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Off Designed-Frequency Behavior of 2 Types of Antennas
NOTE: During conversion from forum’s old BB Code format to current Discourse format last year:
- The images in above post got changed to links .
- Editing of old posts is NOT allowed, so I am unable to correct this discrepancy in original post.
I am re-posting here the post linked above because of above reason.
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Off Designed-Frequency Behavior of 2 Types of Antennas
Frequency Sweep (From 100 MHz to 2500 MHz) of Wire Collinear Antenna and 1/4 Wavelength Ground Plane Antenna.
The frequency sweep results of a high gain wire collinear antenna show that it not only performs best at its designed frequency, but also performs fairly good at or near sub-multiples and multiple frequencies.
This characteristic of collinears is good for multi-band reception such as single antenna used by Armature Radio Hobbyists for 2 meter band and 6 meter bands. However it has disadvantage for single frequency reception that the RF signals picked from all these multiple & sub-multiple bands necessitates a tuner circuit or a filter at front end (i.e. between antenna and receiver).
The frequency sweep results of a 1/4 wavelength ground plane antenna show that it gives good performance at and near its designed frequency only, and at other far away frequencies its performance is poor. Hence the 1/4 wavelength ground plane antenna picks very little harmonic and sub-harmonic frequency signals.
WIRE COLLINEAR ANTENNA WITH DECOUPLING SLEEVE
Click on the thumbnails to see full size images
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1/4 WAVELENGTH GROUND PLANE ANTENNA (Cantenna)
Click on the thumbnails to see full size images
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