Built a switched inductor L match antenna tuner

Peter, VK3YE, has a very neat portable setup that includes a nicely beaten up FT817 and a pocket sized L-Match antenna tuner that seems to work very well for him. He described it on his site and in a video and there are many descriptions of this simple circuit. I built one for QRP use in a small plastic box.

My version allows the capacitance to be switched between the input and output. (Click to enlarge).

So far I've tested with a MiniVNA plugged in to my (currently half down) off centre fed dipole and it certainly changes the reactance wildly when adjusted.

What are all those squiggly lines on the 10m band?

The 10m, 28MHz, band seems rather lively today. I have just a low height wire dipole and am using an AirSpy HF+ but just look at all the visible activity:

(Click to enlarge).

I've often wondered what all those squiggly lines are. They usually, but not always, start and then sweep up in frequency. People have said either that they're high energy particles hitting the upper atmosphere or that they are distant welding machines that can be heard because of good propagation conditions.

It's wonderful to be able to see large parts of the spectrum like this.

Bulk convert MOBI to ePub (or other eBook formats)

I've just switched from a Kindle to a Kobo book reader. I have a collection of old MOBI format books that I wanted to bring over the the Kobo. It does read MOBI books but I see some weird erros like this:

I've found that converting to ePub in Calibre avoids these problems but I have a folder full of files to convert. Calibre has a command line tool called ebook-convert that can convert a file and seems to work well. Based on past work by others I've created this script to convert a directory of ebooks over to ePub in a directory named "converted".

#!/bin/bash

# bulk-convert

# based on https://github.com/captaincouch/lame-bulk-convert

# Set the $SAVEIFS variable as the global Internal Field Separator character.

# This preserves the original global $IFS variable to change it back later.

SAVEIFS=$IFS

# Set the $IFS variable to a space character using substitution escape sequence 

# for the space character.

IFS=$(echo -en "\n\b")

# Create a new directory for the newly-converted files, if not already existing.

mkdir -p ./converted

# Loop and convert each file "i" to mp3. Quotation marks are used to account for

# spaces and illegal characters. The files are placed in ./converted-mp3/filename.mp3.

for i in $(ls)

do

# Set a variable "c" containing the filename with the ".ext" extension removed.

# For example, "sound.wav" would become "sound", and "sound.foo.wav" would

# become "sound.foo".

c="${i%.*}"

ebook-convert "$i" "./converted/$c.epub"

done

# Set the $IFS variable back to previous value, using the value stored in $SAVEIFS

# for safekeeping.

IFS=$SAVEIFS

Switched from Kindle to Kobo ebook reader to borrow from the Library

I love reading books on a small eInk reader. A friend recently lent me a printed book (War by Bob Woodward) and I was enjoying reading it but not enjoying carrying it around so I purchased the book from the Kindle store.

My local library in Kyneton is part of the Goldfields Library Corporation and they have agreements with several eBook lending systems including BorrowBox and Libby. The Kindle does not support eBook borrowing - they want you to buy from their store. 

Another thing the Kindle doesn't support is the Pocket read it later service. (There is some sort of workaround that uses the email to Kindle service).

I've purchased a Kobo Clara BW. (I have little interest in a lower contrast colour eInk device).

The Kobo is a bit smaller than the Kindle I have and the screen is set in from the face unlike the Kindle. It charges and connects with USB-C. Setup was quite easy, I gave it the Wifi credentials and it did a software update.

The first thing I tried was plugging it in to my Mac. It mounts as a disk. I copied over an old MOBI format book and it appeared in the library. MOBI is an old Kindle format that they still support but don't recommend. (I think the DRM has been well and truly cracked). Kobo supports a range of formats natively including ePub, PDF, FlePub, TXT, HTML, RTF and also MOBI.

The MOBI file I copied over works well enough on the Kobo but I noticed some visible formatting incantations in the text. Perhaps their MOBI implementation isn't complete?

I favour ePub and while you can put them on a Kindle you must email them to get them converted.

eBooks from the Library

Setting up the Kobo to be able to browse and download loan eBooks from my library account was a bit of a puzzle. I went to the Discover tab and selected OverDrive (which is the way one accesses BorrowBox). It asked me to add my library. I tried Kyneton without luck, next I tried Goldfields. Finally I found a library in Ballarat and, guessing that it might be in the Goldfields group, chose that. Next I entered my library card number and PIN and it worked!

I am able to scroll through or search for books they have available. They do make it look like you need to purchase the book but tapping the three dot button shows an option to "Borrow with OverDrive". I sucessfully borrowed a book which quickly downloaded. It expires in 14 days.

The option to borrow rather than buy is well hidden. Dark pattern there from someone...

Pocket

Pocket is a service from the FireFox folks where you click a button in your web browser while viewing a story you want to read later and it magically gets cleaned up and sent to your reader. On the Kobo, this is in the More tab and they call it "My Articles" (although the pocket logo is easily recognised.

I had a bit of trouble getting the autentication to work and the Kobo said at one point they were having trouble too and are working on it. I tried again and it went through.

After sending an article to Pocket on my desktop computer I found that I need to tell Pocket on the Kobo to "refresh" (in the ... menu) in order to get what's new. I do like the fact that Pocket documents are separate to books rather than being mingled as they were on the Kindle.

Borrowing eBooks from a library is rediculously confusing. Things have different names, authentication seems unreliable, and I doubt that normal library users would figure it out. Perhaps Libraries are not motivated to make it easy?

Conclusion

So far I like the Kobo. I notice a bug where it seems to think I'm just 1% through books in the main listing even though I'm much more than that. Long tap to show the dictionary definition of a word doesn't work with MOBI books so perhaps that's also why the MOBI book I'm reading doesn't show progress.

Is VarAC legal? Is it even desirable?

I enjoy using digital modes. My favourite used to be PSK31 and these days I find Olivia 8/250 excellent for chatting to people who have high local noise. It gets through.

Quite often I've had people urge me to switch to VarAC which is a chat mode with handshaking and re-transmission, rather like Flmsg, it uses a software modem called VARA.

Mostly use Linux for ham radio and macOS for other computing. VarAC required modem software called VARA and both seem to require Microsoft Windows to operate.

The VARA modem specification says "VARA HF Modem is a propietary system developed by Jose Alberto Nieto Ros EA5HVK and can be used under shareware license".

They do say that it is actually an OFDM modem using an error correction technique called Turbo Codification.

Documentation on VarAC is not from the authors. The english manual says "Please note : These manual were written by brave VarAC users who wanted to contribute to the VarAC community. They may not be up to date... but they are super helpful!".

The VarAC Terms of use

• Selling of VarAC, whether standalone or integrated, is prohibited.
• Reverse engineering of the software is not allowed.
• Copying any part of the software is strictly prohibited.
• Modifying the software files is not permitted.
• It is forbidden to distribute VarAC through any means other than the VarAC official website (varac-hamradio.com)
• Please note that I bear no responsibility for any damage to your computer or transceiver.
• By submitting your email, you permit its use for news, updates, and marketing.
• Show courtesy to your fellow ham radio operators by avoiding the use of offensive language, discussing politics, or engaging in any behavior that deviates from the amateur radio regulations.
• You MUST use an authorized copy of the VARA modem software. Either free or paid version.
• VarAC is free for non-commercial use ONLY. For commercial use, please contact us.

The Amateur Radio operating procedures in Australia have a section as follows:

Encryption/scrambling

Transmissions from an amateur station must not be encrypted or scrambled, except for signals used to control a satellite, signals used to control a remote amateur station or by stations participating in emergency services operations or exercises.

Comments

I'm sure it works well as there are enthusiastic users but it seems to me that it's a proprietary version of an OFDM modem hosting a proprietary chat protocol. Also, VARA only runs on a proprietary commercial operating system from Microsoft. 

The authors are clearly in this to make money, for example an alert is shown every time I do anything asking me to either transfer 68 euros or "continue evaluating" it. I pushed the Tune button in VARAC and it shows an alert saying that to Tune you must pay.

This all seems to go against the open philosophy of amateur radio.

Tech talk on ABC Radio

Our "tech life" affects every member of the family. Scams, supporting the elderly (who are particularly vulnerable to scams), and how long you should keep devices are all covered in Nightlife. Tim Webster is joined by our regular technology commentator Peter Marks, a software developer from Access Informatics and calls from our listeners. 

https://www.abc.net.au/listen/programs/nightlife/tech-life-and-avoiding-scams/104772860  

I hadn't met Tim Webster before, he's a bit of an Australian ledgend of TV, and a real pro. My anxiety about being on national radio for much of an hour was dispelled and even Tim commented on how quickly the time went. 

We had wonderful contributions from the audience.

FNIRSI LCR-P1 Component tester review

Component testers are handy for doing a quick check of components grabbed from the junk box. Those little coloured rings get smaller every year and it's easy to pick up the wrong resistor. Some transistors have surprising lead ordering (I'm looking at you BD139s). 

I've been using my multi-meter, a nicer L/C meter, or a cheap component tester that runs from a 9V battery but recently I noticed a very smart looking new tester called an FNIRSI LCR-P1.

It's smaller than my other testers, has a USB-C rechargeable battery and a bright colour screen.

I purchased it in Australia on eBay for AU$44 which seems comparable with prices on AliExpress etc.

It has the ability to measure zener diodes and some sort of decoder for infrared remote control transmitters but I haven't tried either of those features yet.

Accuracy seems the same as my existing testers so while it's not a calibrated piece of lab gear it is handy for not accintally using a component that's out by orders of magnitude.

The infra-red decoding feature is pretty cool. Not sure that I have a use for it but it certainly works.

The zero insertion force component socket can be removed and replaced with a version designed for surface mount components. I kind of wish the ZIF socket was sunken into the body so the whole thing would actually fit in a pocket. Here's what you get in the box:

When plugged in to a computer via the USB-C port it comes up as a serial device. Presumably this could be used to flash the firmware. I tried connecting a serial terminal to it and sending a few return keys but got no response.

Vendor ID 0x1a86 is QinHeng Electronics. Product ID 0x7523 appears on some Arduino serial ports. 

My tester has firmware version 1.0.5. I can see on their page that 1.0.6 is available via a link to Google Drive containing a RAR file. Windows appears to be required to update the firmware.

I have now updated the firmward to 1.0.6 after a YouTube comment noting that it doesn't correctly report the connection direction of diodes. Tip on firmware update: hold the Zener button while powering on to put it in firmware update mode.

Manufactured PCB for Termination Insensitive Amplifier

The termination insensitive amplifier described by W7ZOI & K3NHI is a useful building block for the RF home constructor. I've been making these using copper pads glued on to copper boards but wondered if there were PCB designs available. I know about the Mostly DIY RF boards and kits but as the boards are out of stock I thought I've see if I could get boards made myself.

I found Craig Weston, VE3CBW, has kindly drawn up a design in KiCAD and shared it publicly. It opens up just fine in KiCad. He has a blog post here.

Craig has done a wonderful job of laying out the board in a logical way.

To get a board made I chose PCBWay, who I've used in the past. I followed their instructions on exporting the Gerber files. There are layers for the copper, hole drilling, solder mask and text - a bit daunting but I just did what they said and as you can see it worked just fine:

I've now populated the board and it works nicely.

The instructions on exporting the required files from KiCad are for an older version but I muddled through and made a zip of all the output files which was uploaded to PCBWay. I can see that they make a plugin for KiCad that does it all and I plan to try that next time. Here's what I zipped and sent. Not sure if everything is required but there were no complaints.

I ordered 10 boards for US$15.60 including postage on 6th December and they arrived on 23rd December. I chose the slowest postal shipping - you can pay much more for a courier if you need it faster.

My thanks to Craig. I would like to comment on his blog but it requires a login to something and I haven't figured out how to get through that so if you read this - thanks! Craig has a fascinating blog and a YouTube channel.

Local ham catchup including Peter, VK3YE

Yesterday, in a Melbourne park, I had the pleasure of a catch up with a bunch of old friends. Ham Radio Home brew hero, Peter, VK3YE, was there and of course he set up a squid pole and was soon making contacts on 10m FT8 and SSB.

Peter inspires me in a number of ways - home brew construction and getting out and participating on air.

His portable gear is satisfyingly minimal and shows beautiful wear and tear from regular use. For FT8 he uses an Android phone with a simple home made coupler.

Here's Peter's wonderfully worn FT817 and the famous home brew L Match:

It was great to catch up with everyone and I took the opportunity to quiz Peter on what I should do about my latest home brew amplifier which is operating with great efficiency as a 150kHz oscillator.