Great moment this afternoon when the Automatic Loop Controller fired up as it should. Happy days.
When I first fired it up, after loading up the Arduino program, all I could see was a dull green glow on the screen. It wasn’t until I remembered a comment from another builder about adjusting the potentiometer on the PCB that controls the LCD contrast.
It was a great relief that my slow and deliberate build – double checking all component values and joints – paid off. Next step is to build the SWR bridge and connect to the stepper motor on the loop.
Also finally managed to make a plate out of perspex to mount my stepper motor on to the supporting bracket on the magnetic loop after much mulling over how to achieve a suitable level of accuracy with my dremel drill press to get the stepper shaft as close to the centre as possible.
Not too bad for a cut with a straight baby hacksaw. The key tool turned out to be my old school compass which had scribing points fitted which were perfect for marking out the perspex. I figured that these ‘cross hairs’ would help orient and centre the piece and the shaft. After these shots I countersunk the holes. If it looks a little skewiff, that’s probably because it is!
Success – part 2
Also successful today getting this instance of the blog back online using AWS. Another steep but satisfying learning curve about the nitty gritty of DNS management! What’s in a CNAME? you might ask.
Midway through building my version of Loftur Jónasson – TF3LJ / VE2LJX‘s Automatic Loop Controller, I came across Leigh Turner’s impassioned plea to consider this noise bridge antenna tuning design mentioned on page 32 of the “Overview”. As a concluding note VK5KLT states that he considers “The perceived need for a slick and salubrious auto-controller for properly tuning an MLA is oftentimes overrated and exaggerated, IMHO”.
He argued that elaborate microcontroller aided automatic loop tuning circuits are unnecessary and people should consider using this more covert and considerate approach. I think the bridge could be an excellent idea and a simpler way of staying in tune as you change frequency for all sorts of antennas. For a magnetic loop, it still requires a way to remotely adjust the tuning capacitor.
“The circuit goes inline between the rig and the antenna and sends a gated broadband noise signal to the antenna using a directional coupler and a noise bridge. You just listen on the desired operating frequency and watch your RX S-meter for a sharp dip whilst adjusting the loop tuning capacitor.
You simply remotely tune the loop with the aid of the receiver S-meter while you are on the wanted frequency without keying up and TX power output. This makes tuning a breeze without having to move off frequency and have the TX put out any RF power.”
VK5KLT mentioned the MFJ-212 Matchmaker that uses this same approach (and which is still on the MFJ catalog at US$99.95) and also referenced ZL3KB’s April 2001 RadCom article (pp17-21) as an easy and more economical way to replicate the same functionality.
“The distinguishing merit of the novel gated coupler/noise bridge loop tuning method is it’s completely passive and covert in operation; you don’t transmit any TX power whatsoever to attain an optimal loop tune setting. The technique makes for fast, QRM free, safe and easy QSY shifts and netting a frequency.” Leigh Turner adds that it’s even simpler if you use a pan adaptor or a modern SDR receiver as you can see the sharp null on the screen of the band scope display.
Kelvin Barnsdale ZL3KB’s RadCom article describes building and using the wide band noise bridge as a silent antenna tuning indicator. These four pages include circuit, PCB design and layout and full details of BOM and balun/transformer construction.
On 14 May 2001 ZL3KB published a 4-page follow-up pdf document “Instructions for Antenna tuning Noise Bridge” with info supplementary to the RadCom article about construction and operation. This article has an updated circuit and parts layout and refers to an issue B of the PCB. The new board includes places for the LED and dropping resistor R14, and pads for the two 100Ω load resistors and the two diodes D2 & D3.
This is the updated circuit with some updated values.
This indicates parts placement with the updated PCB.
Here is the foil side of the updated PCB
I contacted Kelvin Barnsdale and was lucky enough to obtain the PCB above.
I was meandering around the web this morning and stumbled on to a page where famous key collector and curator Tom Perera W1TP had re-created the morse key setup used by Walter Winchell to introduce and punctuate his radio and later TV broadcasts. They were a pair of Vibroplex bugs.
I grew up in Sydney in the 1950s and remember how radio station 2UE would start their news bulletins with a brisk CQ CQ. They were probably inspired by Winchell. Another memory is watching ‘The Untouchables‘ on TV with narration by Walter Winchell.
Ironically in his early years as a gossip journalist he was close to prominent criminal identities and later became friends with J. Edgar Hoover. He was Jewish and in the lead up to the second world war was one of the first Americans to criticise Hitler and those in the US who supported him. Another of his targets was isolationist Charles Lindbergh. His fame followed his reporting the famous kidnapping and subsequent trial.
From the clip you can hear the rapid-fire delivery. In many ways it’s like a precursor to much of what we consume today.
He attacked the Klan and its supporters. After the war he aligned himself with the Senator Joe McCarthy’s hunt for communists. But within this short clip there are a couple of places where he briefly questions a couple of issues that were to haunt the US for the next couple of decades – Vietnam and cigarettes and cancer.
Complex and probably unattractive, what I want to know is if he actually knew how to handle those Vibroplex keys.
I spent the pleasant sunny part of the final day of autumn testing a vertical antenna for 80 metres using Buddipole parts for home.
The back garden space here is barely 4 metres by 4 metres and for the moment the chimney is out of reach. While I have dreams of a magnetic loop for 80m, the vertical is more in reach now.
I installed a counterpoise wire a few feet shy of 66 feet length hidden on a timber fence that runs down the side of the property. The idea is to connect a short fly lead to connect the hidden counterpoise when the antenna is deployed and then disconnect when it’s all packed away. Buddipole components don’t lend themselves to permanent installations. The counterpoise doesn’t follow the recommended dog leg arrangement and is higher off the ground than the 2 feet suggested.
The purpose yesterday was to establish how speedily the antenna could be assembled and adjusted for a frequency of interest such as a net.
Here’s a list of the items used along with the counterpoise:
9′ telescopic whip
2 x 22 inch antenna arms
low band coil + clip
Buddipole short mast
I was surprised how easily it all went together. The adjustment wasn’t as fiddly as I expected such a short antenna for this band would be, and it appeared to give a usable bandwidth.
Assembly was straightforward. Set up the tripod and mast with only bottom two sections telescoped out. Attach the Versatee horizontally to the top of the mast. Connect the Low Band coil. Leave the red fly lead loose for the moment. Attach two 22 inch antenna arms to a long whip antenna fully extended. Then carefully attach that assembly to the top of the Versatee. I also connected a 1:1 balun between the Versatee and the iP30 SWR Analyser.
The next step is to simply drag the fly lead across the coil turns to identify the best spot to tap the coil. Background noise level rises as you get in the zone. I used the iP30 SWR analyser to narrow it down to a spot 16 turns up from the base of the coil.
This means I was shorting out the bottom 16 turns of the coil. The adjustment is too coarse on a turn by turn basis. You appreciate the value of being able to tap at 1/8 of a turn increments. (The coil is on an octagonal former.)
It took me a few measurements to realise that as I progressed left (from my point of view) I was decreasing the amount shorted out and hence increasing the loading inductance and so lowering the resonant frequency. It’s actually more confusing reading that sentence than understanding it in practice!
My target frequency was 3535kHz and this is a chart of the SWR readings I had when the coil tap was set at what I calculate to be 15 3/4 turns up from the base of the coil.
The 1.0:1 bandwidth was 10 kHz while at 1.5:1 it was in excess of 65 kHz.
From readings at the other possible coil tap points my guess is that at this frequency range each face of the coil moves the resonant frequency by about 4 kHz. One thing to be aware of with the Buddipole hardware is not to accidentally short out adjacent turns of the coil with the coil clip. It’s hard to do but I managed and it will throw your readings.
Next step of course is to make some contacts or at least activate the antenna on WSPR or JT65 to get an idea of whether the signal gets over the fence.
From checking the chart on page 146 of the ‘Buddipole in the Field’ book by B. Scott Andersen, NE1RD, I estimate that my shorting tap at about 16 turns from the base means I’m using about 39-40 uH of loading to achieve resonance at 80m. So that’s a starting point if I wanted to build a more permanent and cheaper vertical installation.
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.
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.
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 (free of youtube ads etc) 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.
“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)
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.
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 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 the 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.
News is just in that SOTA – Summits on the Air – starts in a number of new call areas tomorrow including my home state New South Wales, VK2. I understand that Queensland VK4 and Hawaii KH6 may also be launched tomorrow, 1st September.
The new VK2 association adds over a thousand summits to the SOTA database. I was part of the team that surveyed the 16 regions. Hats off to Andrew VK1DA/VK2UH who coordinated the widely dispersed team of surveyors. I should publish a post here soon about the things I learnt along the way, about the resources available for SOTA summit surveying and cracking the mystery of identifying the all-important saddle to ascertain the required prominence. Flooding Google Maps is the clue.
The news of the scheduled start has taken us a little by surprise. I’m not sure how many activators will have had time to properly plan activations for the first day. The other issue is that tomorrow, Sunday 1st September is Father’s Day.
For more news about the accelerating SOTA activity in Australia – it’s already active in VK1, VK3, VK5 and VK9 – you should follow the conversation on the SOTA-Australia Yahoo group and visit VK1NAM’s blog for a list of SOTA blogs from VK activators.
The WIA’s Amateur Radio magazine for September which arrived in letterboxes yesterday features a report on the mass activations on 11 August celebrating six months of SOTA in VK1 as well as three pages of regular SOTA news. It’s brilliant for SOTA that editor Peter VK3PF is also one of the top SOTA activators in VK.
Yesterday I had my final CW Academy session. As an indication of how good it was and how much we valued it, not one of the five of us ever missed a single session! There were sixteen hour-long sessions over two months. And it was all free!
Late last year I noticed a couple of messages from Jack W0UCE inviting hams keen to improve their CW skills to join in and pointing them to this page detailing the thinking behind CW Academy’s approach.
What was on offer was a series of online sessions in a small online group re-learning the code. The hour-long sessions are designed to get you to read in your head and to break or avoid habits (like writing everything down) that will prevent you from increasing speed later.
The target for our beginner group was around 20wpm. The sessions took place using Oovoo which is like Skype for groups. (Apparently it’s important that the instructor can see who is having difficulties.) We logged on twice a week. In between times we were expected to practice daily using a nifty online tool, Morse Translator. This neat web app lets you practice listening to code and adjust both character speed and Farnsworth spacing. Our default setting from day one was 20wpm character speed with gaps to yield an effective speed of 10wpm. Morse translator is a great model to help practice sending as well. I found including sending practice helped lock in recognition of words.
Our teacher or Elmer was Rob K6RB. He shared his intense enthusiasm for CW with us as well as his experience on air. After a few weeks of walking us through the alphabet, numbers and prosigns and practising new letters and words, Rob gradually upped the speed. Then the rubber hit the road about week five when we were QSOing back and forth. Rob patiently introduced us to the format of the typical QSO, contesting and even handling a DXpedition. His aim was to prepare us for these so that we’d know what to expect and what was expected of us when we joined in. We got the benefits of decades of operating experience in these sessions.
The CW Academy is an initiative of the CW Operators Club. CWops is international in focus and it was great to be accommodated as the token DX in the group. As they say on the webpage “available to anyone, anywhere”.
The training has got me confident to get back on the air with a practical code speed and as a bonus, interested for the first time in having a go at contesting, initially the CWops fortnightly Mini-CWT contest which we spent a couple of sessions rehearsing.
A big TU to CWops and Rob K6RB for all their efforts running the CW Academy.