Maker Pro
Maker Pro

Harmonic Notch filter


Martin Brown

Jan 1, 1970
Don't bet on it, since I built the reievers used for radio

For which observatory and wavelengths? Front end or IF stage?

Most of them have in significant house capability for design of the main
amplifier and correlator electronics. They tend to use mass produced
dishes and then add custom interchangeable front ends.

We did aperture synthesis in permitted bands from 151MHz up to 31GHz.
There were tube based power oscilators in the '40s that would drive a
syncronous motor, and could be crystal controlled, so it's taken you 70
years to get it right?

I already told you synchronous motors got phased out around the 60's and
70's in favour of steppers. But computer controlled servos and before
that in some sites paper tape controlled tracking was used.

Martin Brown

Martin Brown

Jan 1, 1970
We built complete, custom microwave receivers for several, but they
didn't tell us the customer's names. They used a LNA at the feedhorn
and fed the output to our equipment. We were rarely told who the
customer was, unless it was a turnkey package or a rush order when they
would tag something to give it the highest priority.

So the first IF gain stage receiver at the dish after the cryogenic LNA?

What a strange place you worked.

The only production slots in our factory that did not have a customer
name on them were the ones being built on spec to avoid line stalls.

I can't see NRAO subcontracting out microwave receivers without going to
the suppliers to acceptance test them (and I certainly can't imagine
them paying extra for quick delivery - less for slow delivery maybe).
The VLA would want sets of 30 which would be a bit of a give-away.
What I described was for those motors, before a computer was

For a price that was nothing like justifiable for the task. The old
synchronous clock motors were good enough. The mechanical gears caused
periodic errors that were way bigger than systematic mains drift.

But the fact remains mains drift was noticeable on a cold winters night.

Martin Brown