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Richard wrote:
All the vertical part of the antenna is made of aluminum tubing. B is a short peice of fatter aluminum tubing than either A or C. C electrically connects with A, so I presume there is a coil within aluminium tube B. Tube B, at the bottom, looks rivited to tube C. So I'm saying B is like: | | A _____|__|_____ | | | | |____|__|_____| | | | | | x | | x | | x | B | x | | x | | x | | x | |____|__|_____| | | |-----| Rivet |____| |_____| | | C | | There are insulated collarsat both ends of B. X represents assumed coil connecting A to C. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] Okay I removed tube B and made measurements. Here are the details that ought to allow someone to do calculations for the vertical part of the antenna: | |------------------- | | | | | | | | | | | | | | p 19" (48 Cm) | | A | _____|__|_____ --- | | | | | | | | | | | | | | | | | q 1.25" | |____|__|_____| | (3Cm) | | | | |------------| | x | | x | | x | B | x | | x | | x | | x | | | | |------------------ | | | | | | |____|__|_____| r 1" (2,5 Cm) | | | | | | | | | |ooooo|--- Rivet | |____| |_____| connecting | | | tube B | | | to tube C | | | | | | s 60" (153 Cm) | | C | | | | | | | | | | | |------------------------ ^ Feedpoint Tube B is a 4"(10 Cm) long tube. Tube B connects to tube C 1" (2,5 Cm)from the top of tube C. Tube B in fact shrouds the top 1" of tube C. Top of tube C connects to the bottom end of a coil shown by x's. The top end of the coil connects to tube A which is 19" (48 Cm)long.The top part of tube B shrouds over the bottom part of tube A by 1.25"(3Cm). I got the inductance of the coil to be appx 3uH. Length: 24mm O.D. coil: 23mm Turns:13 Spacing: Closewound Wire diameter:1.5mm So I suppose next task is to calcuate the resonant frequency of the vertical part of the antenna. Thing is,is it meant to be a quarter wave half wave 5/8th wave or what. The feedpoint impedance I reckon will be 50 or 75 Ohms. I don't know how to calculate this. The 3 radials are 28" (71 Cm)long, but appear to have small coils at the beginning of the radials. The coils on two of the radials look the same, and the coil on the third radial looks about twice as long as the other two coils. The smaller coil inductances seems to be very approximately 0.330 uH, so the inductance of the larger coil on the third radial is about 0.660 uH. Smaller radial coils data: Length: 7.5mm O.D. of coil: 12mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm larger radial coil data: Length: 7.5mm O.D. of coil: 24mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm Perhaps now these data might help figure out what frequency this antenna is for.I hope. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] |
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