Don Pearce wrote:

On Mon, 01 May 2006 17:24:30 GMT, "Michael A. Terrell"
wrote:

My point about microwave is that without filtering you have aditional
noise to deal with in the system. We offered IF bandwidths from 10 KHz
to 20 MHz, and video amps with matching bandwidths to keep as much noise
out of the received signal as possible.


The same receivers are used by NOAA for their weather sat downlinks.
With the improved doppler compensation they are able to lock onto the
sat before it comes over the hrizon five minutes faster than the old
Harris equipment it replaced.

Ah! I see what you mean. Of course matching a receive filter to the
necessary bandwidth means that you neither lose much-needed signal,
nor let in unwanted noise. That goes for IF and baseband. As for RF,
presumably you have a range of input frequencies to deal with, so you
can't implement a channel-width filter there. But what you can do is a
roofing filter and image filters.

I presume your Doppler compensation was predictive, offsetting the
receiver by 17000MPH worth of frequency in anticipation of
acquisition.


A lot is still covered under several NDAs I had to sign, but the rest
of it was making the system as phase clean as frequency stable as
possible. Without that, the additional circuitry didn't stand a chance.
There are only a few things you can do to compensate for the doppler
effect, but that added to careful design and implementation works
wonders. I also worked on the both the fixed and mobile earth station
for Italy's space efforts. My title was production and engineering test
tech, but a lot of the engineers ask why I didn't have a degree due to
the way I not only found problems, but how to correct them. I got
bounced all over the Ocala facility, where ever the current hot spots
were. My boss told me that I wouldn't take "NO" for an answer. I
smiled and told him, "I don't take YES if I don't believe them. ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida