washer at a local DIY store but the steel one will do for the moment. Now any BNC antennas will be fully supported by the body of the radio.

If I use only BNC base antennas from now on I can leave the adapter permanently in place and will not have to keep connecting and removing things from the SMA socket, which I think is rated for only something like 100 connections. I think this is a much better solution: BNC connectors are more robust and in the unlikely event you do get a problem you can just replace the inexpensive adapter - which is why I got two of them!

Now I just have to decide what to do with my arsenal of SMA-based antennas. Probably flog them on eBay!

The Wonder Whip Mk1

I have just completed the first version of what I shall call the G4ILO Wonder Whip. It's a portable HF receiving antenna for the Kenwood TH-F7E and TH-F6A that can also be used for transmit on 2m and 70cm. It allows you to use the radio's wide band receive capability to listen to the HF bands 20m - 10m plus 6m.

The project was not without its complications. In fact it took three attempts to get the antenna to work to my satisfaction. The antenna is a base-loaded short whip with tapping points on the loading coil to resonate the whip on the amateur bands and a fly-lead with a small alligator clip to select the appropriate tap.

I first thought that it would be possible to identify the best tapping point by scraping away some enamel from the coil and touching the fly-lead to it using an insulated handle. The problem is that the bandwidth of such a short antenna is very narrow and the resonant point depends very much on what sort of a ground you have and whether anything - such as my hand - is in close proximity to it. So it proved very difficult to find a tapping point that gave consistent results. What might seem the right point on the antenna analyzer can be way off when using the TH-F7E or the FT-817.

I had to realize that what I was trying to make was a receiving antenna for the TH-F7E that would be used without any ground or counterpoise, and forget about trying to get a good SWR when the antenna was put on my FT-817. I was eventually able - more by luck than calculation - to find tapping points for each of the bands. On HF the antenna should be used with the 48cm telescopic whip fully extended, but it can be fine tuned by retracting sections of the whip until you hear the loudest signals or noise. Retracting the whip provides quite a range of adjustment - enough to allow 12m to be covered using the 15m tap. As this antenna is intended for receive only, getting an exact match is not essential, and you should hear stations without needing to adjust the length of the whip.

The photograph above gives the critical constructional details. The tapping points were created by making a loop of bare wire and twisting the ends together to form a tag to which the wander lead can be clipped when selecting the band in use. Because the tapping points were found by trial and error I wound one continuous coil of enamelled wire and then scraped away a bit of enamel from a turn of the coil next to each tapping point and soldered it using a fine tipped bit. This was a little tricky.

If I was making another antenna to this specification I would install the tapping points first and then wind each section with the indicated number of turns, scrape the enamel and loop the wire round the tapping point before starting the next section. You could even wind each section of coil separately, testing each section for resonance before you start the next one. This would make it easier to adjust the number of turns if the resonant point does not fall exactly in the right place.

The telescopic whip I used is 19 inches (48cm) in length, in other words a quarter wave on 145MHz. In the 2m/70cm position the loading coil is bypassed adding the length of the wander lead to the length of the whip. The top two sections of the whip should be retracted to compensate for this. I have found that when using a hand-held transceiver the best SWR on 2m is achieved with a whip length that is 5 - 7 cm longer than a true quarter wave. This antenna allows you to achieve that.

After testing the antenna, the Wonder Whip was finished off by wrapping the coil in black self-amalgamating tape. This helps protect the coil and gives the antenna an almost professional appearance.

I am quite pleased with this antenna. It is a pity that I cannot make it cover 40m and 80m as well but that would require a considerable number of extra turns on the coil and would make the antenna somewhat unwieldy.

I also fear the plastic pen body is a bit fragile and would be rather easy to break. I broke it in half once by applying too much heat while soldering to one of the tapping points which melted the plastic - fortunately it stuck back together again when the plastic cooled, but I may have weakened it. I would like to make a more robust version if I come across some suitable materials. The current version at least has the advantage of light weight, and does not put too much stress on the SMA connector of the TH-F7E.

A portable HF receiving whip

Most VHF-UHF HTs (or hand-helds, as they tend to be known over here) nowadays provide receive coverage of the HF short wave bands, though only in AM mode. The Kenwood TH-F7E (or TH-F6A in the USA) is unique in that it can receive LSB, USB and CW modes as well. It doesn't use a narrow filter in those modes, so reception is far from optimum, but it is still a nice little radio that allows me to listen to what is happening on HF when I am away from the shack. Or it would be, except for the fact that it needs a proper antenna - or at least a length of wire - to receive anything. There is an internal ferrite bar antenna but it is ineffective on the amateur bands. Consequently I have made little use of this facility, and had got to the point where I was thinking about selling the radio.

A Miracle Whip or Wonder Wand works fine with the TH-F7E, but it doesn't actually fit on the radio so you need a cumbersome collection of adapters and cables to use it. What I wanted was something like a mini ATX Walkabout - essentially a base loaded whip with tapping points on the loading coil for each of the bands. This afternoon I decided to see if I could make something like that.

I cut a crimped-on BNC connector off the end of a cable, leaving about 1cm of cable protruding from the end of the sleeve. I then cut away the jacket and exposed braid to leave just the insulated centre wire. I stripped a small piece of insulation from the end of this and soldered to it the end of a 5m length of 38SWG enamelled copper wire.

Next, I found a plastic ball-point pen whose body fitted nicely over the crimped end of the BNC connector (a bit of insulating tape helped make a good interference fit.) This ball point pen body conveniently had a small hole at the other end through which I dropped a fixing screw for a short telescopic whip antenna. A blob of super-glue held the screw in place since I didn't have a screwdriver long enough to reach the screw head inside the pen body. Once the glue had set I attached the telescopic whip with a solder tag between it and the pen body. Once tightened, the tag was bent down flush with the pen body.

I drilled a small hole in the pen body that would be the same height as the point where the 38SWG wire was soldered to the co-ax centre, then fed the end of the wire through the hole. When it was all the way through I pushed the pen body on to the BNC connector and secured it with another dap of super-glue. I then wound the wire onto the pen body to form a coil. When nearly all of the wire was wound on, I secured the last few turns with a strip of insulating tape, stripped the enamel from the end and soldered it to the solder tag. I then had an antenna that looked like the photo above.

Miraculously - since the mathematics of designing a base-loaded antenna is beyond me and this had been pure trial and error - I ended up with a whip that with a ground wire attached can be tuned to a good match on 20m just by adjusting the length of the telescopic whip. Although I intended it as a receiving antenna it will be interesting to connect it to a QRP transmitter and see if I can make a contact with it.

The next stage of the project will be to try to establish tapping points on the coil to allow coverage of 17m, 15m, 12m, 10m and 6m. I really had hoped to get coverage of 80m, 40m and 30m as well, but obviously I would need a lot more turns on the coil to achieve this. I have a reel of something like 42SWG solenoid wire so I may try to make another version using this. Alternatively perhaps the lower section could be wound on a short ferrite rod to get more inductance with fewer turns. There is a lot of experimentation to be done with this.

One aspect of this antenna that I'm not too happy about is that I have to use an SMA to BNC adapter to fit it to the TH-F7E. This adapter doesn't clamp down to the body of the radio for additional mechanical strength, so the radio's SMA connector is vulnerable to stress and even damage if you knock the antenna.

Why hasn't any manufacturer come up with a ready-made version of what I am trying to make? There are plenty of amateur HTs and hand-held scanners that cover the short wave frequencies. Surely there would be a market for it?

Dead repeaters

I live in a VHF black hole. There is almost no activity here on two metres. I can access two repeaters from home: GB3AS and GB3DG. Most of the time there is no activity on either them, and if you put a call through them it goes unanswered. It's a bit disappointing. One of the reasons I bought the TH-F7E was to get me to go out for a walk and get some exercise. The possibility of making some contacts while I was out was meant to be a bit of incentive. But there is no-one to talk to.

A few years ago the Isle of Man repeater GB3GD used to be a good signal from the hilltops round here, and through it you could have contacts with England, Wales, Scotland, Northern Ireland, the Irish Republic and, of course, the Isle of Man. But nowadays you can barely hear it.

TH-F7E is here!

My TH-F7E is here. Unfortunately I can't play with it, as the first thing you have to do is charge the battery, which takes 6.5 hours. Well, I can always read the manual!