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Helical or paddle antenna for both IEM and WL mics
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<blockquote data-quote="Paul Johnson" data-source="post: 216130" data-attributes="member: 2643"><p>I'm sorry but that is completely wrong. Antenna design is not linked to transmit or receive it is 100% related to polar pattern and gain. A wonderful antenna that has just the performance you want is not special or unique to receive or transmit. If you look at cellular antennas you will not find them in two sections. There is some confusion in some quarters because for efficient transmission the antenna must be matched to the feeder cable and transmitter for optimal signal transfer- something well understood VSWR. Antennas on comms towers are normally designed for omni-directional coverage - as in they are vertical radiators and their polar pattern from above is a nearly perfect circle - equal signal strength in all directions. This is the typical vertical antennas on radio mic receiver units - these may be helical, but usually nowadays are just a ¼ wavelength of wire inside a sheath. There is no helical winding as you would find on bands lower than 200MHz or so, where antennas ¼ wavelength long are a bit big. They can also be directional with beam antennas if needed.</p><p></p><p>Directional antennas have radiation patterns very similar to cardioid or hyper-cardioid mics - and longer shotgun mics look very similar to yagi antennas of 8 or more elements. </p><p></p><p>Transmitter sites use separate antennas to get additional separation, or where they may wish to have different polar patterns - or they can use combiners and filters to use one antenna connected to a transmitter AND a receiver, as long as the frequencies are different. </p><p></p><p>Receive antennas are often poorer designs - it really doesn't matter of they are 50 Ohms, or 40 or 60 - on receive the different has a very small impact. On transmit, the transmitter may detect the poor match and throttle back a little to prevent damage to the output stage.</p><p></p><p>Active antennas are the exception - they will be for receive use only - electronics doesn't;t like RF going the wrong way. The preamp is the issue NOT the antenna, which is totally uninterested in the 'direction'. Indeed - consider a walkie-talkie. That single antenna does both jobs perfectly well. This post to a long dead topic is just poor information, sorry Frank</p></blockquote><p></p>
[QUOTE="Paul Johnson, post: 216130, member: 2643"] I'm sorry but that is completely wrong. Antenna design is not linked to transmit or receive it is 100% related to polar pattern and gain. A wonderful antenna that has just the performance you want is not special or unique to receive or transmit. If you look at cellular antennas you will not find them in two sections. There is some confusion in some quarters because for efficient transmission the antenna must be matched to the feeder cable and transmitter for optimal signal transfer- something well understood VSWR. Antennas on comms towers are normally designed for omni-directional coverage - as in they are vertical radiators and their polar pattern from above is a nearly perfect circle - equal signal strength in all directions. This is the typical vertical antennas on radio mic receiver units - these may be helical, but usually nowadays are just a ¼ wavelength of wire inside a sheath. There is no helical winding as you would find on bands lower than 200MHz or so, where antennas ¼ wavelength long are a bit big. They can also be directional with beam antennas if needed. Directional antennas have radiation patterns very similar to cardioid or hyper-cardioid mics - and longer shotgun mics look very similar to yagi antennas of 8 or more elements. Transmitter sites use separate antennas to get additional separation, or where they may wish to have different polar patterns - or they can use combiners and filters to use one antenna connected to a transmitter AND a receiver, as long as the frequencies are different. Receive antennas are often poorer designs - it really doesn't matter of they are 50 Ohms, or 40 or 60 - on receive the different has a very small impact. On transmit, the transmitter may detect the poor match and throttle back a little to prevent damage to the output stage. Active antennas are the exception - they will be for receive use only - electronics doesn't;t like RF going the wrong way. The preamp is the issue NOT the antenna, which is totally uninterested in the 'direction'. Indeed - consider a walkie-talkie. That single antenna does both jobs perfectly well. This post to a long dead topic is just poor information, sorry Frank [/QUOTE]
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Helical or paddle antenna for both IEM and WL mics
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