First portable test at my garden. FT4 on 20m. RS-918 5 watt to an end fed half wave antenna. Very good result, easy to make QSOs.
Inspired by this excellent article from PeanutPower I decided to build a resonant End Fed Half Wave (EFHW) antenna for portable use. My antenna is designed to be resonant on the digital sections of 15, 20 and 30 meter ham radio bands.
All measurements done with NanoVNA.
You can click on all images below to get a large image.
The 1:64 UNUN is made just like this post that I have published before, with the 100 pF capacitor added later for better 15m SWR. You can see that the SWR is higher on high frequency but it was possible to get a good SWR on 15m, when antenna wire was added.
BNC connector are used because that is my standard for HF and portable connectors.
Sotabeams QRP Pico Traps
Traps used are Sotabeams Pico Traps. It took me a two hours to build, unfortunately I lost the small SMD 100pF capacitor so I used bigger ones. I also need to unwind one turn for each inductor to get in resonant.
Setting up the antenna (wire) sections
This was the most time consuming part. First I used an online antenna calculator to get the sections length. These are the calculated length but I added aprox 50 cm to each before mounting:
|Frq (MHz)||Sections (m)|
|21,1 MHz||6,68 m|
|14,1 MHz||3,4 m|
|10,1 MHz||3,9 m|
Begin with the highest frequency (band). Get the antenna up – measure – down – cut wire – up – measure – down – cut wire…. until you have good SWR for all three bands.
Wire used are from Sotabeams.
This is the result. As you can see very good on 20m and 30m.
On 15m SWR is 1.68:1 – OK but not perfect.
Note: after adding a 100pF capacitor at the input on the UNUN the SWR on 15m got flatter and lower.
This is how the antenna can be used:
And everything ready to go!
I have been using the Minikits EME141 relay kits for both VHF and UHF for a long time but I never did any measurements. Using the NanoVNA I now have done a sweep for HF, VHF and UHF.
HF is excellent, VHF and UHF are very good. See image below (click for large image). Note that the SMA connectors during measurement can add some losses. Insertion loss is -0.76dB at 435 MHz.
The EME144 is now replaced by even better releays.
I’m using the following equipment for portable power. All from Hobbyking.
- 2 pcs LiPo 3s Turnigy 5000 mAh
- Safety bag for the battery
- Balanced charger Turnigy M8
- Low voltage alarm for the battery
The batteries are stored in my garage in a metal trash can… in case of a battery fire… I hope not this will happen!
All my DC connectors are XT60 so I can easy switch between fixed power and battery. I can use the M8 charger from my 13.5V fixed power supply or from a car cig lighter adapter.
Made some small HF-dipoles for portable operation. Very light, easy to setup.
- Small plastic enclosure
- BNC connector
- Light wire from Sotabeams
- Perfect SWR – no tuning!
My new HF transceiver from May 2020 – Recent RS-918SSB, a SDR based HF transceiver. Much fun for money. A way better RX then my old FT-817ND, built in USB sound card with CAT. Only one cable between laptop and radio!
Much cleaner RX on FT8.
Built one in May 2020. See this article on AMSAT-SM web.