My Projects

here you can find my projects, most of them are made of parts that can be 3d printed…

for all updates follow me on Instagram @iu1opk… and push that “like” button 😉

order them!

Don’t have a 3D printer?

Do you like products with industrial grade quality and finish?

Visit my Shapeways page where you can order your parts in several materials, colors and finishes, worldwide shipping.

Some of them can be customized with your callsign…hi

make them!

If you have a 3d printer you can visit my Thingiverse page and download for free the files of the product you like.

I decided to release all projects on Thingiverse for free download, the products that can be ordered on my Shapeways page include a small income fee; I selected the more appropriate materials and finishes.

If you like my projects please contribute with a donation to support next projects, this is really appreciated. Thank you!

IU1OPK Magnetic antennas: Linear magnetic antennas, self resonant versions (v.1.0)

I’m developing new designs of magnetic antennas, different from standard loop, with wire wound on coils, forming a linear magnetic antenna.

The concept is similar to the loopstick antennas with ferrite core used for reception in AM radios, but here the design is optimized to ensure high performance during transmission and avoid any core saturation with high power. The antennas described here are air coil without ferromagnetic core.

I’m also developing extremely compact loopstick antennas with ferromagnetic core, suitable for medium-low power transmission but this is another story.

Here I’m going to provide the instructions and a minimum technical background to build these very simple antennas that are providing good performances during my latest tests. I have also a lot of interesting variants and more complex designs, my intention is to publish by the next year a small book (in Italian and English) to describe all of them, supported by calculation and the related theory.

I decided to release these new concept as open source material, without filing any Patent, so feel free to study, build, test and sell them if you like. Please keep me informed if you have any interesting finding or idea.

Follow me and share your pictures on Instagram @iu1opk

The magnetic antennas described here are self resonant, no capacitors are needed to tune the resonance frequency.

Even if the shape can resembles an EH antenna this is not an EH antenna, nor a CFA antenna, the working principle uses standard concepts of electromagnetic field theory that I’m going to summarize here.

A real solenoid is usually described as an inductor in series with its resistance and in parallel with a stray capacitance. Since it’s a parallel RLC circuit it shows (ONE) resonance frequency called SRF(self-resonance-frequency). Nevertheless such stray capacitance is a fancy concept used to explain the coil behavior, nobody was able to measure it directly over the past centuries. The RLC model is still valid to approximate the solenoid operation at frequencies lower than the SRF but it shows some limits and errors when the frequency is approaching the SRF.

The reason is that at low frequency the current can be approximated constant along the wire, when the operating frequency approaches the SRF the length of wire used in the coil is comparable to the wavelength and the current cannot be considered constant along the wire.

Background theory: solenoids as helical transmission lines

All the details and working principles of the antennas described here can be explained with models used to describe solenoidal coils as helical transmission lines.

To summarize all relevant points in a nutshell:

The solenoid will performs like a transmission line, voltage nodes will be visible across the coil length (e.g. by neon tubes)
The solenoid can be excited also on higher modes. Unfortunately they are overtones, not integer multiples of the first resonant frequency, this is due to the fact that the helix is a frequency dispersive resonator (the impedance and the velocity factor change with frequency.
SRF depends on a velocity factor that, except for L/D (Length to Diameter) ratios close to 2 is quite different to 1.
The helical velocity factor, for L/D ratios greater than 2 (as commonly uses in my antennas) is higher than 1 and lower than 2. I’m not talking about superluminal speeds, it’s an “apparent” speed resulting from helix geometry. A precise calculation of the velocity factor is not an easy task, and is the only challenge in the design of these antennas; there are many graphs where you can extrapolate values.

For those who want to learn more I recommend to read “The self-resonance and self-capacitance of solenoid coils: applicable theory, models and calculation methods. By David W Knight”.

Working principle

My linear magnetic antennas can be considered as a full-wave loop wound as solenoid.

In the schemes described here you can find that the upper end of the coil is connected to the lower end.

Two variants are possible:

Full coil wound on same direction: even this “seems” the most reasonable design I’m not fully satisfied with it. The polarization (with field meter and during tests of a VHF version) seems horizontal-omnidirectional.
Coil made of two coils wound on opposite directions: up to now this is the most promising design, maximum Signal-to-noise ratio and vertical polarization. Even if this design could be seen strange you have to consider that here the current is not constant over the wire. Other RF projects use the same phasing concept: have a look at US4422058 Patent “Folded-over helical resonator” (Motorola) or search on Google “multiple-skirt coaxial antenna”.

Great care must be taken to ensure that the central wire is positioned in the most central position possible and away from the tube walls, otherwise a capacitive coupling will cause losses and shift of the resonance frequency.

Here a picture taken with IR camera where resulting energy loss is visible.

In my antenna prototypes I designed and produced some centering plugs 3D printed (that will be shared in the next future).

You can easily replicate them with cardboard or similar insulating material.

Antenna feeding

The antenna feeding is made by a coupling loop, 50 Ohm impedance matching can be achieved in many positions, the most suitable are around 1/9 or 1/3 of the coil length (measured from the bottom).

By slightly moving up/down the coupling loop some adjustment of the resonance point can be performed. The coupling loop can be secured with a zip tie.
Proper impedance matching (50 Ohm resistive) can be achieved by adjusting the loop length and the distance from the coil wire (capacitive effect). Here a picture of a 3D printed spacer of around 2mm, any insulating material is suitable.

The generated EM field is very concentrated and intense so, even if the antenna design is almost balanced, some unbalancing can occur if the antenna is placed close to obstacles, to stabilize the SWR readings I recommend:

to measure the SWR with VNA or transceiver well grounded
as alternative to apply a choke around 1 meter from the feed line (2-3 turns of coax on a FT-240-43 choke are enough)

I exclude coax radiation as major contribute since many of my tests are carried with 1 m coax and I tested also a portable antenna for 2m band directly attached to my Yaesu FT-3D with same good performance (and without coax or counterposes).

Construction data

Here I provide a table with all information needed to replicate my first two prototypes. Great care must be taken to chose the right tube diameter, otherwise the resonant frequency will be quite different.

I’m using Pestan PP grey tubes widely available in Italy (Leroy Merlin), other tubes can be used. Some tubes (e.g. black ones) can be inadequate for RF applications.

Other materials needed are: a BNC connector, some zip ties and mammuth connectors.

I tested the antennas at 100W power without issues or overheating.

Preliminary results (in progress, to be completed)

With the above antennas I was able to perform many SSB contacts with power from 20 to 100w with antenna placed indoor or on my balcony. No other antennas in the past were able to guarantee these results in such unfavorable conditions, I’m located on second floor in Turin centre, with no clear opening to the sky.

Please visit my Instagram page for latest information.

QSO map (FT8 and SSB) – indoor or balcony antenna

WSPR test (40m) – 10W (indoor antenna)

WSPR test (20m) – 10W (indoor antenna)

Tactical End Fed antenna winder

End Fed winder for 240 size toroids, suitable for EFHW antennas.

2 versions available for BNC or SO239 connectors
the spool can easily accomodate more than 20 meters of AWG20 wire, to build a full size 10-15-20-40m EFHW antenna
easy to build (pictures are self-explaining)
size of heat-shrink tube is 60 mm (diameter), 98 mm (flat). Nylon or other high temperature material is recommended if you chose to put the heat-shrink tube (black version is MJF PA12 industrial grade Nylon)

My builds are made according to standard EFHW projects with FT240-43 toroid and 100pF high voltage capacitor, I use them up to 100w SSB without issues.

My favorite solution is with “split” 10+10m of wire (with quick connectors), so I can use a short 10m antenna for 10-15-20m and deploy 20m of wire to cover 40m band only when needed.

Follow me and share your pictures on Instagram @iu1opk

My favorite material for this kind of product is PLA+

Nylon or other high temperature material is recommended if you chose to put the heat-shrink tube (black version in the pictures above is MJF PA12 industrial grade Nylon)

You can order them also on my Shapeways shop.

(tr)uSDX protection frames and accessories

Protection frame for (tr)uSDX radio, rear wall act as a reflector and improve a little the speaker volume.

Following 3D models are available:

protection frame with 9V battery seat in the rear. Suitable also for 9V Lithium rechargeable batteries that have microUSB charging port in the back
protection frame without battery seat
modified knob (optional), with lower profile and increased diameter
protection sleeve for BNC to SMA adaptors (optional)

Follow me and share your pictures on Instagram @iu1opk

I recommend to print them with three supports, to minimize the effect of supports and get the best finish of surfaces.

My favorite material for this kind of product is PLA+

Materials like PETG or Nylon have better mechanical properties but are more challenging to print with good results.

You can order them also on my Shapeways shop.

Protective cage for Icom IC-705 (unibody version - improved)

Thanks to all your suggestions, I release the improved version with unibody design.

New improvements:

recesses added on top surface to improve fitting when IC-705 has its rubber pads installed
Additional seats for silicone anti-slip pads (12x in total)

Model in the pictures is made with MFJ PA12 nylon and industrial grade process, lightweight and extremely resistant.

Features:

compatible with Windcamp RC-1 antenna bracket (additional small support can be printed to improve bracket resting when used on flat surfaces)
compatible with Manfrotto PIXI mini tripod
upper slots useful to fix external accessories (e.g. mAT-705 tuner)
the mike can be clamped to the lateral bars to avoid falling when not in use
flat base with proper tilting if used as desktop stand
all knobs, dials and connectors are easy accessible
non-slip option, 12x seats for 8 mm rubber pads are available on the lower surface of the base
protection extended also to the back zone of the radio (battery can be removed without disassembly the cage, if Windcamp RC-1 is installed it should be partially unscrewed to change battery)
compact design

Screws required:

4x socket countersunk flat head screws M4x12 or M4x10

For best FDM printing results I recommend PLA+, orient the model vertically and use Tree supports if you are using Cura.

Follow me and share your prints on Instagram and Facebook @IU1OPK

3D model is available for free download on my Thingiverse page. I recommend to print the cage with PLA+ material, 0.20 mm layer thickness, 30-40% infill and “Tree supports”, vertically oriented.

Materials like PETG or Nylon have better mechanical properties but are more challenging to print with good results.

You can order it also on my Shapeways shop, made of industrial grade Nylon.

Micro EFHW antenna for QRP

Micro End Fed Half Wave antenna for QRP

The toroid housing can be removed from the spool and directly connected to the radio with BNC-BNC male adaptor, cables, etc.

Bill of materials:

FT-82-43 toroid (with 49:1 winding ratio)
BNC female connector (Amazon, example: https://www.amazon.it/dp/B07DDDQP5M?)
100pF 3kV ceramic capacitor
Mammut screw connector Art.80596 (cross dimensions 5.85×3.7 mm) (Amazon, example: https://www.amazon.it/dp/B00EAQPWVW?)
BNC-BNC male adaptor, optional, only if you need to attach directly the antenna to the radio (Amazon, example: https://www.amazon.it/dp/B06XX8JBTW?)
23AWG or 26AWG wire (from online suppliers like Farnell, Mouser, DigiKey, RScomponents, etc)

Toroid housing and cap to be glued, fitting can be adjusted by scaling with some percentage one of the two components.

For examples and tutorials about EFHW winding and details visit section “Articles, videos and links (international)” of this website.

3D models are available for free download on my Thingiverse page (link below).

Follow me and share your prints on Instagram and Facebook @IU1OPK

Icom IC-7300 side rails

Side protection rails, perfect for portable and outdoor use.

8x M4 screws are needed, I’m using M4x10mm flanged screws.

If interested I designed also also a mike support, useful for hanging your microphone if like me you never know where to put it.
It can be easily mounted on the original IC-7300 mike: remove the steel plate, insert it and screw the plate.

I recommend to print them as showed in my picture, with three supports, to minimize the effect of supports and get the best finish of surfaces.

My favorite material for this kind of product is PLA+

With my Ultimaker 2+ the printing time is around 16 hours (0.20mm layers, 35% infill, 4 outer contours).

Materials like PETG or Nylon have better mechanical properties but are more challenging to print with good results.

If you live in Europe and don’t have a 3D printer I can made it for 50 Euros + shipping costs (2 rails + mike support, no screws supplied, PLA+ material, black color, like mine in the picture). Write me an email if you are interested, iu1opk@hotmail.com

If you need unibody rails made with robust material like Nylon you can order them on my Shapeways shop, they are available only in white, gray or black (color range is limited due to the size of this product).

Gray and black are more expensive because are made with HP MJF PA12 that ensures better finish and it’s the most advanced material currently available for this kind of projects.

I know that they are quite expensive but it’s due to the size of the product.

Protective cage for Icom IC-705 (improved version)

Thanks to all your suggestion, this is the improved version of my previous IC-705 protective cage and I really like it!

New improvements:

protection extended also to the back zone of the radio (battery can be removed without disassembly the cage, if Windcamp RC-1 is installed it should be partially unscrewed to change battery)
more compact design (lateral dimension reduced by 6 mm)

Features:

compatible with Windcamp RC-1 antenna bracket
compatible with Manfrotto PIXI mini tripod
upper slots useful to fix external accessories (e.g. mAT-705 tuner)
the mike can be clamped to the lateral bars to avoid falling when not in use
flat base with proper tilting if used as desktop stand
all knobs, dials and connectors are easy accessible
non-slip option, 10x seats for 8 mm rubber pads are available on the lower surface of the base

Screws required:

4x socket countersunk flat head screws M4x12 or M4x10
1x M4 short screw (max 5 mm of threaded portion) in the upper bar zone

Follow me and share your prints on Instagram and Facebook @IU1OPK

3D models are available for free download on my Thingiverse page. After all my tests I recommend to print the cage with PLA+ material, 0.20 mm layer thickness, 30-40% infill and “Tree supports”, production time with my 3D printer is around 14 hours if oriented like in these pictures.

Materials like PETG or Nylon have better mechanical properties but are more challenging to print with good results.

If you live in Europe and don’t have a 3D printer I can made it for 50 Euros + shipping costs (protective cage + stainless steel screws + rubber pads, PLA+ material, black or grey color, like mine in the picture). Write me an email if you are interested, iu1opk@hotmail.com

If you don’t have a 3d printer or you need a unibody cage made with robust material like Nylon you can order it on my Shapeways shop, it’s available only in white, gray or black (color range is limited due to the size of this product).

Gray and black are more expensive because are made with HP MJF PA12 that ensures better finish and it’s the most advanced material currently available for this kind of projects.

I know that this is quite expensive but it’s due to the size of the product. I’m looking for other ways to sell this product for people that have no possibilities to print it by themselves, for any request please write me an email.

The front zone can be engraved with your callsign.

(Use the spacebar to center, mouse right-click + “reload frame” to reload if the 3D model is not loading)

Here a short video review from M0FXB that tested my cage… I recommend to subscribe his channel DIGITAL HAM RADIO DIARY-M0FXB where you can find a lot of detailed reviews.

EFHW 10-20-40 m antenna

End Fed Half Wave antenna is my favorite choice for portable operations.

It’s a resonant antenna, easy to deploy and free of RF issues (that usually are found on similar random wires setup). Since I operate mostly with low power, around 30W maximum, I always used it without counterpoises and I never experienced issues.

The complete kit is designed for 10-20-40 m coverage and can be made with 10.1 m wire + 34uH coil + 1.85m additional wire.

The winder include also a second connection for GND if required/preferred.

This project is a complete kit designed to be 3d printed easily, and includes:

Winder base, designed to seat toroids of 140 size (ID 23 mm, OD 23 mm). In my 10-20-40m version I use a FT-140-43 toroid.
Winder cover (4x M3 screws required)
Insulator, designed fro 23AWG wires commonly used for portable operations.
Loading coil support, useful if you need a shortened version able to cover the 40m band. With 23AWG enameled wire it has an inductance of around 34uH and is coupled with an additional wire 1.85m long.

Obviously this kit can be used also to build random wires antennas by changing the toroid type and the winding ratio, the GND connection allow use of counterpoises.

For examples and tutorials about EFHW winding and details visit section “Articles, videos and links (international)” of this website.

3D models are available for free download on my Thingiverse page (link below).

Follow me and share your prints on Instagram and Facebook @IU1OPK

The complete kit is designed to be printed without supports, I recommend an orientation as showed in the picture.

I recommend to print PLA/PLA+, 0.20 mm layer thickness, 30-40% infill , production time with my 3D printer is less than 5 hours.

Materials like PETG or Nylon have better mechanical properties and are able to resist up to higher temperatures but are more challenging to print with good results, I don’t recommend them if you don’t expect to use high powers.

3D models available for download on my Thingiverse page (link below). If you get “404” error please download each single file separately.

Moonraker Whizz Loop Antenna tripod support

Whizz Loop antenna was originally designed to be installed on the rear connector of the Yaesu FT-817 QRP radio.

This support, really simple to print, gives you the possibility to use a Moonraker Whizz Loop antenna with any tripod (screw hole is self threading), it ensures a more flexible positioning and keep the magnetic loop away to your body.

Tested with: Moonraker Whizz Loop 20-6M
https://moonrakeronline.com/moonraker-whizz-loop-v1-20-6m-qrp-antenna

You can download the 3d model from my Thingiverse page.

If you don’t have a 3d printer or you like high quality, industrial grade 3D printed products you can order it on my Shapeways shop (international shipping).

Several colors are available in SLS Nylon (Laser sintered) or MJF Nylon (black or grey)

Yaesu FT-3D desktop stand

Features:

two rear cuts are designed to secure the antenna and mike cables with a velcro strap to achieve a neat and clean small station.
4x seats for 8mm non-slip rubber pads

Follow me on Instagram and Facebook @iu1opk

You can download the 3d model from my Thingiverse page.

If you don’t have a 3d printer or you like high quality, industrial grade 3D printed products you can order it on my Shapeways shop (international shipping).

Several colors are available in SLS Nylon (Laser sintered) or MJF Nylon (black or grey)

The front zone can be engraved with your callsign.

(Use the spacebar to center, mouse right-click + “reload frame” to reload if the 3D model is not loading)

Protective cage for Icom IC-705

Features:

compatible with Windcamp RC-1 antenna bracket
compatible with Manfrotto PIXI mini tripod
upper slots useful to fix external accessories (e.g. mAT-705 tuner)
the mike can be clamped to the lateral bars to avoid falling when not in use
flat base with proper tilting if used as desktop stand
all knobs, dials and connectors are easy accessible
non-slip option, 8x seats for 8 mm rubber pads are available on the lower surface of the base

Screws required:

4x socket countersunk flat head screws M4x12 or M4x10
1x M4 short screw (max 5 mm of threaded portion) in the upper bar zone

Follow me and share your prints on Instagram and Facebook @IU1OPK

I designed also a version made of 2 separated parts, the 3D models are available on Thingiverse, they can be printed with small amount of supports with all 3D printers in 9-12 hours, for this kind of project PLA material is fine if printed with min. 30-40% of infill.

Materials like PETG or Nylon have better mechanical properties but are more challenging to print with good results.

Gray and black are more expensive because are made with HP MJF PA12 that ensures better finish and it’s the most advanced material currently available for this kind of projects.

The lower front zone can be engraved with your callsign (use the spacebar to center).

Yaesu FT-891 protection rails

Features:

Use the same screws supplied with the radio (brackets for mobile installation).

thanks to the special geometry it’s possible to secure external accessories (tuners, batteries, digital modes interfaces) with velcro straps.

I designed them with seats for rubber pads (internal side) but I found that they are not really required.

The 3D model available on Thingiverse is divided in 2 pieces and can be printed with most of 3D printers.

If you like my design and how it fits on your radio, on my Shapeways shop you can find a single-piece version made of laser-sintered Nylon, a material with high mechanical resistance and durability.

It can be assembled with existing screws that are supplied with the radio (used for mobile bracket fixing).

I chosen this version for my outdoor activities.

If you live in Europe and don’t have a 3D printer I can made it for 50 Euros + shipping costs (2 rails, no screws supplied, PLA+ material, black color, like mine in the picture). Write me an email if you are interested, iu1opk@hotmail.com

Compact Morse iambic paddle

Compact design, easy to build, magnetic baseplate with rubber pads seats.

Visit my Instagram profile @iu1opk to see it in action!

Compact design
Adjustable clearance
Magnetic baseplate option with non-slip rubber pads
Easy to print and to build; few standard and widely available parts (2x DIP P4 Normally Open push-buttons, 5x M3x16mm screws, 2x M3x5mm grains, 2x Ø12x2mm neodymium magnets, 4x Ø8x2mm rubber pads)

I found several projects on the web but I was looking for something with few parts , inexpensive and easy to built.

The assembly has only four 3D printed parts (2 paddles, base, cover, baseplate) that can be printed without supports (look at the picture of my buildplate example).

The holes are designed so the screws will be self treading.

The clearance between the paddles noses and the buttons can be adjusted to zero with the 2 threaded grains (or also short M3 screws) placed in the rear zone of each lever. The adjustment can be done also on the assembled product thanks to the rear holes.

The sliding friction of the paddles can be adjusted with 2 screws on the base, I added some Ballistol oil on friction surfaces.

The buttons must be placed in its seats in the following way: bend two legs horizontally, slide the button through the seat in the base, bend down (90°) the two legs. The button now is trapped between the lever nose and the base, the clearance can be adjusted as described above.

I chosen that button switch instead of the classic metal-to-metal contact screws beacuse these buttons are widely available on the market, they ensure long term and reliable switching and if needed are available also with IP dustrproof, waterproof rating.

The baseplate include two seats for neodymium magnets (optional if you like the magnetic effect) with size up to 12mm (diameter) and 2 mm (height), the magnets can be glued.

The base includes two small slots for small zip-tie, to guarantee the cable retention. A version with 3.5mm jack socket will be available in future.

Here you can see a picture that shows how to install the buttons, for all wiring connection please check what are the requirements of your radio (see the instruction manual). In the image below you can find the scheme that I followed .

The buttons are DIP P4 Normally open, check how they work with a multimeter (continuity – “beep”).

The 3D models are available on Thingiverse, they can be printed without supports with all 3D printers in few hours, for this kind of project PLA material is fine.

If you don’t have a 3d printer or you want to built it with premium materials you can order all parts on my Shapeways shop; most suitable material is Nylon, available in several colors.

The cover can be engraved with a custom text like your callsign (use the spacebar to center).

Compact Morse key

Compact design, easy to build, magnetic baseplate with anti-tilting appendix.

Visit my Instagram profile @iu1opk to see it in action!

The assembly has only four 3D printed parts (lever, base, cover, baseplate), 6x M3 screws and 1x pushbutton switch (DIP P4 Normally Open).

The holes are designed so the screws will be self treading.

The clearance between the lever nose and the button can be adjusted to zero with a screw placed in the rear zone of the lever.

The button must be placed in its seat in the following way: bend two legs horizontally, slide the button laterally through the seat in the base, bend down (90°) the two legs. The button now is trapped between the lever nose and the base, the clearance can be adjusted to zero with a rear small screw in the lever.

The baseplate include two seats for neodymium magnets (optional if you like the magnetic effect) with size up to 12mm (diameter) and 2.75mm (height). The magnets can be glued.

The base includes two small slots for zip-tie, to guarantee the cable retention.

I like the precise pushing feeling, maybe this design is not the best for high speed but can be fine for novices; my idea is to use as outdoor and easy to carry key.

The assembly has only four 3D printed parts (2 paddles, base, cover, baseplate) that can be printed without supports (look at the picture of my buildplate example).

The holes are designed so the screws will be self treading.

The sliding friction of the paddles can be adjusted with 2 screws on the base, I added some Ballistol oil on friction surfaces.

The baseplate include two seats for neodymium magnets (optional if you like the magnetic effect) with size up to 12mm (diameter) and 2 mm (height), the magnets can be glued.

The base includes two small slots for small zip-tie, to guarantee the cable retention. A version with 3.5mm jack socket will be available in future.

The 3D models are available on Thingiverse, they can be printed without supports with all 3D printers in few hours, for this kind of project PLA material is fine.

If you don’t have a 3d printer or you want to built it with premium materials you can order all parts on my Shapeways shop; most suitable material is Nylon, available in several colors.

The cover can be engraved with a custom text like your callsign (use the spacebar to center).

SMA to BNC stress relief bushing

A simple accessory to avoid any stress on the SMA connector of your handled radio when using SMA to BNC adaptors.

The 3D model available on Thingiverse can be printed in around 15 minutes and doesn’t require any supports.

If you don’t have a 3D printer or need high quality materials you can order it on my Shapeways shop.