Different indications of frequency

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ik8xld
Posts: 36
Joined: Mon Oct 26, 2020 11:33 am

Different indications of frequency

#1

Unread post by ik8xld »

Hi Simon,
in this period i'm playing on VLF using up converter and RTL-SDR.
I have a difference between the frequency indicated in the bar at the bottom of the signal and the one at the top-left.
The markers are positioned referring to the indication of the bottom bar, underat the signal and therefore do not coincide with FFT.
I can't tell if it's a bug or I'm missing a software setting.

73 Rocco IK8XLD
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sm6fhz
Posts: 179
Joined: Wed Aug 19, 2020 3:21 pm
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Re: Different indications of frequency

#2

Unread post by sm6fhz »

Hi Rocco.
It seems to me that you have a quite odd filter setting; USB ~1.7-1.8 kHz
20.3 + 1.724 = 22.24 kHz i.e. the lower filter limit.
20.3 kHz is the suppressed carrier frequency for the USB setting you have.
Can it be so simple?
73 / Ingolf, SM6FHZ

jdow
Posts: 800
Joined: Mon Aug 10, 2020 8:17 pm

Re: Different indications of frequency

#3

Unread post by jdow »

He can hold a card or piece of stationary vertically up the waterfall edges and note that the signal edges line up with the signal shown in the spectrum display. As noted, his filter definition is somewhat wonkety or possibly even fugly.

{^_^}

Max
Posts: 859
Joined: Thu Aug 13, 2020 9:47 am

Re: Different indications of frequency

#4

Unread post by Max »

sm6fhz wrote: Thu Oct 28, 2021 5:01 pm Hi Rocco.
It seems to me that you have a quite odd filter setting; USB ~1.7-1.8 kHz
20.3 + 1.724 = 22.24 kHz i.e. the lower filter limit.
20.3 kHz is the suppressed carrier frequency for the USB setting you have.
Can it be so simple?
73 / Ingolf, SM6FHZ
Yes, 100% agree Ingolf. It's exactly this.

Rocco, with SDRC (and most other radios), on SSB the displayed frequency is the nominal carrier frequency, not the centre of the set passband. You seem to have a very odd filter setting for USB with lower limit at 1724? Error? Just select another filter frequency (2.2 kHz for example) and all will become clear, assuming they have not been "edited".

Out of interest, if you open the RX Matrix window with the settings exactly as shown in your screenshot, you will see the RX frequencies in RX Matrix DO display the centre of the passband frequency because in the Matrix window, the displayed frequency is "mode blind", so open the RX Matrix window and you will see RX1 shows what I think you are expecting (incorrectly) to see in the main display, that is 22.108 kHz.

Hope it makes sense.

73

Max

ik8xld
Posts: 36
Joined: Mon Oct 26, 2020 11:33 am

Re: Different indications of frequency

#5

Unread post by ik8xld »

thanks for the support, I really had a wrong filter setting
TNX all
73 Rocco IK8XLD

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