Hi Tom, Bob,
I had a look in my Rothammel Antennenbuch (geniune "Militärverlag der Deutschen Demokratischen Republik" version, 1974) and indeed it states 0.007 lambda height.
But what about ground losses if the DDRR antenna uses the ground as counterpoise?
There is also a version with a second ring as counterpoise, but I'm afraid that this even this version needs to be at sufficient height (in wavelengths) to avoid ground losses.
Apart from that: the only way to find out if it works is trying (probieren geht über studieren). If anyone has experience with a DDRR antenna on 137kHz or 475kHz I will be happy to add a chapter to my antenna webpages.
0.007 lambda is barely 4.4m height at 475kHz ... should be easy. For the 0.25 lambda perimeter a 50 x 50 m open area is needed, only for the larger backyards.
73, Rik ON7YD - OR7T
Am 29.05.2015 um 21:59 schrieb Rik Strobbe:
Hi Bob,
small is a relative thing on LF.
A DDRR with a perimeter of 0.25 lambda and a height of 0.025 lamdba is indeed small on 144MHz, but on 137kHz the perimeter becomes 550m and the height a respectable 55m.
Not a backyard antenna ...
73, Rik ON7YD - OR7T
Hi Rik and Bob,
acoording to Rothammel et alt. in my former 10 meter version I used a height of 0,007 lambda, so you should need rods of only 15,4 meters - but anyway ... ;-)
73,
Tom, DK1IS
