Tag Archives: QRP

More Experiments with EFHW Antennas – Part 2

It’s been a couple of years now since my first post on EFHW Antennas. Notably since then I have acquired a Mini 600 Analyser. Armed with technology it was time to revisit this “no-tune” portable antenna. What followed was 3 months of confusion, learning and experimentation.

Before I go any further I would sincerely like to thank David VK3IL for his patience and assistance over the last 2 weeks in helping me troubleshoot my issues and teach me a bit more about what I was doing along the way.

It all started when I thought it would be a good idea to re-test the end-fed antenna now I have a new analyser as I was preparing ready-to-assemble kits for my local radio club and didn’t want to see people ending up with an antenna that didn’t work as described. To my dismay, the antenna definitely was not working as originally described.

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Experiments with an End Fed Half Wave Antenna

Portable on Mount Direction

I went away to the Tasmania’s West Coast in October 2016 and had hoped to work some stations. For radio, the trip was a bit of a disaster with the place we were staying having lots of solar inverter noise. The other thing was that it was very tedious to use a linked dipole in the location I was in. Since that day I had resolved that I would try and end-fed antenna and see how that goes.

The End Fed Half Wave (EFHW) antenna is popular with many QRP Portable stations, particularly for activities such as SOTA or WWFF. The big drawback of the end-fed is the high impedances they have, which means that you need to carry some sort of Antenna tuner to match the impedance with the radio. The thought of lugging around an antenna tuner and then having to retune every time I switched frequency was less than appealing though.

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A Quick Activation of Trevallyn Recreation Nature Area VKFF-1156

I had a day trip to Launceston today to assist a new amateur radio operator get on air with his HF rig. I decided that if I has some spare time left over we could stop by the nearby Trevallyn Recreation Nature Reserve and work a few contacts from it.

VKFF-1156 is again somewhere pretty easy to get to, being part of the tourist trail in Launceston and giving access to Lake Trevallyn and the hydro power dam. Access is via sealed road and I ended up setting up of a flat area a couple of hundred metres up from the boat ramp.

This also gave me an opportunity to try my new portable station. I have done away the the aluminium mast and Icom 706 as my go-to configuration and now have a squid pole, linked dipole and FT-817 QRP radio for portable operation. It all sounds suspiciously like I might be getting into SOTA soon! I will probably boost the in-car configuration with a QRP amplifier.

This also gave me the opportunity to try a tweak to my logging set up by use Fast Log Entry to for WWFF. For those of you who are observant, yes that is an iPad, and yes that does look a lot like Windows! What I actually have is a small 7″Pendo Pad running Windows 8.1 (These can’t be bought any more) that I connect to iPad hotspot with, and then remote desktop to the Pendo tablet to run FLE. Its all a bit complicated, but FLE is the simplest way to log WWFF contacts effectively in an ADIF format.

I’d love to say I jung around and got the 44 contacts, however the Tasmanian sun is very harsh and I was very quickly getting burnt. Also, the bands were incredibly open from that location – I could not find a free frequency to call on on the 20m band, with 40m being equally full. In the end I had to make do with just 3-4 contacts and the knowledge that I really need to go back again and do it properly.

Building A linked Dipole

It’s been a little while since I have posted, and its not because I haven’t been doing anything. I’ve been getting my portable station even more portable that before. Ov er the past 3 weeks where I have had a spare evening I have been putting together a new portable station that is even more lightweight than the previous setup featured in my post on Peter Murrell Reserve. Key to this has been producing a linked dipole.

Linked dipoles provide the benefit of creating a single-wire antenna that is resonant on multiple bands without a tuner by “linking” together lengths of wire with clips. While there is no limit on how many links you make, it may not be practical to make the dipole suit everything between 1.8 and 450 Mhz.

I ended up going for a 5 band antenna – 6m, 10m, 15m, 20m, 40m.

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