microwave relay

The band-with available for control purposes is limited. A supplier operating in an unauthorised band will be stopped. and may interfere with lawful signals.

A normal signal in any band will also give problems. Imagine a person driving down a street and pressing his garage door remote. doors and gates will open ,alarms will sound, TV etc will be switched.

The signals are therefore superimposed and coded the receiver only respond to

The microwave relay is simply a data connection between the transmitter and the antenna.

Instead of running cables over rough terrain or across water, the Radio signal is modulated on a frequency in the microwave band and transmitted to the final antenna transmitter (or next station if daisy chained).

The microwave transmission is line of sight only.

The receiving end will demodulate the data signal from the Microwave frequency and send it to the power amplifier, etc for transmission in the antenna.

Many times, the studio is not located adjacent to the broadcast antenna. So is is very common for the studio to have a low-powered microwave transmitter which sends the broadcast signal to a receiving antenna at the broadcast transmitter location. This was what was mentioned just above. I believe that you confused this with the signal being sent via radio waves from the broadcast transmitter to your radio's receiving antenna.

A few years ago, I knew of a situation where the microwave link had an equipment malfunction, so it was leaking some of its signal in nearby (but unauthorized) wavelengths. It so happened, that the broadcaster's line-of-sight microwave link was close to a water utility's link between two facilities and the leaking signal was causing problems. You can imagine the surprise, disbelief, and eventual respect that the radio station's personnel had when they were informed about this problem by "complete strangers" and then given a choice of fixing it promptly or being shut down by the
government's regulators.

This is an old post, but I will throw in my two cents anyhow.

Lets assume that you have a signal which has to go from one location to another which is NOT line of sight. You could build a relay on a mountain top which is line of sight to both locations. The signal is then transmitted to the relay where it is received, and is re-transmitted to the destination site... OR... it may be re-transmitted to another relay... to another relay... to another relay... etcetera before it is transmitted to the destination site.

In the amateur radio world we used to have radio links such that from Salem Oregon, I could talk to people as far north as British Columbia, and as far east as Montana with nothing but a hand-held radio... although I have not been active in this group in years.

In this case, we used VHF... say 146 MHz to contact the local repeater (or relay in your terms). The local repeater received the signal and up-converted it to UHF around 440 MHz where it was transmitted up the line of repeaters (mountain top to mountain top) to where we wanted to go (say Nanaimo British Columbia). There, the repeater would down-convert the signal back to VHF and transmit it to it's local region. If we wanted to transmit to a location part way up the line (say Seattle Washington), we could instruct THAT repeater to down-link the signal and retransmit it.

The actual system was a bit more complex than this, but this explains it in a nut shell.

Bill NW7L

Feel compeled to include my 2-cents here, even though the posts have become dated and the originator probably bailed. I don't see where the originators post was really answered.

The question appeared to ask about the antenna itself. First, in the US, all point to point is microwave and above 1 GHz, although there may be some lingering UHF and some in government.

The antenna is designed for the acutal application and will have a very narrow distributed beamwidth (vertical and horizontal) for the purpose of achieving optimum electromagnetic energy to the point of receiving. There is nil dispersed RF energy around that propagated space. Again, nil bio-human energy factors, should that be a concern.

Antennas are designed for the application.