Posts Tagged ‘TH-F7E’

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.


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.

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