HFU HF Underground

General Category => General Radio Discussion => Topic started by: Matt285 on December 20, 2019, 2307 UTC

Title: Calibrated receive frequency
Post by: Matt285 on December 20, 2019, 2307 UTC
I feel a bit silly asking this, but I see a lot of postings labeled with such frequencies as 13475.7, 12090.3, 6950.1 etc. What I wanted to know is how do you get such an accurate frequency when the transmission is likely perfectly modulated at a flat frequency such as 14.200? I'm not saying people are proposing it has a guess. I just wonder what factors hone in on dead center when everyone has a different ear for sounds. For instance when im on HF transmitting and receiving I just leave the dial set to where the persons voice is clear and I feel like im likely on frequency as well.
Title: Re: Calibrated receive frequency
Post by: redhat on December 21, 2019, 0009 UTC
If an AM signal is being monitored, it is fairly easy to determine by measuring the carrier frequency on an SDR.  With SSB transmissions, often this needs to be done by ear and takes a lot of practice.  Also, your measurements are only as accurate as your receiver's timebase.  I periodically calibrate my WinRadio against WWV for this reason.

+-RH
Title: Re: Calibrated receive frequency
Post by: Matt285 on December 21, 2019, 0019 UTC
Thanks for the reply. I never thought I would want an SDR receiver, but I plan on buying a RSPdx receiver in a month or so. All the features and full  spectrum monitoring are awesome. Im also really excited about  having 3 switchable antenna ports. I will still always have a love for turning a dial though and will always have a traditional rig. I think I can learn a lot from it though and broaden my skills as a whole from using an SDR.
Title: Re: Calibrated receive frequency
Post by: ChrisSmolinski on December 21, 2019, 1521 UTC
I have several SDSs, my netSDR has a GPS derived 10 MHz reference, so I am able to make 1 Hz or better measurements of carrier frequencies.

Once I went the SDR route, I gave up on using radio with knobs. Barbaric  :)
Title: Re: Calibrated receive frequency
Post by: NJQA on December 21, 2019, 1548 UTC
Once I went the SDR route, I gave up on using radio with knobs. Barbaric  :)

Knobs aren’t the issue.  Isn’t it really giving up on the use of radios without spectral displays?  Listening on a conventional radio feels like driving with blinders on.   I gotta know what is going on around me.
Title: Re: Calibrated receive frequency
Post by: Matt285 on December 21, 2019, 1552 UTC
Yes. i can understand. Im going to post a question on the SDR forum about another aspect.
Title: Re: Calibrated receive frequency
Post by: ChrisSmolinski on December 21, 2019, 1612 UTC
Once I went the SDR route, I gave up on using radio with knobs. Barbaric  :)

Knobs aren’t the issue.  Isn’t it really giving up on the use of radios without spectral displays?  Listening on a conventional radio feels like driving with blinders on.   I gotta know what is going on around me.

Definitely, the waterfall and being able to see the entire band at once is important.

Also for me, the ability to record the entire band overnight, and then quickly go through it looking for transmissions of interest. Once you get used to that, going back to a conventional radio is impossible.
Title: Re: Calibrated receive frequency
Post by: Josh on December 21, 2019, 1637 UTC
Once I went the SDR route, I gave up on using radio with knobs. Barbaric  :)

Knobs aren’t the issue.  Isn’t it really giving up on the use of radios without spectral displays?  Listening on a conventional radio feels like driving with blinders on.   I gotta know what is going on around me.

I had a heck of a time going from a 756 Pro (has fishfinder) to a 746 Pro (does not has fishfinder). Never want to go through those kind of withdrawls again.
Title: Re: Calibrated receive frequency
Post by: Brian on December 21, 2019, 2200 UTC
I switch to USB and tune for min beat.