[Wilseus]

I wonder if anyone can help me? I don't know if anyone here uses the Wolfbane predictor site, but it gives an idea of the signal strength in dBµV/m. I'm having some difficulty understanding the dBµV/m values. What I'm trying to find out is how to convert from such a value to the signal levels generated by any given aerial that I can expect to see in the coax cable that I connect to a meter or a TV. I realise that this of course varies according to the gain of the aerial but I also understand that it's not just a case of adding the gain (in dB) of the aerial to the field strength in dBµV/m. The distance learning course I have completed seems to imply that it does, but I have reason to believe it is wrong.

I have today spent all day playing what I hoped might be the correct equation:

20 log10( 7.94 / (wavelength * square_root ( aerial_gain ) )

but I just cannot seem to get sensible values out of it.

I'd appreciate it if anyone has an answer to this, as I cannot seem to find any information on this anywhere!

[Chris Muriel]

Instead of working with wavelength try working with signal levels at the antenna output.

The bottom table here should help :
Conversion dBm - dBW - W e dBuV - dBV - V

Chris Muriel, Boston, MA but normally....

[Wilseus]

Thanks but that's not what I'm after I don't think. I know how to convert between dBm and dBµV (you just add or subtract 108.75 for a 75 ohm system to do that.)

I want to convert between dBµV/m field strength in the AIR to dBµV in the CABLE, for any given aerial. I cannot find any information anywhere on the net that gives me a simple table or formula to do this.

[Chris Muriel]

I'm not sure that you can directly do that as it depends also on the radiation efficiency of the aerial; you would have to assume a particular figure and also either a perfect match or make allowances for some insertion and readiation loss.
You might find some hints if you Google "link budget"
(I used to use these when I was in telecomms).
There might even be a decent link budget calculator on the web these days.

Chris Muriel, Boston but normally...