Saturday, 27 September 2025

Amateur Android

Google is continuing to increase its security measures restricting the Android system and making it more difficult for niche developers to have their software published, particularly in the amateur radio community. Despite Android tablets being a promising platform for digital radio modes over ten years ago, in 2025, amateur radio enthusiasts are once again exploring Android, with several FT8 applications emerging after an initial decline in Android amateur applications.

Second User

Technology's rapid advancement allows second-user devices to be available at a significantly lower price just five years post-manufacture. This trend can be beneficial, as older versions of the Android operating system will support many of the earlier applications that have been removed from the app store. I believe utilising a second-hand Android device for portable operating is the safest and most economical way of entering this facet of the hobby. 

Finding APK's

Finding amateur communication apps can be challenging since many are not listed in the Google app store. Users may need to resort to APK files, which can be side-loaded onto Android devices if security settings are modified.  

An APK (Android Package Kit) file is a compressed archive file type that contains all the materials required for an Android app to install successfully on an Android device. It is the format of all Android applications; however, those that fail to make it to the Google Play Store, which guarantees them as safe and certificated, can be found in a variety of software archives.

My favourite archives, and maybe the easiest to use, are listed below. These sites are best viewed with a closed browser, such as Brave, because APK archives are generally flooded with adverts, using such confusing layouts that you could easily end up downloading a variety of unwanted products. Modern certified apps are obviously available from the Google App Store. But if you would prefer not to put a Google account on your Android device, you can source most of the modern apps from non-certified sources as APK files. 

Never install APK files on your main device, be it a phone or tablet. Doing so will make the device worthless in a part-exchange deal and may also introduce a virus that could mess with your personal data. That is why I have suggested employing a second-user device specifically for portable amateur operation. 

Worthwhile

Many of the worthwhile communication apps are not detected by the search engine in the APK archives, as they are mainly geared to pushing games; making it necessary to conduct an initial search using your browser. The following is a list of applications I've installed on my portable operating device; the list is not definitive. Some are not communication-oriented, but I've included them as helpful ancillary applications.




 
















Modes

SSTV

Sending and receiving images in the digital and analogue systems can be accomplished with the following application:

Droid SSTV
Robot36
SSTV Encoder
Assempix
Shedpix


Sending images in a digital format can be accomplished with the Assempix & Shredpix applications which are an Android-only experience, as this mode is not recognized by other digital SSTV programs such as EasyPal and QSSTV (QSSTV is an excellent Linux application that decodes & sends in both digital and analogue formats). 

Annotating photos with text before transmission can be achieved with the Add Text application.

Hellschreiber Feld Hell is a form of SSTV text messaging, using mini raster scans of each letter in turn that are then displayed during reception, on a graphic moving tape, using the human eyes and brain to differentiate the text from the noise. It’s a cool mode that works in noisy conditions with a bandwidth of 31Hz. It has been around since WWII and the reference to tape is a hangover from the original receiver hardware which used paper tickertape to show the incoming message. 

Texted

The applications using text to communicate are reasonably self-explanatory and are listed below: 

Droid PSK
Droid RTTY
FT8TW
AndFlmsg
Rattlegram*


AndFlmsg is a cut-down version of the popular PC-based communications suite FLdigi, and while it doesn't cover all modes, it does cover many of the MFSK modes used for mixed text and pictorial data. AndFlmsg was developed as a tablet-based messaging app to be used in emergency communications; it's worth a look, as is FLdigi, if you are not familiar. 

*Rattlegram may be new to you; in Android circles, this is a quick text mode with error correction. It enables packet-like texting between two Android devices and is great for sending and receiving short messages on both HF and VHF.



Logging & Satellites

Portable logging is in my mind, a task best carried out using pencil and paper, but pencils break, and paper can get soggy. Plus, when it's all over, you still have to transfer the data to a computer if you want to enter for an award, so I guess using a tablet-based app has got some benefits.

Ham2k PoLo
HamRS

Both of the above apps are ideal for portable logging, as they output data in the ADIF file format (Amateur Data Interchange Format) recognized by POTA, SOTA, and many other award-based radio events. In my view, HamRS is the easiest to use, whereas Polo leans more towards POTA and SOTA entries. 

W1ANT Satellite Tracker

The above app is not really a communications program, more of a passport to LEO satellite operating. I did a quick survey of the tracking applications, and this seemed to be the most useful. There is a free version to try before going pro, but I was so impressed I purchased the upgrade. 

Beacon Mode 

Week Signal Propagation Reporting (WSPR) is a useful mode for determining band conditions, and I've included two applications, WSPR Beacon and Loud Bang. WSPR Beacon is a transmit-only program and access to the internet is necessary to map your signal (Wi-Fi hot spotting from your mobile phone is an option), while Load Bang enables receiving as well. Like all the applications that transmit, they all rely on the accompanying transceiver to operate via VOX, as there is no hardware transmitter control. 


Utilities 

While many of the above applications provide your locator information via the devices GPS, it is always useful to have one that generates your operating site as an OS grid reference or Lat/Long coordinates. The inclusion of OS Locate is as a nod to the WAB square hunters, as it provides your location's OS grid reference. Work ALL Britain (WAB) squares use the National Grid Reference (NGR) map letters and the first two numbers of your Easting and Northing square. If my location NGR were SU058011, then my WAB square reference would be SU00. In addition, this application also gives you your spot height and a compass, once correctly set.

Amateur Tool Box does what is says on the tin. Its full of useful equations, everything from working out distance between maidenhead locator squares to calculating the length of your antenna and so much more. I use it almost every other week so it’s on all my phones and tablets.  

Installing APK

Installing APK files is not difficult. Transfer the file to your device via USB port adapter or download it straight onto the device. Find the APK in your download folder or wherever you transferred it to, click on it, and follow the prompt. It will warn you that installing such a file may be a security risk and ask if you would like to proceed. This process may seem a little daunting; but the risks are minimal if a dedicated second-user tablet or phone is used solely for this purpose. Just disable the security when asked, and the app should load.

Finals

Those of you that want to make a more permanent connection between their transceiver and Android device, might like to view the YouTube link below showing a simple interface build for use with one of the many cheap Chinese rigs.  Using a Yaesu FT817 like myself, you could build the same interface, but connected  via a ready terminated lead available from Amazon or Ebay at approximately £3.00. As most are plug-to-plug leads, once chopped in half you could offer the other section to a fellow ham maybe in the local radio club.  Pin out data for the FT817 is given in the user manual and in the data found in the Github project linked below.

The beauty of an Android device is that it's self-contained and generally lighter than a PC. A 7-inch tablet or large phone could shrink down your digital QRP station to easily fit in a rucksack; when combined with a tiny Chinese rig and a simple wire end-fed antenna, you are all set to go and enjoy the day and some DX.

73, Rick G6AKG


Search Amazon or Ebay for:  Mini DIN Male Electrical Plug to Plug 6 Pin lead

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Wednesday, 14 May 2025

The “Quick” Versatile Match Box

Operating out in the field with your trusty QRP transceiver nearly always requires an ATU. However, those in the know favour a near resonant antenna as there is less power to be wasted in matching. I have had good results with resonant dipoles and end-fed antennas, the latter always wins in ease of deployment. I see lots of radio amateurs using an Auto ATU which require a power source and are generally quite limited in their impedance working range.

Over the years I've built several miniature antenna match boxes, and I can say that what follows is the best of the bunch; light, versatile and easy to use. It's not just an L-match, as the variable capacitor and inductor can be configured in to three different networks, enabling it to match into just about any impedance, from tens of Ohms to a couple of kilo Ohms on 80m through to 10m.

Circuit

The circuit detailed in Figure 1. shows a 3 pole 3-way switch which enables the variable inductor and capacitor to be configured into one of three networks (Figure 2); making the most of the components and providing maximum versatility. The match box is equipped with ports to terminate coax, single wire, and balanced antenna feeds. The coaxial input being wired in parallel with the random wire connection point and earth.

There is nothing new about the circuit design and has been culled from a copy of the 73 Magazine published in the USA: author being KB4ZGC. In my version I've chosen to use an LED type VSWR indicator lifted from a an excellent QRP ATU designed by DF3OS. I decided not to build the DF3OS design as I thought I could get more versatility out of the components using the KB4ZGC matcher. The only other circuit change is the addition of a 1:1 balun so balanced line antennas could be catered for. 

A moving coil meter was used in the original circuit to show reflected power, but these are now expensive and miniature examples are quite rare. The 1:1 balun is a current type of device, wound on a type 43 material ferrite ring (FT50-43), using the design shown on VK6YFS web pages. 

 


 Figure 1. Circuit  Diagram 

Figure 2. Showing three possible types of tuning network offered by the matchbox.

The dual section 280pF capacitor was purchased from Spectrum Communication. This could be replaced with a similar value single section variable with a fixed 180pF capacitor to be switched in parallel. The variable inductor was wound on an iron dust toroid (FT82-43) as detailed in Figures 3. You will notice that the number of turns needed are not equal on the core, this was to provide a logarithmic type of control, quickly giving a larger inductance for lower frequencies. 

 

Figure 3a. Photo not showing the exact number of turns. 

Figure 3b. The number of turns wound on the FT82-43 toroid are shown in each bubble,  turns are counted by the number of times the wire passes through the toroid. 

I hope you enjoy the project. I have built two of the matchers, the first using a series of toroidal inductors wound in a binary sequence, 2, 4, 8, 16 uH etc. Although it worked very well as a matcher, it was over complex and difficult to operate, plus the extra components took up space and increased the cost of building.  The single control for varying the inductance makes for very slick operation.

73 Rick G6AKG

References:

Original article 73 magazine. Archive. Org is till a treasure trove of article and magazines.
https://archive.org/details/73-magazine-1996-10/page/18/mode/2up

Original article from VK6 YSF home pages. (Well worth a look lots of interesting stuff).
https://vk6ysf.com/balun_choke_balun_hf.htm

Original CPC type ATU with LED VSWR indicator. 
https://sem.pl/sp5jnw/konstrukcje/atudf3oshtm/atudf3oseng.pdf

RF parts supplier Spectrum Communications. 

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