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| Disco Frank |
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yesi need one got me a nice little 4watt cb and now need ariel any one
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| Waggin |
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is it AM or UHF
Where do u plan to mount the antenna Do yo plan to use it for long distance country comms, or short(ish) distance work in built up areas?
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| 4.9 EF Futura |
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Do UHF systems work on a ground plane? i.e. does the position of the aerial dictate the directionality of the singal?
_________________ I promise..... I will never die. |
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| Waggin |
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{USERNAME} wrote: Do UHF systems work on a ground plane? i.e. does the position of the aerial dictate the directionality of the singal?
Yeah they do indeed work on a ground plane, UHF has similar principals to AM, just a different wavelength. You can get ground independant antennae for UHF if there isnt a reliable groundplane available.
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| Disco Frank |
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basically want a nice smallish areill to mount on glass if possible but i was told needs to be earthed to the car body?
mainly used for cruises through perth etc and the country side not long distance so i big f**k off ute one is not needed
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| Waggin |
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Is it UHF or AM ?
If its UHF you have a few options AP454-70-5G: 3.0dB Glass Mount Stainless Steel Colinear Whip (470-490Mhz) AP454-3G: Unity Gain Glass Mount II, Stainless Steel Whip (406-520 Mhz) They are around $160ea. There are no on-glass options that im aware of for 27Mhz
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| Disco Frank |
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yer uhf
uniden 510.. sorry i mean i would like a glass mount ie simalar to the mobile phone style f**k $160! sheesh
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| Waggin |
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Ok cool.
Yeh, $160. You're looking at $110 for PhasemasterII Elevated Feed antennae (These are the ones which you see mounted in the bonnet and boot grooves) They provide 6dB gain
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| Disco Frank |
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damn $110 hey
got any links to online shops so i can havea looksee and what do u mean by 6db gain?
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| Waggin |
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Gain is a measurement of the beamwidth concentration.
Higher gain gives better performance for long distance in flat areas, or high elevation transmission stations Lower gain gives better performance around the city., 6dB is a good all-rounder. Possibly a little too narrow for heavy CBD use, but the Perth CBD is pretty much like rural NSW anyway 
www.rfindustries.com.au / www.tenfour.net.au
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| 4.9 EF Futura |
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{USERNAME} wrote: damn $110 hey
got any links to online shops so i can havea looksee and what do u mean by 6db gain? Gain is a measure of amplification (sort of). In the case of comms equipment, it relates to the relationship between the wavelength of the frequency and the length (effective or otherwise) of the antenna. Example (using 27MHz as i know s**t all about 477Mhz UHF): I had a 27MHz AM CB. The wavelength of this frequency is roughly 11 meters. Power was 4watts. Therefore, an 11 metre antenna would produce 1db of gain. A 22 metre antenna would provide 2db of gain and effectively 8 watts of output. I had a 5.5 meter antenna (which would have procuded 0.5db of gain) but had a 2.25 meter loading coil so was effectively 7.75 mteres long and produced 0.75db gain or 3 watts of output. 477Mhz is an ultra high frequency and therefore has a short wavelength. So a 'normal' sized UHF antenna will produce a s**t of gain. 6db on your 4watt unit would effectively be 24 watts of output. Also affected by the size of the ground plane..... my old 27Mhz setup was ground independant so wasnt an issue.........complicated 
Next week's lesson: Tuning antennae and using the standing wave ratio, lol. Class dismissed.
_________________ I promise..... I will never die. |
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| bowsaw |
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Be careful when listening to claims of gain, just having 6db gain doesnt say gain over what, if it said 6dbd, you would know it has gain over a dipole, complex stuff. You can but on glass ones on ebay, for 25 bucks or so.
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| Clarkey |
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Hey Neil i didnt know u were abrtw!!!!
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| Happy |
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{USERNAME} wrote: but the Perth CBD is pretty much like rural NSW anyway
thems fightin words!!
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| Waggin |
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{USERNAME} wrote: Be careful when listening to claims of gain, just having 6db gain doesnt say gain over what, if it said 6dbd, you would know it has gain over a dipole, complex stuff. You can but on glass ones on ebay, for 25 bucks or so.
This is very true. RFi put all their gain's over a 'Quater wave roof mounted antenna'
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