from SDR to fldigi?

[sblair1290]

folks,

I am at the stage of trying to pipe my audio signal from the SDR software to the dl-fldigi software for decoding:

I have managed to receive an audio signal from my PiTS board on the SDR package but I am having trouble isolating the 'double peak' mentioned in the Pits manual. Instead I have a relatively large peak at 435 251 MHZ and another very small one at approximately 434 325 MHz. I have confirmed these signals by turning the Pits board off and on again. There is also a very large peak at 434 288 MHz that is independent of my Pits board. The dl-fldigi software is running but no significant signal appears in the waterfall. It is set to USB mode (I have a funcube dongle pro+) and all other settings are as described in the Pits manual.

Q1. Why can I not see 2 peaks close together and why is one of them very small.
Q2. What is the bigger peak in the middle these?
Q3. Why is fldigi software not picking up what peaks I do have?

I can supply a screenshot if need be. Might do that later if I have the time! In the meantime, any help would be much appreciated.

Mr Blair

[sblair1290]

Ok - I have increased the signal strength by plugging a quarter length piece of single co-axial wire into the funcube dongle. This basic aerial has boosted the signal but the same basic format of peaks still exists (as you would expect). I am assuming that I have missed a setting somewhere.

SB

[daveake]

First, zoom in to confirm that it is a single peak.

If so then most likely you've disabled the serial port, which is where the data stream goes to feed the RTTY transmitter. No data stream means one peak not two peaks. See the manual or online instructions which explain how to correctly set up the serial port. This is something that changed early in 2016 after some changes to Raspbian serial port support.

Dave

[sblair1290]

We followed the instructions on how to coinfigure the serial ports from the latest Pits manual (includes Pi zero stuff) and that seemed to have no effect. we still get two quite small peaks that are separated by a reasonable amount. I am wondering if the aerial supplied with the Pits board is the wrong length! It is 45 cm long so doesn't match the 17cm (quarter wave) length of our cut up piece of wire that is stuck in the receiving dongle. did they supply extra length so it could be cut down to the actual length required?

SB

[daveake]

You need to use the largest peak. Be aware that cheap SDRs have a false peak right in the centre of the received band, so ignore that one.

When you zoom in to the correct peak (the largest PITS-generated one) it will either be a single peak (meaning PITS is not set up correctly) or 2 peaks separated by approx 800Hz.

The supplied coax cable is long so it can be routed through the payload case. The length of this cable does not affect whether you see one or 2 peaks, and does not affect the distance between those peaks. All it effects is the signal strength. The correct length of the active part of the cable (i.e. the part where the centre core is exposed) is 164mm.

I suggest you join the #highaltitude IRC channel where I or someone else can talk you through this.

Dave

[sblair1290]

Ok - I downloaded the Hexchat IRC client an I am looking at a window that appears to be connected to chat.freenode.net.

What now? sorry for my lack of basic knowledge. I am researching as fast as I can between lessons!

SB

[sblair1290]

have managed to establish that I should type something like "/join #highaltitude" but this returns:

No channel joined. Try /join #<channel>

or

Not connected. Try /server <host> [<port>]

SB

[daveake]

That should work, however it's probably simpler to use the web client - https://ukhas.org.uk/ukhas:irc_channel

Whoever helps, you'll soon be asked to post screenshots of the SDR s/w and dl-fldigi, so you might as well get those ready - e.g. upload to imgur.com. You can then post the links in the chat window.

Dave

[sblair1290]

OK, I'm in - I was having trouble getting around the schools 'zero tolerance' web filter but it seems to be ignoring my little Eee Pc for some reason. Our balloon club runs today so I will task the boys with making use of this facility to send some screen shots.

SB

[sblair1290]

a quick question - I have joined the highaltitude channel and have types a hello in the text box. Where do these messages go? I cannot see my own text appearing anywhere? The help files appear blocked by the school. I assume people will either be logged on (live) or will reply later. Is the list down the RHS people?

[daveake]

I see that a couple of people joined, and posted the same message, but haven't responded to the replies. Replies appear in the large window just above where you type in your own messages.

You/they were asked to post screenshots (as I said would happen).

The other thing you can do is check to see if the tracker software is running. To do this, run it manually by logging in to the Pi and typing:

Code: Select all

cd pits/tracker
sudo killall startup
sudo killall tracker
sudo ./tracker

A screenshot of the tracker output would help.

Dave

[sblair1290]

thanks for the help Dave. It seems I must have overlooked something when setting up the serial ports. I did follow the instructions as laid out in the pits manual but it seems a refresh of the Pi's operating system fixed the issue.

Stuart

[daveake]

Seems like that raspi-config was run at some point and the serial port then disabled. The instructions assume that the serial port is enabled, which is the case on a fresh installation, but you may have disabled it at some point.

Dave