Elecraft KX3 - PX3

Jeg har anskaffet mig en Elecraft KX3 og PX3. Det virker også ok, men der er i gennemgangsområdet en bærebølge som ofte svarer til den aflæste frekvens (den undertrykte bærebølges frekvens). Se vedhæftede billede.
Er der en læser her som ved hvordan man slipper af med dette fænomen?
Vy 73 de OZ8GW, Leif.

Svar til #1:
Prøv at slå isolationsforstærkeren til i KX3.

Svar til #2:
Hej
Tak for svar.
Det har jeg prøvet uden virkning.
Vy 73 de OZ8GW, Leif.

Svar til #1:

Er denne artikel en beskrivelse af problemet du sidder med?

http://elecraft.365791.n2.nabble.com/Elecraft-K X3-IQ-out-and-spectral-display-pograms-t d7596187.html

vh
Robin

Svar til #1:

Det er helt normalt for IQ-nul-IF baserede modtagere:

http://en.wikipedia.org/wiki/IQ_imbalance
Citat: "...
However, a direct-conversion RF front-end suffers from two major drawbacks: one is IQ imbalance and the other is DC offset. When designing a homodyne receiver, control of IQ imbalance is necessary to limit signal demodulation error.

IQ imbalances occur due to mismatches between the parallel sections of the receiver chain dealing with the in-phase (I) and quadrature (Q) signal paths. The local oscillator (LO) generates a sinewave, and a copy of that sinewave that is delayed by 90 degrees. When the direct LO output is mixed with the original signal, this produces the I signal, whereas when the delayed LO output is mixed with the original signal, that produces the Q signal. In the analog domain, the delay is never exactly 90 degrees. Similarly, analog gain is never perfectly matched for each of the signal paths.
..."

Fra:
http://da.wikipedia.org/wiki/Internet-fjernstyr et_radiomodtager

Kig på waterfall - alle IQ-nul-IF-modtagere "lider" af nul Hertz signal:

websdr.org: A WebSDR is a Software-Defined Radio receiver connected to the internet, allowing many listeners to listen and tune it simultaneously:
http://websdr.org/
og
Want to get your receiver online? Download OpenWebRX now! :
http://sdr.hu/?top=kiwi

Sidebåndene til nul Hertz skyldes 1/f hjørne støj fra halvledere/op-amps.

June 1, 2001, On the Direct Conversion Receiver -- A Tutorial.
A detailed look at the characteristics of the direct conversion receiver:
http://www.microwavejournal.com/articles/3226-o n-the-direct-conversion-receiver-a-tutor ial
http://web.archive.org/web/20170509233931/http: //www.microwavejournal.com/articles/3226 -on-the-direct-conversion-receiver-a-tut orial
Citat: "...
In direct conversion, as the signal of interest is converted to baseband very early in the receive chain, without any filtering other than RF band-selection, various phenomena contribute to the creation of DC signals, which directly appear as interfering signals in the band of interest, as shown in Figure 8.
...
The leakage of LO or RF signals to the opposite mixer port is not the only way in which unwanted DC can be produced. Any stage that exhibits even-order nonlinearity will also generate a DC output. This is covered in more detail later.
...
More importantly, however, large blocking signals also cause DC in the direct conversion receiver, whether on a spurious frequency or not.
...
An analog IQ demodulator exhibits gain and phase imbalances between the two branches, as well as the introduction of DC offsets.
...
CONCLUSION
The direct conversion receiver is an attractive yet challenging receiving technique. It has been successfully applied to devices such as pagers, mobile phones, PC and internet wireless connectivity cards, and satellite receivers, etc. in a variety of process technologies and increasing integration levels. It is poised to appear in many more applications in the near future.
..."

http://web.archive.org/web/20171118140245/https ://www.ofcom.org.uk/__data/assets/pdf_fi le/0015/31911/receiver.pdf
Citat: "...
These issues are mainly centred on needing a lot of amplifier gain to amplify signals near or at DC. These include:
* Second order receiver nonlinearity causing spurious products at DC.
* Local oscillator leakage causing varying levels of DC offsets.
* Amplifier DC offsets.
* Flicker noise reducing sensitivity.
These limitations detract from the simplicity of the zero-IF approach requiring a receiver with good IP2 performance and extensive calibration to overcome the DC offset issues.
..."

Low IF receiver:
http://en.wikipedia.org/wiki/Low_IF_receiver
Citat: "...
Low-IF receiver topologies have many of the desirable properties of zero-IF architectures, but avoid the DC offset and 1/f noise problems.
The use of a non-zero IF re-introduces the image issue.
..."

Svar til #1:
Hvis der er eftermonteret roofing filterkan det være at den tuningsprocedure der normalt følger med ikke er blevet udført. Du kan evt. finde installation og calibration på Elecrafts internetside. Mvh Per

Svar til #1:
Vær opmærksom på side 25 i manual til PX3 panadapter

Svar til #7:
Tak for svarene.
Nogle mere videnskabelige end andre. Jeg håber da ikke man skal være elektroingenør for at tilkoble en PX3.
Jeg har købt sættet for godt en uge siden med roofing-filter indbygget og håber så at de som har installeret dette filter har gjort det korrekt.
Jeg har netop fundet ud af at når roofing-filteret ikke er indkoblet (FL1) ligger den synlige bærebølge på den aflæste frekvens (den undertrykte bærebølges frekvens) hvorimod når roofing-filteret er indkoblet (FL2/FL3) flytter bærebølgen ud midt i filterområder.
Jeg kan ikke høre bærebølgen på KX3, men hvis jeg med en anden RX lytter på KX3s antennetilslutning kan jeg modtage en bærebølge på frekvensen som er synlig på PX3.
På diverse billeder af PX3 (manuals og you tube) har jeg ikke set en sådan bærebølge, så den må jo kunne fjernes.
Vy 73 de OZ8GW, Leif.