Category Archives: Accessories

Bioenno Power Thanksgiving Sale

I find the 4.5 aH 12V Bioenno LiFePo battery to be the perfect portable power source for my 12V radio gear.

Just a heads up that Bioenno Power is having a 2020 Thanksgiving sale and offering a 10% discount with the coupon code “THANKS”.

I’m a huge fan of Bioenno’s batteries and just pulled the trigger on yet another LiFePo battery. This time, a compact 3 aH battery. This will be more than enough battery to play QRP for hours without recharging.

Side note: I’m also working on a project for my parents converting their living room lamp into a DC LED lamp with battery backup. Their power outages seem to be so frequent as of late, I know they’ll appreciate a lamp that will work regardless if the power grid is up or not. I’ve already purchased a 12V LED Edison-style bulb and now will pair it with a 4.5 aH Bioenno battery.

Click here to check out Bioenno’s website.

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Portable tuner (ATU) options for the new Icom IC-705

Many thanks to SWLing Post contributor, Paul, who asks:

What are good choices for ATU and 100W amplifier for the IC-705? [Also] will the Icom AH-4 antenna tuner work well with the IC-705?

Great questions, Paul!

100 Watt Amplifiers

I’ve limited experience pairing the IC-705 with external 100 watt amplifiers. I own the Elecraft KXPA100 and it pairs well with the IC-705 via RF sensing. My hope is that SWLing Post readers may be able to chime in here and offer more suggestions as there are a number of inexpensive, basic, amplifiers on the market now but I’ve never personally used or tested them. I can say that the KXPA100 is a beautifully-engineered amplifier.

Antenna tuners

Icom AH-4

First off, regarding the Icom AH-4 ATU, I’m not certain if the IC-705 has the same control commands as the AH-4 (I’m guessing it does, but perhaps someone can confirm–?).

It would not be my first choice as a portable antenna tuner for field work. For one thing, it’s a pricey at $300. That, and I’ve always viewed the AH-4 as more of a remote antenna tuner for those who need a permanent matching box outside the shack near the antenna feed point. For that application, I’m sure it’s amazing.

According to the AH-4 specifications, it requires “10 W (5–15 W)” of tuning power. I’m not quite sure what the “5-15” watts means, but the IC-705’s max output power is 10 watts using an external 12-13.8V battery, and only 5 watts using the BP-272 Li-ion Battery. Not sure if that would be adequate to trigger the AH-4 to find a match without some sort of command cable connection.

For portable ATUs, let’s take a look:

IC-705 Portable ATU Options

The Icom IC-705 actually has a port on the side of the radio that allows one to connect the rig to an ATU for some level automatic ATU control. At time of posting, there are two ATUs in the works that are able to use this port: the Mat-Tuner mAT-705 and the Icom AH-705 (there could be more, but I’m not aware of them).

Mat-Tuner mAT-705 ($220 US)

I reviewed the mAT-705 on QRPer.com (click here to read). In short, it’s absolutely brilliant at matching antennas quickly and efficiently, but it has a few design shortcomings. The main issue is that you must use a mechanical switch to turn it on and off, else you deplete the internal 9V battery within a week. Most similar ATUs either have auto-off functionality, or at least an external power option. Since the mAT-705 can connect directly to the IC-705, it automatically knows when you need to tune to a frequency and will do this anytime you send a carrier, hit PTT, or initiate tuning via the menu option. It can also remember frequencies you’ve already matches to make the process quicker. The mAT-705 is also RF-sensing, thus can work with other radios. Vibroplex is the US distributor of the mAT-705. Note, too, that there are a number of portable Mat-Tuners that will work with the IC-705–the mAT-705 is the only one that uses the IC-705 control cable (which I feel is actually unnecessary).  Check out their full product line before ordering.

Icom AH-705 ($T.B.A.)

The Icom AH-705 is Icom’s own external ATU designed to work with the IC-705 and fit in the LC-192 backpack. Since the AH-705 will be able to connect directly to the IC-705, its functionality will be very similar to the mAT-705. I’m speaking in future tense here because, at time of posting (18 November 2020), the AH-705 is not yet in production and we’ve no retail price. With that said, Icom has a legacy of making fine ATUs, so I’ve no doubt it’ll function well. Like the mAT-705, it has a mechanical on/off button so you may have to be aware of turning it off when not in use to preserve the internal alkaline batteries. Unlike the mAT-705, it has an external 13.8 VDC power connection. Universal Radio will update their site with pricing and shipping information once available.

Elecraft T1 ($160-$190 US)

The Elecraft T1 ATU has been in production for many years now and is a fabulous portable ATU. Not only is it incredibly adept at finding matches, but it’s also efficient in terms of power usage. It will run for months on an internal 9V battery (that’s very easy to replace in the field). The T1 has no special connection for the IC-705, but it does have an optional T1-FT817 adapter for the Yaesu FT-817 series transceivers. In truth though? I find control cables unnecessary because tuning the T1 only requires pressing the tune button on the ATU, then keying the transceiver. Once it finds a match, it shuts down and locks it in. You can purchase the T1 directly from Elecraft ($160 kit/$190 assembled). The Elecraft T1 is my portable ATU of choice.

LDG Z-100A ($180 US)

I’ve owned a number of LDG tuners over the years an absolutely love them. I find that they offer great bang-for-buck, perform amazingly well, and are built well. In fact, I designed an outdoor remote antenna tuning unit around their original Z-11 Pro auto tuner. It’s housed in a sealed waterproof enclosure, but is completely exposed to outdoor humidity and temperature changes (which can be dramatic here on the mountain). I’ve been powering the Z-11 Pro for 10 years off of a discarded sealed lead acid battery that’s being charged by a Micro M+ charge controller and 5 watt BP solar panel. I’ve never needed to maintenance it. One of LDG’s latest portable ATUs is the Z-100A. I’ve never used it, but I imagine it’ll perform well and I may very well reach out to LDG and ask for a loaner to review with the IC-705. It does have a command cable port that works with Icom radios, but I’m checking with LDG to see if it works with the IC-705 (I’ll update this post when I hear back). The LDG Z-100A retails for $180 via LDG’s website.

Emtech ZM-2

Shortwave radio listeners, especially, should take note of the Emtech ZM-2 balanced line tuner! Unlike the ATUs above, the ZM-2 is manual–meaning, you manually adjust the tuner’s L/C controls to achieve a match with your antenna. I’ve owned the ZM-2 for many years and have used it with a number of QRP transceivers. Since it’s not automatic, it might take a minute or so to find a match, but it’s worth the wait. The ZM-2 requires no batteries to operate, which makes it an invaluable and reliable little tool in the field. In addition, since the ZM-2 doesn’t require RF energy in order to find a match, it’s a brilliant choice for SWLs who want to tweak their wire antennas. I find it functions as well as if not better than other manual tuners designed specifically for receivers. The ZM-2 is also the most affordable of the bunch: you can purchase a pre-built unit for $87.50 from Emtech or $62.50 as a kit. I would advise purchasing one even if you also have an automatic antenna tuner–makes for a great back-up!

Other options?

This is by no means a comprehensive list of portable ATUs to pair with the IC-705, just a few suggestions. In fact, companies like MFJ Enterprises make a number of manual tuners that could easily be taken to the field and require no power source (much like the ZM-2 above).

Please comment if you have experience with other types of ATUs and please include links if possible!

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My Obsession with Muji A6 Mini Logging Notebooks

In many ways, I’m old school. While I love leveraging technology to make the most of my radio world, I also have a sincere appreciation for simple “analog world” solutions to my needs.

I’m a notepad guy.

When I moved to France to do undergraduate studies in the early 90s, I became reliant on small notepads to keep my brain organized and maintain some sense of sanity. I kept one in my pocket, my backpack, and had larger notepads for each one of my classes. It was in France I discovered the amazingly wide variety of notepads that could be found in a Papeterie or stationery store. While I could hardly afford notepads and pens/pencils I found in those stores, I did occasionally splurge.

To this day, I keep notepads in my EDC bag and near my radio desk. I find that the act of writing something down–pen to paper–locks thoughts/memos in my memory much better than taking notes on a digital device.

Paper Logging

If you’ve followed any of my field reports for Parks On The Air (POTA) here on the SWLing Post  or on QRPer.com, you’ve probably seen me employ a wide variety of note pads and logging sheets.

While I often do live logging with my Microsoft Surface Go tablet to speed up log submissions, I always log on paper first. Always.

For one thing, when I’m copying a callsign in Morse Code (CW), I prefer writing down the call as it’s being sent. Regardless if a contact is in CW or phone, I copy the callsign and exchange information on paper first, then immediately transfer it to my logging software on the tablet. I carry the Surface Go tablet with me on about 75% of my field activations, but leave it at home if I’m doing a substantial amount of hiking.

Not only do I find it easier to log on paper first, but by having a full set of logs in notebooks, I know I’ve got a proper archive of the activation if my tablet fails me.

Plus–if I’m being completely honest here–I love seeing my handwritten logs after an activation. It gives me more of a sense of accomplishment for some reason. Don’t ask me why.

Muji A6 Notebooks

A couple months ago, I was searching for a notepad that could easily fit in one of my compact field radio kits.

My wife (an artist) suggested I check out Muji Notepads of Japan because she’s both pleased with the quality and price as compared with other quality notebooks. She measured my field kit pack and suggested the Muji A6 lined notebook. On Amazon, they’re sold in packs of 5 books for $12.00 US. I was skeptical about the size, but placed an order anyway.

Each book has 30 pages which means if I write on the front and back of each sheet, it should last me up to 30 average park activations (assuming roughly 25-40 contacts per activation). Since my activations tend to be short, it’s rare that I exceed 40 contacts.

I purchased a pack of five notebooks and put one notebook in each of my radio field kits. I even dedicate one for my Elecraft AX1 antenna kit.

I love these Muji notepads–they’re compact and thin, but the paper quality is nice and it’s large enough I can use “normal” hand writing. While I tend to prefer spiral-bound notebooks for logging, I like the binding on these notebooks because it doesn’t catch on anything and keeps the profile super thin which is perfect for small packs and cases. The pages lay flat once open, too.

For the record, I also keep a few Rite in the Rain weatherproof notebooks handy if I’m heading to a park or summit after heavy rainfall, if there’s the possibility of rain in the forecast, or if I’m camping. They’re also indispensable. The Muji Noteboooks aren’t designed to handle water, but in truth it’s very rare that I’m playing radio in the rain. I prefer the slim profile of the Muji Notebooks for day-to-day field work.

I just ordered another pack of five this Muji A6 Notebooks this week and plan to put one in my portable SDR kit, and two of my portable receiver kits. In truth, my shortwave radio logs are less organized than my ham radio logs, but I’m constantly jotting down broadcasters, times, frequencies and receiver performance notes.

Click here to check out Muji A6 Notebooks on Amazon (affiliate link supports the SWLing Post). 

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The new Raspberry Pi 400 All-In-One Keyboard PC Released

On Monday, I received the announcement about the new Raspberry Pi 400 via the Pi Hut.

The Pi 400 is essentially a Raspberry Pi 4 built into a keyboard. Wonderful concept that very much takes me back to my first personal computer.

Of course, in the spirit of all things Raspberry, the complete kit price is pretty reasonable at about $100 US. Here are details via Pi Hut:

The Pi400 has all of the great features of a Raspberry Pi 4 wrapped in a convenient and compact keyboard – it’s the ultimate coding machine!

The keyboard is available as a kit with everything you need in one box (minus a monitor), or on its own.

The Pi400 doesn’t compromise on performance either – in fact, the CPU is clocked to a whopping 1.8GHz which is made possible thanks to the large metal heatsink inside the keyboard.

CPU aside, the Pi400 boasts the same great specs and connectivity as a Raspberry Pi 4 – 4GB RAM, dual-band wireless networking, Gigabit Ethernet, dual-display output and 4K video playback.

USB, power, video, Ethernet and SD ports are located at the rear of the keyboard, including the familiar 40-pin GPIO connector.

The Raspberry Pi 400 is also available in a number of different regional variants (some international variants coming soon!).

Many thanks to SWLing Post contributor, Richard Langley, who shares the following Pi 400 review from Tom’s Hardware:

The Raspberry Pi Model B has seen the same board layout since the Raspberry Pi B+ arrived in 2014. Sure the Raspberry Pi 4 swapped the Ethernet and USB ports around, but the same basic design has persisted. So when we received a parcel from Raspberry Pi Trading and opened the box to find a keyboard, we were somewhat puzzled as to the contents. Inside this compact and well designed keyboard is a Raspberry Pi 400, a variant of the Raspberry Pi 4 4GB designed specifically for this purpose.

Retailing as a single unit for $70 or as a complete $100 kit with mouse, power supply, cables, micro SD card and a copy of the Raspberry Pi Beginner’s Guide, the Raspberry Pi 400 could be the ideal way to introduce the Raspberry Pi to your home.

[…]Despite the change in form factor, this is still a Raspberry Pi 4 4GB and, as such, it behaves in exactly the same manner, with one exception. The Raspberry Pi 400 lacks the CSI and DSI connectors, used for the Camera and Official Touchscreen. Without these connectors there is no way to use those devices. This loss of the touchscreen connector is not such a big deal, but the camera connector is.

The range of Raspberry Pi cameras are cheap and effective add-ons (see our list of best Raspberry Pi accessories) that provide a fun stream of projects. If you want to create camera projects, then the Raspberry Pi 400 is not for you.[…]

Click here to read the full review.

I normally scoop up new Raspberry Pi products as soon as they’re released, but I’m flush with RPi’s at the moment! I do believe, however, I’ll eventually replace out my daughters’ Pi 4s with these all-in-ones.

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Steve builds a simple SWL antenna tuner that pairs brilliantly with the Belka-DX

Many thanks to SWLing Post contributor, Steve Allen (KZ4TN), who shares the following guest post:


A Simple Antenna Tuner for SWL Radios

by Steve Allen, KZ4TN

After reading 13DKA’s excellent review of the Belka-DSP on SWLing.com a few weeks ago I knew I had to have one! The size, features, and performance of the Belka-DX (latest version of the Belka-DSP) is phenomenal. I won’t go into reviewing the radio as I couldn’t come close to 13DKA extensive review. If you are considering this SWL receiver his review is a must read.

I love bedtime SWLing and have been putting off setting up an outside antenna specifically to feed into the bedroom for too long. Given that the resonant frequency of the antenna would not be broad enough for the tuning range of the Belka-DX I decided to build a small antenna tuner just for SWLing.

After a couple of hours searching the internet for a simple tuner I found just what I was looking for on http://www.hard-core-dx.com/nordicdx/antenna/lab/tuner.html. It’s a simple L match using a single variable capacitor and coil.

For the coil I wound ~100 turns of 26 Ga wire on a one inch diameter wooden dowel. The wire size can be whatever you have on hand. I twisted a tap every 10 turns. I drilled a hole in each end and glued in a machine screw to mount the coil to the bottom of the enclosure. I’ve had this enclosure in my junk box for a long time and have been waiting for just the right project. The variable capacitor I used was one I found on EBay a few years ago that had two sections, 330 pF and 120 pF. I tied them together for 450 pF. For the rotary switch I had to scratch around on eBay for a while until I found a 12 position single pole.

The plans for the tuner suggested adding a fixed value capacitor with a toggle switch to increase the lower end of the tuning range. I found a 510 pF silver mica and wired it into the circuit.

The antenna I put up is a sloper about 30 feet long.The high end is up about 40 feet and the low end is at about 12 feet. I put the antenna and tuner to the test last evening and the reception on the Belka-DX was superb. With the tuner the strength of the signal would peak about 2-3 units when I found the sweet spot.

The tuner also does double duty as an attenuator for very strong signals.

One mod I made to the Belka-DX was the addition of some grip tape to the tuning knob. It makes fine tuning much easier.

I believe we will continue to see a number of innovative receivers coming to market in the near term utilizing SDR technology. The ratio of performance to size of the Belka-DX is truly amazing in my opinion.


Thank you, Steve, for sharing this brilliant weekend project! As always, brilliant craftsmanship!

Click here to read Steve’s other posts and projects.

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A Tecsun PL-330 features reference sheet

Many thanks to SWLing Post contributor,  Jaap de Goede, who shares the following as an update to his Tecsun PL-330 review. Jack writes:

I discovered several features that are not displayed on the keyboard both on the Internet and by fiddling with the radio. Maybe these features are in the Chinese manual but I simply can’t read that language. What became clear is that the PL-330 resembles the PL-990x. But I couldn’t find if DNR and Muting Threshold are supported in the firmware I have (3302). Here is a table with the features and how to operate:

Click here to download as a PDF.

Many thanks for creating and sharing this excellent reference sheet, Jaap!

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How to install a mechanical SSB filter on the Yaesu FRG-7

Many thanks to SWLing Post contributor, Kostas (SV3ORA), for sharing the following guest post which originally appeared on his radio website:


How to install a mechanical SSB filter on the Yaesu FRG-7

by Kostas (SV3ORA)

The Yaesu FRG-7 is a general coverage MW/SW receiver that uses the Wadley Loop system for stabilizing the frequency tuning. The receiver has a good sound on AM mode, that reminds me the tube receivers sound. However, on sideband mode, it is pretty much useless. The IF ceramic filter that is used, does not have enough selectivity to reject the opposite sideband. No matter if the front panel mode selector switch states USB/CW and LSB, these just shift the BFO, nothing more. The receiver is a DSB set not SSB. A cheap way you can accomplish single signal sideband reception with the FRG-7 is described in this link. Whereas it works, it increases the audio bandwidth of the signals to the high pitch.

A better approach is to install an additional mechanical filter to the receiver. This of course requires expensive 455KHz mechanical filters, but if you have one in hand or if you are willing to pay for the improvement in performance, then this is the recommended option. But you can’t just desolder the ceramic filter of the receiver and solder a mechanical filter in place. On AM mode, you need wider bandwidth, but on SSB mode you need narrower. So both filters must be in place and a selection must be done in each mode. Thankfully, this modification is pretty easy on the FRG-7 and it does not require any modification of the external appearance of the radio.

The schematic of the FRG-7 is shown above. Everything with red color, are part of the modification. The modification is pretty straight forward. You have to desolder the original ceramic filter from the FRG-7 PCB and install it on a separate PCB along with the new 455KHz mechanical filter. To select between the two filters, a 9-12v DPDT relay can be used and it must be connected as shown in the schematic. The power for the relay coil is derived from one section of the mode switch (S3d). On USB or LSB modes, the BFO is energized and this power is also used to energize the relay, which in turn switches to the narrow mechanical filter on these modes.

A good place for the new PCB that accommodates the filters, is just below the main tuning dial of the receiver. There is a hole there and three screws, which can be used to also hold this PCB in place. I needed to replace these screws in mine with longer ones, because I used spacers to prevent the PCB from touching the chassis. But this is optional.

Two small pieces of coaxial cables are used to connect the new PCB to the pads of the ceramic filter, that has been now removed from the original PCB of the receiver. Ground these cables on both ends.

The power cables for the relay coil (shown with red and black in the picture above), are passed below the PCB to the chassis opening and through a hole to the bottom of the original PCB of the receiver. The ground wire is soldered to the filter ground point and the red wire is soldered to the mode selector switch S3d. S3d is the outer wafer onto the switch. Use a multimeter to find the contact of the switch that has VCC when the mode is switched to USB or LSB. This is the point where you want to connect the red wire.

After installing everything, you should perform an alignment of the TC404 and the T406 in the BFO section as described in the manual. This requires a frequency counter, but I did my alignment by simply adjusting the two controls by ear, until I got roughly the same pitch on LSB and SSB audio bandpass. These controls interact, so you have to do a bit of back and forth in both of them. It is very easy.

After installing the modification and aligning the receiver, the result is pretty obvious. No more DSB reception, SSB signals are received just once in the dial and their bandwidth is limited as it should on SSB. The mechanical filter I had, was a bit narrow (2.1KHz) so I can also hear a bit os “seashell” sound on SSB, but SSB voice signals are perfectly understood. It is interesting that the audio volume between the ceramic filter and the mechanical filter was just about the same, which indicates that there is no additional loss in the newly installed filter. Another interesting thing is that there was no need for any impedance matching using active devices or transformers on the mechanical filter. It worked just by directly connecting it. Neither it’s loss, not it’s response seems to be affected by any possible impedance mismatches.

Note that Collins produced both symmetrical and asymmetrical mechanical filters (yes they used two filters, one for USB and one for SSB in some of their gear). My filter is a symmetrical one (same roll-off response curve on both sides of the filter passband). If you use an asymmetrical filter, expect a bit different pitch when switching from LSB to USB and vice versa. Not a huge problem, but just a note.

By performing this simple modification, you will end up with an FRG-7 receiver that is trully selective, allowing for real SSB reception. Most importantly you do not ruin the appearance of your precious FRG-7, but just improving it’s performance. This modification would probably be appreciated much when deciding to sell your FRG-7 to someone else.


Thank you for sharing this practical and affordable project with us, Kostas!

Post Readers: Check out this project and numerous others on Kostas’ excellent website.

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