Redesigned Capacitor and Experiments Planned

As I mentioned in the last post, I believe it is possible to 3D print the dielectric used in my cylindrical variable capacitor such that it becomes part of the structure. The only concern I have with this is that the dielectric constant is likely to change depending on the amount of infill I use when printing. Infill is a percentage specification of how much plastic will be used in each layer. Typically I use anywhere from 15% to about 60% depending on the strength I need for the part. In this case, I am not after strength, I am after maintaining  a constant dielectric constant and voltage breakdown. I will likely buy some copper and print some test pieces this weekend to test things out with various infills.

I have a preliminary design to show what the 3D printed capacitor would look like including a stepper motor mounted to provide remote tuning:

new capacitor

As you can see this is very similar in layout to the PVC pipe prototype made last year.


Rethinking the Cylindrical HV Variable Capacitor

I have been doing quite a bit of 3D printing lately and have been making various gadgets for the Office/Shack. I just completed a set of mounting brackets that mount an old Ipad 2 to my workstation just below the PC monitor. I can use this as a secondary screen or as a TV to monitor news etc.


The  red “Whale tail” is a stand for my phone. Both of these items have opened up a lot of space on my physical desktop and were fun to build. I have also built adapters to mount the mag loop and homebrew buddistick to a camera tripod:


Building these has allowed me to practice with Fusion 360 and I am feeling more confident in using it for design work.

These projects have got me to thinking on how the 3D printer could improve on my cylindrical HV capacitor design I previously discussed:


I am thinking of designing custom 3D printed components for this design and possibly adding motorized control. I am also considering the possibility of replacing the PE sheet as a dielectric with a printed sleeve of PLA material. Looking up the dielectric constants and see how it would work out.

Summer Season Officially Over…Sort of…

Labor day is now behind us marking the “official” end of the 2018 summer. The temperatures outside, while still hot, are starting to come down slowly and there is actually a good chance of rain in the forecast. The weather will start getting good for antenna projects.

So I have some projects on the back burner that I am going to start working on soon. First up is trying a satellite contact with the arrow antenna and a Baofeng HT.  I just need to get my HT programmed to start trying this out.

I have also ordered a uBITX board from The uBITX is a SSB/CW transceiver for 160m – 10m at a 10W level. Nice homebrew and tinker project that hopefully will allow me to make contacts at places I would not normally take by FT-817ND (i.e., the beach).


I plan to 3D print a custom case for this rig.

Also can report that I have updated the programming of the TYT MD-380 DMR HT this weekend. This adds coverage for most of the valley on DMR now.

Back on the Air for NA QSO Party

Unbelievable that I have been so busy as to not make a QSO in a month. Wow! That life thing….

Did some casual operating today on 20m for the North Americao QSO party. Nice to see everything was still working! I probably should take down the S9 vertical for some routine maintenance but it is just to darn hot! The canicula ends on the 24th so I expect the weather should be more reasonable after that. I continue to 3D print some radio components and have a big project in mind for a portable hexbeam. More to come.

First 3D Printed Antenna Parts

I 3D printed my first antenna parts today using designs I downloaded and used as is from Thingiverse. The first piece is a wire dipole center piece. It accepts a screw on PL-259 connector and has features to strain relieve the elements and to support the center.


I chose not to use the end insulators for this design as I wanted something a bit smaller so I printed two of these:


I am going to finish this up as a 20m inverted V and test it out this weekend. I printed these in PLA which should be OK for portable work. A permanent installation would be better with ABS or PETG.

Mini60 Antenna Analyzer Replacement Battery

I get a lot of questions on the Mini60. Sometimes I have an answer and sometimes I don’t. One question I seemed to have answered successfully is what type of rechargeable battery pack to use on the Mini60. Apparently some units sold out of China do not include a battery. I did not get a specific number off my unit when I opened it up but after doing some research found out that it uses a 3.7V LiPo battery pack. Based on the size it also appears to be in the 2000mAh range. Here is a link to a battery that has been shown to work with the Mini60. This uses a JST style connect on the end and plugs right in.

Hinged Solar Panels

The 3D printed hinges I downloaded from Thingiverse didn’t fit my solar panels. Fortuantley the source for the design was done using a program called openscad. This is a unique cad program in that the models are not developed graphically. Instead you right a sort of script “code” which build up the solid model as a description. This came in handy for this project as I needed an additional 10mm of length on the hinge links. Here is the finished result ready now for field use:


Initial 3D Printing Results

The Creality CR-10S is certainly living up to its great reviews. The fiddly bit is getting the bed level but once that is dialed in it appears to print very reliably. The leveling is important to get the first layer to stick well to the glass bed. I have also been using a wide brim on each piece to increase the contact area of the first layer. I printed four parts yesterday to form a hinge for my two solar panels:


Next up was a holding bracket for my Koss SB-45 Headset. Here is the part being built on the printer:


Here is the completed part:


Mounting is via a piece of double sided carpet tape. Both of these models were downloaded from which is a very large repository of printable items. Do a search for things like “ham radio” or “dipole” for some idea of the possibilities for the hobby.

Busy Summer!

It has been a busy summer this year. Work has been demanding with several international trips now behind me. Just finished up an active Fourth of July holiday that involved the beach and good family time. I missed field day activity this year and have just yesterday logged my first QSO’s in over two weeks. Things are settling down now and I am starting to work on some fun projects related to Ham radio. First up, I have an Arrow antenna on order for use in working the ham satellites. I actually ordered this some time ago but an item was back-ordered and so this has only just shipped yesterday. Looking forward to working the satellites soon!


My next couple of projects are not truly ham radio projects but will assist many ham radio activities. I previously mentioned how my HP Z400 workstation had a hard drive that is failing. I decided to upgrade to a more powerful computer so I have ordered a used HP 620 workstation with dual Xeon processors for a total of 8-cores, 16GB of ram, dual 1TB hard drives and a Nvidia K4000 video card. I have been very impressed with the HP Z series workstations as they are very reliable. This computer will eventually replace the Z400 as my main machine. I’ll replace the drive on the Z400 and reload everything on it for use on my new 3D printer.

Yes, I bought a new Creality CR-10S 3D printer.


This printer has gotten great reviews and is assembled in about an hour. I was an early adopter of 3D printing years before i got into ham radio. I had a Makerbot CupCake back then and enjoyed the technology but didn’t like the constant fiddling with the hardware to make it work. The machines are still a bit fiddly but my build volume is now 300x300x400mm! This machine can build a variety of very useful ham radio tools. Things like dipole centers, wire antenna insulators, small custom enclosures, power pole break-outs etc. As I type this post is it building up a set of brackets and hinges to tie together my two 15W solar panels which I use portable.

I no longer have the Makerbot machine but I do have a Rostock-mini Delta printer and a Prusa I3 that I had acquired used many years ago but never got working. I can use the new printer to make replacement parts for these machines and will see if I can get them working.




Listening to Ham Satellites

I have long wanted to try the amateur satellites. Back when I was a kid I had my trusty Allied receiver and my AO-7 tracking tool but try as I might I never picked up a signal. Today I loaded up the GoSatWatch app on my iPhone and started looking for passes with the aim to at least pick up a signal. There was a decent pass of AO-92 Fox-1D so I tuned by rig to 145.880 Mhz and turned off the squelch. Sure enough a few minutes after the pass started I began picking up signals from the satellite.  This was using my standard discone base antenna. The signals never got really strong but it was encouraging to know that the timing piece worked out well. You can guess what will be coming next…a handheld dual-band yagi.