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#11
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Need base station antenna for RV
Andy,
I decided to go with a bigger ground plane and followed your suggestion. There is now a patio on top of my RV g. It's a little top heavy (a hot tub and 5-burner grill will do that), but wtf, there will be killer stargazing at Parowan, where applicants outnumber the 18M nationals 42 to 1, 182 days out. ~tuno (really ... not counting the days) |
#12
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Need base station antenna for RV
In article Tuno writes:
Saying it is' a "whip" does not tell us much. It's a 64 inch whip on a Radiall/Larson magnetic base that contains the frequency matching coil, from Tim@W&W. What frequency are you planning on operating on? If it is around 123 MHz, and a 1/4 wave, it should be about 23 inches long. For a 5/8 wave, I calculate 59 inches in length. If I understand you, the ground plane *radius* has to be at least 64 inches. That's one big piece of sheet metal! I'll have to make due with 12, unless that's going to bother my radio when I xmit. The ground plane radius should be about 1/4 wavelength plus about 5% (these figures from radials such as wire). The wavelength at 123 MHz is about 96 inches, so 1/4 wavelength would be 24 inches. Add 5 % and you would build with radials of 25.2 inches. Planting the magmount somewhere near the middle of the roof should do just fine. Note: this is for a 1/4 wave antenna. For a 5/8 wave antenna, the ground current should be lower due to the higher base impedance, so the ground plane will have less impact. I suspect that the 64 inch whip was added to a 5/8 wave base transformer, and may be just a bit long for the aircraft band. On top of a motor home, a 64 inch whip will hit a lot of things as you drive. Alan wa6azp |
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