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Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

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Old 04-20-2017, 4:39 PM
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Join Date: Apr 2017
Location: uk sussex
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Default use of 449.09375mhz

i need help

in the south of uk there is a small group using PWR frequency 446.09375

thats great but i cannot make a antenna resonate at that frequency?

i want to talk to my pals about 12miles down to coast

ive spent two nights trying to build an antenna

various combinations of standard aerials with reduced wip

ive tried a di pole of two 160mm length wires and various combinations

ive tried j pole with adjustable setting and various combinations

and changed to different coaxs

always antennas seem to resonate at around 430mhz and again at 451mhz but swr at 446 is way out

has any one a idea of what im doing wrong?

i would make a yaga antenna but i dont want to spend ages making antenna for it not to work
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Old 04-21-2017, 4:16 PM
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Location: Campbell County, Wyoming
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Not sure about the legality of what you are doing but for an antenna at that frequency I would go with a 1/4 wave or a vertical dipole.
radio waves slow down a bit in copper or aluminum (about 5%). So a easy 'starting point' is

(0.95)( 300)/(frequency in Mhz)=wavelength in meters (for the frequency 446.093 this would be about .6388 m)

divide the above by 4 to get a quarter wave=16 cm.

a dipole is a half wave fed in the middle so the ends are a quarter wave from the center feedpoint. the gap should be as small as practical. Make the antenna a bit long then use an SWR meter to 'trim' as needed. Make sure both stations are using the same polarization (either vertical or horizontal).

12 miles range at that frequency would require a clear 'line of sight' so the antennas should be high enough up to be able to 'see' each other. Height of the antenna is going to affect range the most.

Here in the US that is a ham radio frequency and unlicensed use would merit a possible fine. Stay out of trouble.
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Old 04-21-2017, 4:43 PM
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Location: WNC
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That's the UK equivalent of our FRS
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Old 04-21-2017, 4:52 PM
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Location: uk sussex
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thanks for reply, I finally found an antenna that works, we are calling it a bazooka
the lenght is what you worked out, 16cm inner core as live, 11cm folded back outer sheath and 15 turns balum, it works great and swr 1:1
in UK this frequency is pwr and restricted to 500Mw
although i can go up to 50watts i would not want to cause interference for my neighbors and have the old bill knocking on my door
thanks for idea of vertical dipole i will give it another try over the weekend, cheers robin
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Old 04-21-2017, 5:21 PM
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Quote:
Originally Posted by robin321 View Post
i need help

in the south of uk there is a small group using PWR frequency 446.09375

thats great but i cannot make a antenna resonate at that frequency?

i want to talk to my pals about 12miles down to coast

ive spent two nights trying to build an antenna

various combinations of standard aerials with reduced wip

ive tried a di pole of two 160mm length wires and various combinations

ive tried j pole with adjustable setting and various combinations

and changed to different coaxs

always antennas seem to resonate at around 430mhz and again at 451mhz but swr at 446 is way out

has any one a idea of what im doing wrong?

i would make a yaga antenna but i dont want to spend ages making antenna for it not to work
Have you tried fabricating a ground plane? That should be fairly small and simple for that frequency!
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