Bad ground

If you read any of the text books on setting up an amateur radio station they always tell you that you should connect everything to a good RF ground. What none of them tell you is how you get a good RF ground if your shack isn't located on the ground floor of the building. I have always tried to use co-ax fed antennas that are properly matched so that there is no RF on the shield of the cable to cause any problems. But in a nod to the text books I have always grounded everything to the copper pipes of the central heating system, which is the nearest thing to ground available in the G4ILO shack.

Today I noticed that 15m was open and there was quite a bit of activity on PSK31. I put out a call and was alarmed to find that my PSK IMD Meter was showing an IMD of around -22dB. Jan, UT5CO replied to my call, so I completed the contact and then investigated. The problem was only bad on 15m, and only when using the magnetic loop antenna.

First I tried my usual solution, which is to put clamp-on suppression ferrites on any cables that might be causing RF to get into the K3. I thought that solved the problem, but I was mistaken. I tried various other things without success and had reached the point where I thought I would have to avoid using the magnetic loop on 15m. (To my surprise, I found that my multiband dipole, which doesn't have a 15m element but is linear loaded on 40, can be matched by the K3 on 15m and works just as well as the loop, so that wouldn't have been too big a hardship.)

On a whim, I disconnected the ground wire from the K3 and the IMD immediately went down. Not all the way to -34dB which I got using the dipole, but around -32dB. I did some checks and there did not appear to be any ill effects on other bands. So the ground wire has been permanently removed. Needless to say, by the time I had got this sorted out, 15m had closed!

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.

Why Elecraft should terminate its reflector

I have been a subscriber to the Elecraft email reflector almost continuously since 1999 when I ordered my K2, and for most of that time have found it useful. But over the last few weeks I have come to the conclusion that the best thing the company could to do would be to close it.

The reflector has been a good forum for communication between Elecraft and its customers. But postings about the K3 have swamped postings about other Elecraft products, making it a frustrating forum for kit constructors. Now that the K3 has reached maturity there are very few useful suggestions for improvements to be made about it. Instead, most postings now seem to be nit-picking complaints, which often result in ill-tempered responses from others who feel there is nothing to complain about, which generate further ill-tempered replies suggesting that some people don't use their radios and don't even understand the problem.

The overall impression conveyed to any would-be K3 purchaser who subscribes to the reflector is that the K3 is a very flawed radio with some serious problems. That isn't how I see it. The K3 isn't a perfect radio but I don't think there is anything better around at the moment.

The obvious thing to do would be to unsubscribe. Except for the fact that the reflector is the only way to keep up to date with news from Elecraft. If you want to know about new firmware releases and what's in them, or know when new products like the P3 panadapter are ready to be released, the only way to get that information is to subscribe to the reflector. I have repeatedly suggested that Elecraft should create an "elecraft-announce" mailing list that contains only news from the company, and they have equally repeatedly ignored my suggestion.

Because the Elecraft reflector is an email list, every subscriber receives a copy of every posting, including every complaint, whinge, gripe and fanboy denial of the criticisms. This tempts everyone to have their say in topics regardless of whether their contribution is useful. Even if you resist the temptation to comment, reading of these "issues" sows seeds of doubt that perhaps there really is something wrong with the radio after all.

I think the reflector is turning into a public relations disaster for Elecraft that also serves to unnecessarily alarm its current and would-be customers. I think the best thing to do would be to put it out of its misery. But I doubt they will take my advice on this either. :)

Shopping in Keswick

It was a beautiful morning, the sun was shining from a cloudless blue sky and it felt warm, although the temperature was just above freezing. Olga and I decided to go to Keswick, which is one of my favourite places in the entire world, and where I'd live if property prices weren't astronomical. Though being a conservation area in a national park and surrounded by mountains it is probably one of the worst locations for ham radio imaginable.

I thought we would go for a stroll through the town and have a coffee and a look in the shops, which we did, but I also spent rather a lot of time standing around being bored while Olga looked at clothes. I loathe shopping, and would buy everything possible - including groceries - online if I could. If I decide I need something I generally purchase the first thing I see that will do the job. Olga has to examine every possible candidate and then agonizes over the decision for hours. Consequently we rarely buy anything for the house requiring a joint decision as I have usually lost interest in buying anything after my first couple of suggestions have been rejected.

In Keswick we saw very little evidence of any damage caused by the November floods - unlike the devastation that occurred in our home town Cockermouth. We walked down to the lake, where I took this picture using my phone, since I wasn't carrying the camera. The ducks and geese are very tame and you can walk right up to them. I'm sure they would take food from your hand if you had any.

Trying the XBM80

For months I've been saying that I was going to try building a Pixie II transceiver but I never got around to it. Then Roger G3XBM started writing about an even simpler transceiver that he was experimenting with called the XBM80-2. It is a crystal controlled QRP transceiver for 80m that uses just two transistors and a handful of other parts. It looked so easy to build that I couldn't resist trying to make one. I recently purchased a breadboard to use for experimenting with different circuits so I made up Roger's circuit using it.

I didn't have any 80m QRP frequency crystals but I did have some for 40m, 30m and 20m. Roger had commented that the design should work on other bands and indeed it does. However on 20m the transmitter chirps rather badly. It was much more stable on 40m where I measured 100mW output, and it would probably be better still on 80m, the frequency Roger designed it for.

Reducing the value of L1 helps on the higher frequencies. With a smaller inductance it is possible to see 200mW or more output. However as well as chirp I observed the frequency starting to drift which suggested that perhaps I was running too much power and warming the crystal. The power may be increased or decreased by reducing or increasing the value of R3, which is in series with the key line.

With the transmitter on 40m I noticed the second harmonic on 20m was also very loud. Anything is very loud when you are very close to it and I don't have a spectrum analyzer to measure how the harmonic compares to the main signal, but if I was going to use this little radio into my multiband dipole a low pass filter made for the band in use would be a very good idea.

The main problem with the receiver is that there is almost no audio output below 2KHz. All of the signals I heard were very high pitched. I tuned across the receiver passband while transmitting a carrier and the signal which was clearly audible a few kHz away disappeared at around 2Khz and only reappeared after I tuned through zero-beat and reached 2kHz away on the other side. So I'm not going to hear anyone who called me. This isn't simply the frequency response of the crystal earpiece because I plugged in an external amplifier and it was just the same.

Roger doesn't mention this issue so I wonder if there is something wrong. However it is such a simple circuit that I can't see what to change that would affect this. I tried increasing the coupling capacitor to the audio amplifier stage and it made no difference at all.

With such a simple receiver circuit one should not expect miracles. Nevertheless I did (just!) detect a 1uV signal from my signal generator - though only when it was tuned far enough away from the crystal frequency to make a high pitched tone. If I could solve this problem of not being able to receive signals close to the crystal frequency then this would make an amazing little radio.