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#1
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90 degree phase shifter
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 |
#2
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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 |
#3
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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 |
#4
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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 |
#5
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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 |
#6
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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 |
#7
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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 |
#8
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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 |
#9
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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 |
#10
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"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 |
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