Roll your own valves (tubes)

A few weeks back – in the post about wartime crystal production – I made a tangential reference to my all time favourite YouTube video – Claude Paillard F2FO distilling down to less than 20 minutes his meticulous work making a triode valve, effectively by hand. Watching it again, this time I spent a bit more time looking over the many pages of background information he had posted on his website detailing his research into triodes of the 1920s, the techniques he used and the equipment he used or made to complete this project and create a very cute looking valve wearing blue shorts.

This prompted me to start a more methodical reading of the documents, and to work through the translations to ensure I understood what he had done. (Google translate is great, but it missed a significant amount.) If you’re vaguely interested in the technology of the earliest days of radio, and have ever wondered how these valves were made, the documents take you on a special journey through the eyes of an explorer with a brilliant workshop and skills to match. His research is comprehensive. By way of exploring how early valves were made he produces a full detailed and illustrated life story of the evolution of valve types and introduces important valve families like the 6L6 and its descendants like the 6V6 and the 807 of the late 1930s. He also takes you on an excursion to discover the history of creating an effective vacuum, critical in the creation of the valve aka the vacuum tube.

It’s also an enjoyable way to build up a French vocab for the terminology of valve radio gear. Along the way I stumbled across the Electropedia, a brilliant resource for translating technical terms from French to English with a number of other languages included. But some of the terms Claude Paillard uses reflect an earlier era and vocabulary. He talks about the plaque (plate) of a valve rather than l’anode. I’d love to find online versions of the French radio engineering references he cites from the 1920s.

Edouard-CLIQUET
Edouard Cliquet wrote a number of books explaining radio

Another plus of this experience is reading the history of radio from the perspective of a country other than Britain or the US. The French version of radio history introduces interesting characters and stories to the familiar names and places. An inspiration behind the work of F2FO is the history of the triode TM (Télégraphie Militaire). A good outline is at Michel Siméon’s website.

Paul Berché was another prolific author of French radio texts

Bringing an 12 V SLA back to life from 9V

I’ve spent the last four hours or so – in between other tasks – nursing an almost expired 12 V SLA. The charger usually has the green LED glowing to indicate a charge, but not so with this battery – a Power-Sonic PS1229A 12V 2.9Ah SLA which has been a little neglected over the last 6 or more months.

It was registering 9V and was still very low after an hour of charging at 500mA so I feared the worst. About 3 hours later the battery is showing about 10.9V and rising. It may need more than one re-charge though to get it back to something near normal.

While it retails for US$20 in the US or about US$31 from Mouser, here in Australia I’ve seen it selling for about A$29 plus A$11 shipping from a Melbourne dealer or A$50 (free shipping) from an Adelaide one. So it’s a relief that it may not be completely dead.

It sits inside a K2. I’m preparing to drill a hole in the back of the K2 to accommodate a power connector with a direct connection to the SLA for float charging it.

I am amazed how much time you can spend finding out about the care and maintenance of SLA batteries to enable you to operate, time I can’t help feeling would be more enjoyably spent, well operating.

Warp drive

I’m awaiting a parcel from the US and got a bit of a shock when the latest update on the USPS tracking page showed me this result…

However you look at it that's traveling fast from Sydney to Hong Kong. Shame I actually live in Sydney though!
However you look at it that’s traveling fast from Sydney to Hong Kong. Shame I actually live in Sydney though!

The item made its way briskly from North Carolina to Miami and then appeared in Sydney only to be whisked away to more exotic parts. How I wonder can an item depart Sydney and then 5 minutes later depart Hong Kong? But HK was 3 hours behind Sydney on the 4th April, the night before the end of Daylight Saving in Australia. (Now it’s only 2 hours behind). Even so, it’s travelling incredibly fast. And I’d like it to come back to Sydney soon…. It sounds like it forgot to get off.

I don’t think I really know what USPS means with the words ‘Arrived’ and ‘Departed’.

Replacement ear pads for the Yamaha CM500 headset

Apparently Yamaha do not sell replacement ear pads for their CM500 headset.

Originally intended for gamers, it’s become quite popular with hams due to comfort and sound quality. You can wear them for extended periods such as contests without being all that aware you have them on. While the electret mike is considered ‘hotter’ than normal this is not a concern to most. Also it plugs in directly to rigs like the Elecraft K3 (rear sockets) or the KX3 (but they consume as much volume as the radio here).

There are a few complaints (on the Elecraft email list, of course) about the pivot for the mike on the left hand headphone of the CM500. Mine is a little loose-ish but nothing I am worried about. It probably wouldn’t stand up to being carted about without some sort of solid box to protect it. Most people on eham rave about it with 5 out of 5 ratings.

There is no shortage of people prepared to sell replacement ear pads for all sorts of headphones at reasonable prices with little or no postage. But none of them describe any of their offerings as suited for the Yamaha CM500.

I pulled mine apart to get a better idea of the shape and dimensions of the ear pad to see if I can identify one that would fit properly.

The pad is slightly oval in shape. The longest dimension of the pad is 105mm. The actual plastic of the headset here is 100mm. The shorter dimension of the ear pad is 95mm. The thickness of the pad is about 13mm (just over 1/2″).

The internal opening in the ear pad is more elongated at 70mm by 50mm.

One Elecraft user has recommended the Beyerdynamic DT880/DT990 velour earpads might be a suitable replacement. On eBay the pads identified as brand specific often have no actual dimensions while generic pads may include detailed dimensions.

If I find something that works I’ll add details to this post – which is an elaborate (but simple?) way of noting the dimensions.

Grinding quartz and holding a frequency during World War II

I’m a great fan of the Prelinger Archives which is home to so many items like this video I’ve heard about recently from various ham radio email lists.

I like how the components of the earliest electronics and wireless were so basic and ‘natural’. Think of hand made capacitors and resistors using traces of graphite on paper. Valves (or tubes) of course were another story but still capable of being ‘homemade‘.

I love the idea that an accurate, literally rock solid frequency could be achieved using a piece of a very common rock – admittedly a pure piece of quartz cut just so.

This video details the elaborate and meticulous manufacture of quartz crystals during World War 2 by Reeves Sound Laboratories in 1943.

The 41’24” video can also be viewed and downloaded via the Prelinger Archives.

Most of the ‘radio quality’ quartz was mined in Brazil which ceased its neutrality in 1942 and joined the Allies.

The story of quartz crystals during WWII is told in ‘Crystal Clear‘ by Richard J. Thompson Jr. (Wiley) 2011.

Crystal-Clear

“In Crystal Clear, Richard Thompson relates the story of the quartz crystal in World War II, from its early days as a curiosity for amateur radio enthusiasts, to its use by the United States Armed Forces. It follows the intrepid group of scientists and engineers from the Office of the Chief Signal Officer of the U.S. Army as they raced to create an effective quartz crystal unit. They had to find a reliable supply of radio-quality quartz; devise methods to reach, mine, and transport the quartz; find a way to manufacture quartz crystal oscillators rapidly; and then solve the puzzling “ageing problem” that plagued the early units. Ultimately, the development of quartz oscillators became the second largest scientific undertaking in World War II after the Manhattan Project.” (from the book’s blurb)

atbtcut
Illustrating the precise angles needed for the AT and BT cuts of a quartz crystal…

 

Reading in your head – the long path to morse code bliss

I’m one of those people who learnt morse code completely the wrong way. Starting off in the seventies with no guide I simply tuned into nightly morse transmissions sent by local hams at a very slow rate. I think they started at 5 words a minute. The main risk there was nodding off between words or impatiently guessing the wrong word.

Contemporary wisdom is that you should start listening at a much faster rate, say 15 or 20 words per minute. This is to prevent you counting dots and dashes in your head, and to make it easier for you to recognise the letters, numbers and even words by their sound.

Learning 15 wpm after mastering say 8 wpm is almost like learning a new language. Students of morse talk of ‘a plateau’ at 10 which is a mighty barrier to progressing up to a more useful conversational speed.

My personal goal is to be able to copy and send at 25 wpm and be able to sustain it over a couple of hours, and to be able to read mostly ‘in my head’, only using pencil and paper for details like names and callsigns.

Now that morse code is no longer compulsory for any ham licenses, surprisingly it seems to be more popular than ever! Especially with those hams who like to use low power to make contacts, or to take the lightest possible transceiver to a remote mountain top as part of the global ‘Summits on the Air‘ activity. Morse gets more mileage than voice per watt, and often these tiny transmitters are only putting out a couple of watts power.
And there’s something delightful in having the skill to read the beeps.

But for me it’s a skill I have to keep working on. I think in my twenties I was quite at ease chattering away at about 12 wpm seemingly for hours on end. Four decades on with a large slab of radio silence in between, I’m quite rusty, even though I know the basics are still there like riding a bike.

I’m a bit wobbly at the paddles, having grown up with the old fashioned straight key (the type you’re likely to have seen in old westerns). But you can feel slow but definite progress from every bit of practice you put in.

Lightweight portable antennas

One of my favourite sites is Martin DK7ZB’s collection of pages detailing the construction of practical antennas for VHF and UHF.

I first visited the site following a link to designs for lightweight portable yagis that would be suitable for SOTA VHF activations. Under the link ‘2m/70cm-Yagis ultralight’, Martin describes a number of yagis for 2m and 70cm that use thin metre long aluminium welding rods mounted on PVC booms.

These Yagis are constructed with cheap lightweight materials for electric installations and you can mount and dismantle them without any tools. The boom is made of PVC-tubes with 16mm, 20mm or 25mm diameter, the element holders are the clamps for these tubes.” DK7ZB

What makes the designs particularly attractive is that they can be quickly assembled from a compact (admittedly metre long for 2m) pack you can carry on your ascent, even designs using a 2 metre long boom.

The components of a DK7ZB lightweight yagi suitable for SOTA or any portable operation

The welding rods – used for TIG welding – are available in Australia in 2.8mm and 3.2mm diameters from welding supplies shops. I’m still on the lookout for 4mm diameter rods. PVC conduit and the mounting clamps are readily available in VK from hardware stores.

I’ve managed to cut a suitable slot in the end of a 3.2mm aluminium welding rod using a Dremel with a thin cutting wheel. One suggested way of attaching the feedline to the driven element is to crimp the lines into thin slots like this.

Also of interest to  portable operator are the J Pole designs based on Wireman 450Ω window feedline. There are dimensions for bands from 2m down to 40m. The J pole is essentially a half wavelength dipole where the high feed impedance is transformed by a quarter-wave length matching section (the tail of the J) tapped at a suitable distance to yield a 50Ω match. Follow the ‘Wireman-J-Pole’ link in the left navigation. These pages remind you that the J-pole can be configured in any way so a 40m J pole in a Zepp arrangement starts to look quite practical if you have just under 10m of 450Ω feedline available. I want to start with the 6m design and see if I can make it robust enough with heat shrink etc for portable work.

Kits for the DK7ZB yagi designs are also available from nuxcom.de, Attila Kocis DL1NUX’s website. Both sites are in German and English.

Back online

The blog is back online after a relatively long break.

The interruption was partly caused by the original host going belly-up and all content being vapourised – without any word of warning!

I’m seeing this as an opportunity to re-think a purpose and course  for the blog. Not sure about whether to re-instate earlier content or archive that somewhere else.

Focus will remain as the tagline says QRP, homebrew, CW and SOTA.

I also want to develop a better way of presenting and organising useful info about portable operation and gear, in a way that doesn’t lead some people to think this is an online shop.