Thursday 28 July 2016

Repairing a cross-needle SWR meter

The SWR meter - working 100% again.
I've owned an AEA ET-1 antenna tuning unit for the last 20+ years. In that time I've had to replace the inductor switch as it burned out and also replace the meter.

Luckily, it uses exactly the same meter as MFJ ATUs so I was able to buy a replacement from them. I also resprayed the case at some point.

But recently the meter started playing up – it would only indicate 20W maximum forward power instead of 100W.

It was more of a problem on the less than 30W setting as I often use QRP radios and need to know if I am putting out 2W or 5W.

You could ask “why not just bin it?”, but that's not in my DNA!

Anyway, after asking for advice on the CDXC forum and looking at the schematic I decided that it could only really be down to a failed capacitor, resistor or diode. Given that semiconductors would be the first suspect I ordered two new 1N270 diodes from a UK supplier on Ebay for £3.98.

When they arrived I unsoldered the old ones, and checked them – one measured 1K Ohm resistance in both directions – not good and definitely not diode-like behaviour.

I soldered in the new diodes and bingo the meter is back to normal again. I've since ordered some 10 more 1N270s from China for just £1.12 inc. postage. These will do as spares.

I'm writing this as it might be useful to owners of cross-needle SWR meters in future. If you start to get low readings it may be the diodes. If you get no reading at all it is probably the meter.

Friday 22 July 2016

Elecraft K1 QRP radio finally finished

My Elecraft K1 (click to enlarge)

You could say that this project has been a long time in the making. The kit for this Elecraft two-band (40m/20m) K1 5W CW radio was actually a Christmas present back in 2004.

Heck, I still have the invoice for $329 plus the £44.97 import duty, making it about £230.97 at the exchange rate of the day (nearly £300 at today's rates).

When I first got the kit I had a couple of reads of the instruction manual, went “wooah” and put it in the loft. It even moved house with me eight years ago.

Anyway, a conversation with Colin M1BUU (a more enthusiastic QRP builder and SOTA operator you couldn't wish to meet) at the 2014 G-QRP Convention convinced me that I really should put it together.

In the intervening 10 years I have built a lot of other kits, including a Hunter SDR, Rockmites, MKARS 80 and a Steve Weber MTR, so I had picked up a lot of construction skills.

Last Christmas I actually started the build and, while not difficult, it was time consuming. Fast forward to July and I thought it was about time I finished it.

The build wasn't too bad, but I had a few problems, such as the wiring on the multi-turn pot for the VFO control – I thought the numbers on the side of the pot represented the numbers in the manual. They didn't.

I also managed to lose a couple of components down the back of the bench, which were subsequently found, and also couldn't find the insulating spacer for the power transistor – this I managed to improvise with insulating tape and fibre washers.

The final c*ck-up was missing out two capacitors, which meant the receiver didn't work at all. I'm glad I eventually managed to debug it without any help.

In all, I think I spent about 22-25 hours putting it together, but the end result is worth it.

The Elecraft K1 has a fantastic little receiver and a built in keyer and puts out around 7W if pushed. I have had a couple of QSOs with it so far and it is a very useable QRP radio.

I can thoroughly recommend it as a QRP project, although Elecraft have now moved on quite a way with the KX2 and KX3 - but then my K1 kit is 12 years old!

Tuesday 19 July 2016

Operating QRP from Beeston Bump (TG14) in North Norfolk

Update: YouTube video now available

Jim G3YLA and I operated HF and VHF QRP from the top of Beeston Bump in Norfolk as planned today.

It turned out to be the hottest day of the year, so not exactly ideal. Nevertheless, after parking up and walking to the top we were met by a fantastic 360 degree view.

I quickly set up by 40m inverted L end fed half wave (EFHW) on a 10m fishing pole, bungeed to a bench and fed it with my homebrew EFHW matching unit, while Jim tried some CW on 2m from a little beam. He didn't get anywhere with that so switched to FM and had a quick chat with some locals on 145.275MHz.

Once the HF antenna was erected I handed Jim the coax and he set to on 40m CW and quickly worked a station in Germany using 2.5W from his Yaesu FT-817.

Jim G3YLA working Germany on 40m CW.
I meanwhile tried to see what I could work on 2m FM and could raise the GB3FR repeater across the water in Spilsby, Lincolnshire, but there was no one on it. I switched to GB3NB in Norfolk and worked John G8VPE.

I then took over on HF, but 40m was hard work and 20m was not much better. I eventually went back to 40m CW using my 2.5W Steve Weber-designed Mountain Topper Radio (MTR) and raised fellow G-QRP club member Peter G3XJS near Wrotham, Kent who was using 5W to a doublet. I was very pleased to make the contact as that was the first time the MTR has been used in the field.

Looking at the Chilton Digisonde data I think this was via Sporadic E (Es) on 40m as the F2 critical frequency was only about 5MHz - we don't normally associate Es with 40m, but you could see the Es on the plot.

Jim G3YLA then took over again using his FT-817 and had a long CW QSO on 40m with a station in the Netherlands. 

The information board for the Y station.
There were a lot of walkers on the hill and we were able to explain what we were doing - it was quite apt as this was the location for the Beeston Hill Y Station, a secret listening post during World War Two. The chain of Y stations were on the front line, feeding Enigma intercepts to the War Office’s Bletchley Park.

There is an information board all about the Y station and the concrete foundations are still there.

Propagation was iffy at best and the heat was getting to us, so we decided to take the station down and head for the nearest pub for fish and chips and cold refreshments.

My home-made EFHW matcher and SWR
All in a great day and we both agreed we'll go back, perhaps in late September when propagation is better and the temperature is a bit more reasonable.

I also shot some video and I'll try and edit that over the next few days.
My three-band (40, 30 and 20m) Mountain Topper Radio.
3W CW on 40m raised Peter G3XJS in Kent.


I thought I would do a Reverse Beacon Network (RBN) check tonight.

I was pleasantly surprised to see I was picked up all over the place, including the US, from the top of the bump.

Jim G3YLA wasn't for some reason - not sure why as his CW is waaaay better than mine. Perhaps it was because he responded to CQs and didn't call CQ himself.

Reverse Beacon Network captures from the day -
chuffed I was picked up in the US (just) with 2.5W to an EFHW for 40m (click to enlarge).
Update: YouTube video now available

Saturday 16 July 2016

G0KYA to operate a "BOTA" station - "Bumps on the Air"

Beeston Hill near Sheringham in North Norfolk.
Image Wikimedia/Stavros1
I plan to operate QRP from Beeston Hill in North Norfolk on Tuesday 19th July as part of a new "BOTA" activation.

BOTA stands for "Bumps on the Air" a wholly-fictitious new organisation for radio amateurs who don't have access to real summits and mountains.

Beeston Hill (known locally as 'Beeston Bump') is not the highest point in Norfolk, but at 63m (207ft) above mean sea level it offers a good view of the coast and excellent HF take off.

I wanted to have some outdoor local QRP SOTA fun, but Norfolk is a little short of suitable summits (well, none actually) and Beeston Bump will have to do.

The highest point in Norfolk is nearby Beacon Hill at 103m (338ft), but I don't want to overstretch myself! Anyway, the view is better at Beeston and there are more ice cream shops nearby.

I've been meaning to do this for years!

Beeston Hill Y station circa 1940.
Image; Wikipedia.
I plan to operate 40m and 20m QRP CW using one or more of a variety of commercial and kit-built radios, including a Yaesu FT-817, Elecraft K1, Mountain Topper Radio (MTR) by Steve Weber KD1JV and a 1W Rockmite. Antennas will be end-fed half wave (EFHW) dipoles.

Beeston Bump is no stranger to Morse code. Beeston Hill Y Station was a secret listening post located on the summit during World War Two. The chain of Y stations were on the front line, feeding Enigma intercepts to the War Office’s Bletchley Park.

There are no awards for working me on Beeston Bump, no certificates and no special QSL cards - just my normal one. And just the fun of working CW at about 16-20 wpm around the usual QRP watering holes on 20 and 40m. I hope to be there from about 10:30am.

Jim G3YLA, a fellow QRP enthusiast, might be with me too.

(With apologies to the excellent Summits on the Air (SOTA) organisation!)