3D Printing HF Portable

K1FM Magnetic Loop: 2020 edition

I really, really like magnetic loops.

After making a bit of a splash with at the Dayton Hamvention and publishing how to make your own on QST I decided to improve the design a bit more, so here I am with the latest iteration of the K1FM Magnetic Loop.

The new design improves the older one in a few key aspects:

Entirely 3D printed
Readily available, made in the USA variable capacitor
Easy to assemble

Basic geometry and main electrical characteristics remain unchanged:
– 4o to 10 meters
125 inches radiator
165pF variable capacitor (dual gang series)
QRP power (it actually can handle a lot more but, as you know, using a magnetic loop in close proximity with more than a few Watt is against FCC guidelines and potentially dangerous. Don’t do that)

Fully 3D printed, capacitor enclosure

The new enclosure requires no rework in order to be mounted. It is now quickly detachable by using the same mount type as the radiator/exciter assembly. This makes the antenna even more portable and, at the same time, opens the possibility of using other support types in place of the selfie-stick (fishing rods, PVC pipes etc.).
The capacitor uses a 3:1 planar reduction that, combined with the a fairly large knob, makes tuning quick and easy. A 3D printed indicator (blue) shows the current shaft position: just by looking at enclosure you can tell where about you are currently tuned and act accordingly when it’s time to tune again.

Exciter loop splitter

Thanks to a new splitter design, the exciter loop is now conveniently made out of a standard LMR240 BNC-male to BNC-male pigtail. The splitter also allows the possibility of using multiple radiator/exciter assemblies in order to, for example, work 6 meters.

Radiator loop mount

I also redesigned the radiator mount to follow the different bending radiuses of the radiator and the exciter loops. Both cables now snap-in with just the right amount of force, therefore zip-ties are no longer needed.

The new loop looks great and works better!
I’ve decided to call it K1FM-Loop. If you want to build your own, here are the instructions to do that

EME Hacks

How to make your first EME contact using Remote Ham Radio – Part 2

In part 1 I have described how to setup your RHR account your Mac in order to try EME contacts. This time I will explain some of the operational challenges that you need to understand in order to be successful.

Be advised that I am far from being an expert. In fact I am precisely the opposite as, at the time of this writing, I have logged a total of just 8 valid EME contacts. Still I believe this might be useful to some: If made an EME contact, so can you!

Finding the Moon

This might be unsurprising but in order to do EME contacts you need the moon to be visible. Having no Moon in the sky feels exactly like having no propagation on 20 meters. You just have to wait.

Some great tools to predict Moon visibility are and

Both website are useful to determine the Moon direction and elevation as well as its distance from the Earth. Distance plays a big role in this: having the Moon at “just” 360000 Kilometers is much better than having it at 405000 Kilometers, for obvious reasons. More simply, you might end up using those sites (or similar others) to predict when the Moon availability is compatible with schedule.

Please note that WSJT-X can display some of the same info within its “Astronomical Data” window however I still like to use these websites as I find them more accessible and useful. is useful to display realtime Moon parameters.’s Table function can be used to predict Moonrise/Moonset times as well as Moon Distance.

Pinging the Moon

Before you go into action – especially if it is your very first attempt – you might want verify if you can receive your own echos bouncing off the Moon.

Doing this test is relatively easy as WSJT-X has a specific mode called “Echo” just for that purpose. The documentation goes in depth in explaining how the mode works so you can refer to it.

In a nutshell: with your station ready to go on a clear frequency, select the “Echo” mode and click on “Enable TX”. Pinging will begin immediately. VHF does not require Doppler correction at the Rig level so you cal leave Doppler Tracking on the Astronomical Data Window unchecked.

Here is a successful example:

As per the documentation, the reply quality is represented in the Q column on a scale from 0 (no echo) to 10 (perfect echo).

Echos won’t always come back from the moon. That might indicate a problem with your setup (is power being actually transmitted? is the antenna pointed towards the moon? is the RX chain working properly? the list could be long…) or it could also indicate – as they say – poor “Moon conditions“.

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EME Hacks

How to make your first EME contact using Remote Ham Radio – Part 1

Original Picture By Gregory H. Revera, CC BY-SA 3.0


Ever since I embarked on my journey in Amateur Radio, I have always regarded EME as the pinnacle of the hobby. The concept of bouncing signals off the Moon held a tremendous allure, but the immense distance, substantial link budget, and the requirement for massive antennas made it seem completely unattainable.

However, over the years, moonbounce has become increasingly accessible. The proliferation of digital modes has enabled ordinary hams to achieve Earth-Moon-Earth contacts even with relatively modest setups. You no longer need an antenna that would grace the front cover of a magazine to engage with the moon.

More recently Remote Ham Radio mada available a quite decent EME station for anyone to utilize. Consequently, if you wish to try EME today, all you need is your laptop. Pretty neat, isn’t it?

Before we move on, let me clarify two things:

  1. This is intended for Mac users. If you use Windows… I’m sorry!
  2. Remote Ham Radio isn’t sponsoring me in any way. I actually paid with my own money in order to use their service and research its functionalities. But… hey I did for science so that’s OK. I also did for fun. Actually, I did it just for fun. Whatever… let’s get into it!


Remote Ham Radio is a company that offers some kind of an “Amateur Radio as a Service” model. The concept is simple: they build powerful stations and you paid to use them. One of their stations – called Jefferson – is EME VHF capable.

Jefferson has an array of 4×16 elements Yagis and a 1KW amplifier. This is far from being a Big Gun in the world of EME, but is definitely enough to make a lot of contacts. Using the station currently costs $0.79 per minute + membership fee ($99 per year or $20 per month) . As you can see this isn’t cheap but it is still certainly cheaper than building your own station from nothing.

What you will need

Unfortunately RHR’s documentation about EME isn’t super descriptive. In the process of learning how to use their station I ended up with a setup that is a bit different. I find mine to be more convenient for the simple reason that it doesn’t require you to alter your Mac’s default security settings. Also, you will not need to pay extra $99 in order to purchase a third party program (see below).

This is what you are going to need:

Contrary to what RHR recommends, in my setup you DON’T NEED:

  • Amoeba Loopback ($99)
  • xDAX by DL3LSM

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Japan again!

During the past year I practically ended all ham radio related activities due to some family updates 👶 🙂

In the summer however I visited Italy again and… guess what? I had an opportunity to make another Japanese contact on 20 meters SSB, this time with JH1GEX Yutaka, near Tokyo.

Yutaka is an excellent operator: he routinely halts his pile-up to allow mobile / portable stations to make it through. If everyone would be so kind, portable operations would be much, much easier! Thank you Yutaka san!

HF Portable

Another Japan Voice QSO! This time from Italy

I am again in Italy, active as IZ6BYY.

With the help of Antonio IK6ZRX (who cut through the pile-up) I was able to work Kazu, JH3NGD with my portable loop and 10W on 20meters SSB.

Here is the video:

Unfortunately It was night and I could not properly ready Kazu’s call, so I misread it the whole time (rookie mistake). Besides that, I was given a 53 and was able to have a nice little QSO with Kazu, who speaks perfect Italian!

This obviously was a much easier QSO than It could have been because I had been announced by Antonio. Nevertheless it was for me a remarkable one. Thanks Kazu and thanks Antonio!

3D Printing HF Portable

Build the K1FM-Loop

The latest version of the K1FM-Loop is electrically similar to the previous one, but it is designed around off-the-shelf parts or, more generically, items you can readily order online.

This antenna relies – heavily – on 3D printing. Acquiring the non-printed parts and assembling them should be fast and easy as no reworking at all is necessary. The needed tools are screwdrivers, wrench keys and a soldering iron. You also need a 3D printer, of course, or at least access to one.

Lets’s start from the parts list:

  • 3D Printed parts
  • Exciter Loop Splitter PCB (available shielded or unshielded – see below)
  • Variable Capacitor – Oren Elliot Products P/N S2-332x2P (21 blades, 2 gangs of 9.3 – 332.4 pF used in series)
  • ~40 inch selfie-stick
  • gopro bike mount
  • 15 inch photographic tripod
  • PL259 to PL259 LMR400 cable 125 inch long (for the radiator loop)
  • BNC-male straight to BNC-male straight LMR240 cable 25 inch long (for the exciter loop)
  • BNC-male straight to BNC-male straight RG316 cable ~6 ft long (for the feed line)
  • BNC-female Molex P/N 0731000105 (3 pieces for the Exciter Loop splitter)
  • SO239 panel connector (2 pieces for the capacitor enclosure)
  • MF-A05 Knob, 1/4inch shaft
  • Socket Head Cap Screw, M5-0.8mm Thread, 12mm Long, Alloy Steel, Black Oxide (8 pieces)
  • Button Head Socket Cap Screws, 6-32 x 5/16″, Black Oxide Alloy Steel (3 pieces)
  • Hex Socket Head Cap Screws Bolts, M3-0.5mm, 9mm Long, Alloy Steel , Black Oxide (8 pieces)
  • Hex Self Clinching Nuts, M3-0.5mm (8 pieces)
  • 18AWG electric cable ~5 inch
  • M3 Ring Cable Lugs Terminals (4 pieces)

The antenna is composed of three parts that I am going to describe separately. They are:

  1. Capacitor assembly
  2. Radiator / Exciter assembly
  3. Supporting structure

Let’s see them one by one:

Capacitor assembly

First of all, you need to print the necessary 3D printed parts. It might be opportune to print the Dial Bushing in a different color, in order to make more visible against the rest of the box.
I printed the box in PETG because of the enhanced mechanical and thermal characteristics. ABS would also be opportune I think, or even PLA (provided you are careful not to leave it inside of a burning car).

As the print goes, you can start working on the other parts.
All you need to do is solder a piece of cable on each gang terminal, on opposite sides. Terminate the cable extensions with a ring contact, like so:

Optionally, you could solder the same extension on the center connector of each SO239. This will allows to use the center conductor as part of the radiator (Do I think this is useful? I don’t, but I’m going to do it to avoid the complaints). Here are the connectors, ready to be used:

Now you can begin assembling the box.