Search found 112 matches

by F1BJB
Sun Jul 16, 2017 9:08 am
Forum: General
Topic: Having bad AM broadcast interfernce
Replies: 8
Views: 3468

Re: Having bad AM broadcast interfernce

HI
In case of local interference by a single transmitter a sharp notch filter tuned on the frequency
is the best solution.
It can be left permanently and it helps receiving stations very close to the strong one
by F1BJB
Wed Jul 05, 2017 6:43 pm
Forum: SDRplay related
Topic: RSP2 LO 3rd harmonic spurious response only -20dBC
Replies: 17
Views: 7360

Re: RSP2 LO 3rd harmonic spurious response only -20dBC

but the truth is, that if you connect a decent antenna into RSP2, during nighttime / good condix in MW band you will also be hearing a lot of signals which actually don't reside in MW band, but are from somewhere higher. I totally agree with you . The nice thing is that playing with LO frequency an...
by F1BJB
Wed Jul 05, 2017 6:25 pm
Forum: SDRplay related
Topic: RSP2 LO 3rd harmonic spurious response only -20dBC
Replies: 17
Views: 7360

Re: RSP2 LO 3rd harmonic spurious response only -20dBC

It looks like the IQ mixers are not analog multipliers like in old Motorola MC1496 circuit but instead IQ mixers are working in switched mode. So the LO is like a square wave. The spectrum of that includes odd harmonics and the only way to get rid of spurious conversion products is to filter input ...
by F1BJB
Wed Jul 05, 2017 2:33 pm
Forum: SDRplay related
Topic: RSP2 LO 3rd harmonic spurious response only -20dBC
Replies: 17
Views: 7360

Re: RSP2 LO 3rd harmonic spurious response only -20dBC

Hi
On HF bands RSP is using up conversion so the problem of third harmonic LO responses should not occur.
Or am I wrong somewhere ? :)
by F1BJB
Fri Jun 30, 2017 8:03 am
Forum: General
Topic: Computer specification suggestions?
Replies: 3
Views: 2229

Re: Computer specification suggestions?

In fact the annoying dropouts in the sound are not impairing too much the spectrum display. And displaying a wide range means sharing the dynamic range with many signals that can impair demodulation of the wanted one even with big computing power. The main case I miss it is on the 118/136 MHZ air band
by F1BJB
Mon Mar 20, 2017 8:21 am
Forum: General
Topic: Exercise Blue Ham?
Replies: 2
Views: 1694

Re: Exercise Blue Ham?

Hi
Thanks for the link.
It seems a good idea ,in shared bands, to use the amateur community to get an estimation of the efficiency ,or lack of it,
of a commercial/military installation.
by F1BJB
Tue Jan 17, 2017 8:57 pm
Forum: General
Topic: dump1090 - 2 vs. 8MHz and RSSI
Replies: 2
Views: 2089

Re: dump1090 - 2 vs. 8MHz and RSSI

If you use more than 2 MHz bandwidth you will pick up interference
Mainly DME signals.
by F1BJB
Fri Jan 13, 2017 8:56 pm
Forum: SDRuno
Topic: What is "Decimation"?
Replies: 10
Views: 7061

Re: What is "Decimation"?

How would I effectively use Decimation in my situation. I believe there is very little gain to use decimation with a 5 MHz bandwidth. It would require a sampling frequency of 10MHz and this is pretty close to the 480 Mbps limit of USB2 10MHz x 32 bits(I/Q) =320Mbps and USB2 is half duplex and there...
by F1BJB
Fri Jan 13, 2017 8:29 pm
Forum: SDRuno
Topic: What is "Decimation"?
Replies: 10
Views: 7061

Re: What is "Decimation"?

You're saying Decimation causes multiple successive samples to be added/averaged, I get that, but samples of... What, exactly? l In fact SDR is a mix of analog and digital technology. The bridge between those two worlds is the Shannon theorem https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sa...
by F1BJB
Thu Jan 12, 2017 10:21 am
Forum: SDRuno
Topic: Initial Frequency On Startup Distorted
Replies: 7
Views: 3745

Re: Initial Frequency On Startup Distorted

Hi In fact I found that the zero IF notch can be quite useful. With a sound card it is hard to use because you pickup a lot of hum noises due to ground loops around it. Two examples: In Europe if you want to receive Boston on 1510 KHz you get a 2KHz tone due to European stations on 1512. putting 151...

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