Hmmmm, couldn't find online info for ya, but a bunch of good bibliography
on the subject :-)

http://www.home.earthlink.net/~christrask/pshift.html

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

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

Hi,

I'm looking for the element values of the 2Q4 phase shifter as
described in the 1992 ARRL Handbook.

The 2Q4 was an 8-pin plug-in (octal?) and this is how it is shown in
the 51SB-B sideband generator schematic.

Pin 1 - 680pF - 487k - Pin 2 - 770k||430pF - Pin 3

Pin 5 - 680pF - 125k - Pin 6 - 198k||430pF - Pin 7

Pins 1 & 5 were strapped and fed with one side of a balanced, band-
limited audio input and 3 & 7 (also strapped) with the other. Phase-
shifted outputs were then taken from 2 & 6. I guess that 4 or 8 could have
been a grounded shell.

I haven't worked it out but wouldn't be surprised if these are not just
Wein Bridge values for a certain frequency.


Cheers - Joe

Pin 1 - 2 : 680pF in series with 487k

Pin 2 - 3 : 430pF in parallel with 770k

Pin 5 - 6 : 680pF in series with 125k

Pin 6 - 7 : 430pF in parallel with 198k

Inputs across 1/5 and 3/7 with the quadrature outputs from 2
and 6.

Bama website has the schematic of the B&W transmitter


73 Gary N4AST

Alan Peake wrote:
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

These days the way to do it would be to use a DSP. If this is for
a receiver the DSP would have two A/D converters and a single D/A
unit. The DSP would combine the two quadature signals and apply
bandwidth filtering. The quadature RF drive to the mixer would
come from a DDS circuit with both sine and cosine waveform
outputs (AD9853/54).

For a transmitter the DSP would have a single A/D and two D/A
stages, and would split the audio into two quadature signals
after applying bandwidth limiting and compression filtering.

Having said this, I wish I knew how to write the required DSP
software! However I'm sure there are some reading this list
with the required skill (talent?). (My software experience
lies in other areas, such as embedded controllers, NOT
math with imaginary numbers!).