At 04:35 PM 6/5/2007, Mark Beckwith wrote:
>We measured what was coming down the feedline and using the receiver specs,
>calculated how much attenuation would be needed on each band to keep the
>level acceptable to the radio - I recall the numbers were between 45 and mid
>70s in db depending on the TX/RX combination being calculated.
>
>Then we worked out combinations of bandpass filters and stubs until we got
>maybe 10 db more than was needed in some cases. Don't ask me how we did
>this, I am an appliance operator who picks my operating buddies wisely :) I
>was responsible for working 200 guys an hour.
We do exactly the same thing at work (JPL) for spacecraft trading off
the filter losses and stopband attenuation so that the X-band
transmitter at 8450 MHz doesn't interfere with the X-band receiver at
7150, and that harmonics of the transmitter don't interfere with
science instruments or other comm devices. ALl this while not
attenuating the uplink signal too much nor losing power in the
downlink. There's a lot of interesting problems, for instance,
there's a Ka-band receive frequency around 34GHz, and the high power
amplifier at X band might have enough broadband noise power up at 34
GHz to cause a problem with weak signal reception.
Jim,W6RMK
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