retx
New Member
Posts: 49 
|
Post by retx on Jul 30, 2013 12:30:42 GMT -6
MrBruce,
The antenna you depicted is a monopole, and I forgot to add, that if one varies the length of the radiator, the take off angle (and conversely the receiving signal angle) will vary too.
If too short a radiator, the coverage will also be reduced.
This happens a lot with MF broadcasters using this sort of antenna, but the "radial" system they use is at a 90ยบ angle relative to the radiatior, and are burried in the ground, typically 120 of them, and almost as long as the vertical element itself.
For instance, a 1 kW tx fed to a half wave monopole will have a larger coverage than the same tx fed to a 1/4 wavelength monopole.
73,
Carlos.
|
|
MrEd
Junior Member
Posts: 68
|
Post by MrEd on Jul 31, 2013 13:45:26 GMT -6
Carlos this antenna is being used for the FM broadcast band.
I used the program that that image came from which is n2imf calculator using the N2IMF Antenna.exe antenna calculator to determine the radiator length and I am using 4 radials angled at 45 degrees.
I just wanted to know if feeding this antenna with 50 Ohm coax required any type of BALUN transformer.
I have the ground side of the transmission line grounded to a rod buried 3 feet in the ground. The radiator and radials have no physical connection to each other from the antenna to the transmitter.
Bruce.
|
|
retx
New Member
Posts: 49
|
Post by retx on Jul 31, 2013 15:34:35 GMT -6
MrBrunce,
Sorry for having said too much about the whole thing.
Sometimes, adding transformers turns the process too complicated and they're often not needed at all.
I never understood there would be any physical connection between the radiator and the artificial ground plane except for the insulator.
73 & good luck with that omnid. antenna,
Carlos.
|
|
MrEd
Junior Member
Posts: 68
|
Post by MrEd on Aug 1, 2013 8:59:59 GMT -6
retx based on your last reply, it looks like I may have misunderstood you. I thought when you stated MF, you were referring to Medium Wave.
My mistake.
Thanks for your reply, it answered my question.
73's
Bruce.
|
|
retx
New Member
Posts: 49
|
Post by retx on Aug 2, 2013 3:47:53 GMT -6
MrBruce,
No, you are quite correct, MF stands for medium freq. <> M.Wave. I rarely use abbreviations such as LW, MW, SW; I prefer the ones referring to freq. rather than wavelength.
And if there's something I particularly hate is the use of the terms "AM" & "FM" being applied to freqs. or waves.
73,
Carlos.
|
|
