FSK

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NL13856
Posts: 3
Joined: Thu Oct 26, 2017 9:27 pm

FSK

Postby NL13856 » Thu Oct 26, 2017 10:00 pm

Hi all,

I am a bit of a newby into HF so that’s why I’m asking possibly something silly here.

I was toying around with some DSC tools, started two instances of YaND on 490 kHz and the other on 518 kHz. Because I wasn’t sure on which “side” of the carrier the signal would come I put both receivers on DSB, hoping the AFC of YaND would correct my possible misunderstanding of FSK signals. I then connected the YaNDs with SDRUno using two VACs (Line 1 and Line 2) and after 24 hours had nothing but garbled characters....

So yesterday night I waited for a signal to come up and noticed that my IF (on 518 kHz) was right in the middle of the FSK signal. I tuned 2 kHz lower and there it went spilling out all kinds of information about oil rigs without lights et cetera.

My question is what kind of modulation settings must I use in SDRUno to be able to set the “official” frequency (like 490) instead of 488 and receive a workable FSK signal?

I checked out some of the more expensive SDRs (like TitanSDR) and they seem to have an FSK “button”, which made me wonder and I thought I should ask on this forum.

Many thanks upfront!

Wim
Last edited by NL13856 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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g1hbe
Posts: 224
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: FSK

Postby g1hbe » Fri Oct 27, 2017 8:27 am

The tradition for commercial traffic (ie not amateur) is USB. Tune until the text appears and that will be the correct frequency.

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Andy

DanubeBCL
Posts: 179
Joined: Sat Jul 02, 2016 12:39 pm

Re: FSK

Postby DanubeBCL » Fri Oct 27, 2017 10:33 am

NL13856 wrote:and they seem to have an FSK “button”, which made me wonder and I thought I should ask on this forum.
The SDR softwares follow a different approach. Some keep the nominal frequency and shift the passband when digi modes are selected, others keep the passband and shift the frequency. When a software does not have an RTTY, FSK, DIG button (or similar) at all, use USB and finetune the frequency until your decoding software "sees" the signal.
73, Heinrich

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NL13856
Posts: 3
Joined: Thu Oct 26, 2017 9:27 pm

Re: FSK

Postby NL13856 » Fri Oct 27, 2017 11:12 am

thanks for the replies guys.

I took your tips and tune like this now: for better reception I filter 1kHz wide, I "undertune" 500 Hz and so I capture -500 Hz to +500 Hz calculated from the IF which works just fine.
Only wish left is to be able to set the filter width by entering numbers in SDRUno instead of some mouse-acrobatics to get it right... But perhaps I overlooked an option somewhere...

Thanks again!
Last edited by NL13856 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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