Electron wrote:
> At 00.33 2010.04.26, you wrote:
>   =

>> UK records
>> =95 1.3GHz 2617km
>> =95 2.3GHz 1083km
>> =95 3.4GHz 980km
>> =95 5.7GHz 1244km
>> =95 10GHz 1275km
>> =95 24GHz 391km
>> =95 47GHz 203km
>> =95 76GHz 79.6km
>> =95 134GHz 17.7km
>> =95 145GHz 1.29km
>>     =

>
> Looks like the higher the frequency, the lower the range.. why?
>
> Is it a limit of physics or just of technology?
>
>   =

Both. Nowadays, more Atmospheric issues. Look at dates.

Moisture and dust and even just oxygen, C02, Nitrogen all become more a =

problem at higher frequencies. Sunsets are Red and Sky is Blue.
Look at how often a hill only 15km distance is really clear and sharp.

At 10GHz you can use a regular silicon transistor colpits oscillator, =

even hand made on stripboard / vero board using a 6GHz FT transistor =

that runs at 3.3GHz. It's about 1.5cm x 1.5cm and built on trackside =

with track as inductor tuned by a varicap. Copper foil and lots of earth =

links on "top" side of board. A special mixer diode triples to 10GHz.

LNBs (sat receivers) use a DRO (Probabily a YIG puck) in a cavity at =

12GHz or so. You can actually sand or file the puck to change the =

frequency. If it comes loose, (LNB or other DRO based osc "dropped") =

sticking it back on PCB with a dot of "super glue" amazingly works. I've =

changed frequency of "printed" stripline filters at 10 .. 12GHz by =

silver pen and craft knife.

There is a lot you can do if you have an old HP 141T 18GHz spectrum =

analyser (a 48GHz or so adaptor is available, but I've never used it) to =

look and see what is happening. Cheap surface mount components really =

can be soldered on track side of vero/stripboard with a piece of coax =

copper foil as as "ground plane". Knowledge of microwave layout and =

gazillions of earth links (every unused hole practically). Loads of free =

stripline CAD/CAE tools .

Above 24GHz it's harder to get stability, and power. Receivers are =

poorer too.

Even if 47GHz gear was cheap, in Atmosphere it's going to be always =

short range.



-- =

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