Questions tagged [rf]
Short for Radio Frequency, i.e. frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.
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Smith Chart Verification - Transmission Line Load Impedance
I’m struggling a bit with the Smith chart and tried to solve the following exercise. I would appreciate it if someone could check whether my Smith chart construction and reasoning are correct.
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Does the inside surface of pipe material conduct significant RF current in small TX loop antennas?
Small transmitting aka "magnetic" loop antennas are often constructed out of copper or aluminum pipe material. Antennas don't need to be solid due to the skin effect.
Does the skin effect ...
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How does this oscillator circuit act as a radio reciever?
Sorry for the long text I am really sorry
So I was saw a youtube video about a MW reciever(I know I shouldn't trust videos on youtube for electronic circuits,but the circuit seemed easy and had barely ...
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Why is my AM crystal radio reciever not working?
I am trying to make a simple crystal radio as you can see in the diagram, the problem is when I connect the diode output to the r/l pin of the amp (CA-8403) and the ground to the GND pin, I do not ...
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AM-only radio picking up FM signals
I’m having a very confusing problem with a project of mine.
Last year, I built a one-tube AM radio (if you are unfamiliar with vacuum tubes, rest assured that my problem is not with the tube), with ...
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Why is the equivalent circuit for the unfolded Lange coupler valid?
In Microwave Engineering by David M. Pozar, Section 7.7 shows an effective capacitance network for the unfolded Lange coupler (Figure 7.40a).
I noticed that the nodes 1 and 3 are shorted, but this ...
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Power line communication circuit [closed]
I am looking to create a power line communication system that converts the 60Hz current into a modulated RF signal for long-range communication in rural areas. I am thinking I will use a high ...
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AN6305 “resistor bridge” connection—are both pads GND-to-GND (parallel to ground) for antenna tuning?
I’m following the ST application note AN6305, which recommends adding a “resistor bridge” [Page No-17, Fig-21] (a tuning component network) to allow fine antenna matching. The document shows this ...
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How can an antenna that is only 1 m long receive AM radio with a wavelength of 281 meters? [closed]
I was looking at the US Frequency Allocations Chart (2003) and it stated that AM radio falls in the range of 535 to 1605 kHz. I converted this to wavenlength and thats at least 281 meters. From my ...
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Impedance matching for extreme ratios
I am trying to design a power amplifier at 865 MHz, having min 10 dB gain and around 10 MHz bandwidth centered around 865 MHz.
For this amp, I have selected the AMPLEON BLP9G0722-20G transistor and am ...
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Ground Plane as radial for monopole on PCB
How do the attributes / characteristics of a PCB ground plane affect the performance of a single-pole wire antenna? I'm developing a 4-layer board (signal-ground-power-signal, both signal layers with ...
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How can I reduce or remove close-in spurs in a direct digital frequency synthesizer (DDFS?)
I am working with a direct digital frequency synthesizer (DDFS) and I am observing close-in spurs near the carrier frequency in the output spectrum.
I understand that DDFS spurs can be caused by ...
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10 GHz BFP640 Oscillator Design (Simulation to PCB)
I want to design a low-power 10 GHz signal source and have simulated the shown BFP640-based oscillator, where an LC tank is placed between base–emitter and a second BFP640 is used as a buffer. Is this ...
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High frequency low pass filter performs badly
I'm trying to build a low pass filter with a cutoff point at 450 MHz (50 Ohm impedance). I calculated a 5th order Chebyshev filter for that (see image #1). I'm using a double sided copper PCB (see ...
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Best filter type for RF [closed]
I am trying to design a bandpass and lowpass filter for a receiver for a project I am doing. I'm not very familiar with the advantages of passive filters compared to active filters but I saw on here ...
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