Helicone S-band, with mechanical bandpass filter and preamp
S-band helicone with round reflector , in bucket, with mechanical bandpass filter and preamp
Any explanation for this ?
Looking at the terretrial/spurs on the lower one, they’re also modulated in the same way. So I’m guessing somehow a low frequency (few kHz) squarewave is finding it’s way into the rx path.
That’s a point… Now let me find the source, the HackRF is the one with the extra lines, and that one is fed with 10 MHz. Time to investigate…
It will be useful to take in account the gain of two devices, RTL and HackRF. I am looking for something similar in UHF and lowering the gain solve sometimes some spurs, keeping the same SN ratio or obtaining a better one. This form of signal I have also in UHF, in both configuration. You can see some examples in attachement.
Cristian - YO4DFT
HackRF vs RTL V4.pdf (688.3 KB)
Hi, thanks, I noticed that info and this reminds me I did not reply about my thoughts for the top 4 images 
I think I clearly notice an FM modulated signal, being corrected through your waterfall by doppler correction. Might there be a (mirrorred ?) FM modulated signal being around, narrow band, like a local repeater or something ?
For me, my observations are Pluto vs HackRF so not easy to compare, I might check my strf observations if I get a similar output if I am accidently scanning the same band part.
In this momment I am using RTL V4; I reduced the gain from 19.7 to 12.5, and the perturbation at 436.750 almost disapeard, but the perturbation from 437.505 is still there, same level…
You give me a good ideea, I shall try to listen the audio at 436.750 to see if is related of a broadcast emission.
