Posts Tagged ‘amateur radio’

Elecraft K1 Excessive Current on Transmit

April 20, 2008

Inside the K1

My K1 with the top cover removed

Several years I had a great time building an Elecraft K1, which I later took on honeymoon to the Drakensberg mountains. Last year I offered to lend it to my good friend Vidi ZS1EL to take with him on a visit to the USA. However while I was checking it out, it started drawing excessive current on transmit, so I wasn’t able to lend it to him after all. Fortunately Vidi borrowed an Elecraft K2 in the USA which he later purchased and brought back with him, so i guess things worked out after all. Since then fixing my K1 has been sitting on my “to do” list.

Last night I was calling CQ on 40m when Vidi called me with his K2. During our chat, he asked whether I had fixed the K1 yet, and very kindly offered me a spare 2SC1969 final transistor if necessary, as he has one left over after a repair to his K2. Now it just so happens that my wife and I are going on holiday to the Drakensberg later this month, and I had been idly thinking that I really should take a look at the K1, but hadn’t got around to it. So Vidi shook me out of my complacency, and this morning I retrieved the K1 from a box in the store room and had a look at it.

Thanks to this post by OZ9AEC I soon located the problem. Diode D19, a 1N4753 Zener which protects the final Q7 from excessive collector voltage caused by high VSWR, had blown, and was now acting like a 1.4 Ohm resistor, not a 36 V Zener. I replaced it this evening, and made a couple of test QSOs on 40m to Russia and the Ukraine on 5W, so I think the final transistor has survived.

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ARRL International DX Contest 2008

February 20, 2008

ARRL DX CW was the first international contest I entered (in 2003 as ZS1AN with 131,100 points) and still one of my favourites. For me it is a bit more relaxed than CQWW, WPX and IARU as the bands are not always open to NA from here so it is possible to spend some time with my family and still achieve a reasonably competitive score. The pileups are also noticably better mannered than in some other contests thanks to all the fine NA ops.

Propagation was poorer than last year for the first 36 hours of the contest, with only 40m and 20m opening to NA. My new two-element beam helped me to play on 40m, but I didn’t hear even one NA station on 80m where I have only an inverted L. After taking Sunday morning off, I knew that I would need some multipliers on 15m in the afternoon to turn in a reasonable score. This didn’t seem likely given my total of five 15m QSOs on Saturday, all with big guns.

Fortunately conditions improved on Sunday afternoon and I managed a nice run on 15m, and then continued on 20m until about midnight local (2200 Z). For the last couple of hours I was really struggling to put callsigns together in my head, so appologies to those of you who had to give multiple repeats and thanks for your patience.

Needless to say there was no trade on 10m, although I kept a watch for openings with the second radio.

I didn’t have much opportunity to SO2R as it was rare for two bands to be open simultaneously, except during the 15m opening on Sunday afternoon when I didn’t want to divide my attention as I was desperate for as many 15m mults as possible. Overall I was satisfied with my effort, although I need to try to be a bit more focussed next time (and get more sleep before the contest!).

Here’s a summary of my claimed score:

Class: SOAB LP
QTH: Johannesburg
Operating Time (hrs): 28

Summary:
 Band  QSOs  Mults
-------------------
  160:
   80:
   40:  603    50
   20:  929    55
   15:  217    37
   10:
-------------------
Total: 1749   144  Total Score = 755,568

The image shows my QSO rate (number of QSOs per hour) through the contest:

ARRL DX CW 2008 Rate


CQWW CW Contest 2007

November 26, 2007

I’ve had my eye on the South African CQWW SOAB LP record of 582,920 points for a while. I came close in 2004 as ZS1AN with wire antennas but wasn’t able to mount a proper challenge in 2005 or 2006. Now with an 18m tower, C-31XR tribander and OB2-40 40m beam (installed a week before the contest), I was determined to break the record at last!

I started late, at 0130Z (3:30am local) due to a violent hailstorm that damaged my rotator. Fortunately I was able to turn the antenna using the “CW” and “CCW” controls, but the direction reading was random so I had to run into the garden
to see which way the antenna was actually pointing! So I adopted a simple “follow the sun” pointing strategy – Asia in the early morning, Europe during the day, and North America at night!

Conditions were much better than anticipated. 40m was rocking, and the new two element beam made a huge difference – previously, 40m has been a very frustrating experience from here, consisting of spending literally minutes at a time calling the same station until I’m eventually heard, or give up and move on. Now all of a sudden it felt like 20m, and I was able to S&P effectively and even run occasionally.

After a break for another thunderstorm (fortunately no hail) in the early morning, I was able to run on 15m to Asia and Europe almost nonstop from 10am until 8pm, averaging over 100 QSOs per hour. So much for the “almost zero”
sunspots editorial in QST! I must admit that I didn’t even look at the other bands, as my SO2R ability currently stops somewhere short of the 60 QSOs/hour rate. That evening I added a few on 20m and 40m before taking a nap.

Starting at 3am local again on Sunday, I was hoping for a repeat performance. After working 40m and 20m for a few hours, 15m opened again at about 0800Z, although conditions did not seem quite as good as Saturday. This gave me time
for some SO2R, S&P on 20m while running on 15m. At about 0930Z I idly checked 10m on my S&P radio. I heard a few stations, and when I called them they came back to me, so I switched my run operation to 10m in the hope of picking up a
few more multipliers. The propagation was sketchy, with lots of fading – a station would be here one minute, gone the next, and back again a moment later. However I managed to run on 10m for about 2 hours, picking up 228 QSOs, mostly
to Europe. (In retrospect, looking at the DX Summit spots database, I see that ZS4TX was also active on 10m on Saturday, so I should probably have been more vigilent). 15m closed earlier than on Saturday, and I spent some time S&P on
20m to address the imbalance in my band scores – I had worked many stations on 15m and 40m, but few on 20m, and didn’t want to overlook some easy mults.

Then it was back to 40m, with some S&P and some runs – although running was hard due to the crowded band (can’t spread the pile-up), weak signals and local band noise. I eventually quit at 2230Z (0030 local) as I had to go to work the
following day, and in any case the dits and dahs were no longer joining themselves up to make letters and callsigns.

Call: ZS6AA
Operator(s): ZS6AA
Station: ZS6AA

Class: SOAB LP
QTH: Johannesburg
Operating Time (hrs): 39
Radios: SO2R

Summary:
Band  QSOs  Zones  Countries
——————————
160:
80:
40:  738    24       76
20:  461    24       67
15: 1348    20       72
10:  228     6       33
——————————
Total: 2775    74      248  Total Score = 2,642,010

CQWW CW 2007 Rate

CQWW WPX 2007

May 28, 2007

Call: ZS6AA
Operator(s): ZS6AA
Station: ZS6AA

Class: SOAB LP
QTH: Johannesburg
Operating Time (hrs): 22
Radios: SO2R

Summary:
Band  QSOs
————
160:
80:
40:   17
20:  319
15:  393
10:
————
Total:  729  Prefixes = 367  Total Score = 812,538

Club:

Comments:

A last minute problem with my 40m antenna saw me out in the garden at 3 am (0100 Z) on Saturday morning converting my 80m dipole to 40m. Conditions on the low bands into Europe and NA were poor from here – I could hear you, but you couldn’t hear my puny 100W from a dipole most of the time. 15m was open to Europe much of the day although family activities demanded some down time. 20m
good late afternoon and early evening, but everything closed down around 8pm local time.