Hello all,
Years ago I read about an antenna called the DDRR (directional discontinuity ring radiator) which was developed for shipboard use. It is rather compact since it bends back on itself and is tuned via a capacitor at the end.
I wonder if it could be adapted to part 15 AM use. If you are interested, do a search on "DDRR antenna".
It sure would be a discussion point about the 3 meter rule in that you could have 30 feet of wire in a 3 meter circle.
Hello all,
Years ago I read about an antenna called the DDRR (directional discontinuity ring radiator) which was developed for shipboard use. It is rather compact since it bends back on itself and is tuned via a capacitor at the end.
I wonder if it could be adapted to part 15 AM use. If you are interested, do a search on "DDRR antenna".
It sure would be a discussion point about the 3 meter rule in that you could have 30 feet of wire in a 3 meter circle.
What do you think? Worth a try?
Neil
I have seen plans for the DDRR at CB frequencies, mounted on a large vehicle roof for mobile or over a metal plate or mesh for fixed location. 1.5 Mhz would be pretty big, I think you're about right at 10 foot diameter.
160 meter banders also use tuned loops!
by MRAM 1500 kHz
I've always heard that you can't use a "continuously loaded" antenna which is basically just a helical wound coil, even if the length of the coil is under 3 meters, because the coil itself is the radiator and the wire it's made of is longer than 3 meters.
Would seem that same reasoning would apply to the DDRR as the length of the radiator is more than 3 meters even though it's arranged into a 3 meter circle.
A capacitive "top hat" doesn't radiate but some say that the diameter of the hat must be included in the 3 meter antenna rule.
Wouldn't it be great if the FCC had a Q&A page on their site. I emailed a question to them once but received no response.
Hello again,
These antennas seem to be 1/4 wave long so the length is determined by the operating frequency. I was just wondering if it would operate if it was a fraction of a wave length such as the typical AM antenna, and if so if there would be any advantage.
Maybe someone has tried it and will comment.
If it is not worth pursuing technically, then I am not going to pursue the legality.
You comment about the loop antenna is interesting. I have used one abut 3 feet square for receiving, but not for transmitting. They are directional and that could be an advantage in some situations.
Neil
Hello again,
These antennas seem to be 1/4 wave long so the length is determined by the operating frequency. I was just wondering if it would operate if it was a fraction of a wave length such as the typical AM antenna, and if so if there would be any advantage.
Maybe someone has tried it and will comment.
If it is not worth pursuing technically, then I am not going to pursue the legality.
You comment about the loop antenna is interesting. I have used one abut 3 feet square for receiving, but not for transmitting. They are directional and that could be an advantage in some situations.
Neil
Actually, I though about making such an antenna for Part 15 use. Can you imagine the size/diameter of the muffler pipe for that frequency? LOL!!
John,
That would make my local muffler shop owner very happy. It took me a while but I think I figured out how this thing works. It is a bent transmission line that radiates though a real transmission line does not. The attraction is that it can be tuned at the "hot" end with a capacitor rather than fooling around with coils and taps.
The dimensions for part 15 AM are probably not realistic but I thought it was worth asking.
Neil
See if this link works. There is a version for 160 meters that can be tweaked a little lower I am sure especially if you don't mind a 32 foot diameter pipe.
http://www.arrl.org/members-only/tis/info/pdf/7112028.pdf
WDCX AM1610 Part 15
John
Owner-Operator-Chief Engineer-Program Manager
Hi John,
Your link is password protected and only works for ARRL members (which I am not).
However, if it would be possible to post it here or elsewhere (perhaps it is not copyrighted or you could ask their permission...) I would be indebted to you.
Thanks.
No Problem. Go here, and click on Downloads
http://home.earthlink.net/~wa4jm/
WDCX AM1610 Part 15
John
Owner-Operator-Chief Engineer-Program Manager
Many thanks, John.
And you ham web page is pretty funny too!