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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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