Two versions of the cheap Chinese whip antenna from AliExpress

After following the discussions and reports on the SOTA Reflector about this cheap antenna, I couldn't resist to order one myself.

I did not buy the complete antenna set, but only the telescopic whip of 5.6m length. I didn't like the base, which has an SO-239 connector, and from the reports it seemed the radials were just rubbish (thin computer flatcable). So I intended to build my own version. 

Another inspiration came from a report by Jos, ON6WJ, in the EUQRPFOX newsgroup, who added an adjustable coil to make a 40m band antenna.

VERSION 1 - multi band, base loaded vertical 

step 1 : order a 5.6m whip on Ali Express, it arrived undamaged (not always the case it seems) 

step 2 : find a solution to mount it + add a coil for bands lower than 20m + add radials

The telescopic whip has an M10 thread at the base, and ON6WJ pointed me to these "Plate Nut Three-hole Flanges" on Ali Express : https://nl.aliexpress.com/item/1005007182945817.html

I used a thick wall PVC tube of 40mm, made a round wooden insert to which the flange is fixed, the wooden insert itself is then fixed with three Parker screws.

 

Now, how to put this construction in the ground ?

Another inspiration came from this "weed cutter" (top item in the picture above), an idea from good friend  Geert ON5GL.

Now, this weed cutter is very handy to put up a 6m fishing pole from Decathlon, but is too thin for the 40mm PVC tube, there is too much slack to keep the antenna stable.

I had some steel tubes from a vacuum cleaner that would fit, but those are a bit heavy, so instead, I took a piece of aluminium tube (old TV antenna mast), and copied the weed cutter design (2nd item in the picture above).

The fit was not perfect, so I added a piece of bicycle inner tube over the aluminium, and now it's a perfect fit !

 

Then the coil ... I found a roller inductor in the junk box of 0.4 ... 10 µH
Then added a ringcore T130-2 with 30 windings , adding another 10 µH
With a switch I can use three different settings: direct connection to the whip, 0.4 -10 µH and 10.4 - 20 µH.

The whole circuit is mounted on an aluminium plate , and attached to the PVC tube with two 'PVC 40mm clips' (normally used to fix tubes to the wall)

For the radials, I took the lengths of the set of radials from a Yaesu Atas-25 (https://www.yaesu.com/jp/manuals/yaesu_m/ATAS-25_EJ.pdf) 

The real lengths as measured by an owner of such an antenna were 2.18m + 3.00m + 6.71m (tnx Rob ON4ROB).

For transport, the whip + ground stake fit inside the PVC tube, not lightweight like for SOTA, but maybe handy for POTA. 

Whip is well protected inside the tube

And how does it work ?

I did a few POTA activations in a local park, setting up was very easy.

Here a few pics that show the steps to set up the antenna.

Put ground stake in the ground

Put base assembly on the stake

Put whip on top and attach radials

  

Extend whip to correct length

Operate !

I could tune the antenna on all bands 20m-10m, by adjusting the length of the whip. With the 0-10µH coil, I could tune 30m and 40m, and with the 10-20µH setting, I could use it on 60m. The lowest frequency I could reach was 4.755 MHz.

I suppose I could also use this antenna on 6m, but did not check that band.

Conclusion : this would be a 9 band antenna which doesn't need a lot of real estate to setup.

BUT ... I was not satisfied !

When operating SOTA or POTA, I like to switch bands very often (to hunt  for S2S or P2P QSO's).
With this setup that means I have to go to the antenna, adjust the length of the whip, or change the tuning of the coil ... too much fiddling !

So I came up with ...

VERSION 2 - multi band, NON-resonant whip antenna.

My favourite SOTA antenna is a 9.15m non-resonant wire with a 9:1 UNUN. Using an autotuner, I can use all bands from 60m to 10m, and have made many QSO's that way. 

So my idea was to change the whip, which is about a quarter wave on 20m into a non-resonant whip, by adding 1.4m of wire, and make the total length of the antenna around 7m.

Then using either a 9:1 UNUN (or a 4:1 UNUN), let a ATU-100 autotuner do its thing.

This makes for a much slimmer antenna, as seen in the picture above.

Some more POTA activations in the local park proved that it worked. I had QSO's all over Europe, and some DX as well (K and EA8).

Just out of curiosity, I built a 4:1 UNUN, and checked wether my ATU-100 could tune any differently, compared to the 9:1 UNUN.

I put the ATU-100 at the antenna base, so that the coax to the transceiver had no influence.

To the ground post I connected only 1 counterpoise of 4m.

Resulting SWR after tuning with a 2.5W carrier:

So my preference goes to the trusted 9:1 UNUN I have been using for years.

73,

Luc ON7DQ