[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [IRCA] dual receiver SDRs for diversity reception / phasing

I haven't seen an answer so I will jump in.

Digital phasing has the advantage that the phase shift is independent  of hardware and perfectly linear across the MW band, Slight changes to ferrite permeability are not a problem when you do the phase shift with a simple transform.

Recording 2 channels and phasing them post facto really doesn't require a different wav file for each channel. It does require that the PC software be able to locate the samples in each file that were sampled at the same time..

As far as your problems with finding time to play back files, I'll pass on that and view it as a generic problem that is not caused by phasing.

Chuck

________________________________
From: IRCA <irca-bounces@xxxxxxxxxxxxxxxx> on behalf of Nick Hall-Patch <nhp@xxxxxxxx>
Sent: Tuesday, January 15, 2019 8:33 PM
To: Mailing list for the International Radio Club of America; CapeDX@xxxxxxxxxxxxxxx
Cc: Mark Connelly
Subject: Re: [IRCA] dual receiver SDRs for diversity reception / phasing

Thanks for addressing this Mark, and saving me
fine tuning my own comments, which were essentially:

Is SDR phasing live any better than hardware
phasing?  If it's not, then all you're doing is
replacing a piece of hardware with perhaps a
heavier duty computer, are you not?

Phasing files as they are played back would be
the technological game changer.   I suspect that
doing that means recording a different kind of
.wav file that includes a counter in its header,
so that samples recorded from one locked receiver
can be matched up with samples from the other
during playback.   More informed folks than I
could comment on the feasibility of that, or whether it exists already.

Would it make any difference to the average
DXer?   I don't seem to have time to play back
some of the files from my good openings at home,
let alone from DXpeditions.  The
enhanced  ability to winkle out more DX from
files that I'm not listening to anyway may not be
all that helpful, hi.  (of course, if I stopped
bloviating, there might be more time...)

I seem to recall one SDR manufacturer a few years
ago thinking that there would be little market
for such a device, even if you provided all
manner of hand-holding software, which is the
quite expensive to produce, especially if you want it to function well.

best wishes,

Nick






At 04:06 2019-01-16, Mark Connelly via IRCA wrote:


>I would be willing to have a receiver that just
>saved half the MW bandwidth, e.g. 700 kHz, in
>capture files if it had the I/Q streams from the
>two receivers.  But with receivers doing 3, 6,
>and more MHz of capture these days, why can't we
>get the whole 510-1710 stretch?
>
>Basic requirements:
>
>*** Phasing can be done after the fact on
>capture files both manually and, when channels
>are reasonably similar, automatically.
>
>*** The two receivers can be slaved to each
>other for diversity and phasing applications or tuned independently.
>
>*** There must be the provision for separate antenna inputs.
>
>*** User can save null solution data to an INI
>file that can be recalled later.  This file
>should be plain text suitable for importation
>into antenna-testing technical articles, DXpedition reports, etc.
>
>You need to be able to adjust both gain of each
>channel and the delta-phase / delta-time between
>them.  You are not always using identical gain
>and pattern antennas. In fact you could be using
>two opposite ends of the same SuperLoop or
>DKAZ.  East end could have 880 WCBS at S-9 and
>882 UK at S-8; west end might have WCBS S9+20
>and UK S-5.  So why should you not be able to
>put 20 dB attenuation on the west end to make
>WCBS S-9 and then phase it against the east end
>to provide vastly cleaner pick-up of 882 UK?  I
>can certainly do that with the Quantum Phaser and several homebrew models.
>
>If you can adjust after the fact on capture
>files you can run several different gain / phase
>scenarios on, let's say, a graveyard
>channel.  By moving the null around the
>compass, as with a conventional rotatable loop,
>you could pull as many as 6 to 8 different ID's
>out of a single channel at a particular time.
>
>You could also think about applying a gain /
>phase curve.  Let's say you used an (A vs. B) 8
>dB delta gain / 100 ns delta time solution to
>take down 770 WABC and 6 dB / 90 ns to take out
>880 WCBS.  In-between frequencies could be
>adjusted "on the curve".  820 WNYC, in a
>similar direction as 770 and 880, could be
>expected to null at something like 7 dB delta
>gain / 95 ns delta time.  This sort of
>mathematical manipulation of the data streams
>could help to broadband the nulling pattern when
>using two antennas that don't quite fit the
>textbook scheme of spatially-separated elements
>of identical gain and pick-up pattern.
>
>Phasing only during live DX is not the game
>changer or killer app here.  It's nice maybe to
>eliminate one box on the table but what we
>really want is post facto phasing as well as live DX use.
>
>The baby steps are being taken but
>ready-for-prime-time software and hardware
>hasn't arrived yet as far as I can tell.  Ham
>DXpeditions / contest stations, MW guys in
>Finland etc. would be all over it if it had.
>
>Mark Connelly, WA1ION
>South Yarmouth, MA
>
><<
>A couple of drawbacks for the Afedri:
>
>(1) As of a year ago (I have not checked since),
>the phasing only worked on the live signals. No
>phasing was possible on a recorded file.
>
>(2) It has only a 12 bit converter so is not top of the line.
>
>And something that needs verification: the
>Afedri was only spec'ed to record 900 kHz of
>bandwidth. I see it has recently been changed to
>1100 kHz. That's enough for me if it performs as advertised.
>
>Chuck
> >>
>
><<
>Did I miss something?  As far as I can tell,
>nothing discussed here comes close to what we
>need - the ability to phase null synchronized RF
>spectrum captures.  Everything described here
>is no different than using two receivers (SDR or
>analog) on different antennas, or
>phasing/combining two antennas into one
>receiver, for the purposes of live monitoring
>and making single RF spectrum captures.  While
>it is possible to make two RF spectrum captures
>using two SDR receivers simultaneously, then
>perfectly synchronizing playback of the two RF
>spectrum captures for diversity reception (i.e.
>audio from one RF spectrum capture in the left,
>the other in the right), it's difficult to get
>the audio from each spectrum capture in sync and
>the results usually not worth the effort.  The
>WiNRADiO Excalibur has three receivers in one,
>but they all operate off the same antenna.  So
>the Excalibur can be used for 'diversity
>reception' of parallel frequencies by tuning Rx1
>to 1053 TalkSport and Rx2 to 1089 TalkSport,
>then combining the audio using the Mix functions
>of the Excalibur for example, but it's not
>really diversity reception by definition which
>would have two SDR receivers each with their own
>antenna.  I see nothing groundbreaking here.
>
>--
>Bruce Conti
>B.A.Conti Photography www.baconti.com<http://www.baconti.com>
>¡BAMLog! www.bamlog.com<http://www.bamlog.com>
> >>
>
><<
>Hi Mark, I have one of the newer Afedri V3.0
>dual input radios here. I bought it out of
>curiosity and am pleased with how well it
>phases. It only has a 1.2Mhz span width in dual
>channel mode, but that gets most of MW. It works
>as well as phased loops/flags but without as
>much loss. I use it with HDSDR after setup with
>the connection tool provided with the Afedri
>radio. SDR# is another software that works, but
>I haven't figured out how to get more than a 192K span from it.
>
>In the Afedri, the 2 ports can be combined, with
>the ability to change the phase but not the
>signal levels. So, your antennas need to be the
>same and cable lengths need to be equal also (or
>length adjusted to prebalance the phase).
>
>Dave Aichelman     N7NZH     Grants Pass, Oregon
>__._,_.___
> >>
>
>The subject of SDRs containing two phase-locked
>receivers came up recently on the Topband (160m
>ham) list (
>http://lists.contesting.com/archives//html/topband/2019-01/threads.html ).
>
>The discussion dealt primarily with diversity
>reception: audio from antenna A's RF goes to
>your left headphone, antenna B to the right.? In
>some cases a weak or interfered-with signal that
>isn't quite readable on either channel
>independently can "pop out of the mud" when both
>channels are presented, one to the left and one
>to the right as mentioned. Typically you're on
>the same frequency, mode, bandwidth, and AGC for
>this.? Maybe you use USB one channel and LSB the
>other if the interference is different owing to
>antenna pick-up patterns.? For MW DX, sometimes
>two different frequencies would be fed to the
>headphones for quick comparison of parallel
>audio content (e.g. Spain 684 & 855, Cuba 670 & 710, Japan 747 & 774).
>
>More of interest to me is phasing based in the
>receiver.? This should be available under
>complete (manual) operator control of each
>channel's gain and phase / time delay.? There
>should be a way to save successful null or peak
>set-ups to a look-up table text file that can be
>invoked later to speed up DXing.? The file
>should also be importable into Excel / Word /
>Access / PowerPoint for producing technical
>articles.? Additionally the receiver should
>provide a degree of auto-nulling, at least when
>the two synchronized receivers are getting the
>same dominant "pest" signal (or noise) a
>reasonable amount above co-channel and adjacent interference.
>
>The subject has been chatted up here before and
>I think that one or more receivers
>hardware-capable of this were out there but
>there was no clear software solution, at least
>anything that has been adequately "road tested"
>by cutting edge contester hams and the top MW
>talent in Scandinavia, North America, and east Asia.
>
>If there is new information on this topic, feel free to comment.
>
>Mark Connelly, WA1ION
>South Yarmouth, MA
>
>These are some posts recently appearing on the
>Topband list under the "Re: Topband: Dual RX SDR
>receivers (diversity capable)" header.
>
><<
>Have you looked at
>http://www.afedri-sdr.com/index.php/new-afe822x-sdr-net-dual-channel ?
>
>73
>Nick
>VE7DXR
> >>
>
><<
>Cross Country Wireless SDR-4++ dual diversity SDR general coverage receiver
>
>Digitally signed mail - John? M0ELS
> >>
>
><<
>Hi Bjorn
>
>If you are interested, I have a dual Softrock
>160m SDR receiver (two receivers in one diecast
>box) that was built up about ten years ago or so
>for diversity reception, using Alex VE3NEA?s
>Rock 2.0 diversity version ? see http://www.dxatlas.com/Download.asp.
>
>Owing to family/business pressures I never got
>around to using it. My recollection is JC N4IS
>may have built up something similar?
>
>The receiver is just sitting on a shelf here and
>I am happy to part with it. Also have a M-Audio
>D44 professional soundcard that was going to used with it.
>
>Vy 73
>
>Steve, VK6VZ
> >>
>
>_______________________________________________
>IRCA mailing list
>IRCA@xxxxxxxxxxxxxxxx
>http://montreal.kotalampi.com/mailman/listinfo/irca
>
>Opinions expressed in messages on this mailing
>list are those of the original contributors and
>do not necessarily reflect the opinion of the
>IRCA, its editors, publishing staff, or officers
>
>For more information: http://www.ircaonline.org
>
>To Post a message: irca@xxxxxxxxxxxxxxxx

Nick Hall-Patch
Victoria, BC
Canada

_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx

_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx