Radarspotting

Miscellaneous => Other Topics => Antennas => Topic started by: Radio2.0 on December 20, 2014, 11:52:40 PM

Title: bad signal
Post by: Radio2.0 on December 20, 2014, 11:52:40 PM
Hey
I use an 1090 Yagi Antenna. Before my dad attached the new Antenna (and turn the Mast a little) the Signal decreased.
RTL1090 show me THR: -72db [19]
What does it mean?!
What could happened to my Antenna that the Signal dropped so much?
Thx
Title: Re: bad signal
Post by: G4UMW on December 22, 2014, 11:52:56 PM
THR shows the average noise level, not the signal level. It's all explained in the RTL1090 documentation.
Title: Re: bad signal
Post by: Radio2.0 on December 22, 2014, 11:54:31 PM
So which Number is better 19 or 8 ?!
Sorry the documentation is worst for RTL1090.
Title: Re: bad signal
Post by: G4UMW on December 22, 2014, 11:57:18 PM
The 19 is the absolute hex equivalent of -72 so effectively they are the same thing. What was your db figure before?
Title: Re: bad signal
Post by: Radio2.0 on December 23, 2014, 12:00:09 AM
sorry i dont understand anything in the "Radio Language".
Is the value good or bad?
Title: Re: bad signal
Post by: G4UMW on December 23, 2014, 12:03:13 AM
See my previous question - what was the db figure before?
Title: Re: bad signal
Post by: Radio2.0 on December 23, 2014, 12:05:41 AM
http://radarspotting.com/forum/index.php/topic,4750.msg22292.html#msg22292
Title: Re: bad signal
Post by: G4UMW on December 23, 2014, 12:17:09 AM
The -79 db figure appears better as it implies less noise.
Title: Re: bad signal
Post by: Radio2.0 on December 23, 2014, 12:31:14 AM
That means the noise level on the dongle with LNA is much higher?
Title: Re: bad signal
Post by: G4UMW on December 23, 2014, 12:39:55 AM
Yes. You may well be overloading your dongle with the signal from your amplifier. This could appear as noise to the  RTL1090  software. An article in a UK radio magazine this month also described signal overload of a dongle when using a preamp.
Title: Re: bad signal
Post by: Radio2.0 on December 24, 2014, 12:36:47 PM
Is there an way to see the Signal Quality?
I know the software is a beta... (I fond no way to use some other SDR 1090 Application wo support more than one SDR Dongle. In RTL1090 i use one as an master and the other send there UDP Data.)
Title: Re: bad signal
Post by: G4UMW on December 24, 2014, 03:25:14 PM
Not as far as I know.

The problem is that both your dongle and the preamp are wide-band devices. Anything your antenna collects will be amplified, not just the wanted signal.

A preamp should only have enough gain to overcome the signal loss in the feeder between antenna and receiver. It is NOT designed to function as a substitute for a poor or badly-sited antenna.