UHF TV transmitters for 50km range

Hi there

Our community is looking to set up a 24hour UHF TV transmitter.
Transmission frequency has not been worked out yet. That will be sorted out with the authorities later.

What we need to know is for a range of about 50km radius what type of transmitter would be required? That is at what power (watts) do we need to transmit to achieve this range?

Is it possible to design this transmitter using kitset components?

We would really appreciate it if any person with knowledge in this field could respond with some good information.
Any info on the net would be helpful as well

Thanks

gunmaster

Hi,

A typical model used to calculate propagation distances is Okumura-Hata.
See the following link (or google for more references):

http://www.csi.uottawa.ca/~sloyka/el.../Lecture_3.pdf

50Km is a distance that would typically require a transmitter in the KW range. The exact number dependes on the terrain, and on the coverage you want provide.

These transmitters are not in kit form. They have to be certified by the government agencies to be used in broadcast stations. You should ask your government agency to give you a list of authorized transmitting equipment.

With the switch to digital transmission in many countries, your analog equipment may not be allowed on the air after a certain date. You should do a lot of research before making a large investment.

Thanks for the replies

flatulent,
with the major networks switching to digital transmission would that not provide more UHF frequencies to the smaller groups. By the way what frequency band will digital transmission use?

And why should analog equipment not be allowed?
Will it be because of interference?

Thanks

gunmaster

I think that the analog TV bands are going to be put to other uses. Remember that they were assigned around 1945 or so when technology was restricted in frequency range.

Each country is different. You should check your countries regulations. There may be some restricting the ownership of TV stations to the government or some specific group of industrial companies or some educational organizations.

hi, i am from india & have worked on design and testing of analog vhf uhf transmitters.
the 500w tx in our design met spects for 30 km of range in uhf band, ( so called primery reception area ). secondary area ranged to 45 km ( noisy picture).
the switchover to digital is very very gradual, taking upto one or two decades, thereafter analog will be switched off.
one more thing there are transmitters now a days designed to work both in analog and digital modulation with little modification. there are some in india of same design working for analog as well as digital test transmission ( commercial broadcast is yet to begin).