Search found 179 matches

by snn47
Thu Mar 16, 2017 4:32 am
Forum: RTL-SDR Discussion
Topic: Placement of LNA
Replies: 19
Views: 10331

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: 10331

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: 7662

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: 4686

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: 4430

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: 10331

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...
by snn47
Tue Mar 14, 2017 4:01 pm
Forum: RTL-SDR Discussion
Topic: How to count and identify carrier frequencies?
Replies: 13
Views: 7662

Locating RFI

Since you did not specify the frequency range you want to look into here some general comments. Without receiver selectivity it's difficult to say what is interference and what is generated by a strong RF environment at where you live. If you add a 20 to 40 dB attenuator between the antenna and the ...
by snn47
Tue Mar 14, 2017 3:00 pm
Forum: RTL-SDR Discussion
Topic: Has cooling sticks <=0°C been tested (e.g. dry ice/freezer)?
Replies: 7
Views: 4430

Has cooling sticks <=0°C been tested (e.g. dry ice/freezer)?

It's curiosity on my side to know if performance improves, if at all, when the die temperature is reduced to 20°C or lower. I already have receiver and converter to receive a wide frequency range, but cannot use them, except for below 30 MHz, since have basically no radio line of sight in all direct...
by snn47
Tue Mar 14, 2017 2:52 am
Forum: RTL-SDR Discussion
Topic: Has cooling sticks <=0°C been tested (e.g. dry ice/freezer)?
Replies: 7
Views: 4430

Has cooling sticks <=0°C been tested (e.g. dry ice/freezer)?

Unfortunately there is seldomly, if at all, a reference to the ambient temperature during time that tests were conducted. There should be some differnece if a stick is operated outside at temperatures below 0° Celsius during winter, or with dry ice/freezer/peltier box/freezer, compared to >20° C roo...
by snn47
Sat Mar 11, 2017 6:44 am
Forum: Antennas
Topic: Simple dipole for FM-BC reception. To balun or not to balun?
Replies: 9
Views: 9409

Important info Symetrical Twin-Wire-Feeder or Twin-Lead

A few more important information for all not familiar with twin lead cable, which is not necessarily complete: Symetrical Twin-Wire-Feeder or Twin-Lead was the only (affordable) means to connect an antenna to BC and TV receiver. Since there is not to much that you can find in the internet today her ...