The use of SDR's and FreeDV

[Barry Theodore]

What are SDRs and how can we use them with FreeDV? First:SDRs (Software Defined Radios) are receivers located all around the world and are connected to the internet. There are a number of different software variants for SDRs but the main 2 are KIWISDR and WEBSDR. You can find the locations of SDRs by looking at the websites of these.

During the recent "FreeDV Activity Day" I could hear a station from St Louis on an SDR in San Francisco but I could not contact this station because being from Australia I could not make contact because of the frequency, time of day or the distance.

How can we use SDRs? Let me share my setup. I have my main computer set up with FreeDV 1.8.0 and connected to my Tranceiver. This is my Transmitter and receiver where I can listen to and contact local stations and some times DX stations. I also have a laptop which can browse to SDR's. This laptop also has FreeDV 1.8.0 running on it. The browser and FreeDV are connected via a Virtual Audio Cable. This way I can choose an SDR which is local to or which the transmitting station is getting in to. That way I can here everything from the transmitting station. Now if the transmitting station was listening to an SDR which I am getting in to we could have an excellent 2 way conversation.

Every night we (VK3BRT and others in Australia and New Zealand) have a session with Jose LU5DKI in Argentina on 7,180. Sometimes we can hear Jose direct but not decode properly. We use SDRs in New Zealand, Paraguay and Chile to hear Jose and he uses SDRs in Australia or New Zealand to hear us and we have an excellent chat.

Now I suggest during the next FreeDV activity day we give this a try.

73's Barry VK3BRT

[Mooneer Salem]

Hi Barry,

It'd be useful to write up and send out a howto document for those who want to try this. I believe it should be possible to do this without a second PC as well, especially since a second FreeDV instance can be told to use an alternate configuration. Definitely enough time to experiment before the next one, regardless :)

Thanks,

-Mooneer K6AQ

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[Barry Theodore]

First, why an I using SDRs you might ask. At my location I have about a strength 9 noise on all bands which makes it difficult to talk with distant stations.

3 nights a week a friend and I talk to Jose in Argentina (this happens at around 1100 UTC on Tuesday, Friday and Saturday) we usually use 7.180 Mhz +/- QRM. Recently in Australia we transmit on 3.692 Mhz with Jose still on 40 Mtrs. A direct contact with Jose would not be possible so we use SDRs to receive good copy from him. Jose listens to us on one of the SDRs in Australia or New Zealand and we listen to him sometimes on a SDR in New Zealand but often it will be an SDR closer to him in Argentina, Chile or Brazil. We occasionally get in to the KFS KIWISDR | HALF MOON BAY, CALIFORNIA. I have a separate computer running SDRs (yes SDRs, I have a number set up and just open the audio on the one which is best and can monitor my signal on another one). You can only have one connected to the FReeDV software via a Virtual Audio Cable. I can hear Jose through that and I can hear my friend direct. Maybe we could publish (on freedv.org) when we are on FReeDV, the frequency we are using and a SDR we can be heard on so others can listen and may be join in.

I have attached some of the SDR setups my friend has published in the past. There is not one set up that suits everyone. I have also had it working on one computer where you can have 2 instances of FReeDV running. I have also tried one instance and have the receive signal come in via a Virtual Audio Cable. I personally don't like this as there can be quite a bit of messing around with the Audio configuration in you PC.

I hope this helps and maybe some time we can make contact using a SDR near you.

Please follow up with any questions.

73's

Barry VK3BRT

[Al Beard]

Hi Barry and all,

OpenWebRX should be able to decode Codec2 modes. BUT, it is open to us to add other modes, other than 1600.

OpenWebRX is a "stack" of Python scripts feeding audio generated by "csdr" into various decoders, FT8 etc..

Please, please, please, all those of you using Codec2, please login to "qso.freedv.org" and announce your presence!!!!!

BTW: I run an OpenWebRX receiver at www.nepeanshed.org.au:8073 this is at a Men's Shed 1 acre site in Western Sydney, QF56IF.

          Yes, it has a 9KW solar system but not too bad. Antenna, a 9m vertical pole on 900 sqm of metal roof.

For some reason, the SDR, a SDRplay RSP1 on a Raspberry Pi is off line just now.

I'll have a go at adding more FreeDV modes, just for you guys.

Alan VK2ZIW

On Sun, 3 Jul 2022 18:08:21 -0700 (PDT), Barry Theodore wrote

> To view this discussion on the web visit https://groups.google.com/d/msgid/digitalvoice/7f6e99f6-c9c8-4244-b6da-16216befb956n%40googlegroups.com.


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Alan VK2ZIW
Before the Big Bang, God, Sela.
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