Now that it will be slowly fall with dropping temperatures portable-DX would not be recommend anymore unless you are sitting in a camper equipped with a heater but indeed being home at the Transceiver could be also an event. Therefore I have build such an easy antenna which also could be interesting to bring it up for the next field day or something like that.
A Delta-Loop-Antenna like that one I've built is an inverted triangle which could be very easy to be installed if you have a portable mast build of fiber. I used to do it with a copper wire of 2.5mm diameter and 11.1m length which will bring the antenna about in range of 27.2 up to 28 MHz.
Usually a Delta-Loop will have a high impedance of about 100 to 200 Ohms depending on the length of each side of the triangle. The more those three sides having an equal size the higher will be the impedance. But don't worry about 200 Ohms. You can bring it down on the wanted 50 Ohms easily by using an about 1.80m. long koax of 75 Ohms like those TV cables which has to be connected between the antenna and the 50 ohm antenna cable. You could use two simple lamp terminals for fix it between the antenna and the 50 ohm koax just with a little screw driver.
In my case I have already two masts on my balcony and unfortunately there is no more room to build up wider antennas like i.e. a dipole antenna which for the 11 meter band will be at least 5,5m wide so the only chance I have is to do it vertical, that's what I thought until now.
 |
| 3 Antenna Masts on balcony - Delta Loop in the middle |
The electric length of a Delta-Loop-Antenna works for fact equal compared to a Dipole-antenna so your signal being received by someone will be about the same as from a dipole. One more point for the delta-loop is that while a dipole will be installed without the possibility to turn it easy in the right position you can do it easily with a Delta-Loop because of its smaller size. The second good point which speaks for a delta-loop is that you only need one mast while a dipole has two points on which you bring em up in the air. Like every antenna also a delta loop works best if it is installed at least one wave length above the ground which in my case is 11m for the CB-band.
 |
| Above the roof (from left to right): 11m. vertical, 11m. Delta Loop, 2 Antennas VHF/UHF |
I simply took a PVC-plastic-pipe of 3.20m length and drilled a hole in the middle of it so the top element of my 14 meter long fiber mast from the German specialists Spiderbeam could get through that hole. Then I also got a piece of rope fixing it on top of the mast and to both sides of the pipe to hold the ends of the pipe in an upright position. Then I put the antenna-wire through the PVC-pipe and bend to rest of wire at each side down until it reached back to the mast in equal length. Now, because of my other Antenna's on the balcony which gave me less space to put a wider antenna between it, I measured only 3.20 meters of pipe so I was able to turn that antenna between those other antenna's and, additional to this size the delta-loop has been automatically matched to have 50 ohms impedance so I didn't need the piece of TV-cable to be installed and the SWR shows 1,1:1 at 27.5 MHz.
 |
| Delta Loop Antenna: The Drawing |
As the band was wide open on that sunny day in October 2024 there were lots of stations to hear. So I called CQ and made contacts all over the world. Sometimes I found out to turn the antenna will be more effective for some stations which were not in the right direction before. In the afternoon there was a spot open to Melbourne, Australia coming in with S7 and I was been heard by S3. Same experience I made with Iceland. My reading was S7 and I was been heard by S3. The States of Maine, Kentucky, Tennessee, and also Nebraska in the US were showing the same effect. They all have been about 4 steps stronger on my S-meter as they could hear me but at last it was good enough to make the connection. The horizontal polarization works really great because of its flat radiation angle which will be reflected somewhere in the Ionosphere or other magnetic charged air layers while on the other hand stations under ground wave conditions I still work better with a vertical because they do the same polarization.
All in total I can say that a smaller antenna won't be the super power thing. That's for sure. But it will be useful if you're having less space to build bigger antennas. The more space you have available the bigger antennas you can build up in the air and the stronger your signal will be received at the other side of the planet. The more elements you will add to one of those delta-loops the more gain it will have. The horizontal polarization will made up a plus of possibilities by intercontinental DX connections and you can turn it into the right direction to get rid of QRM what comes from other sides. A delta-loop like mine with only one element works equal in both directions as in front and back so if you turning it north you will also work south the same quality. Probably there will be something happen to the regular ways of the radiating HF between antennas set up so close beside each other like mine. Happily I couldn't find any interference but who knows how the aluminum masts having influence on the HF coming out of the delta-loop. I was actually very impressed how this antenna is still working. According to many antenna books there won't be the best antenna for everything, such for any frequency or even for every situation, but all I could say after testing this one is that the Delta-Loop is one of a kind !
Yours Alex, 13CT30.
No comments:
Post a Comment