Regarding Observation 10391348 …
I am not sure what I am doing wrong here…
This is an overhead pass and I have no data in the waterfall…
I have a generic V Dipole antenna and the VNA shows it is resonant on 136Mhz…
The kit consists of:
Nooelec NESDR SMArTee v2 SDR
Nooelec SAWbird+ NOAA LNA/Filter
Generic V-Dipole antenna (78M-1 GHz Frequency Receive 137MHz Positive V Horn Antenna Rod V-dipole DIY Kits | eBay)
Any Ideas?
So,
Cristian - YO4DFT
Use a SDR program like SDR++, GQRX or similar and do some manual observations to see what is happening.
Maybe there is some strong local interference that is responsible for this behavior.
- where is the LNA (under antenna, how much coaxial and type, antenna to LNA)
- distance from LNA to SDR (also, what type of coaxial)
- do you have FM station (88-108 Mhz) in proximity ?
LNA is under the antenna with a 3 foot cable - Mini8 Coax
LNA is directly attached to SDR
FM station at 104MHz hence why I decided to go with SAW Filter.
Use a SDR program like SDR++, GQRX or similar and do some manual observations to see what is happening.
Maybe there is some strong local interference that is responsible for this behavior.
I have tried this in the past with the V-Dipole outside my window and I was able to get very good results even without a LNA/SAW Filter… Not sure what is happening…
let me understand, only 1 meter form antenna to SDR ?
OK, I suppose you have the antenna somewhere outside, or you have all in the attic ?
What is the distance from SDR to computer / RPI ?
Cristian -YO4DFT
let me understand, only 1 meter form antenna to SDR ?
OK, I suppose you have the antenna somewhere outside, or you have all in the attic ?
What is the distance from SDR to computer / RPI ?
Cristian -YO4DFT
Yes everything is in the attic, SDR is 30cm from Pi with a small USB pigtail with ferrite cores around it for minimizing EMI.
If it is too complicated to use SDR software to check what is the source of interference, try in the attic without LNA, or go back to the windows, and check without and with LNA. I saw you tried several gains, form few db to more than 40. What gain you used without LNA ?
If it is too complicated to use SDR software to check what is the source of interference, try in the attic without LNA, or go back to the windows, and check without and with LNA. I saw you tried several gains, form few db to more than 40. What gain you used without LNA ?
Good shout, thank you!
I have removed the LNA/Filter and I have scheduled NOAA15 with the same gain (22.9) of a previous observation which used the LNA/Filter. Also, the satellite pass on both observations is similar so this will provide a good comparison to see if the LNA/Filter is giving me the issue.
The last reception (Meteor, at 16:02 UTC) was with or without LNA ?
The last reception (Meteor, at 16:02 UTC) was with or without LNA ?
With LNA
OK, lets remove for the moment. You can schedule everything, it doesnt matter what, only to see how is the waterfall. Not necesary to wait NOAA.
I have scheduled ERS-15 for two passes in the next 30 minutes…
Let’s see what we get…
Much better, but you have a perturbation around you. Led lamps, something radiating a strong signal in VHF.
Much better, but you have a perturbation around you. Led lamps, something radiating a strong signal in VHF.
When you say much better, what do you base it on?
Also the perturbation, is it depicted by the horizontal bars in the waterfall?
OK so NOAA 15, is it my eyes or can you see very faint signal lines in the waterfall?
Faint trace of APT, yes.
still looks like pretty strong interference affecting it, using a graphical sdr client where you can see the spectrum live and adjust gain and frequency is a lot faster than changing things and waiting for satellite passes.
that LNA has two gain stages and a whopping 41dB gain. you should have the rtlsdr set to something like 3dB up to maybe 10dB at a maximum.
Rpi close to the antenna is usually not good if it isn’t properly shielded and choked.
unbalanced antenna needs chokes close to the antenna feedpoint to balance it.
Thank you!
I have now relocated the SDR and LNA to be directly attached to the antenna.
I have a high quality shielded 3m USB cable running from the antenna to the Pi and I have also attached ferrite cores to both ends of the USB cable.
I have set the gain to 3.7 and waiting for the next pass of NOAA 18 in couple of hours.
What I meant was, that with that gain in the LNA, you can have the SDR and Rpi tens of meters away from the antenna+LNA without having to worry about signal loss at all.
That also helps with keeping the digital noise from usb, ethernet, high speed buses on the rpi etc, away from the antenna.
good luck
What I meant was, that with that gain in the LNA, you can have the SDR and Rpi tens of meters away from the antenna+LNA without having to worry about signal loss at all.
That also helps with keeping the digital noise from usb, ethernet, high speed buses on the rpi etc, away from the antenna.
Ah, my bad!
I have tweaked the setup, put the LNA direct to the antenna and have a 2m coax to the SDR which is directly connected to the Pi away from the antenna.