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KG6BAJ > NWSGRP 29.09.09 20:25l 50 Lines 1889 Bytes #999 (0) @ WW
BID : 12062_N1OES
Read: GUEST
Subj: Re: medium waves match antenna-transmitter 50ohm s
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Sent: 090929/0800Z @:KG6BAJ.#NCA.CA.USA.NOAM #:12062 [Grass Valley] InterGate $
** NEWSGROUP: rec.radio.amateur.antenna
** FROM : Wimpie <wimabctel@tetech.nl>
On 27 sep, 18:43, tzitzikas <tzitzikas.5059...@radiobanter.com> wrote:
> i have an 500w medium waves transmitter (output 50ohm) at 1431khz. i
> have the components and i have decide to construct thishttp://www.tzitzikas.webs.com/match.JPGmatch system. it is ok? i must
> connect the power/swr meter before this system (between transmitter and
> match system) or after this system (between match system and antenna)?
> my antenna is an inverted L 5l/16 antenna.
> do you have to propose any better system? thank you
>
> --
> tzitzikas
Hello,
Do you mean 16m vertical and 51m horizontal or 51m total with 16m
vertical? How big is the coverage area?
For ease of matching it is best to have a quarter wavelength (so about
51m totally). To get reasonable antenna efficiency and safe operation,
you need a ground network. For best efficiency and local coverage,
you need a large vertical part.
Without some form of grounding you will get sufficient RF voltage on
your cable (and maybe transmitter installation) that may result in
(skin)burn and other (EMC) problems.
Best way ahead is first design the antenna with ground system (local
coverage assumed). Then you can measure the impedance and maybe change
the antenna setup to get reasonable impedance. After that you can
design the matching network en select the components.
You are right; VSWR meter is between transmitter and antenna matching
unit. When you are unfamiliar with antennas and RF power, I would
recommend you to visit a local radio amateur club for advise, as with
500W AM many things can (and will) go wrong. Did you also check the
legal aspects?
Best regards,
Wim
PA3DJS
www.tetech.nl
Please remove abc in case of PM.
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