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Building the PA0RDT Mini-Whip Antenna

The PA0RDT Mini-Whip Antenna is a small and compact active antenna that acts as a full-size antenna for bands ranging from VLF to HF. It’s ideal for cases where you can’t put up a large antenna or are restricted on space. Most of the feedback on the design I found online was quite positive, so I decided I’d get one and try it out for myself.

A few weeks back I bought a Mini-Whip active antenna kit from a seller on eBay. While I could have built it completely myself, I liked the idea of having a neat and tidy antenna on a printed circuit board, so this was great, and I was able to put it together in about half an hour.

PA0RDT kit

PA0RDT kit

A lot of people house their Mini-Whip antennae in PVC tubes and I considered doing this. However, I wanted to be able to easily stand the antenna on a table and point it in different directions without having difficulty. So, despite the antenna’s ideal location being high up in the air, I decided on using a rectangular box so that I could also use it closer to the ground. Its shape also means that it easily stands upright on a table or wall and can be adjusted easily.

In keeping with the idea of having everything neat and tidy, I also decided to house the power supply for the antenna in the same box and use a toggle switch to power it on and off. I would use a 9V batter for power instead of an external 12V DC supply (I’m not sure how much this will impact on performance).

I drilled two holes in the box cover: one for the F-connector and one for the toggle switch. Internally, I simply fastened everything down using sticky foam pads so I wouldn’t have to drill more holes and find more screws. The pads turned out to be much more sturdy than I thought they would be. The twin lead I used for wiring was probably a bit too heavy for the kit, but nonetheless the soldered connections seem to be solid throughout.

Finished antenna

Having finished assembling the Mini-Whip, I decided to try to test it. I made up a crude coax to 3.5mm jack adapter to connect the antenna to my Tecsun PL-600, but the jack I used was from an old pair of stereo earphones whereas the input on the radio is mono. I have no idea where the positive and negative parts on the jack are and was a bit too lazy to check. When I plugged everything in I couldn’t hear much of a difference in signal strength when I tuned to Voice of America in Africa on (I think) 13630 kHz. It turned out that the space weather conditions today aren’t great anyway, and around that frequency is particularly bad. So, there are several possible reasons why this quick test didn’t show much.

For proper testing, I will feed the antenna into a RTL-SDR so I can monitor the changes in signal strength on screen, rather than just judging by ear. When I do this, I’ll post up the results and comparisons with my regular antenna setup.

Overall, I’m quite happy with the build and very much looking forward to putting the Mini-Whip to use!

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Completed Mini-Whip

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