RTL DC spike

[moonbounce]

I have an RTL R820T dongle, when I bought it I opted for the R820T over the E4000 for a couple of reasons, one of them being the dc spike in the E4000.
Turns out that my R820T has this same dc spike, and I did check to see if the chip is indeed a 2832u and not an E4000. Anyone know why I have this and is it possible to get rid of it?
I am currently waiting on the arrival of my next dongle, the R820T2, I hope it doesn't have the same dc spike.

Moonbounce

 

[SCPD]

The spike on the E4000 is much larger. The spike on the R820T (and R820T2) is normal.

In programs like SDR#, you can check "IQ Correction" to get rid of the spike.

 

[moonbounce]

The spike on the E4000 is much larger. The spike on the R820T (and R820T2) is normal.

In programs like SDR#, you can check "IQ Correction" to get rid of the spike.

That worked, always wondered what that was for, lol.

MB

 

[Flatliner]

The DC offset is where I & Q meet. There is a slight difference between the channels, and the spike is the result. It's not removed as such, but it's an estimation of what the level should be to, effectively, remove or reduce it significantly. You'll normally get a better result, especially on narrow signals, if you avoid that part of the display altogether. In other-words, don't let a signal straddle each side of the spike, whether present, or suppressed.

 

[majoco]

To lose that spike is why I like SDR# where it's done automatically - and not HDSDR where you have to do it "manually" and even then it only cancels the spike when your received frequency is near the centre and the image frequency is not too strong. But what do you expect from a 20 buck radio?

 

[SCPD]

Think beyond what you were taught..There is more to it!!!

I have an RTL R820T dongle, when I bought it I opted for the R820T over the E4000 for a couple of reasons, one of them being the dc spike in the E4000.
Turns out that my R820T has this same dc spike, and I did check to see if the chip is indeed a 2832u and not an E4000. Anyone know why I have this and is it possible to get rid of it?
I am currently waiting on the arrival of my next dongle, the R820T2, I hope it doesn't have the same dc spike.

Moonbounce

HDSDR has a auto setting to remove the dc spike. Use fixed tune frequency and LO (in misc options). It'll always be away from the null point (where the spike is). Also HDSDR won't lock up in fixed tune. The LO will always show 10khz offset each time you change frequency, or your preferred offset. It'll be like tuning a dial string analogue radio as you move up or down in frequency per se. It is a radio!!

That spike can be useful to lock phase with the dongle (use ECSS mode). Use a signal generator or a known TV frequency with a pilot tone to let HDSDR find the right ppm correction to 100ths and 10ths accuracy. Tune the spike right on the pilot tone for phase lock(do not use fixed tune to LO) This way you don't have to input ppm in the EXTIO dialogue. Useful for usage that needs that extra fine ppm calibration. SDR# doesn't give us this much freedom to play with :-(

Please take note the auto calibration find and phase lock doesn't work when HDSDR is in up converter mode.