Batteries for Portable and Field Radio

 EFHW from Aliexpress

Always on the lookout for a good, rugged, cheap antenna that's simple to set up, for field operations and SOTA work, I happened upon this one at Aliexpress. 

A bit of background first. My radio operations are currently almost exclusively outdoors, in the hills, or where I am happiest, up a mountain. I currently have three antennas that I rely on, a homemade chalkline random wire and a doublet, and my only purchased ready made antenna, a SOTABeams Band Hopper II which is a linked dipole. All of these three antennas are used mostly with my IC-705 turning out 10 watts. The IC-705 not having a an inbuilt tuner, I rely an Emtech ZM-2 tuner and more recently a QRP Z-Match, also sourced from Aliexpress, to match the longwire and the doublet antennas. The band Hopper II, being a dipole has no requirement for a tuner. Of the three antennas, the one that is by far the most reliable is is the dipole; you just connect it to the radio and no messing around with trying to find a match, you are on the air. The only downside to this antenna is there is only a choice of two bands, 40 and 20 meters, and the pole has to be lowered in order to swap between them.

The longwire I find can be a little more particular to its surrounding and the height it is hoisted to. That said I have never not been able to match it with either on the two tuners I rely on. The doublet is by far my best performer - after all it is essentially a dipole - and can tune seamlessly between 80 to 10 meters. Its only drawback is that it is only a fair weather antenna. It is very susceptible to windy conditions and thus gets used the least on mountain tops, plus it requires a lot more real estate to set up, not something a lot of craggy peaks in the Southern Alps give up easily.

In the past, I have made some attempts at making an EFHW antenna, but I have not had a lot of success apart from some Base Antennas that I used for a couple years before moving to my new QTH. Then earlier this year I and ZL3MR were on top of Mount Hutt, with only a cramped, craggy little peak at 7168 feet to setup our operations. I had my Band Hopper II linked dipole,  John (ZL3MR) had a homemade EFHW. The choice of space left us with no option other than to use the EFHW, and even then its setup was less than textbook, it sort of hung over the edge of a mountain. To my surprise the IC-705 gave a reasonable match on 40, 20 and 15 meters though in this instance we couldn't match 10 meters. We put this down to the less than desirable way that we had it setup. Basically, I was quite impressed with its performance and decided then that I would again attempt making my own EFHW for use in the field. 

Fast forward a few months. I had decided, as this EFHW was going to be exclusively outdoor and more so up mountains, I wanted something that was light, sturdy and would pack well. While looking to source parts I came across an EFHW on Aliexpress. The specs and build of it looked reasonably impressive and it was very much the size I was looking for. 

Here are the features and specs as displayed on Aliexpress

Features:
【Wideband Coverage and Power Adaptability】: This K24 pocket EFHW antenna has superior wideband performance, covering the 3-30MHz band, suitable for low power operation of ≤12W in CW mode and ≤24W in SSB mode, which meets the needs of amateur radio shortwave communication.
【Convenient Storage and Portability】: This product is designed to be compact and lightweight and offers premium portability. It comes with a convenient carry bag, making it easy to store and transport. You can effortlessly unfold it for use wherever and whenever needed.
【Multi-functional Test Application】: Multifunctional design, this device is not only suitable for routine 2450 ohm resistance testing but also adept at conducting 20-meter oscillator tests and various other tasks, thereby thoroughly showcasing its extensive applicability within the realm of amateur radio.
【Flexible Installation】: Providing a simple and quick installation process, it supports a variety of installation options, allowing users to choose the most suitable installation method according to the actual environment and needs. 20 meter long oscillator installation requires trimming.
【Grounding Optimization and Safety】: According to the actual use requirements, users can install the grounding terminal at the right time to ensure the antenna works in a fine grounding state, effectively improve the signal transmission quality, reduce interference, and enhance the safety of the equipment operation at the same time.

Specifications:
Name: EFHW Antenna 
Material: metal
Color: black
Item size: 50 * 30 * 23mm / 1.97 * 1.18 * 0.91in
Item weight: 220g / 7.76ounce
Package size: 135 * 121 * 61mm / 5.31 * 4.76 * 2.40in
Package weight: 281g / 9.91ounce

Packing List:
1 * EFHW Antenna 
1 * Storage Bag

My first thoughts were even if it didn't match up to its claims I could surely use the box and wire in my own construction plus the price was NZ$67 or US$41. To get any other brand name antenna from the States or Europe to New Zealand usually cost ballpark NZ$200 by the time exchange rate and shipping is added. So I took the gamble, as it can often be with Aliexpress, and ordered it.

I was pleasantly surprised when it turned up in my mailbox only two weeks later, further, it was compact, appeared to be very sturdily constructed and from what I could see, of quality components and it also came in its own drawstring carry pouch. I was impressed. Then, I decided that I would take the top off the box and inspect the componentry inside. The four screws came out easily but then when I came to prise the top off I realised that it was sealed hard. With a little further thought I decided to leave the internal inspection and set it up and test it. My reasoning was if it is sealed this tightly and it tunes up as hoped, why break a perfectly good waterproof seal.

So, I strung it up on a 7 meter SOTA pole and attached a NanoVNA to it. I set the range up for 7 Mhz to 30 Mhz as that would include all the bands I was interested in plus the radiator element was approximately 70 feet, indicating that it would most probably only tune from 7 Mhz and upwards.  

It was measured without trimming the radiator, however there were dips below 1.5:1 SWR which seemed correspond to all the relevant bands; it was only a matter of trimming the radiator to get the dips to move one way or another to match the frequencies I was looking for. But that had to wait until last week.

In the interim I had been thinking that the issue I have had previously with EFHW has been trimming the radiator either too short or leaving it to long and getting poor SWR readings. And then the thought struck me. Don't cut off the excess wire, just keep it wound on a wire winder and only feed out as much length as is needed to give resonance. And then, if in a situation requiring more or less wire, just further wind it on or off as required. Problem solved. The picture to the right shows the wire unwound with the excess wire still on the winder.

So yesterday afternoon I then took it to a spot slightly raised above the village in which I live. and set it up, again using the 7 metre SOTA pole.  I attached a Nano VNA and with slowly varying the length of the wire off the winder I finally returned a reading of below 1.5:1 on 40, 20, 15 and 10 metres. This was very encouraging. I then replaced the Nano VNA with the IC-705 and, just because I could, I did a SWR sweep on all bands from 3.5 Mhz to 430 Mhz. Now I was elated. I had readings under 1.5:1 not only on the  40, 20, 15 and 10 metre bands but also had less than 1.5:1 on 6 and 2 meters and 70 cm. I had an EFHW that could match my radio to 7 bands. 

The time now was only 2 pm in the afternoon so for the next 1 1/2 hours I flicked up and down the bands chasing operators calling CQ. In that time I made total of eleven QSO's to the far north of New Zealand, Australia, Japan and the California. Those QSO's were made on 40, 20, 15 and 10 meters. 

So far I think this EFHW represents extremely good value for such a small investment.  I will carry out further testing as I take it into the hills and get to try it in various weathers and situations and I shall post further updates.