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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
¡BAMLog! 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
>>
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