Grip Packs
Contents:
- 18dBi 23cm-band Gridpack Antennas (900mm)
- A TDJ-2400SPD4 High Gain 17dBi 2.4G WIFI Wireless Grid Parabolic Antenna with N-type Female connector
- An Unknown Tube Grid
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Related Pages:
- 23cm Beacons and Repeaters near Brisbane
- 23cm Beacons and Repeaters near Brisbane
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https://www.spooktech.net/ham-radio/antennas
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18dBi 23cm-band Gridpack Antennas (900mm)
- 23cm/1296MHz/1.3GHz Antenna
- Freq Range: 1.24-1.3GHz
- Bandwidth 60Mhz
- Gain: 18dBi
- VerBeamwidth: 18 (Horizontal Beamwidth when used in Horizontal polarisation)
- HorBeamwidth: 28
- F/B Ratio: ;gt&25dB
- VSWR: ;lt&1.5
- Impedence: 50 Ohm
- Polarization: Vertical or Horizontal
- Max Power: 100W
- Connector: N-Female
- Dimensions: W600xH900mm (Horizontal Polarity orientation)
- Weight: 4.5Kg
- Rated Wind Velocity: 60m/s
- Mast Diameter: 40-50mm
- Manufactured: 2021
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A TDJ-2400SPD4 High Gain 17dBi 2.4G WIFI Wireless Grid Parabolic Antenna with N-type Female connector
eBay item number: 201984584638:
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An Unknown Tube Grid
Diamensions:
- Length: 930
- Centre Width: 810
- End Width: 380
- Tube Diameter: 13
- Tube Spacing: 60 centre to centre (40mm gap)
- Bolt Holes: 110 x 110 centres
Advise from Bruce, VK4BMI:
To find focal length, (diameter squared/16) x depth. Units don’t matter as long
as they are all the same. Measure the diameter diagonally across widest point,
then measure depth at the centre of dish.
Now you have focal length you can work out f/D, focal length to diameter ratio.
Then google feeds for parabolic antenna to find suggestions for this f/D. This
is a flattish dish, it probably had a disk reflector and a dipole.
The gaps between “ribs” should be up to about 1/10 wavelength so 40mm is a bit
higher than optimum (looks like a UHF grid pack) for 1296.
It could be lined with conductive wire, this would also make it polarisation independent.
Diameter at widest point is 930 and the depth to centre is 170.
Fical Length = (930 x 930) / (16 x 170) = 318 mm.
F/D ratio is therefore 318 / 930 = 0.34. This agrees with it being a flattish dish,
a deep dish might be 0.45 to 0.5 and difficult to illuminate efficiently.
You could google parabolic dish feeds or 23cm dish feeds. However, a half wave
dipole with disk reflector about 5 to 10% bigger than the dipole. This is what
it would probably have had at UHF, hence the elliptical shape to match dipole
E & H planes. Grid packs with scalar feeds were round.
A brass or copper dipole and solder a nut and screw to make the length adjustable
for tuning woiuld be suitable
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Glenn Lyons VK4PK
glenn@LyonsComputer.com.au
Ver:gnl20211213 - pre published v0.9