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swarg_eu
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Everything posted by swarg_eu
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Selfmade RF frontend for Video signal (Analog, DVB-T, DVB-T2, CATV) amplification in a 75 Ohm system. The RF frontend contains the following building blocks: 4-Way Wilkinson power combiner - combines the signal from 4 antennas (~6dB gain) bandpass filter - eliminates the interfering radio signals (FM...) low noise amplifier with a voltage regulator - for sensitivity improvement (~21dB gain, NF~1dB ) Interconnections: 4 F type connector 75 Ohm inputs (antenna) 1 F type connector 75 Ohm output (receiver side), requires a bias voltage in the range of 6-20 VDC and ~60 mA (for example: ZS300 antenna power injector ) Technical data: Frequency range from ~460 to ~880 MHz Noise figure >2,5 dB (including insertion losses) Gain <25 dB (including insertion losses and combiner gain) P1dB ~19dBm Max Pin 17dBm Size ~250x120x25 mm The use of this RF frontend is recommended in one of the following scenarios: the picture is pixelated but you are already using a high gain antenna and amplifier you are in a high power RF environment, Amateur Radio, FM radio is attenuated by more than 80dB ... you want to combine the signal from multiple directions to a single cable (signal quality will/can be reduced) Basic knowledge in antenna (phase) arrays is recommended to exploit the benefits of the RF frontend. Protective housing not included. Antennas not included. Power injector not included. Coax cable not included. Test results (scenario with a pixelated picture and high power RF environment) DVB-T2 Transmitter side cordinates 45,89938 N; 15,94786 E; DVB-T2 Reciever side coordinates 44,47105 N; 17,97297 E; Link distance ~225 km, no line of sight. Receiver side 2x2 antenna array with Triplex Loga Iskra P-47N (without an amplifier, marked on radio tower picture), connected with ~1m RG-6/U coax cable (length variation between antennas <1cm) to RF frontend. Received signal strength (SNR) above the threshold including fading effects (SNR range 29-37 dB). Successful elimination of interfering radio signals (see measured transmission response) on the receiver side (4 FM station with 400 W ....) Free worldwide shipping with DHL.
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There are 2:1 4:1 combiner, filer, LNA separately and the 4:1 filer and LNA on single board
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Your cable (connectors) seems to be badly assembled (happens to the best, there is usually a QC to avoid this), the central pin has 191,8 ohm !!!!! It should tend like the other conductor to 0 ohm!! and check that additionally, you don't have a problem with SMA to RP-SMA
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1. it depends on the cable, for example, the cable has a loss of 0,5 dB/m multiplied with the 10m gives 5dB of signal loss the 7dBi antenna acts now as a 2dBi antenna 2. no TV and WIFI are at different frequencies and a TV antenna is not optimized for 2,4 GHz 3. no it can't, the power of the USB dongle is not high enough to cause any damage due to a mismatch 4. depends on the cable (check the cable specification, the type is usually written on the cable or post a picture of the cable). 2,4 GHz is not that sensitive to small mistakes, make sure that you don't have a short circuit 5. no you don't need a shielding on the USB modem, 21 dBi make sure that the antenna is for 2,4 GHz
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1. the ground of the antenna needs to be at the defined position to get a proper radiation pattern and impedance matching (mount it on a separate horizontal arm) 2. the parabolic grid antenna is made for a dipole (you don't use the full reflection area of the grid), you reflect only one part of the polarised wave (-3dB for TX and RX, MIMO is not gonna work in this particular case) an offset satellite dish is a much better choice for a reflector, kip in mind that there is a polarisation change after a reflection (SISO system limitation)
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If your goal is to get to 15GHz and more you are using the wrong connector. You need an SMT edge connector (I would prefer a 2.92mm connector), lowers the problem with ground Why did you cut open all metal layers? There is no need for that it only introduces unwanted effects.
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Expanded Polystyrene er 1,02-1,04 (99% air, water-resistant...) https://www.epsindustry.org/sites/default/files/-Properties%2C Performance and Design Fundamentals of Expanded Polystyrene Packaging.pdf end of page 4
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that not a problem, but depending on the frequency a 90 deg hybrid or a ratrace is a better solution
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it depends on how you look on the splitter/combiner - splitter, 2 output ports with a 3dB "loose" compared to the input - combiner the output has a 3dB "gain" compared to the 2 input ports (assuming the phase and amplitude match) the question is actually what you do with the splitted/combined signal in the case of an antenna, the feeding network for the patches splits the power while TX and combines the power while RX the TX antenna gain and the radiation pattern is a result of the superposition (amplitude and phase) of the patches radiation the RX antenna gain and pattern are the results of the combined patch (pattern) signals (amplitude and phase) in the case of a passive antenna, the feeding network is the same for TX & RX resulting in the same pattern for TX & RX and doubling the patch count increases the antenna gain by 3dB (combiner/slpitter)
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for what?
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for this type of antenna, a simple power splitter is not a solution (no phase shift between ports) the patches need to be driven with a 180 deg phase shift, otherwise, there will be no main lobe in the radiation pattern (in its place will be a zero) Therefore it uses a transformer (wire loop) that transforms the single-ended (asymmetric) to differential (symmetric, 180 deg phase shift) port the rest of the PCB traces (GND below) ensures a proper impedance match
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everything else is 50 ohm
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that is a power splitter (impedance matching) 2x H pol. on one splitter 2x V pol. on the other splitter
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there is a problem: your antenna is used to RX and TX (TDD, FDD...), and putting a PA or LNA can benefit only TX or RX the other one gets attenuated the devices have usually an RF front end IC that switches between PA and LNA mode based on control pin voltage ................. (pain in the ass to manipulate) checkup list: check that the KIP9-1700/2700 antenna is in the focus of the parabolic dish the dish is correctly oriented (not a side lobe) measure the cable & antenna (if you have some equipment), there's maybe water inside the cable... Easy improvement: get the router as close to the antenna as possible (5 meters more of ethernet cable has a lower impact on the connection than 5 meters of coax) Spend money: get a router that is integrated with the irradiator for example Kroks Rt-Pot sHw DS get a bigger parabolic dish
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draw me a basic schematic of what you are planig antenna impedance, source impedance ...
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Something that you can build by your self
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the important thing isn't RSSI but SNR by rotating the antenna for 45 deg, you RSSI dropped bay 3dB but you SNR increased you seem to be a victim of CSMA/CD & CSMA/CA there are maximum 14 (Japan2) channels on 2,45 GHz WIFI and there is someone on the same channel Get a directional antenna ~18 dBi, with some luck the interfering signal is not in the direct line between you and the AP. If needed with the 18dBi antenna, you have some space to get rid of the negative effects of the CSMA by putting a 5~10 m long cable to attenuate the interference to a level where the CSMA won't react (it won't stop the transmitting, package drop)
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on the 75 ohm line, the radius is 7 mm, 3 mm from the end of the PCB 6 mm long line with a cut in the middle of 0,4 mm to solder the 150 Ohm resistors All 3 splitters have the same dimensions: the radius on the transformer lines is 2,5 mm and the axial distance before the bending (from 75 Ohm line) is also 2,5 mm the axial distance in the Wilkins splitter is 11,28 mm between the centers of the two radius bends the axial distance of the transformer lines is 2,88 mm (near the 150 Ohm resistor) The horizontal distance between the two spitters is 25 mm 75 Omh line 1,2 mm transformer line 0,48 mm
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finally got the time 4-way_TOP_75.dxf
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that no problem waths the frequency range?
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yes, I would choose v2
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finally got the time for the splitter version 1 - a combination of Wilkinson and impedance transformer isolation >10 dB between the 4-antenna ports version 2 - Wilkinson (the 50 Ohm line between the splitters is long and introduces some side effects in S33) isolation > 20dB between the 4-antenna ports for both versions, the GND VIA connection is modeled as a solid in the substrate (faster simulation), port 1 antenna input port 3 combiner output 4-way_v1_TOP.dxf 4-way_v1_VIA.dxf 4-way_v2_TOP.dxf 4-way_v2_VIA.dxf
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75 or 50 ohm system? 2 or 4 way splitter? Is FR4 1.6 mm ok?
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Yes the length of the transmission line needs to adjusted https://www.microwaves101.com/encyclopedias/wilkinson-power-splitters The simulation results for the DVB-T2 splitter