Amateur Radio

First HF portable test

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.

Amateur Radio

Trapped End Fed Half Wave (EFHW) for 15/20/30 meter

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.

UNUN without 100pF
UNUN with 100 pF
UNUN with 100 pF
Test measurement of UNUN with a 5k ohm resistor

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.

14 MHz trap
21 MHz trap

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 MHz6,68 m
14,1 MHz3,4 m
10,1 MHz3,9 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.

Antenna SWR for all three bands

This is how the antenna can be used:

And everything ready to go!

Amateur Radio

Minikits EME144 SMA relay

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.

Amateur Radio

Portable batteries for ham radio

I’m using the following equipment for portable power. All from Hobbyking.

The batteries are stored in my garage in a metal trash can… in case of a battery fire… I hope not this will happen!

M8 Balanced charger

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.

Kontakt XT60 1 Par - Skånehobby
Amateur Radio

HF dipoles for 15m and 20m

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!
Amateur Radio

Recent RS-918SSB HF SDR

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.

Amateur Radio

Moxon Dual Band VHF/UHF portable satellite antenna

Built one in May 2020. See this article on AMSAT-SM web.