Diversity Receive as Noise Canceling?
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Diversity Receive as Noise Canceling?
 
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OK, I realize the Timewave and MFJ noise cancellers operate at RF and
not AF...But I was thinking of the amazing noise reduction that SDR's accomplish in the digital relm. I understand it may not be that simple. But sometimes asking the question gets new thinking going. For example the second IF of 15-KHz is digitized and run thru FIR filters; could two separate digitized data streams from the two receivers be added out of phase digitally? 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [hidden email] ====================================== *temp not in service ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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There is also the issue that the various AGC's may be varying the amplitude,
so the process would have to address both instant amplitude and phase to affect cancellation. Should be able to program that, though. How hard to code, who knows??? 73, Guy. On Sun, Nov 28, 2010 at 1:15 PM, Edward R. Cole <[hidden email]> wrote: > OK, I realize the Timewave and MFJ noise cancellers operate at RF and > not AF...But I was thinking of the amazing noise reduction that SDR's > accomplish in the digital relm. I understand it may not be that > simple. But sometimes asking the question gets new thinking going. > > For example the second IF of 15-KHz is digitized and run thru FIR > filters; could two separate digitized data streams from the two > receivers be added out of phase digitally? > > > 73, Ed - KL7UW, WD2XSH/45 > ====================================== > BP40IQ 500 KHz - 10-GHz www.kl7uw.com > EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? > DUBUS Magazine USA Rep [hidden email] > ====================================== > *temp not in service > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Diversity Receive as Noise Canceling?
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As I understand the operation of the phasing noise cancellation
units, they have both phase and amplitude adjustments. I'm sure that can be done digitally. How difficult, what issues? Have to leave that to the SDR experts. If not feasible, no harm in asking. ******* BTW I home-built a 144-MHz adjustable polarity control using a variable phase and amplitude control. This is now done in sw by Linrad with two receivers looking at Horz and Vert polarity signals. It is essentially a dual-channel SDR with orthogonal RF inputs. I will be implementing this with a new 144-MHz dual-channel receiving transverter feeding my dual-Rx K3. The dual audio streams will feed a soundcard for the A/D conversion input to Linrad. Linrad has the ability to extract the phase information to display the angle of polarization. 73, Ed At 12:10 PM 11/28/2010, Guy Olinger K2AV wrote: >There is also the issue that the various AGC's may be varying the >amplitude, so the process would have to address both instant >amplitude and phase to affect cancellation. Should be able to >program that, though. How hard to code, who knows??? > >73, Guy. > >On Sun, Nov 28, 2010 at 1:15 PM, Edward R. Cole ><<mailto:[hidden email]>[hidden email]> wrote: >OK, I realize the Timewave and MFJ noise cancellers operate at RF and >not AF...But I was thinking of the amazing noise reduction that SDR's >accomplish in the digital relm. I understand it may not be that >simple. But sometimes asking the question gets new thinking going. > >For example the second IF of 15-KHz is digitized and run thru FIR >filters; could two separate digitized data streams from the two >receivers be added out of phase digitally? > > >73, Ed - KL7UW, WD2XSH/45 >====================================== >BP40IQ 500 KHz - 10-GHz <http://www.kl7uw.com>www.kl7uw.com >EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? >DUBUS Magazine USA Rep <mailto:[hidden email]>[hidden email] >====================================== >*temp not in service >______________________________________________________________ >Elecraft mailing list >Home: ><http://mailman.qth.net/mailman/listinfo/elecraft>http://mailman.qth.net/mailman/listinfo/elecraft >Help: <http://mailman.qth.net/mmfaq.htm>http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >This list hosted by: <http://www.qsl.net>http://www.qsl.net >Please help support this email list: ><http://www.qsl.net/donate.html>http://www.qsl.net/donate.html > 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [hidden email] ====================================== *temp not in service ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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This post was updated on .
In reply to this post by Edward R Cole
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73 de LA3RK Olaf
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I believe the problem with attempting to do this internally in the K3 is that, while the VCOs are phase locked on a given frequency, the phase shift is not predictable if you touch the VFO. In other words, you could adjust phase cancellation on one frequency, but it would need to be readjusted every time you touched the VFO. I asked Lyle about this a few years ago and I recall that was what he said. 73, Bill |
Re: Diversity Receive as Noise Canceling?
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In reply to this post by Edward R Cole
At 10:06 PM 11/29/2010, you wrote:
>Noted your comment on noise reduction by phase nulling. Have you >looked on info on pages by pa0sim, see www.pa0sim.nl, he has done >more or less what I think you are considering. Ie connecting the >output from 2 phase locked receivers fed with separate antennas and >do the amplitude/phase nulling at AF level. > >Some of the sound samples on his website are impressive in terms of >noise reduction. > >I would love to see an application which could do this, would be >nice to check out if phase nulling works at a site before trying an >MFJ unit or similar. I really would like to see this done in the K3 >as all the hardware is there to do such phasenulling in software, >could eg use the VFO B knob for phase control and the volume knobs >for amplitude control. Only requirement is to feed the 2 RXs with >separate antennas, ie an alternative use of diversity capability. > >I was not able to respond on the reflector. Would be nice if you >could keep the group updated if you get more info on this. > >73 de Olaf LA3RK Olaf, Thanks for writing. I somehow lost your e-mail and wanted to look at the pa0sim webpage. I merely suggested the idea. I really have no prospect for doing this. I thought maybe Elecraft might be interested in the idea; provide firmware to do it. A modification on doing diversity reception was what I had in mind. Use a small "sniffer" antenna on the aux Rx input to sample noise and null it from the main receiver in sw. I think it would be easiest to accomplish in digital before conversion to audio. All the DSP routines are done there: NB, NR, AGC, APF, DSP bandwidth. Phase shift and amplitude adjustments would be possible in digital, so assigning VFO-B would be relatively simple for phase and use the sub-Rx volume for amplitude adjustment. I guess it's now up to Elecraft if they want to explore this. 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [hidden email] ====================================== *temp not in service ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re： Diversity Receive as Noise Canceling?
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Hello Edward,
This will depend on how much 'brain power' is left in the DSP. Apparently, currently, quite a work load of the DSP has been used to eliminate the internal birdies. Having said that, thanks for the modular design of K3, a 'heart-transplant' of exchanging the DSP board with more powerful version may be feasible. cheers, Johnny VR2XMC ----- 郵件原件 ---- 寄件人﹕ Edward R. Cole <[hidden email]> 收件人﹕ [hidden email] 副本(CC) [hidden email] 傳送日期﹕ 2010/11/30 (二) 3:44:10 PM 主題： Re: [Elecraft] Diversity Receive as Noise Canceling? At 10:06 PM 11/29/2010, you wrote: >Noted your comment on noise reduction by phase nulling. Have you >looked on info on pages by pa0sim, see www.pa0sim.nl, he has done >more or less what I think you are considering. Ie connecting the >output from 2 phase locked receivers fed with separate antennas and >do the amplitude/phase nulling at AF level. > >Some of the sound samples on his website are impressive in terms of >noise reduction. > >I would love to see an application which could do this, would be >nice to check out if phase nulling works at a site before trying an >MFJ unit or similar. I really would like to see this done in the K3 >as all the hardware is there to do such phasenulling in software, >could eg use the VFO B knob for phase control and the volume knobs >for amplitude control. Only requirement is to feed the 2 RXs with >separate antennas, ie an alternative use of diversity capability. > >I was not able to respond on the reflector. Would be nice if you >could keep the group updated if you get more info on this. > >73 de Olaf LA3RK Olaf, Thanks for writing. I somehow lost your e-mail and wanted to look at the pa0sim webpage. I merely suggested the idea. I really have no prospect for doing this. I thought maybe Elecraft might be interested in the idea; provide firmware to do it. A modification on doing diversity reception was what I had in mind. Use a small "sniffer" antenna on the aux Rx input to sample noise and null it from the main receiver in sw. I think it would be easiest to accomplish in digital before conversion to audio. All the DSP routines are done there: NB, NR, AGC, APF, DSP bandwidth. Phase shift and amplitude adjustments would be possible in digital, so assigning VFO-B would be relatively simple for phase and use the sub-Rx volume for amplitude adjustment. I guess it's now up to Elecraft if they want to explore this. 73, Ed - KL7UW, WD2XSH/45 ====================================== ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Diversity Receive as Noise Canceling?
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In reply to this post by Edward R Cole
I'm rather surprised that nobody has noticed the connection between this discussion and the one we had a few weeks ago about using the two phase-locked receivers in the K3 for directional nulling. It's really the same thing .... feed separate antennas into the two receivers while in diversity mode and process the audio to null whatever you want. It's all based upon the fact that the time differential between two RF signals is preserved when both are down converted to audio by phase locked local oscillators. And yes, assuming enough remaining processing power in the K3, the necessary time shifting and inversion to accomplish a suitable null could be done in the K3 (assuming a knob could be highjacked for the adjustment), but it doesn't need to be. It could more practically be done in the sound card of almost any computer, and with a lot more flexibility. It just requires two things: a. Elecraft to make the phase lock between the two receivers remain constant as the frequency is changed. Ideally the phase differential of the local oscillators would be zero ... either forced that way by the DSP or by using the same L.O. for both receivers. If that wasn't possible, it would still be usable if the differential were known or could be interrogated by a command. b. Someone to write a simple bit of software for the computer that took the sound card inputs, shifted and processed them, and then feed them back out through the sound card to headphones or speakers. There are several possible uses of such a capability: 1. Nulling directional noise, assuming two antennas separated horizontally. The software could even automatically search for the phase that gave the best reduction in noise. 2. Nulling an interfering station from one direction, assuming two antennas separated horizontally 3. Nulling an interfering station from a particular arrival angle, assuming two antennas separate vertically. Picture a stack of two horizontally polarized antennas (yagis or dipoles), with a loud stateside station covering up a weaker DX station. Presumably (but not always) the stateside station would be arriving at a higher arrival angle that might possibly be discriminated against by adjusting the phase of the two audio signals to put a notch on it, the same as if it were possible to continuously adjust the phase of the two antennas at RF. Granted, ground reflections limit the range of notch adjustment, but if the antennas were high enough the concept might be practical, although I haven't checked it with EZNEC to see what the limits might be. 4. Real time monitoring of the azimuth of an arriving signal for propagation studies (looking for skew paths, etc). Just continuously rotate the phase shift and look for nulls. 5. Real time monitoring of the elevation angle of an arriving signal (such as the full time beacons) for propagation studies. Just continuously rotate the phase shift and look for nulls. 6. Real time monitoring of elliptical polarization (both direction of the rotation and the relative magnitudes of the two components) ala the recent request from KL7AJ. There are probably others I haven't thought of. At the time of the prior message thread Elecraft indicated it might be possible for them to consider some modifications (either hardware or software) in the future that would predictably lock the two receivers, but I haven't heard anything more since then. It seems like too valuable a potential capability to just ignore, though. 73, Dave AB7E On 11/30/2010 12:44 AM, Edward R. Cole wrote: > At 10:06 PM 11/29/2010, you wrote: >> Noted your comment on noise reduction by phase nulling. Have you >> looked on info on pages by pa0sim, see www.pa0sim.nl, he has done >> more or less what I think you are considering. Ie connecting the >> output from 2 phase locked receivers fed with separate antennas and >> do the amplitude/phase nulling at AF level. >> >> Some of the sound samples on his website are impressive in terms of >> noise reduction. >> >> I would love to see an application which could do this, would be >> nice to check out if phase nulling works at a site before trying an >> MFJ unit or similar. I really would like to see this done in the K3 >> as all the hardware is there to do such phasenulling in software, >> could eg use the VFO B knob for phase control and the volume knobs >> for amplitude control. Only requirement is to feed the 2 RXs with >> separate antennas, ie an alternative use of diversity capability. >> >> I was not able to respond on the reflector. Would be nice if you >> could keep the group updated if you get more info on this. >> >> 73 de Olaf LA3RK > Olaf, > > Thanks for writing. I somehow lost your e-mail and wanted to look at > the pa0sim webpage. I merely suggested the idea. I really have no > prospect for doing this. I thought maybe Elecraft might be > interested in the idea; provide firmware to do it. > > A modification on doing diversity reception was what I had in > mind. Use a small "sniffer" antenna on the aux Rx input to sample > noise and null it from the main receiver in sw. I think it would be > easiest to accomplish in digital before conversion to audio. All the > DSP routines are done there: NB, NR, AGC, APF, DSP bandwidth. Phase > shift and amplitude adjustments would be possible in digital, so > assigning VFO-B would be relatively simple for phase and use the > sub-Rx volume for amplitude adjustment. > > I guess it's now up to Elecraft if they want to explore this. > > > > 73, Ed - KL7UW, WD2XSH/45 Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Reï¼ Diversity Receive as Noise C anceling?
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In reply to this post by Johnny Siu
I'm not sure that adapting the sw for noise
cancellation will take that much extra processing. Reversing phase is a simple digital inversion. Adjusting amplitude is already done on both receivers. Continuous phase shifting for the sub-Rx might take some processing, but probably not as much as you guess. But the K3 will likely get an upgraded cpu chip someday, due to continuous improvements in firmware. Would that be a DSP board? Elecraft seems to have their radios configured for continual upgrading. (nice!). 73, Ed - KL7UW At 10:52 PM 11/29/2010, Johnny Siu wrote: >Hello Edward, This will depend on how much >'brain power' is left in the DSP. > Apparently, currently, quite a work load of >the DSP has been used to eliminate the internal >birdies. Having said that, thanks for the >modular design of K3, a 'heart-transplant' of >exchanging the DSP board with more powerful >version may be feasible.  cheers, Johnny VR2XMC >----- éµä»¶å件 ---- å¯ä»¶äººï¹ Edward R. >Cole <[hidden email]> æ¶ä»¶äººï¹ >[hidden email] å¯æ¬(CC) >[hidden email] å³éæ¥æï¹ >2010/11/30 (äº) 3:44:10 PM 主é¡ï¼ Re: >[Elecraft] Diversity Receive as Noise Canceling? >At 10:06 PM 11/29/2010, you wrote: >Noted your >comment on noise reduction by phase nulling. >Have you >looked on info on pages by pa0sim, see >www.pa0sim.nl, he has done >more or less what I >think you are considering. Ie connecting >the >output from 2 phase locked receivers fed >with separate antennas and >do the >amplitude/phase nulling at AF level. > >Some of >the sound samples on his website are impressive >in terms of >noise reduction. > >I would love to >see an application which could do this, would >be >nice to check out if phase nulling works at >a site before trying an >MFJ unit or similar. I >really would like to see this done in the K3 >as >all the hardware is there to do such >phasenulling in software, >could eg use the VFO >B knob for phase control and the volume >knobs >for amplitude control. Only requirement >is to feed the 2 RXs with >separate antennas, ie >an alternative use of diversity capability. > >I >was not able to respond on the reflector. Would >be nice if you >could keep the group updated if >you get more info on this. > >73 de Olaf LA3RK >Olaf, Thanks for writing. I somehow lost your >e-mail and wanted to look at the pa0sim >webpage. I merely suggested the idea. I >really have no prospect for doing this. I >thought maybe Elecraft might be interested in >the idea; provide firmware to do it. A >modification on doing diversity reception was >what I had in mind. Use a small "sniffer" >antenna on the aux Rx input to sample noise and >null it from the main receiver in sw. I think >it would be easiest to accomplish in digital >before conversion to audio. All the DSP >routines are done there: NB, NR, AGC, APF, DSP >bandwidth. Phase shift and amplitude >adjustments would be possible in digital, so >assigning VFO-B would be relatively simple for >phase and use the sub-Rx volume for amplitude >adjustment. I guess it's now up to Elecraft if >they want to explore this. 73, Ed - KL7UW, >WD2XSH/45 ====================================== 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [hidden email] ====================================== *temp not in service ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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It's also very simple to do at RF with one of the external phase boxes. I've used all 3 of these and rate them in the following order: 1. DXE NCC-1 (the best but expensive) 2. MFJ-1025 (very good with W8JI's mods below) 3. Timewave ANC-4 References: http://www.dxengineering.com/Parts.asp?ID=1227&PLID=215&SecID=114&DeptID=12&PartNo=DXE-NCC-1 http://www.mfjenterprises.com/Product.php?productid=MFJ-1025 http://www.w8ji.com/mfj-1025_1026.htm http://www.timewave.com/support/ANC-4/anc4.html I personally wouldn't give up diversity for noise canceling, but I don't live on a city lot. I'd use an external phase box with noise sense antenna aimed at the noise source combined with an RX antenna via a phasing box into RX ANT and a second RX antenna into AUX RF for diversity. Using DSP to do what a $180 box does reasonably well seems like overkill. This reminds me of the Flex Radio guru who proposed a 4 RX/TX solution to what an external 4SQ phase box does for $350...plus you need only one feedline to the controller instead of 4 to the shack, one 1.5 kW amp instead of 4 each $375 amps, and much less complexity. "A technical solution looking for an application" comes to mind. 73, Bill |
Re: Reï¼? Diversity Receive as Noise C anceling?
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Granted this thread is moribund at this point, but... With Bill's nice
summary of existing products, it got me to thinking about this again after comparing the MFJ and Timewave products a few years back. I believe the DXE product is new since my last survey of the field. I'm primarily a 6-meter weak-signal operator, and neither the DXE not the MFJ product is characterized for operation above 30 MHz. The ANC is, last time I checked. (Their website is down right now so can't re-check.) I've studied enough about the designs of the MFJ and ANC to understand why the ANC is at the bottom of Bill's list. I think. It has to do with phasing range, mostly, in which both the MFJ and ANC products are deficient, but the ANC more so. There may be other faults in the ANC design as well; I believe the MFJ's ability, not present in the ANC, to phase to an "add" (0 degrees) condition and then invert has been mentioned. If the phasing need in your particular situation happens to be within the range that the ANC can match, you're probably going to think it's great. But that's a crap-shoot. My question from several years ago is still the same now, with the addition of the DXE product to the mix: Why are the MFJ (and now DXE) products characterized only through 30 MHz? Would they really not work acceptably at 50 MHz, or are we talking about a small amount of degradation in performance that might be seen as an acceptable trade-off? Or do they just flat-out not work on 6 meters? What would be necessary in the way of design mods to get the DXE product, for example, to perform at 50 MHz? Has anybody ever looked into this? Bill W5WVO -----Original Message----- From: Bill W4ZV Sent: Tuesday, November 30, 2010 15:08 To: [hidden email] Subject: Re: [Elecraft] Reï¼ Diversity Receive as Noise C anceling? Edward R. Cole wrote: > > I'm not sure that adapting the sw for noise > cancellation will take that much extra > processing. Reversing phase is a simple digital > inversion. > It's also very simple to do at RF with one of the external phase boxes. I've used all 3 of these and rate them in the following order: 1. DXE NCC-1 (the best but expensive) 2. MFJ-1025 (very good with W8JI's mods below) 3. Timewave ANC-4 References: http://www.dxengineering.com/Parts.asp?ID=1227&PLID=215&SecID=114&DeptID=12&PartNo=DXE-NCC-1 http://www.mfjenterprises.com/Product.php?productid=MFJ-1025 http://www.w8ji.com/mfj-1025_1026.htm http://www.timewave.com/support/ANC-4/anc4.html I personally wouldn't give up diversity for noise canceling, but I don't live on a city lot. I'd use an external phase box with noise sense antenna aimed at the noise source combined with an RX antenna via a phasing box into RX ANT and a second RX antenna into AUX RF for diversity. Using DSP to do what a $180 box does reasonably well seems like overkill. This reminds me of the Flex Radio guru who proposed a 4 RX/TX solution to what an external 4SQ phase box does for $350...plus you need only one feedline to the controller instead of 4 to the shack, one 1.5 kW amp instead of 4 each $375 amps, and much less complexity. "A technical solution looking for an application" comes to mind. 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/Diversity-Receive-as-Noise-Canceling-tp5782138p5788410.html Sent from the [K3] mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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