Shorty antennas
#1
12-24-2012, 12:46 PM
Join Date: Oct 2011
Location: Texas
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#2
12-25-2012, 05:55 PM
any short antenna is going to be a problem with CB reception and transmission. You don't have much of a ground plane to work with to begin with and shortening the stock antenna is only going to make it worse.
To answer your question though, no sir I do not have any experience with the Antenna X products but I will tell you that dealing with FM signals vs HF signals are 2 totally different beasts. FM is fairly easy to tune; HF not so easy and there are several factors to come into play with HF with the 2 major being the ground plane the antenna is attached to and the number/length of winds on a CB "whip"
To answer your question though, no sir I do not have any experience with the Antenna X products but I will tell you that dealing with FM signals vs HF signals are 2 totally different beasts. FM is fairly easy to tune; HF not so easy and there are several factors to come into play with HF with the 2 major being the ground plane the antenna is attached to and the number/length of winds on a CB "whip"
Last edited by UltraNutZ; 12-27-2012 at 02:08 PM.
#3
12-25-2012, 07:33 PM
Road Master
What does UHF have to do with it ? 40-ch CB's operate on 27 mHz., +/_ , which is the 11-meter band in the HF spectrum. IF CB's operated at UHF (412-570 mHz)., there would be plenty of sheet metal for a RF ground plane in the rear fender alone...
And the antenna does NOT care what method of signal modulation is used, AM, FM, PSK or other..
All CB antennas on motorcycles are compromises.... natural resonant length would be unwieldy at over 9' for a quarter-wavelength vertical antenna in the CB band, so the physical length is shortened by one of several means, most common is a loading-coil somewhere along the length of the antenna, generally center-loaded or base-loaded variety. A loading coil is simply a portion of the antenna length rolled around a form so the physical length of the antenna can be decreased but the "electrical" length appears the same to the transmitter..
The tradeoff is in antenna efficiency- shorter physical length equals less radiated signal. The power is dissipated as heat within the loading coil instead of electrons transferred into the atmosphere.
The shorter the antenna, the less efficient... period. That theory also applies to receiving ability... efficiency is efficiency whether transmitting or receiving. Of course one will not damage their receiver with a too-short antenna, just suffer very poor reception. The antenna mismatch with a transmitter can cause damage to the final transistors if the antenna isn't matched by other means (a matching network of some type).
Ground plane reflector size is a major part of antenna efficiency, and HD motorcycles do not have enough reflector area for 11 meters, so there is a compromise there as well. The shorter the radiating element, the greater importance the ground-plane size takes on-another problem on a motorcycle... there is only so much metal on a bike.... you can't shorten your radiating element and expect receiving and transmitting not to be effectively reduced...
And the antenna does NOT care what method of signal modulation is used, AM, FM, PSK or other..
All CB antennas on motorcycles are compromises.... natural resonant length would be unwieldy at over 9' for a quarter-wavelength vertical antenna in the CB band, so the physical length is shortened by one of several means, most common is a loading-coil somewhere along the length of the antenna, generally center-loaded or base-loaded variety. A loading coil is simply a portion of the antenna length rolled around a form so the physical length of the antenna can be decreased but the "electrical" length appears the same to the transmitter..
The tradeoff is in antenna efficiency- shorter physical length equals less radiated signal. The power is dissipated as heat within the loading coil instead of electrons transferred into the atmosphere.
The shorter the antenna, the less efficient... period. That theory also applies to receiving ability... efficiency is efficiency whether transmitting or receiving. Of course one will not damage their receiver with a too-short antenna, just suffer very poor reception. The antenna mismatch with a transmitter can cause damage to the final transistors if the antenna isn't matched by other means (a matching network of some type).
Ground plane reflector size is a major part of antenna efficiency, and HD motorcycles do not have enough reflector area for 11 meters, so there is a compromise there as well. The shorter the radiating element, the greater importance the ground-plane size takes on-another problem on a motorcycle... there is only so much metal on a bike.... you can't shorten your radiating element and expect receiving and transmitting not to be effectively reduced...
#5
03-22-2013, 08:06 AM
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