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

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

"Ashhar Farhan" wrote in message
om...
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.

Thanks Farhan. I actually used 0.1% resistors, and matched the capacitors
also to 0.1% by adding parallel capacitance. Of course, all that could
change with temperature due to the different parallel capacitances drifting
different amounts.

I believe the passive polyphase network to be superior to the active phase
shifting networks which use op-amps. For any given level of component
tolerance, a passive network will give much better opposite sideband
suppression (I recall seeing 10-20dB reported somewhere but can't provide
references). Provided attention is paid to the values used, the network can
be made lossless which overcomes any concerns about gain distribution and
harming the overall receiver dynamic range.

So the way I tend to put it, is if you _have_ to use active components ...

73 de Hans G0UPL
http://www.HansSummers.com

Thanks Farhan. I actually used 0.1% resistors, and matched the capacitors
also to 0.1% by adding parallel capacitance. Of course, all that could
change with temperature due to the different parallel capacitances drifting
different amounts.

This may be why the 2Q4 network is enclosed in a can. The can may also
be filled with something like thermal grease to keep all the components
at the same temperature.
Alan

Thanks Farhan. I actually used 0.1% resistors, and matched the capacitors
also to 0.1% by adding parallel capacitance. Of course, all that could
change with temperature due to the different parallel capacitances drifting
different amounts.

This may be why the 2Q4 network is enclosed in a can. The can may also
be filled with something like thermal grease to keep all the components
at the same temperature.
Alan

Thanks for the suggestions. I'm reluctant to use the computer as I'm on
solar power and can't use the machine for too long, particularly on
cloudy days in winter - such as today.
I do have some DSP stuff though - ADSP2100- but as it's fixed point, I'm
not sure if it has the precision needed.
I really want to use this an exciter and while filters are probably
easier, the phasing method always struck me as more "elegant".
73s
Alan

"Ashhar Farhan" wrote in message
om...
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.

Thanks Farhan. I actually used 0.1% resistors, and matched the capacitors
also to 0.1% by adding parallel capacitance. Of course, all that could
change with temperature due to the different parallel capacitances drifting
different amounts.

I believe the passive polyphase network to be superior to the active phase
shifting networks which use op-amps. For any given level of component
tolerance, a passive network will give much better opposite sideband
suppression (I recall seeing 10-20dB reported somewhere but can't provide
references). Provided attention is paid to the values used, the network can
be made lossless which overcomes any concerns about gain distribution and
harming the overall receiver dynamic range.

So the way I tend to put it, is if you _have_ to use active components ...

73 de Hans G0UPL
http://www.HansSummers.com

Thanks for the suggestions. I'm reluctant to use the computer as I'm on
solar power and can't use the machine for too long, particularly on
cloudy days in winter - such as today.
I do have some DSP stuff though - ADSP2100- but as it's fixed point, I'm
not sure if it has the precision needed.
I really want to use this an exciter and while filters are probably
easier, the phasing method always struck me as more "elegant".
73s
Alan

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