After a Qth change last year, I was fortunate to get permission for an outside antenna. The new antenna was built with the following considerations in mind.
At least 10 – 20m coverage
Open wire feed to simplify matching the various impedances
Loop design, because it is less sensitive to nearby objects and it requires less real estate, considering the length of the antenna. Broadside radiation on all bands as the antenna is running N/S and I wanted most of the power into E/W direction.
While studying “Cubical Quad Antennas” by Orr/W6SAI & Cowan/W2LX, I notices the mini-X-Q (eXtended Quad) which is basically a 3/2 wave open loop with 3 db gain. Because of limited space and height 928ft), I have built the 10m mini-X-Q and modified it into a delta.
The next step was to convert it into a multiband antenna, giving comparable results to a mono-band loop or dipole. At the open end of the loop a 1/4 wave shorted stub for 28Mhz was added. The stub and the feed line is made of 450 ohm ladder line. The stub opens the loop on 28Mhz, on all other frequencies the antenna is working as a closed loop.
The antenna has been in use for a few weeks now and produced solid signals within Europe, nevertheless DX has also been worked e.g 20m with Dave FY/DJ0PJ as one of the first QSOs, 2 way QRP of course. I have also used the antenna on 30m and 40m to contact other Euopean stations.
72/3 Bert DL2HCB
Hi Bert , I am very interested in making my own delta loop multiband and want to know all the dimensions of the one you built . It looks much like the Moplk delta loop but you use an open line in the middle .
Kind regards ,
ON6EF , Eddy
Hi Eddy,
the loop dimensions are found in the picture (16ft/20ft/16ft = 4,9m/6,1m/4,9m).
The lengths of the stub depends on the frequency and the velocity factor of the ladder line:
F = 28.0 MHz, ladder line 450 Ohm CQ-553 (vf=0,905), l = 7.81ft or 2.42m
F = 28.5 MHz, ladder line 450 Ohm CQ-553 (vf=0,905), l = 7.941ft 2.38m
The function of the the stub (“open line in the middle”), is to change the elevation angle to a lower value on the 10m band.
Yes, the antenna looks similar to the M0PLK. But where the ladder line feedpoint in my antenna is, the M0PLK loop is closed and the feedpoint of the M0PLK including including 4:1 balun is at the end of the vertical ladder line. The M0PLK is fed with 50 Ohm coax cable.
73 de Bert DM1BM (ex DL2HCB)