Looking around for an extremely small, extremely portable and fast deployable HF field antenna for my QRP transceivers, I stumbled upon the AX-1 from Elecraft. Basicly its a tuned whip antenna. Many other manufacturers are selling those, but the nice feature of (for instance) the AX-1 is that it can be taken apart to make the package even smaller.
The AX-1 consists of a switchable coil-pack, a telescopic whip and a radial. It is easy to set up and small when stored. Other pro’s of the AX-1 are that the product is ready-made and well build. The con: it is quite expensive for such a simple device (AX-1, about 150 Euro, and when you add the 40m extension coil: count on an extra 80 Euro). This for ‘just a loaded telescopic whip’ that only works on the 20 meter band (with some retuning also on 15, 17 meter bands) and (with the extension-pack) on 40 meters! Besides the price: another serious con for me is that there is no way to attach the radials to the antenna itself. Elecraft relies on the ground connection of their rigs for this.
For my QRP field use I would rather like to have a simple all in one solution: a ‘fit in the pocket when collapsed’ antenne much like the AX-1, but also more versatile. It should be useable on the 6, 10m, 20 and 40m bands and without seperate ‘extension-coils’. And also it should have a contraption to attach several radials (instead of one). More radials should enhance the (low) efficiency of a shortened whip and also help the tuning for each band.
So I decided to build my own AX-1-ish-version. Firstly I ordered a seven segment 115 cm telescopic whip in China. It was about five euro’s, shipping included 😉 Then I DIY-ed the loading coil(s). A tedious and time consuming job. As you can see in the image below there is no switch. Selecting bands is done by choosing the right tap (shorting out a part of the coil assembly). The initial tuning (in the fase when I was winding the coils to find out how much windings per band I would need) was done with the help of my trusty nanoVNA.
This is the result:
Basically what I did to make the antenna suitable for the desired bands was winding a base loading coil with taps. Each tap has a terminal. For the taps I used silver coated PCB-pins. The loading coils are wound around a plastic tube, OD 12 mm ID 10 mm. This tube also holds the BNC connector (it’s core connected to the base of the coil) and a nut/wing (connected to mass) to connect the radials.
At the top of the loading coils the telescopic whip screws in (it fits snug). The whip connects electrically to a band selection wire.
Band-tuning is done by selecting the right coil(s) (i.e short out the not desired inductances). In-band tuning is done by adjusting the whip length.
Each coil is pre-tuned to the bottom of it’s band (with the whip fully extended). Shortening the whip enables in band tuning: the shorter the whip, the higher the frequency.
The radials (one for each band, so a bundle of four radials) are soldered to a spade connector that fits the ground terminal. I also made four non conductive small pins for fixing the radial-ends in the soil if needed.
To attach the antenna directy to my Xiegu X6100 I use an BNC-elbow and an improvised ‘bi-pod’. Off course it could be used in any other set up. Like on a small tripod.
Does it work? Yes. But keep in mind that such a short whip is a compromise antenna!
fig 2: antenna when tuned to the middel of the 10m band
Fig 4: antenna when tuned to the middle of the 40 m band
pseudo voice 
Hi great antenna .. could you post the number of windings of the coil?
73,
OE3TBU
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Hi Thomas,
Thank you for your question!
I don’t know the exact number of windings, but maybe you can count the number windings using the pictures I posted. Sorry.
If you plan to make the antenna yourself, keep in mind that the number of windings also depends on the actual wire size and coil diameter.
Anyway, I didn’t count the number of windings because I used my VNA to determine if the coil has the right inductance. My advise for you would be to do the same. However you could certainly have a headstart when you just copy the amount of windings I used. Just add a few extra for tuning purposes: it’s easier to shorten than to make a wire longer!
This how I experimented and determined the right inductance/amount of windings per band:
I started with the highest band (6m). What I did was guestimate and wound the coil a few windings too long on purpose for a start. Then, using my VNA on the antenna -with counterpoises and whip fully erected (and connected off course)- measured and reduced a few windings, measured again, etc. Until the VNA indicated that the antenna was on the lowest part of this band.
Then I fixed the coil with a tad of glue and soldered the end-wire to a pin. This pin also acts as the tap-point for that band. And … went along, adding the next coil (for 10m). Same procedure, etc.
Hope this helps you! * by the way: this is my old stack, my new website can be found here: https://pseudovoice.com/
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