RSPDuo dual tuner mode

[Eric Allan]

Hi everyone,

I stumbled across linrad while trying to find a better option than SDRUno for my needs. I was hoping to do stereo diversity with the RSPDuo, but the audio streams from two separate instances of SDRUno are far from being time aligned.

I understand that linrad does not currently support the version 3 API and was curious if this is something that is being worked on?

[Rick Kunath]

The latest version of Linrad does work with the SDRplay API now. I
source built Linrad and am running it on Suse Tumbleweed using the API.
There is a Windows version but I have never used it. I know the Windows
version requires USB driver substitution/replacement using Zadig on
Windows and I did not want to do that.

Linrad doesn't do dual tuner mode (or diversity) on the RSPduo. I'm told
this is a hardware issue with the way the tuners are synced. I have
asked about that feature, but more requests are always helpful. The last
I heard Leif does not have an SDRduo and was depending on others to
handle the SDRplay part of the code. I don't know if that is true or not
still. We might see a lot more Duo features added if Leif had the
hardware to experiment on.

Linrad will do diversity on other devices. And it does have several
coherent modes as well as a way to separate the AM and FM (helpful in
real time fading) components of the AM signal. And it also can phase
lock to one and only one of the many carriers on the channel to increase
readability of one of the stations. Leif has some good videos on how all
of that works on YouTube. All of this is very useful on the Duo
especially when using headphones.

Stereo diversity using the Duo does work well and I use it all of the
time in SDRuno. I suspect you are having trouble because of the way you
are doing it.

Here's how I do it:

Don't use dual-tuner mode.

Step 1 - Tune in a station and get on the desired frequency. Enable
synchronous AM and select LSB. Set the audio out to left only in the VRX.

Step 2 - Start a new VRX and setup the windows the way you want them
(main spectrum, aux spectrum, RX control). You can create a new
workspace to save this separately if you want to.

Step 3 - Set the VRX1 frequency to the same frequency as VRX0. Enable
synchronous AM and select USB. Set the audio to right only in the VRX.

Step 4 - At this point you have the lower sideband in your left ear and
the upper sideband in your right ear. If you mouse-wheel tune VRX0 then
VRX1 will follow.

It sounds very nice and it is helpful having the sidebands separately in
each ear on certain signals and on certain crowded mediumwave channels.
It's fascinating to hear on shortwave too. But it does not get you
antenna diversity between the left and right ears.

See what you think...

73,
Rick Kunath, K9AO

[chavy levy]

Hey Eric,

Were you able to achieve the binaural diversity reception (two antenna) with the RSPduo? 

[Rick Kunath]

It looks like there is some confusion in this post...

Linrad has supported the SDRplay 3.x API for years. The APIs are not
backwards compatible, so Linrad has kept step with these as the versions
changed. You must have the latest SDRplay API version 3.15 installed to
use an SDRplay RSP with Linrad (Windows or Linux).

Linrad does do active phasing, diversity, dual-channel recording,
straight X + Y diversity to the ears, coherent detection with a 3D
soundscape presented to your ears (binaural but better), it can sync to
a carrier and display with millihertz accuracy, it has carrier based and
audio based AGC, superb noise blankers, time or frequency domain
processing, and far far more.

I hope that helped clear things up.

Rick Kunath, K9AO

[chavy levy]

Thank you Rick.

Can you please direct me to some documentation (guide or info) on how to to do binaural diversity reception with the two tuners of RSPduo each going into a different ear. This is a standard feature on ICOM 7610, FTDX101 and others. I am trying to achieve the same with the RSPduo.

Thank you in advance.

lz1abc

[chavy levy]

I guess it is this one: https://www.sm5bsz.com/linuxdsp/run/phasing/linrad%20phasing%20window,%20v6%20open%20office.html

[Rick Kunath]

No, that is for active phasing either auto adaptive or manual.

The straight old-school diversity is X +Y mode in the baseband window.
But there is so much more that you can do too. Still, I see why you are
interested in the separateness and letting your ears to the work.

Coherent mode is useful too.

If you are a new user I'd be happy to do a screen share session some
time next week and go over some things with you. Ping me off list if you
are interested. My callsign at yahoo dot com.

Rick Kunath, K9AO

[Eric Allan]

Hi Chavy,

It looks like Rick got you straightened out. Yes, I was able to achive binaural diversity reception using a RSPduo, which I'm sure you'll soon experience, is a pleasureable way of listening!

I recently replaced the RSPduo with an IC-7610 which for making contacts is much easier than managing transmit-receive switching and muting. I am almost always listening in binaural diversity mode.

That being said, Rick mentioned a number of features of Linrad that the 7610 doesn't have, and for SWL DXing Linrad is much more capable.

73,

Eric / NQ8J

[W Jozef. S.]

Hi.

Perhaps one day we will see an nRSP model with true RF-stage diversity — that is, diversity combining from two coherent receivers at the RF front-end rather than at the audio stage.

In remote or Internet-based installations, or in shacks located away from the operator (with only LAN and power lines running to the shack), there is usually far more physical space available for two or more dedicated receive antennas.

With proper phase and amplitude control, even a setup with just two verticals and an nRSP enables smooth, continuous steering of the reception pattern — from end-fire to broadside and any intermediate direction.

73, Joe LB1HI

--
There is an excellent Linrad User Guide by Gaetan, ON4KHG, at:
http://w3sz.com/Linrad%20Installation%20&%20Configuration%20User%20Guide%20-%20V1-0.pdf
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[Rick Kunath]

Joe,

First off, you can do that now with the RSPduo. The active phasing (i.e.
diversity) in the Duo is handled at the RF stage and not the audio
stage. That is what you are asking for :)

Who knows, someday we might see some dual-channel nRSP-type SDR. I
haven't heard anything though about that.

The latest SDRconnect now has the capability to control an RSPduo
remotely using the server portion of it. Previously the server only
handled single-channel mode but now it can handle dual-channel mode too.

No SDRplay company application can record in dual-channel mode. Only
Linrad and Franco Venturi's rsp-recorder can record in dual-channel
mode. WavView DX can play these dual-channel (or single-channel)
recordings back as can Linrad.

So you can do what you want to do right now. Run the SDRconenct server
on an old PC or a Pi and connect an RSPduo to that and you are good to
go - today.

Rick Kunath, K9AO