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Kevin, GW0KIG, has just written in his blog about struggling to brush up his Morse. He first learnt the code at the age of 19 and has “memories of a Morse code tutor program on a borrowed ZX81 computer (remember those?)”

I remember the ZX81 and its wobbly 16KB RAM pack very well. In fact, a Morse tutor was one of the first programs I wrote for it. I wrote an article for Short Wave Magazine which described the program, together with a Morse keyboard with programmable memory and a high-speed Morse sender for meteor-scatter work. It is amusing today to read my conclusion that “it is possible to program the ZX81 to create sophisticated memory keyers.” These primitive programs would hardly seem sophisticated today.

The article was published in the August 1982 issue of Short Wave Magazine. I kept a copy and you can see it here. I wonder if my program was the one Kevin used to learn Morse when he was 19? One of these days I might try downloading a ZX81 emulator and see if these old programs will run on it.

I have been browsing for information about various circuits recently. Two books that are often recommended are “Solid State Design for the Radio Amateur” (which is now quite old) and its successor “Experimental Methods in RF Design”. I decided to get a copy of the latter and was gobsmacked to find on Amazon.co.uk that only used copies are available, priced from £557.14. No, that’s not a misprint, it’s about 800 bucks in real money.

I clicked over to Amazon.com and found the same book listed as available new for a slightly more reasonable (joke) $600.00, or I could buy a used one for a whisker under $500.00. Who are these sellers kidding? Do people really pay $600 for a book that was published by the ARRL in 2003 with a cover price of about $40? I wish I’d invested in a pile of them – they would have been a better return on my investment than my shareholdings (sick joke.)

I browsed down the Amazon.com page to see the usual stuff Amazon tells you about a book and found that 37% of people (rich or insane people, presumably) buy the item featured on the page, while 36% buy “Experimental Mathods (sic – not a joke) in RF Design” for a mere $42.70. That’s 36% who can’t spell, I guess, but I can live with a misprint in the title if it saves me $550.

But seriously, what’s going on here? Is “Experimental Mathods” a pirate copy using a mis-spelt title to avoid copyright infringement? Is a joke being played on somebody? If I buy it will I receive something other than what I expected, like searching for “mammaries” instead of “memories” on Google? I’m off to confused.com.

Series Three Episode Fiver of the ICQ Amateur / Ham Radio Podcast. News Stories include:-

• Ham killed in Connecticut explosion
• Cuban HF Number Stations
• Sat-nav's face big errors
• Ham radio's roll expanding in Haiti
• Mod to transmission mode GB3TM
• Windermere Triangle
• Police search for missing ham
• Move of GB3VHF beacon
• Unlicensed Police drone grounded
• NAQCC - Lifetime membership FREE!
• New mode - ROS
• VK2BWI slow morse broadcast
• Iceland's access 70 MHz & 500 KHz

Your feedback, Hints, Tips and Tricks and Martin (M1MRB) discusses completing the building of the TenTec 1330.

I’m preparing to build my 40m version of Roger G3XBM’s XBM80-2 QRPP transceiver into a little box but before I start I have one thing more to do. I have to design an output filter for the transmitter.

Roger didn’t bother. Comments from him suggest that he was aiming for a low parts count and assuming that any filtering would be provided by an external ATU. However Alan VK2ZAY comments that the output was more like a square wave. The second harmonic of my 7.030MHz signal would be on 14.060MHz, also a QRP frequency and I can’t be sure that my antenna won’t radiate this too. So I think an output filter is a good idea.

Alan used a two-stage pi network, each stage consisting of two 820pF capacitors and a 2.2uF inductor. I built this up on my breadboard, terminated the end with a 50 ohm load (actually 47 ohms, the nearest resistor value I had) and checked it with my SWR analyzer. The picture above shows the result.

Out of interest I also checked the response of a single stage of filtering using the same values, shown in the next picture. You can see that the cut-off frequency is a lot shallower than when two stages of filtering are used, so clearly attenuation of harmonics would not be as effective.

My problem is that I need a filter for 40m not 80m. I tried searching the web to see if I could find some online design tools, and I did here, here and here. However when I fed the design parameters for 80m into the calculators the results they came up with were a lot different from each other and also from the values VK2ZAY used.

In the end I decided to use trial and error. I figured that since the frequency is higher the values I would need to use would be lower. The next lower value inductor I had in my parts box was 1uH, so I don’t have a lot of choice in the matter. I substituted that for the 2.2uH. The result shown by the SWR analyzer was promising, but there was a big hump below the cut-off frequency and the SWR at 7.030MHz was a bit on the high side. So I then tried lower values of capacitors. The lower I went, the shallower the cut-off but the lower the hump as well.

In the end, I settled on 680pF capacitors with the 1uH inductor. There is still quite a steep hump below the cut-off frequency but I’m only concerned with the performance at 7.030MHz where the SWR is 1.2:1, which I don’t think is too bad. The cut-off curve of this one stage filter seems as steep as the two-stage one VK2ZAY used on 80m so I think one stage of filtering will do.

After I’d written the above, the thought occurred to me to try the low pass filter in the circuit while it was on the breadboard. I’m glad I did, because I’d have been disappointed to find after soldering everything into place that the output power had fallen from 100mW to 25mW. After a bit of experimentation, it appears that connecting the low pass filter directly to the collector of the first transistor as VK2ZAY did in his version of the transceiver loads the circuit and reduces both transmit power and receive sensitivity. The solution seems to be to couple the transistor to the filter using a small value capacitor – I found 180pF gave the best results. This removes the need for the DC blocking capacitor on the output. The power is still down quite a lot, but part of this may be due to all the harmonic energy which is now not making it through to the power meter.

Cox and Brockman (1978) said, “People sure like to have a good time. The 1977 CQ WW Contest attests to this fact. In spite of less than normal conditions, interest and activity were never higher.” (p 10)

What makes a RadioSport event fun to operate like CQ World Wide franchise?

One answer is DXpeditions according to Cox and Brockman (1978) and another may include antenna system(s) and/or one’s receiver. The broader answer maybe active involvement of RadioSport clubs where resources and talent are focused around a specific goal like number one in the Club Box.

Cox and Brockman stated, “Not to be outdone, the Frankford Radio Club (FRC) repaired their antennas, turned their rigs, and walked off with the fierce Club competition title with a total of 62.7 M points. That’s alot of work and cooperation.” (p 10, 1977).

One senses club strategy beginning to develop with a score target inside the box. Additionally, FRC channeled their knowledge and resources into improving antenna systems-to-radios inside the shack. I believe individual initiative is important in addition to having a stake in the overall success of one’s RadioSport club.

If there is a moment when design specifications are pushed to the extreme, it must be during an event like CQ World Wide; when was the last time one thought about their audio gain control (AGC)?

For example, Richard Norton, N6AA operated from Trinidad and Tobago, as 9Y4AA in 1977 and logged 1400 Qs on 20m that year. He moved from third place in 1976 to winning first place in 1977 while establishing a world record. Undoubtedly, he understood the design specifications of his radio, inside and out.

An on-going conversation on CQ Contest Digest reflector inspired researching how-to improve my receiver and/or decrease listening fatigue. Admittedly, I set controls at near maximum, according to Eric, K3NA many operators run their gain controls too high, and I’m one of them.

His suggestions are straightforward and easy to implement to include adjustments for a specific set of headphones.

Additionally, when considering a DXpedition designed for an event like CQ World Wide, understand point structuring as part of one’s decision tree.

Cox and Brockman (1978) stated, “The Sochi Radio Club decided that 3 points per QSO would be better than 2, so they took a trip down to the Black Sea coast to UF6. It was well worth it, because their crew set a new world multi-single record with an incredible 4058 Q totaling out at 6M points.” (p 10)

Several fun factors contribute to the overall success of an event like CQ World Wide such as 1.) An active RadioSport club focusing resources and talent on specific achievable targets, 2.) Learning design specifications of one’s radio, and 3.) Understand an event’s point structuring and maximize operating time and/or operating location to that of the point structure.

Believe in your signal!

Reference: Brockman, L. N6AR, Cox, B. K3EST (September, 1978). CQ Magazine: 1977 CQ World Wide DX Contest: C.W. Results. pp. 10 – 12, 14 – 24.