Re: Reverse Spectrum


Several beginning with "that's a clever hack" but it's not really very good for anything or at least anything I wanted. So I never opened any of mine up to make the necessary change to allow proper direct sampling. (The rtlsdr.dll I drive sports a hack that detunes the front end far enough HF can be received on leakage through the circuits. That's not very useful either, in practice. It achieves the difficult feat of creating a radio that has too high a noise figure to be useful.)

For HF the rtlsdr hacks give you dynamic range that is too small to make them as useful as you might wish. And 14.4 MHz and 28.8 MHz are both interesting and useless for designed in reasons. (20 meters is so marginal I never heard a signal there with a lengthy long wire antenna. Lots of Los Angeles radio stations drive the poor things into saturation so I had to desensitize them leaving 20 meters somewhat (cough) numb.

(At the moment I have five of them running all on VHF. One pair is being debugged. Another pair reads sets of digital sensors on 433.9 MHz and 915 MHz. And the fifth provides background music, Hor Nachbar Hob 23d By Joseph Haydn at the moment.)

For HF plus or minus some I got one AirSpy HF+and one AirSpy HF+ Discovery. They are VERY good for most uses. Lately I also got myself a pair of direct sampling receivers.


On 20211224 03:41:14, caeroslp wrote:

Yes, I have to swap I/Q. I buyed some RTL-Stick because i know there is some function ( Direct Sampling ). But nothing changes. Somebody an idea?

donaldhawbaker via <> schrieb am Mi., 22. Dez. 2021, 01:56:
You need to swap I and Q if possible.

Sent from Yahoo Mail for iPad

On Sunday, December 19, 2021, 9:12 AM, caeroslp <caeroslp@...> wrote:

Thanks for your fast answer. Now i feel a littlebit dumb, because i not reading the manual. 


Simon Brown <simon@...> schrieb am So., 19. Dez. 2021, 15:03:


Simon Brown, G4ELI


From: <> On Behalf Of caeroslp
Sent: 19 December 2021 13:50
Subject: [SDR-Radio] Reverse Spectrum


Hey Guys,


Today I built a panadapter for my FT-100D. It works nice with SDR-Console and the External Radio is a perfect feature for this. I have only one Problem:


I dont know why, but the spectrum is not right located. I mean the upper frequencies are at the lower end. 


Is there a function to reverse spectrum? It would helps me a lot.


73 de Dominik DL1DJH 


PS: Merry christmas to you all.

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