Antenna link

found.

I think that this size dish is too small for the 2.4 GHz that the can antenna is putting out. Probably a lot of the signal just goes out the back and is wasted.

wrote in

i

can

the

fine!

You'd better recalculate that wavelength. More like it's a bit less than 5 inches. And that antenna dish was made for frequencies much higher than 2.45 GHz with wavelengths much shorter.

....

In my universe, the wavelength in free space is more like 4.9 inches at 2.4 GHz. I'm willing to believe c is different in your neighborhood, but please tell me how you post here from over there.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

??? At 2.4GHz a full wave is .00041 inches. The reflector will work just fine! getting it at the focus is more of a problem.

wrote in

SB 4.1 inches....... !

Yes, bad copy.... The point was that the reflector is made for 8 to 10GHz, so it will work. IF the feed is at the focalpoint.

wrote in

Gee, I guess I shouldn't try to convert from meters to inches in my head...

12.5 mm IS closer to 4.9 inches.

Nope: Ignoring the banter. It's 4.9 inches!

At 2.4 gHz One Wavelength = 300/2400 = 0.125 metres = 12.5 centimetres

Centimetres! (A typical 6" 8" doorway is roughly two metres or two hundred centimetres high). And one hundred centimetres is roughly 39.3 inches. So 12.5/100 x 39.3 = 4.9 inches.

But the 'probe' that launches and receives the signal would presumably be one quarter wavelength? To match the 50 ohm feed line? So probe length (inside the can and hopefully at the dish focal point?) would be 4.9/4 = 1.23 inches approx?????????

The dish being 'too small', having been designed for 10 gigahertz would have only a portion of the capture area . It would therefore exhibit a 'loss' or 'lower gain' at 2.4 gHz? Possibly expressed in decibels?

f w m.hertz centimetres 300 100 (One metre) 600 50

1200 25 2400 12.5 4800 6.25 9600 ` 3.125

Here in Canada we are becoming pretty well bilingual in regard to metric or non-metric. We measure building materials both ways. Gasoline in litres and distances in kilometres. Car engines in may countries have been measured in litres/ccs for years! Radio wavelength which is inversely related to frequency has been measured in metres almost from the word go. I've never heard of radio station frequency or wavelength measured in feet or miles?

Terry.

One quarter the size would reduce the gain by about 6db. Still substantial!

Can't spell it, but it MUST be the way to go? BTW, you buy 'petrol' in liters, distance is approximated in Kilometers, and all are convertible to usable numbers with care if the person doing it isn't too tired!

Seems pretty easy to tweak you guys. (:>) However 'metric meters' are a rather recent invention. Feet and inches were used since the invention of radio. Before that "Cubits" "fathoms" and 'leagues' were the standard!

No it isn't...12.5 cm is 4.9-whatever inches.

Tom

12.5 mm is 0.4921259 inches on this planet and has been since the French invented the metre.

But then the metre is an unknown standard in the USA isn't it?

--
John G

Wot's Your Real Problem?

Perhaps you mean 4.9212598?

Wrong again.

Whatever you think, 12.5 mm is really 0.4921259 inches.

Yes the wavelength at 2.4 gigahertz is 4.92 inches or 12.5 CENTIMETRES but I was replying to the conversion in the previous post which was MILLImetres to inches

--
John G

Wot's Your Real Problem?
.

message

can

out the

head...

I think you had better try again - practice makes perfect. 4.9 inches is right, but 12.5 mm is about a half inch. Try 12.5 CM.

the

French

No, it is not. Rulers and tape measures come with both scales. So the ultimate question is, "Wot's Your Real Problem?"

Well, the way I figured it is 3x10^8 / 2.45x10^9 = .12245 meters =

12.245 CM

..12245 * 39.37 = 4.82 inches.

Of course, that xdoesn't take into account that the speed of light is a bit less in the antenna, so it's maybe 5% too long.