antenna-theory.com

[pistol2012]

Hi, and thanks for your attention.

I am trying to work out the best was to get a transmission signal out of this low powered circuit (3volt) battery.

I basically have a 1200mm long round galvanized steel pipe which is 90mm (outside diam.) This pipe sits in the ground
This sits outdoors and will be painted.

I need to have the electronics circuit encased within the pipe, and the antenna must be vandal /weather resistant.

If we used a slot antenna, will things like weather affect the transmission?
Does the fact that this is a very low volts transmission (200metres max) will the steel on the pipe cause the battery to drain very quickly?

Would you recommend use of any different kind of antenna?

Thanks for any advise

Tas.

[bigSteve]

Rule #1 is to ask what frequency you intend to use? That's the most important question in determining anything about the antenna. If you are talking about trying to radiate d.c., you have no chance.

[pistol2012]

Forgot to add that,

It's 433mhz.

Tas.

[bigSteve]

At 433 MHz I don't think the weather will affect you, no matter what type of antenna you are using.

For a slot antenna, you can't just cut that into your pipe, because the diameter is too narrow. Possibly I would split the pipe and make a simple dipole with a small gap for the feed.

I'm not sure why you would ask why low voltage transmission will drain the battery....low voltage is usually associated with less power.

How deep in the ground will the pipe be? I'm not sure how dirt affects antennas at 433 MHz. Generally I would guess you would want it as shallow as possible, and also note that the dielectric constant of whatever the soil or dirt is will reduce the half-wavelength needed. So if you design the antenna in air and then put it in dirt it might not resonate at the proper frequency.