Search found 223 matches

by snn47
Tue Apr 25, 2017 11:12 am
Forum: Antennas
Topic: Loop antenna for frequency range of 160 meters to 10 meters
Replies: 6
Views: 7552

Loop Antennas !!!!!!!!!!!!!!! if you do it right

A tuned magnetic antenna works also well inside a building, unless you have steel increased concrete. A short overview is also on https://en.wikipedia.org/wiki/Loop_antenna The word I couldn't remember and added to my above post was High Frequency Litz wire, which is a multi-stranded wire each isola...
by snn47
Mon Apr 24, 2017 9:40 pm
Forum: RTL-SDR Discussion
Topic: New project idea!
Replies: 3
Views: 4125

Re: New project idea!

i need to detect the presence of a mobile phone in a area You should be more precise when you ask, which mobile phone services e.g. 3g, Edge, LTE .... what is the diameter of the area you are interested in, which bands do you want to monitor? Due to frequency auctioning in many parts of the world t...
by snn47
Mon Apr 24, 2017 9:31 pm
Forum: Antennas
Topic: Loop antenna for frequency range of 160 meters to 10 meters
Replies: 6
Views: 7552

Re: Loop Antennas ????????????

Somethings that I come to understand about loop antennas from surfing the internet. The fatter the loop the better it works. Thirty six inch's diameter single loop for a wide band loop antenna . Wide band loop antenna should be half wave of the lowest frequency you want to receive . Surfing the net...
by snn47
Thu Mar 16, 2017 5:30 am
Forum: RTL-SDR Discussion
Topic: Placement of LNA
Replies: 19
Views: 15583

Re: Placement of LNA

PS: Did your supplier specify the impedance for the
Sirio SD 1300 fom DNJ Radio
at Amazon.com there is no Impedance speciifed
by snn47
Thu Mar 16, 2017 4:32 am
Forum: RTL-SDR Discussion
Topic: Placement of LNA
Replies: 19
Views: 15583

Re: Placement of LNA

While shielding is important, low attenuation for short pigtail is imho a secondary priority to mechanical stability. Every connector will add at best best a few tenth of a dB attenuation. The longer you use, (dis)connect connectors and cable repeatedly, the worse it will get. Then you need to have ...
by snn47
Thu Mar 16, 2017 2:30 am
Forum: RTL-SDR Discussion
Topic: Placement of LNA
Replies: 19
Views: 15583

Re: Placement of LNA

walrusgumboot I was speaking about the COM/NAV/SUR equipment designs that I know about. The definition of wideband will vary with the bands and signal width and operational use of the frequency band and age of the equipment. Selectivity was a must in case of (T)Rx for SW or below. ATC-COM at VHF you...
by snn47
Wed Mar 15, 2017 2:45 pm
Forum: RTL-SDR Discussion
Topic: How to count and identify carrier frequencies?
Replies: 13
Views: 11466

Re: How to count and identify carrier frequencies?

For your use it it is not important to have a precise value of attenuation to the tenth of a dB like it is necessary for measurements, but that the Pi or T Attenuator used, which consists of 3 resistors, matches the impedance of your cable/receiver/antenna. An ATT overview and explanations can be fo...
by snn47
Wed Mar 15, 2017 9:50 am
Forum: RTL-SDR Discussion
Topic: I need help to build an L-band antenna and decode Inmarsat
Replies: 6
Views: 6840

Which

Your needs depend on the signal you want to decode, the signal strength delivered by the (spot) beam footprint at your location. From the picture I assume you intend to adopt an discarded X-band SAT-TV of about 60 to 100 cm size. Due to the factor 10 in frequency difference the achieveable gain shou...
by snn47
Wed Mar 15, 2017 9:19 am
Forum: RTL-SDR Discussion
Topic: Has cooling sticks <=0°C been tested (e.g. dry ice/freezer)?
Replies: 7
Views: 6673

Re: Has cooling sticks <=0°C been tested (e.g. dry ice/freez

walrusgumboot, I only wondered about the main chips performance if operating at 20°C or lower,since the reference oscillator or TXCO can be replaced by an external frequency refernce source.
by snn47
Tue Mar 14, 2017 4:20 pm
Forum: RTL-SDR Discussion
Topic: Placement of LNA
Replies: 19
Views: 15583

Re: Placement of LNA

The problems around intermodulation and dynamic range in the first RF stage are such that in the 1970s and 1980s there was a trend in mission critical comms receiver designs (e.g. military) to do away with all RF amplification before the mixer, simply placing passive LC selectivity - bandpass filte...