AO 6-13-00

Alan Parrish

120 Pulpit Hill Rd

Amherst, MA 01002

Phone: 413-549-1807

Dear Al,

I left a message on your answering machine asking if you can tell me the maximum clock rate of the "birdcage" correlator you and Vern Pankonin used back around 1971. The editor of the AO Newsletter wants a couple of paragraphs about AO correlators down through the ages.

I remember that it had 100 lags and I suspect it could clock up to 10 MHz. Vern didn't include that scrap of info in his thesis, nor did you and he in an Ap J. paper. Vern does show some spectra 1 MHz, so he thinks the max. clock rate was 2 MHz. Weinreb's original correlator could clock only up to 300 kHz, but his thesis includes schematics of a 10 MHz correlator under construction at the same company that was contracted to build the 300 kHz original (21 lags, $18,000 in 1961). I suppose that 10 MHz one might have been the birdcage, maybe used at Haystack for 6 or 7 years before it was sent down to AO. I can't remember what became of it. Did AO send it back or scrap it?

Freddie and I are flying up to Boston on Monday, June 26. We'll be at John and Carmen's for about a week. It's partly work; Signatron in Concord will be ready for acceptance tests of a Mark 4 VLBI/VLBA terminal they've been building for AO. Our son, Ron, has a summer job in Bedford and is staying with the Comellas. Then we'll drive over to Ithaca for about 3 days and then to NYC to see Lorna, our now married daughter, before we return to PR.

Hope you're enjoying a good summer up there.

Sincerely, Jon