[pups] PDP-11 / vacuum tube interface

Ian King IanK at vulcan.com
Wed Dec 10 13:33:50 AEST 2008

In addition to the DECtalk standalone device, there was a Qbus module called DECVoice (DTC04) that was intended for telephone systems (voice response systems).  I have the module in my personal collection; unfortunately, what I've been told is that there's a lot of others' intellectual property in the software (it's a microcoded device) so it would be a serious challenge to get the code to run it - too bad.  -- Ian
From: pups-bounces at minnie.tuhs.org [pups-bounces at minnie.tuhs.org] On Behalf Of Ross Tucker [rjtucke at gmail.com]
Sent: Tuesday, December 09, 2008 6:49 PM
To: pups at minnie.tuhs.org
Subject: [pups] PDP-11 / vacuum tube interface

Dear all,
(This has got to be the strangest cross-post I've ever done.)

I have just taken a bet from a friend to challenge my geekiness. I was
telling him about my love of Vintage Technology and he proposed that I
combine two hitherto separate hobbies and see what happens. The
topics: the DEC PDP-11 minicomputer (vintage: 1970s) and vacuum-tube
ham radios (vintage: 1960s). I do sincerely apologize for
cross-posting, but I am rather younger than either of these
technologies (vintage: 1984) and this seems like a monumental

My question for y'all: how could I possibly design+build a project
that uses both of these technologies? My thought is to port some radio
receiver Digital Signal Processing (DSP) application into PDP-11
assembler, compile and run it via emulator on my PC, then use it with
the vacuum-tube regenerative receiver that I built a few years ago...
Does anybody know if PDP-11 UNIXes even had the capability for a
"sound card"? Or, to get ambitious, I would LOVE to design some
interface circuitry between PDP-11 digital circuitry and vacuum-tube
electronics... The challenges are legion: the tube side of the circuit
operates around 350V DC levels with radio-frequency (RF) signals at 7
MHz (almost the clock rate of some PDP-11s!) and I don't have the DEC
Handbooks, but I'm pretty sure that even those ancient pre-TTL
circuits operate below 350V!

So... any, er, "ideas"?

Best regards,
Ross Tucker

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