Mini-whips: junk, right?

I still have little time for radio these days. When I do get some time, I've tended to develop the listening side of things over on the MW, LW and VLF frequencies, herded there by recent efforts to receive SAQ, which have been successful.

For the 17.2kHz SAQ signal, I first tried the standard solution of a 3m-circumference coax sheath loop (RG-213) with a nice amplifier made by George Smart (WellGood). This yields good, strongly directional reception, though I found SAQ was only weakly heard from a domestic location. It would, of course, be better from a quieter location.

Early tests of the amplified loop (rear) and unamplified (passive) loop. The passive loop is pretty useless for SAQ, at least at my distance from it.

 

A later SAQ transmission was due, and I packed the loop in the car, ready for some beach deployment. Unfortunately, I forgot the battery and had to return home, which I did just in time to connect-up a very much larger, 18m-long coax loop, slung in loose vertical arrangement in a hedge.

The signal from this was very good, even in a noisy domestic environment, hitting a steady S6. I made a recording of the full transmission, which you can see and hear, here.

To avoid the noise for the next SAQ transmission, I headed for the local lakeside, just a few minutes away. The large loop was slung from the densely-branched evergreen trees, and the signal was again around S6, but with none of the noise. You can hear that event, here.

Windy and threatening rain for the Xmas Eve 2023 SAQ event - hence the tent!

 

I did the same for the Xmas Eve, 2023 event and again, S6 or just under. 

Then I started wondering if there was an alternative to lugging a big loop of heavy RG-213 around to the woods and spending several minutes setting it up. So, on Xmas Eve, I ordered a generic Chinese amplified 'mini-whip' system for the grand total of £23, delivered. Just six days later, it arrived - amazing! But would the performance be equally impressive?

Just six days from China to Wales, even over the Xmas period!

 

Well, I will wait until the next SAQ transmission to compare the mini-whip against the large coax loop. But I did manage to get out during a brief spell of dry weather, at night, to test the 3m-circumference amplified loop against the mini-whip.

Test conditions for the amplified loop were: centre height of about 1.5m, WellGood amplifier boards via ~10m RG8-X coax, coax-wound choke known to have extremely low return loss at the lower end of HF (>>46dB), SDRPlay RSP1a receiver and a laptop running SDRConsole, CW peak enabled where a CW signal was in contention and synchronous AM for commercial AM stations. The loop was aligned by compass on great circle paths to the relevant transmitters, determined earlier via Google Earth.

For the amplified mini-whip, mounting was at roughly 4m atop a PVC pipe installed in a plastic ground screw; the coax sheath was grounded at the base of the pipe via a ~30cm copper pipe of 15mm diameter. Feed arrangements the same as for the loop. Ground conditions are very moist ground, almost freshwater due to the peaty lake shore location.

The results were very surprising, at least to me, where I hadn't expected much from the mini-whip at all. Overall, it was giving the loop a good run for its money and gave a better signal on some stations, and you can see the evidence for yourself in this hastily-assembled sequence of clips from the evening.

Testing the mini-whip on the Anthorn (UK) time signal at 60kHz.

Very much encouraged, I ran a very quick test of the mini-whip at 2m and then 4m height. The signal from DCF77 time signal in Germany during daylight showed an increase from S9+9dB at 2m to S9+13dB at 4m. It was about to rain again and I took the wrong keys for the field shack, so I couldn't get it up any higher. I've ordered a 9m fibreglass pole, which fits nicely into a standard clothes line plastic ground screw and from which the very lightweight antenna unit can be hung at around 7-8m up. 

Stay tuned for the next, increased height tests and, maybe around February, a 'Grand Comparison' between the mini-whip, 18m coax loop and a terminated 50m Beverage! I've also ordered the 'original' PA0RDT miniwhip, to see how well that compares with the Chinese edition. There is always so much to do, and so many ways to keep the 'anorak' image alive!

Some very useful and reliable resources on the mini-whip can be found here and here.