Search found 217 matches

by snn47
Wed Feb 26, 2020 5:56 am
Forum: Signal Identification Help
Topic: AM-radio with unstable frequency?
Replies: 4
Views: 9366

Re: AM-radio with unstable frequency?

It could just be receiver intermodulation. If you have a 10 or 20 dB attenuator insert it and see if you still receive the station.
by snn47
Wed Feb 26, 2020 5:48 am
Forum: RTL-SDR Discussion
Topic: Bluetooth Classic Sniffing
Replies: 3
Views: 5612

Re: Bluetooth Classic Sniffing

Even if you use a converter that would mix the BT-frequencies to below 1700 MHz, you would need also to be able to folloe the frequency hopping pattern of BT see https://en.wikipedia.org/wiki/Bluetooth
by snn47
Wed Feb 26, 2020 5:36 am
Forum: RTL-SDR Discussion
Topic: Received Audio
Replies: 1
Views: 4033

Re: Received Audio

Audio for voice from my HP Z-books isn't to bad so I havn't had the need to use external speaker. If I did I would use one of my BT speakers on battery to avoid humming from an AC loop.
vy 73
_.. .._. ..... .__. _.__
by snn47
Wed Feb 26, 2020 5:26 am
Forum: RTL-SDR Discussion
Topic: Can I use the SDR very close to the RF source?
Replies: 11
Views: 14651

Re: Can I use the SDR very close to the RF source?

Why do you want to place the SDR antenna so close to the transmitter antenna ? Even a 50 ohm termination on your SDR should be enough to receive the transmitted signal at this distance and make it safe for your SDR. With antennas at VHF beeing about 1 m appart you cannot calculate/estimate the isola...
by snn47
Wed Feb 26, 2020 4:56 am
Forum: Antennas
Topic: Simple but effective DIY Civil and Military Airband Antenna
Replies: 8
Views: 10905

Re: Simple but effective DIY Civil and Military Airband Antenna

Welcome to the forum merseyradar. I am not aware of any froum where anyone, except the initial author (and on some forums also not), can change the title of the thread. However beeing able to create your own Subject-Title when you post a reply is standard operational practice in forums I participate...
by snn47
Tue Feb 25, 2020 5:00 am
Forum: Antennas
Topic: Simple but effective DIY Civil and Military Airband Antenna
Replies: 8
Views: 10905

Low VSWR is not an indication for good antenna performance!

@HighSNR There isn't much material in this build that is likely to add loss(at this frequency) to the antenna, so in this case, I would expect S11 to be a fairly good proxy for the true performance. You seem to confuse a lot of factors that define good antenna performance. VSWR is defined by the rat...
by snn47
Mon Feb 24, 2020 8:28 am
Forum: Antennas
Topic: Simple but effective DIY Civil and Military Airband Antenna
Replies: 8
Views: 10905

Re: Simple but not broadband Antenna

The only thing missing from your blog is any final measurements of the antenna performance. The frequency is right in the sweet spot for a £50 nanoVNA. The S11(vswr) will give you an excellent idea of how close to optimal this antenna really is. Good antenna performancance is not just having a low ...
by snn47
Tue Feb 18, 2020 8:29 am
Forum: RTL-SDR Discussion
Topic: Lots of activity on RF, is it all real?
Replies: 6
Views: 3970

Re: Lots of activity on RF, is it all real?

It is hard to judge until you get yourself a switchable 10 or 20 dB attenuator. With attenuation switched on a signal should be reduced by the selected attenuation factor. If signals are gone or loose much more in strength it is most like intermodulation in the receiver due, meaning it is overloaded...
by snn47
Tue Feb 18, 2020 5:31 am
Forum: RTL-SDR Discussion
Topic: Beginner-Want to listen air traffic
Replies: 21
Views: 13057

Re: Beginner-Want to listen air traffic

While the length of coax is not irrelevant, it is the loss of the cable that attenuates your signals. The loss of coax will increase with frequency and quality, e.g. design and materials used. If your coax cable will add only a few dB loss you will not need a LNA. Since a LNA will amplify all freque...
by snn47
Tue Feb 18, 2020 5:23 am
Forum: Antennas
Topic: Question regarding loop designs
Replies: 8
Views: 5319

Re: Question regarding loop designs

You did not specify the frequency range you want to use the loop and if you intend to use a untuned or a tuned (magnetic) loop. The grid will do two things increase capacitance = detune it and shield electrical antennas. Magnetic loops unless completely shielded in a metall cage will be detuned due ...