Search found 102 matches

by snn47
Thu Oct 25, 2018 7:33 pm
Forum: Antennas
Topic: COAX Stub notch 88-108 bandstop filter for stock antenna
Replies: 2
Views: 460

Re: COAX Stub notch 88-108 bandstop filter for stock antenna

Depends on what Parameter you need if a stub is the solution for you, since a coax stub would also attenuate the 70 to 80 MHz MHz segment somewhat to, varying on design. I'm not specific because it depends on many factors. In short a Notch filter or coax stub is a piece of cable of n * 1/4 wavelengt...
by snn47
Sun Oct 21, 2018 4:42 pm
Forum: Other SDR Devices
Topic: TV adapter brings DVB-T2 for the Raspberry Pi
Replies: 0
Views: 420

TV adapter brings DVB-T2 for the Raspberry Pi

https://translate.google.de/translate?s ... edit-text=

However this will work only with unencrypted DVB-T2 programms.
by snn47
Wed Oct 03, 2018 5:55 am
Forum: RTL-SDR Discussion
Topic: SDR - Bandwidth
Replies: 4
Views: 923

Re: SDR - Bandwidth

To help you get an idea what to look for There are different types of receiver designs, with and without selectivity 1. a single resonant circuit tuned to the the receive frequency and a dector diode works for AM-BC if BC stations are separated sufficiently Bandwdith and therefore receiver RF select...
by snn47
Wed Oct 03, 2018 5:33 am
Forum: RTL-SDR Discussion
Topic: AGC and rtl-sdr dongles
Replies: 3
Views: 868

Re: AGC and rtl-sdr dongles

Receiver designs may or may not employ AGC, since as said before the dongles are designed with a specific task (DVB-T) in mind, when all DVB-T signals are strong, not changing in strength and therefore you don't need to receive weak signals in presence of much stronger signals. Lack of a large dynam...
by snn47
Wed Oct 03, 2018 4:54 am
Forum: User Projects
Topic: Potting ADS-B LNA
Replies: 4
Views: 870

Re: Potting ADS-B LNA

You have all the advice on condensation, except for adding heating with temperature control to get rid of condensation. Keep in mind that the coax connectors are also sensitive to weather too. Consider using a bucket upside down, acting as a sleever to protect Preamp and coax connector from weather....
by snn47
Wed Oct 03, 2018 4:41 am
Forum: Antennas
Topic: Antenna combiner
Replies: 8
Views: 1063

Re: Antenna combiner

@P-40 Warhawk illllmhad asked about combining his antennas and if the referenced combiner would work for him. Any passive device can be used as spltter combiner, but the problem is that cutoff frequencies have to match the antenna frequency range. In this case, since designed for BC/TV for most part...
by snn47
Mon Oct 01, 2018 9:52 pm
Forum: Antennas
Topic: Antenna combiner
Replies: 8
Views: 1063

Re: Antenna combiner

Combining different frequency ranges is possible, but requires that the filters provide separation between the antennas in frequency, This requires the cutover frequency ranges of filters and antennas don’t overlapp. If you combine the same signal received by different antennas, due to varying phase...
by snn47
Sun Jul 22, 2018 7:38 pm
Forum: Antennas
Topic: Balanced antenna for direct sampling
Replies: 5
Views: 1290

Re: Balanced antenna for direct sampling

WIth a 1/2 wave dipole you only get resonance at multiples of the dipole. e.g. if it's 40m in diameter (1/2 wave for 80) m then its more or less in resonance 40m 20 m 10 m wavelength, but the antenna pattern will vary with frequency and height above ground level. Since you said you don't want to tra...
by snn47
Sat Jul 21, 2018 4:50 pm
Forum: RTL-SDR Discussion
Topic: 10 feet / 3 meters USB extension cord
Replies: 13
Views: 1519

USB Filter box already offered by Würth as design kit

Würth already offers this design bag that provides you with the PCB layout and design shown in ANP024c_EN_The_USB_interface_from_EMC_point_of_view.pdf. I only wonder if replcing the plastic with a metall shield box box would not reduce RFI further. The Complete USB 2.0 EMI & ESD Solution You have tr...
by snn47
Sat Jul 21, 2018 7:47 am
Forum: RTL-SDR Discussion
Topic: 10 feet / 3 meters USB extension cord
Replies: 13
Views: 1519

EMC of USB cables and extension cords

While having shielding to improve electromagnetic Compatibility (EMC) is always a good advise it is imho, if at all, hard to achieve and therefore only make believe. Unlike coax cable, you will not be able to find the necessary shielding information for USB cable or connector because the USB as syst...