Hello

I would like to have some help. I have a school job to build a medium
wave antenna omnidirectional for a area 60km radius. the frequency of
the station is 999KHz.
Where can i find some material to do this.

Tanks

In message . com,
wadjet writes
Hello

I would like to have some help. I have a school job to build a medium
wave antenna omnidirectional for a area 60km radius. the frequency of
the station is 999KHz.
Where can i find some material to do this.

Just copy one of these :-

http://tx.mb21.co.uk/gallery/westerglen.asp

Brian
--
Brian Howie

Assuming you really are wanting information and are not being silly!

Generally speaking MF stations that want that kind of range in a average
broadcast mode of operation (ie the people receiving it only have small
portables/car radios etc rather than well tuned antenna arrays
themselves) need to have something close to a 1/4 wave vertical in a
very large paddock with an underground earth mat. You can use longer
antennas and feed them as half waves etc but your dimensions become a
problem.

A 1/4 wave on 999kHz is 150 metres or thereabout. Thats roughly how high
a guyed lattice tower/structure you would need. The ground mat would
probably need to be at least 15 metres out from the antenna base.

This is of course not cut and dry. Varying conditions and topography
govern what kind of performance you will really get. Most MF stations
also run quite a lot of RF power. Something you didnt specify.

You can of course make a loaded antenna of any length and suffer the
loss of performance. I cant remember the figure off hand but something
like a 97% loss of antenna effiency wouldnt be unrealistic if you used a
6 metre loaded vertical.

Probably your best "bang for buck" would be to float an antenna from a
kite. There may be air regs to consider though.

If you really are trying to do this pls repost some more detail of what
you are trying to achieve.

Bob VK2YQA

wadjet wrote:

Hello

I would like to have some help. I have a school job to build a medium
wave antenna omnidirectional for a area 60km radius. the frequency of
the station is 999KHz.
Where can i find some material to do this.

Tanks

Sorry 150 metres. Wide fingers on keyboard...

Bob Bob wrote:
The ground mat would
probably need to be at least 15 metres out from the antenna base.