For the past several years, I have been getting together with some like-minded QRPers for Field Day. We tent camp in French Creek State Park in Elverson, PA, and operate QRP on battery power (typically, class 2AB). Our little group, known as the French Creek QRP Renegades, runs a very laid-back style of Field Day and likes to keep things very simple. This includes antennas we use for the HF stations. Since I've never been too fond of launching wire antennas in trees and putting up a tower and beam just seems like too much work, I've focused my attention on antennas that can be deployed in minutes.
A few years back, I did some experimenting with 4:1 Un-Uns to feed wire antennas for multi-band use. For Field Day 2010, I used a 26-foot vertical wire fed with an Un-Un to cover 40M through 10M. The vertical wire was supported by my trusty 28-foot Jackite pole. I used six 16-foot radials and ran 15 feet of RG-8x between the Un-Un and my auto tuner. The tuner loaded it up well and it seemed to perform very well. I was pleased, especially since our Field Day site was in a bit of an RF hole that year.
The following year, I used a similar configuration but made some changes to cover the 80 meter band, as well. I used a 50-foot wire for the radiator (25 feet vertical, 25 feet horizontal.) I also added two 33-foot radials. That year, we were in a much better location for Field Day. This configuration worked like gang-busters for our CW station.
After seeing how well my antenna worked, Ed WA3WSJ came up with a similar version of this antenna. Ed uses a 31-foot Jackite pole for a support and uses six 15-foot radials and one 33-foot radial. Instead of the 4:1 Un-Un, Ed uses a 1:1 Un-Un. While we've had success with both UnUns, some quick modelling of the antenna suggests that the 1:1 ratio is a better choice. Ed likes to keep the feedpoint about 3 feet above ground. For the past few years, Ed used his inverted L for our SSB/digital station and he has had great results with it.
My current configuration is shown in Figure 1. The radials are just spread out on the ground, so they aren't really tuned radials. I use a ground mount from Jackite to support the pole. The Un-Un is attached to the pole with a small bungee cord. There's nothing magical about the 53-foot radiator. I had previously cut the wire for another antenna configuration and just went with it here. It works pretty much the same as the 50-foot version I had used in the past. I'm also switching over to a 1:1 Un-Un for this antenna. If you haven't already figured it out, you need to use a tuner with this antenna. Also, I would recommend keeping the coax feedline as short a practical. Depending on the installation particulars, I typically, use 20 to 30 feet of RG-8x to feed the antenna.
As you can tell, the inverted L has become the HF antenna of choice for the QRP Renegades. While it's not completely freestanding, it only requires one line to be lauched into a tree to support the end of the horizontal wire. Given the success we've had with these inverted L antennas, I suspect we'll be using them for many Field Days to come.
73, Craig WB3GCK