EMC Bilog Antenna

Are you talking about 30 mHz (milliHerz) to 1 GHz antenna or 30 m (10 MHz) to 1 GHz antenna ?

From memory, the 'butterfly' antenna is used 30-300MHz, a 10 to 1 range, then you're supposed to change to the log periodic which is 300 to 1GHz range, only a 3 to 1 range. However, our Lab simply 'calibrated' the butterfly for up to 1GHz and only switched if close to a limit. Back then, there was not much energy above 300MHz, and almost none above 500MHz.

How do all those DIY sites to make antennas for TV's work?

Yes the Biconical is for 30 - ~200ish MHz, and the Log is for 200MHz to 1GHz. I see some Biconicals up on ebay, price varies $500 to $3000

Those DTV antennas don't have published frequency respose. I might just make a couple of dipoles...

They are easy to construct and they should be close to the curves. They are availble too, dont know what price.

I'm just looking for something on a tiny budget that will give 'really' close' results. I have a Signalhound and it works well enough for EMC work that a good antenna would be ideal to comlete the test setup.

Cheers

I was just going to suggest making a Roberts antenna. I did that with a set of remade rabbit ears once. You can pretty closely calculate that response. Plus, you can abuse it a bit outside its range and still 'look around'

Although it's worthwhile to concentrate on your antenna, you'll actually get a lot more variation caused by your ground plane, etc. If you're outside, even a small rise in the earth at the edge of the plane [like you put this in a parking lot with landscaping edges] can shift you quite a bit. Galvanized sheets, connected by copper tape strips is a quick roll/throw down. I've seen woven 'hardware cloth' used but if you use that, you may find that you match the FCC specs [all measured with well-behaved 50 ohm systems and antennas] fairly closely, but the emanations from your EUT will be all over the place in comparison to 'other' sites.

If you're simply building a 'pre-compliance' check, you can do that inside a building, but don't line up on the overhead grids of hanging metal ceilings, set a bit diagonally to break up the grid pattern, else you can get a lot of 'interactions' from those metal strips and buried rebar in the ceiling.

Let us know how it works out, plus pics!