RadioBanter - View Single Post

December 14th 03, 05:47 PM

On Sun, 14 Dec 2003 15:18:34 +0000,
said...
On Sun, 14 Dec 2003 13:59:38 GMT, Active8
,invalid wrote:

Yup. gave you the eqs to figure out your ballpark figure. I figured
a ballpark figure might work if you gould figure out how much
voltage appeared at your RFSM antenna. had I known you had a
reference transmitter i might have suggested checking your RFSM
reading at one location with the ref and another closer location
with the test Tx, identical readings indicating sucess or close to
it.

I'll use a distance of 6m.

Noted, thanks.

Just curious, but would carrying out comparative measurements at say
only 6 to 10 feet give rise to invalid readings??

Lots of things can foul you up.

I think I estimated the near field/far-field at 3.7m so I wouldn't
do it. IIRC the change in field strengh with respect to distance in
one of the zones of the near field varies inversely with the cube
of the distance, as opposed to the square as it does in the far-
field.

BTW, I've seen other far-field eqs where the antenna diameter (not
aperature size) is used and I haven't bothered looking into the
origin, but I'm just trying to impress upon you the fact that
nothing's written in stone.

The 6m I gave as an example might not be all that great. These
short distances you mention have me thinking you're locked in a
dungeon somewhere so I tried to keep it reasonable. A sniffer might
be ok at close range and an active RFSM would be good at greater
distances.

Personally, since you've got a reference Tx, I'd take the whole
deal outside (they do let you out, don't they) and see what happens
with greater distances. Even a gym or auditorium would work if
you're concerned with how well it works indoors.

I remember the 40MHz part, but I'm not sure what yer up to. Just
curious.

-mike