My main project for at least the last 12 months has been building a solid magnetic loop antenna and its companion automatic loop controller. I’ve been roughly tracking its progress at my magnetic loop antenna project page on this blog.
As usual, life has got in the way, but I want to get back on track and complete the project. To start pumping some RF current through it again, over the weekend I spent a short time playing with the loop on WSPR on 40, 30 & 20m. The tests were too brief but they certainly confirm that the loop is capable of transmitting a signal in spite of the fact the loop is only half a metre above ground and surrounded by metal garden furniture, a steel framed awning and gutters.
I used the WSPR Beacon android app to control my transmitter. There was some discrepancy (tens of Hz) between the actual output frequencies on the app and those shown on WSPRnet. I also found that tuning the loop to each WSPR frequency using the iP30 antenna analyzer was easy and the KX2 gave lower SWR figures.
The brief test became an exercise in understanding theWSPRnet results taking into account propagation and loop orientation which was aligned north-south.
This map view combines all 20 spots of the 1W VK2RH transmissions from grid square QF56oc. The first test was logged at 2017-05-07 01:36 UTC. (I’ve trimmed repeated info from the chart below to improve its fit on the page.)
40 metres favoured north-south, while 30 metres was literally an all-rounder and 20 metres was too brief. These results probably say more about propagation than the loop, not to mention the heavy lifting done by all the reporter stations extracting my down to -26 or -27 dB signals from the noise! Impressive all round!
About midway through January, I heard via a Sunday morning WIA broadcast that a group of ARRL Volunteer Examiners was offering to hold exam sessions at the Wyong Field Day at the end of February.
I passed my original amateur license exam here in Australia almost 40 years ago. My AOCP (Amateur Operator’s Certificate of Proficiency) says I passed a test on 21st November 1978. (That was probably the date of my second or third attempt to pass the morse at 10 wpm test.)
For the exam, I also had to answer questions about radio regulations and to demonstrate “a knowledge of wireless telegraphy and wireless telephony and electrical principles”, I had to write a number of essays about things like neutralizing a valve (tube) power amplifier or how a superheterodyne receiver works. A lot has changed since then. New technology like software defined radio and the internet.
After I heard that local hams were conducting US license exams here, my first resolution of the year was to pass the US exams for all three levels.
I was surprised that I was able to do this. All the FCC required was an online registration of an FRN (an FCC Registration Number) using a US address which was easy enough to obtain without having to pay a monthly fee. Also for the US, there is no license fee and licenses have a term of ten years.
With just on six weeks to prepare I planned to work sequentially through the three levels, spending more time on the hardest level, Extra. With no time to spare I ordered Kindle versions of the license manuals for all three levels. I also downloaded copies of the freely available complete question pools for each level. The exams are objective tests based on random selections from every part of all of the ten main exam topics – 35 questions for Technician and General, and 50 for Extra.
The license manuals essentially re-arrange the hundreds of disparate questions into a more or less flowing narrative about how to be a modern ham radio operator.
As I worked my way through the manuals I would mark up the questions and answers in my copies of the question pools and make notes if necessary to explain the answer.
The information in the manuals was very well presented and manageable and digestible. I loved the way liberal amounts of ham radio wisdom about operating practice was added to the mix. It was really like having your own personal Elmer guiding you through the intricacies of aspects of the hobby that previously were unclear or were new to me.
Best of all for me the study process demystified a lot of the mathematics of electronics and set me on a path to better understand what after all is the basis of the ‘magic’ of radio. I love the fact that the Scottish mathematician Maxwell concluded radio waves must exist, just from the maths, many years before they were actually discovered or produced by Hertz and others.
I’m happy to say I passed all three exams. I received an email from the FC about two weeks after the tests. There was no real need to do it, but it was a personal challenge – a little like voluntarily doing a driving test again, times three. It also turned out to be a convenient way to calibrate and update my ham radio knowledge.
The session was well organised and afterward, one of the VEs demonstrated how he uses his US call by connecting via remoteham.com on his iPad to a contest-grade station high in the hills in New York state. Amazing and fast! At rates around a US$ a minute, this must be a good way to turn a remote location into a source of revenue to be earned from the hordes of hams living in cities with a high level of local electrical noise.
Just read about Scandinavian versions of untranslatable concepts (like German’s gemütlich or Portuguese’s saudade) at Quartz.
One example is the Danish word hygge (pronounced ‘hooga’)…
There’s no direct English translation for hygge, but the word evokes both coziness and togetherness. “It’s not just cozy with a blanket and a glass of wine,” Kurtz tells Quartz. “It’s also interpersonally cozy—so having a few people with you talking about issues and things you care deeply about. Having some candles lit, maybe a nice warm drink in your hand. Feeling safe and content.”
The Norwegian equivalent is koselig.
Psychologists working at the University of Tromsø have found that those further north in Norway have more positive wintertime mindsets. Kari Leibowitz wrote a piece for The Atlantic explaining how people flourished there during winter.
It all helps explain the popularity of Dxing and SWL as a group activity as written about here a while ago.
The Smartlock is an accessory for my SGC SG-239 HF Smartuner, and other ATUs they make. It can be bought ready made or built.
There are indicator LEDs that signal status (TND, l ‘Z’, 2:1, PHZ, FWD, Auto & Man) on the lower section of the PCB of the SG-239 but they are only visible near the unit. As they recommend mounting the unit in a weatherproof container and as close to the feed point as possible, it’s unlikely these will be useable except in testing and servicing.
For reference – here are the indicators and connections on the transceiver end of the SG-239:
B.I.T.E.* Status LED Descriptions – *Built In Test Equipment
TND This LED will light when the tuner has found an acceptable match. It will remain lit until conditions have changed which will cause the tuner to find a different match. (i.e. A new transmit frequency has been detected, or tuner has been reset.)
L ‘Z’ This LED shows the status of the antenna impedance. When lit, the impedance is 50 ohms or less. When off, the impedance is greater than 50 ohms.
2:1 This LED will light when the VSWR is greater than 2:1. It will extinguish when VSWR is less than 2:1.
PHZ This LED indicates the status of the antenna reactance. When lit, reactance is inductive. When off, reactance is capacitive.
FWD This LED indicates the presence or lack of RF power from the radio. When transmitting, the LED will light to indicate RF is being detected. In receive, the LED should be extinguished.
OTHER All LEDs will blink on and off at a rate of 2Hz to indicate the tuner was not able to find a valid match.
The LEDs are very small and quite faint and almost impossible to see on a sunny day.
As the ad below indicates the Smartlock provides two controls that can be used remotely from the tuner and close by the radio – allowing the operator to lock or stop the ATU constantly retuning as the load changes and to reset which forces a retune the next time a signal is transmitted.
The Smartlock also indicates if the ATU managed to tune the antenna and if the lock is on. The lock can be invoked when the antenna is to be used for receive or when there are too frequent changes in the physical environment of the antenna such as when mobile and passing trucks or going under bridges….
Installation requires normal coax and a four conductor cable for power and control.
SMARTLOCK, FOR SG-230/237/239 SMARTUNER
The SmartLock provides two external controls for the SG-230/237/239 Smartuner. The locking function prevents retuning despite changing antenna loads. The reset function forces the coupler into a retune cycle the next time a signal is transmitted. Tune and lock status is indicated by one green and one red blinking LED. Supplied with 9 feet (2.5 metres) connecting cable. For use with SG-230/237/239 couplers manufactured after July 1, 1993, only.
Its simplicity and the cost of the assembled unit have inspired a number of people to roll their own.
The colour code of the cable to the Smartuner appears to be:
TND = Green,
HLD/RSET = White
+12V = Red
Gnd = Black
Phil Salas – AD5X – decided to remove the components making up the voltage regulator part of the circuit.
“I wanted to build a SmartLock to use with my SG-239. After studying the SmartLock schematic, I couldn’t figure out why SGC put in the transistor and zener diode. The ST-TNE input on the SG-239 is just a 1.5K resistor to an open collector transistor to ground. So I eliminated Q1, R3, D1 and C3 on the SGC SmartLock schematic. My final circuit is shown below. I used a DB9S connector to interface with the SGC tuner (I attached a DB9P to the tuner interface wires), and a PowerPole interface for 12VDC. This way I could use a standard DB9 extension cable as necessary for interfacing between the tuner and SmartLock. I used ultra-bright LEDs (3000mcd or so) to provide plenty of visibility.”
This uses a tiny PCB available on Italian eBay from a seller who wanted 50 € to send one to Australia!
I worked out a way to use a scrap of veroboard to hold the two capacitors and one of the resistors and to manage the wiring between the base and the panel of the enclosure which is probably more efficient and certainly faster. As well I noticed that the PCB seems to be designed for a different kind of DPDT switch where the centre poles are not in the centre!?! So I can add the satisfaction of saving whatever Euros I would have ultimately paid to the greater satisfaction of having nutted out the layout of the veroboard scrap…
Luca used the simplified circuit by Hans Nussbaum DJ1UGA which appears to have in turn have some subsequent input from OE7OPJ (who by the way has a very interesting website at http://www.qth.at/oe7opj/).
L’accordatore automatico SGC-239 indubbiamente è un gran bello strumento. Si collega e funziona ottimamente con qualunque radio (HF) semplicemente utilizzando un cavo coassiale e una fonte d’alimentazione a 12 volts. Non è particolarmente esoso di corrente e anche in utilizzo SOTA non va a gravare sull’autonomia giornaliera. Ne ho trovato uno usato sui soliti canali nazionali ad un prezzo decente e non mi sono fatto scappare l’acquisto. Accorda davvero di tutto gestendo potenze da 1,5 a 200 watt. Ottimo per il mio Yaesu 817, ma altrettanto utile per le “normali” radio munite dei canonici 100 watt. Per poterlo però utilizzare al meglio, si rende necessario l’acquisto di un interfaccia che permette di resettare o bloccare lo stato d’accordo del SGC-239. Tale interfaccia (SMARTLOCK) si trova però in vendita a quasi 100 euro, decisamente troppi per 2 condensatori, 2 resistenze, 2 led e un paio di interruttori. La prima idea è stata quella di prendere lo schema presente sul manuale dell’accordatore e realizzare su basetta forata il circuito. Cosa questa realizzabile, ma che avrebbe dato un idea di “precarietà” a tutta la realizzazione. La scelta a questo punto è ricaduta su un mini circuito stampato realizzato con maestria da Danilo Cramaglia (lo trovate su Ebay come utente Martelloman), che partendo dallo schema elettrico mi ha consegnato quanto riportato in foto:
The SGC-239 automatic tuner is undoubtedly a very nice tool.It connects and works well with any radio (HF) simply by using a coaxial cable, and a power source to 12 volts.It is not particularly power hungry and even practical to use on a routine SOTA outing.I found one used on the usual national channels at a decent price. It really suits around handling power output from 1.5 to 200 watts.Great for my Yaesu 817, but just as useful for “normal” radio equipped with 100 watt “cannons”.
But in order to make the best use, it is necessary to obtain an interface that allows you to reset or block the status of the SGC-239.This interface (SMARTLOCK), however, is for sale at nearly 100 euro, far too much for 2 capacitors, 2 resistors, 2 LEDs and a pair of switches.The first idea was to use the circuit in the tuner’s manual and build it on perforated board.While this is feasible, it could give an idea of “insecurity” to the whole creation. Instead I chose a mini PCB made with skill by Danilo Cramaglia (Ebay-user Martelloman), which, starting from the wiring diagram handed me what is reported in the picture:
I plan to use this wiring arrangement for the 4 pin plugs, socket and line.
In the hand book to the SGC SG237 Auto Antenna Tuner there is a circuit for an interface they call the SmartLock and it allows some manual control over the AATU and more importantly, it indicates when the tuner has tuned successfully.
The shielded 4 core wire is clamped in the cable tie through a pull through bushing. The case uses a diecast aluminum box TD 5-8-3B (55x30x80) by TAKACHI. The front of the enclosure has the Normal / Lock switch (2-pole, double-throw), the Tuned LED (Green), the Locked LED (Red) and the Reset switch (Make contact). It includes the three-terminal regulator. The bypass capacitors on the circuit diagram are omitted here.
(3) box overview and operation
Once tuning is complete the Tuned LED (Green) glows. If the Normal / Lock switch is pointing to the right, the Lock side, the Lock LED (Red) is lit and fluctuating SWR, etc. does not cause automatic re-tuning.
If the switch is set to the Normal side, normal operating conditions prevail, the SG-239 will automatically start tuning if SWR or the band is changed.
If you press the RESET (red) button, the ATU will re-tune.
>So here is my effort successfully completed today…
I used the simplified circuit by Hans Nussbaum DJ1UGA and the front panel layout of Phil Salas AD5X. I managed to squeeze everything into a compact package – a small die cast aluminium enclosure 64 x 58 x 35mm which Jaycar sell for $9.95. And that was the main cost. Everything else was on hand.
I’ve yet to label the panel, but the green LED indicates a successful tune, the red LED is on when the switch is in the Locked position, and the push button switch is the reset. I used 4 pin sockets and line plugs to connect to and power the Smartuner. And I used a DC socket to supply 12V power. I had planned to use power poles but decided that would not fit comfortably in this small enclosure.
The ATU is housed in a plastic lunchbox which can be protected by a larger rubber waste paper bin as recommended in the SGC manual.
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)