i have an 500w medium waves transmitter (output 50ohm) at 1431khz. i have the components and i have decide to construct this http://www.tzitzikas.webs.com/match.JPG match 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" wrote in message
...

i have an 500w medium waves transmitter (output 50ohm) at 1431khz. i
have the components and i have decide to construct this
http://www.tzitzikas.webs.com/match.JPG match 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


Are you allowed to operate a 500 watt transmitter in the medium wave band in
your country for student radio? That sounds a lot of power to cover a
campus.

What is a 51/16 antenna? ... is that 3.19 wavelengths long? ... if so, that
would be inefficient as a medium wave radiator.

You'll find that a pi network, as you propose, can be made to match almost
anything to anything at a spot frequency, as long as the L and Cs have
sufficient range, but you might have difficulty achieving adequate
uniformity over the nominal 9 kHz bandwidth of a normal medium-wave
transmission (i.e. a broadcast service).

Chris

On 27 sep, 18:43, tzitzikas 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.

"Wimpie" ha scritto nel messaggio
...
Did you also check the
legal aspects?

I think is the last problem for those guys
http://www.harriku.com/photos2008/radio98_1.jpg and more on
http://kotisivu.dnainternet.net/harriku/greeks.htm


Best regards,
Wim
PA3DJS

Regards,
-.-. --.-

my match Pi system http://www.tzitzikas.webs.com/match.JPG is ok or i must modificate this to LC match system? it is ok or i must remove the 1500pf capacitor and increase the the first capacitor and add constant capacitors to 500pf capacitor? thank you.

"tzitzikas" wrote in message
...

my match Pi system http://www.tzitzikas.webs.com/match.JPG is ok or i
must modificate this to LC match system? it is ok or i must remove the
1500pf capacitor and increase the the first capacitor and add constant
capacitors to 500pf capacitor? thank you.

--
tzitzikas


You probably need to answer the questions you were asked before anyone could
advise on matching, like what's the length of the antenna?

Also, is this for pirate radio?

Chris

In message , christofire
writes

"tzitzikas" wrote in message
...

my match Pi system http://www.tzitzikas.webs.com/match.JPG is ok or i
must modificate this to LC match system? it is ok or i must remove the
1500pf capacitor and increase the the first capacitor and add constant
capacitors to 500pf capacitor? thank you.

--
tzitzikas


You probably need to answer the questions you were asked before anyone could
advise on matching, like what's the length of the antenna?

Also, is this for pirate radio?

For 'educational purposes only', you could try these two programs. One
calculates the impedance at the feed-point of an inverted-L end-fed
antenna, and the other calculates the values of the L and C which you
need for an L-match tuner circuit.

endfeed.exe
l_tuner.exe (that's L-TUNER-EXE)

These - and many more wonderful programs - are available from this
website:
http://www.zerobeat.net/G4FGQ/
http://www.zerobeat.net/G4FGQ/page3.html#S301"

--
Ian

my antenna is (5 x wavelength) / 16 . it is ok or i must modificate it to wavelength/4??? the horizontal part is about 45 meters and the vertical is about 20 meters.

"tzitzikas" wrote in message
...

my antenna is (5 x wavelength) / 16 . it is ok or i must modificate it
to wavelength/4??? the horizontal part is about 45 meters and the
vertical is about 20 meters.

--
tzitzikas


If the wavelength is 209.6 m then those dimensions sound like 0.21 and 0.1
of a wavelength so now I understand: the total length is 5/16 of a
wavelength, not 51/16 as you wrote before.

Why don't you make use of the programs Ian Jackson offered, for educational
purposes as he put it.

If this is pirate radio then you probably don't care about the audio
quality, so there's no point in me banging on about keeping the Q of the
system low.

Chris

On 30 sep, 19:11, tzitzikas wrote:
my antenna is (5 x wavelength) / 16 . it is ok or i must modificate it
to wavelength/4??? the horizontal part is about 45 meters and the
vertical is about 20 meters.

--
tzitzikas

Hello,

It can or cannot. It depends on your required coverage area, soil
characteristics and ground network. Assuming local coverage, it will
definitely work less then a vertical quarter or half wave fed over a
very good ground network.

When you have a relative bad ground circuit, you may only need a
capacitor in series with the antenna wire to do the matching. When you
have a good ground, you need an additional inductor.

When you provide some more info, you might get better feedback.

Best regards,

Wim
PA3DJS
www.tetech.nl