How to get a range of 1 kilometer with blocking buildings in between?

[seadolphine2000]

Hi,..

I have a small question concerning an FM Transmitter.

" I've made a transmitter with power approximatly 10mWatt, I live in an appartement in the 1st floor, when I place my antenna from the window, I got a range about 500meters without barriers and 100meters with some blocking buildings between my TX and the RX. "

My question is "HOW to get a range 1Kilometer with blocking buildings in between.???"
Thanks very much for all your help and time.

 

[IanP]

Re: Transmitter Antenna

10mW doesn't sound much, 100mW wou;ld be better ..
If you can limit the beamwidth to, say, 60°, you can consider a 3-element YAGI antenna which gives you at least 7dBi gain compering with an isotropic whip ..

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks for reply, but I can't undersatnd what you want to say.

please be simpler.

Thanks again

 

[biff44]

Re: Transmitter Antenna

You may be asking to do something that is illegal in the country that you are in.

In countries that allow it, you can go to a higher transmit power for the LAN card at BOTH ENDS of the link, and that will give you more range. Also, if allowed, you can use a higher gain antenna an carefully point it at the destination, which will give you greater range, but only to that one destination.

 

[Debeli]

Re: Transmitter Antenna

I have made a short calculation.
If you want to get 1 km with building obstacles like you said, you should increase your system gain for approx 27 dB (exact number largely depends on the number of buildings and can vary even ±10 dB). For example, than you can reach the distance using the same antennas and 5W amplifier (I do not think that it is the best solution, because building such amplifier is usualy not a trivial task) or you can use better antennas for both transmitter and receiver and increase the transmitter power for 10-13 dB on 100-200mW. More can be said when you describe your application and system more precisely.
Of course, you should be avare if the transmission of larger power is allowed in the frequency band you use.

Regards,
D.

 

[IanP]

Re: Transmitter Antenna

Before we go any further, please tell us what is the frequency of your system and what antenna do you use: 360° (omnidirectional) ?

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks for your consideration,

My TX is a simple FM tx at 87.7MHz and I want to make a small music station, don't worry as it's legal to transmit till 5Km range and I need only 1Km.

My antenna is just a wire 1mm in diameter and 1.5meters long placed from the window of my appartement (3-4 meters above ground).

I could increase the output power till 200mwatt, but what about using the TV antenna with this 10mwatt or with the 200mwatt.????
The TV antenna will be elevated 15meters above ground.

Note: please mention the power in watts and not in dB.

Thanks again for all your consideration.

 

[IanP]

Re: Transmitter Antenna

200mW sounds more realistic for this purpose ..
TV antenna is a directional antenna, and if you would like to have 360° reception you should consider antenna build of 2 perpendicular half wave dipoles mounted on a high mast ..

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks,..

Is it possible to get that range with any antenna elevated at that height(1.5meters) and with 200mwatt.???

If yes, what is the antenna used for that purpose.? Can I buy it, or how to build it.?

Note: 200mwatt and 1.5meters are all what I can do.

Thannks again

 

[IanP]

Re: Transmitter Antenna

For FM operation, such as yours, the ease of construction and low cost of a ¼-λ ground-plane antenna make it an ideal choice (360°).
In brief, it has a vertical rod (length ≈¼-λ, what for ≈90MHz is 76-78cm), a square horizontal metal plate (aluminium, ≈10cm x 10cm, dimensions not critical) and 4 horizontal radials (same length as the vertical rod).
This can be elevated to the hight of your convenience (the higher the better) and should cover (at 200mW) quite a substancial area ..

Can you visualize this antenna?

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks,..

Do you think that this antenna will cover the required area(1Km in radius).???
If yes, please tell me in details how can I construct it.??

I really appreciate your consideration.

 

[IanP]

Re: Transmitter Antenna

Tansmitter of 200mW with ground-plane antenna described below should cover more than 1km ..

The vertical element and radials can be made of brass welding rod (Θ≈3-5mm),
and the vertical element can be soldered directly to the center pin of a coax connector .. choice of a coax connector depends on the availability at your local stores ..

Good luck and regards ..

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks very much for this consideration, but ...

I can't extract the full dimensions of the antenna so , I really appreciate your help.

Thanks again very much

 

[seadolphine2000]

Re: Transmitter Antenna

Hi,..

What about using the satellite antenna.???

Will it work with the transmitter.???

 

[IanP]

Re: Transmitter Antenna

Satellite antennas are designed to operate at much, much higher frequency and they are very, very directional ..

Attached is the enlarged drawing, so I hope this time you will be able to identify dimensions without problems.
Diameters of mounting holes and the central hole for coax connector are to be chosen by you after you select proper and locally available connector ..

regards ..

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks for the pdf, but where can I solder the Ground of the COAX.?????

 

[IanP]

Re: Transmitter Antenna

1- What are the 5 circles found in the plan view (they take a cross shape).??
2- Where to solder the coaxial cable terminals.???
3- The square plate is 1meter X 1meter. Right.???

4 holes are just mounting holes, the bigger one in the middle is for BNC (TNC, N or any other) RF connector, and as this connector is mounted directly to the square plate ground is already connected there.
The square plate is 10cm x 10cm or so (not critical).
Regards,
IanP

 

[seadolphine2000]

Re: Transmitter Antenna

Thanks for help but please be patient as I still can't imagine how it's connected.

The vertical rod is the length of the antenna right.?? This rod how can I connect to the RF connector(BNC).?? This rod is it solid or hollow.?? diameter.?? Where is the +ve terminal and the ground terminal.??

Also, the for small bend rods, what are their diameter.?? Hollow or solid.??

I'm very sorry for these questions but it's really important for me to make this antenna.

Thanks

 

[IanP]

Re: Transmitter Antenna

The vertical element and radials can be made of brass welding rod (Θ≈3-5mm),
and the vertical element can be soldered directly to the center pin of a coax connector .. choice of a coax connector depends on the availability at your local stores ..

This centre pin is your +, - will be connected through the shell of RF connector the the square plate and through it to all 4 radials.
I suggested brass welding wire as it will be easy to solder it to the RF connector pin, but any other metal will be just fine, and it can be solid or hollow rod.
Regards,
IanP

 

[seadolphine2000]

Re: Transmitter Antenna

Mr Ianp,...

Thanks , but I still can't imagine the connections between these components (vertical rod, coax cable from my Tx, RF connector and the square plate).
I'm really confused, all what I got is that the 4 radial rods are soldered horizontally over the square plate.

please help me.

Thanks ops