Buying Parts or Buying Products
Do you prefer to buy commercial products that are proven technology with good reviews and recommendations? May be you don’t mind paying extra for the convenience and lower risk and you like to support the actual developers of the idea, especially if they are also regular Radio Amateurs. Let us take a look at a few examples, starting with the low priced end, for a product that every HF HAM going portable will consider at some point in time.
The EFHW (End Fed Half Wave) Antenna
A simple piece of wire and a ferrite transformer to match the coax feed-line impedance with the antenna, typically 49:1 or 64:1.
There are hundreds of videos on Youtube describing how to make these or where to buy one, all with amazing results – SWR values below 1.5 across the whole HF band and it wraps up and fits in your pocket. Add your pocket sized QRP Radio and a palm sized battery and you are off to the nearest mountain summit for a SSB SOTA. Is it really that easy? We will talk about making these in the Home Brew section, but for now, let us look at the Commercial options for obtaining one.
Looking for a small sized, well designed and built transformer, from a recognized supplier, you would quickly come across the QRPGuys who provide a host of smaller project kits at very reasonable prices including this EFHW built on a circuit board designed as a wire winder, all for just USD $30 (as of Dec 2023).
No question, a great product, from a good group of HAM guys, easy kit to build and does the job. What if you buy things on-line from the likes of Amazon, eBay, Ali-Express etc. If you heard of QRPGuys but didn’t look at their web site yet. Would you buy one of these, on Amazon:
What about this one … This is what came to me when I ordered from Amazon.ca.
I should have paid more attention, and checked out the real web site first, but the advert said it was a QRPGuys item, and they point you to their web site for further details, and it comes pre-built. I figured that all the items are there and I could strip it down and re-build it if there was a problem. It’s not that easy to buy these parts in small quantities and the price of toroids can be very high with no easy way to test what you receive. Anyway, does the Fake EFHW that I received actually work?
Short answer – NO! You can see how messy the toroid winding is, well, if you could look even closer, you would see that there are only 3 connections to make, to connect it to the board, and all three were incorrect. I didn’t have any equipment that would be able to “show” that the transformer was bad, but it couldn’t receive anything when I connected it to my antenna wire and radio. I knew I was going to need some kind of test equipment, if I was planning on building and modifying my own QRP and portable antenna systems, and I don’t like spending more money than necessary, so after borrowing a Rig Expert to test the state of the transformer, I decided I would “invest” in the lowest priced NanoVNA (Vector Network Analyser) I could find. These things are also swamped with fake versions and variations on the official models, and when you get it, they are quite complex to use, with many electronic functions that go way beyond the needs of antenna testing. Once mastered, the basic frequency sweep analysis are really useful and enlightening.
I removed the toroid and unwound it. Using the same piece of wire (magnet wire), I rewound it using the QRPGuys web site build instructions (there kit instructions are very good). Once wound properly, the three leads just line up and drop in the correct holes. It still didn’t work.
I removed the toroid and the capacitor and tried to check the circuit paths on the board, but I kept getting a short circuit from the ground to the antenna post. That didn’t sound good, especially with no coil or capacitor in the circuit. I removed the post bolt and the short disappeared. When I put the post bolt back in, it was now OK. I figure there must have been a problem with the internal tracks under pressure. I put the toroid and capacitor back on and then there was a reasonable frequency response – not great, so I changed the capacitor, but the toroid ferrite material may be less than ideal. So, now it works, but not very well.
What would be some of the warning signs when being faced with Fake items on some of the popular selling sites? For this specific item, we can now see that the item “looks” identical and even has the QRPGuys web site address printed on the board. Put next to a Real one, we can see that there is a Serial Number on the official version, under the web address. There is typically a spelling mistake or other “error” in the printing – here the “… Eed Half …” replaces the full text “… End Fed Half …”. We can also see the quality of the correctly wound toroid and the fact that it has 2 tie-wraps holding it to the board. The advertised items also typically use a subject photograph that displays a well made version and all ads placed by a variety of sellers often use exactly the same images. So, it’s not easy to tell what you are buying until it arrives.
I’ve made at least 6 end fed half wave transformers and antenna lines of 10, 20 and 40 meter lengths. The VNA has been invaluable and I just recently added a CLR (Capacitance Inductance Resistance) meter to my collection of tools – it makes it so much easier for identifying those capacitor values and confirming the Inductance of my home brew 40 to 80m coil.
There’s plenty more portable antennas to build, so an 80m Mag-Loop might be my next attempt to increase the performance of my “official” tiny TruSDX Radio.
Happy Experimenting, John JEY