alan,

the polyphase network used by hans
(http://www.hanssummers.com/radio/polyphase/index.htm) is a very good
idea if you _have_ to use passive components. although hans has used
1% tolerance components, you can get away with even lesser tolerence
and use ordinary capacitors with 1% resistors.

alternatively, you can try using the approach of rick campbell in
using op-amp based all-pass network. these require fewer components
and only 0.01uf capacitors. the resistors can be easily measured on a
digital VOM for precise value and soldered into the circuit. search
the net for R2 direct conversion receiver.

unless you are planning some portable work, an exciting way to do this
is to make your computer do the audio processing work. If you feed the
left and right channels with I and Q, the rest of the receiver can be
implemented in software.

this kind of a receiver can be really simple. an rf amplifier followed
by two singly balanced diode mixers, each followed by a single stage
audio amplifier that will directly feed left and right channels of the
sound card. the rest is software. if you find dsp software to be
messy, you can probably download the freely available software from
www.flex-radio.com and use the ssb modules.

- farhan

Alan Peake wrote in message . ..
Hi all,
I'm looking for the element values of the 2Q4 phase shifter as
described in the 1992 ARRL Handbook.
Alternatively, can anyone recommend an active (analog) all-pass that
would give the same or better results. I have some precision capacitors
so that's no problem.
Thanks,
Alan
VK2TWB