Search found 166 matches

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: 4534

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: 4264

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: 9987

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: 7410

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: 4264

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: 4264

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: 9201

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 ...
by snn47
Sun Feb 12, 2017 9:28 pm
Forum: Antennas
Topic: Simple dipole for FM-BC reception. To balun or not to balun?
Replies: 9
Views: 9201

Stacked Quad with reflector

My best advice for your tests is to use a stacked Quad with reflectors. I remember a very light foldable 4 stacked Quad design used for portable HAM Radio contests, for which everything had to by as light as possible, since you had to carry all. I looked through my old UKW-Berichte/VHF-Communication...
by snn47
Wed Feb 08, 2017 11:46 am
Forum: Antennas
Topic: Simple dipole for FM-BC reception. To balun or not to balun?
Replies: 9
Views: 9201

Re: Simple dipole for FM-BC reception. To balun or not to ba

A dipole should give you a =8= antenna pattern to dipole elements shown as ==, meaning if you rotate it by 90° horizontally the signal of a station which you had at max. before, should decrease significantly or not be receiveable at all. If not it does not work as a folded full wave dipole. There we...
by snn47
Tue Feb 07, 2017 8:04 am
Forum: Antennas
Topic: Simple dipole for FM-BC reception. To balun or not to balun?
Replies: 9
Views: 9201

Re: Simple dipole for FM-BC reception. To balun or not to ba

Most FM-BC antennas are vertically polarized, unless you want directivity, a 1/4 wave ground plane is mechanically shorter. A 1/4 wave ground plane is basically a 1/2 wave dipole, were the 1/4 vertical radiatior is reflected by a conducting ground/counterpoise or 1/4 wave radials, it is asymetrical ...