Search found 213 matches

by snn47
Wed Feb 26, 2020 4:56 am
Forum: Antennas
Topic: Simple but effective DIY Civil and Military Airband Antenna
Replies: 8
Views: 4818

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: 4818

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: 4818

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: 1902

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: 14
Views: 4624

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: 2177

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 ...
by snn47
Wed Jan 22, 2020 1:13 am
Forum: Troubleshooting Help
Topic: Received 433MHz signal not as expected
Replies: 2
Views: 1150

Re: Received 433MHz signal not as expected

Did you use the same hardware, softwareversion and settings to record the files? Did you use a soundcard and windows? Selecting not the correct device maybe the reason for the second one, selecting microphone instead of line in an explanation for the clipping in the old one. The old one is not offse...
by snn47
Tue Jan 14, 2020 5:51 pm
Forum: Antennas
Topic: Balum and Unun
Replies: 3
Views: 1226

BALUN and Unun

Have you read the information provided here? https://www.rtl-sdr.com/forum/viewtopic.php?f=6&t=4649&p=10992&hilit=BALUN#p10948 antenna and cable can be symetrical e.g. dipole or parallel wire cable and asymetrical e.g groundplane and coax cable. A Balun adopts symetrical devices to a or unsymetrical...
by snn47
Tue Dec 31, 2019 2:38 am
Forum: Signal Identification Help
Topic: Schedules ?
Replies: 2
Views: 1856

Re: Schedules ?

It varies/depends on the weather services in your area, if, when and how often they launch weather ballons that transmitt weather data. Have you tried asking them politely and they may tell you (or choose not to)? Or you can do search and maybe find the information for your area Adelaide e.g. here h...
by snn47
Tue Dec 31, 2019 2:24 am
Forum: KerberosSDR
Topic: Locate Tetra radios/transmitters - help
Replies: 5
Views: 936

Direction finding vs. locating transmitters

Hello Jompa, How accurate dou you want to be? I'll try to explain the different options as I know them Direction finding (DF) requires at minimum 1 receiver and a (highly) rotateable directional Antenna, and provide the direction towards the transmitter from the antenna direction, but no distance, u...