Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [vhf]

VHF stands for Very High Frequency and it is generally used to denote the range of radio frequency electromagnetic waves between 30 to 300 MHz.

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"56k modem" found in VHF band

While scanning the VHF spectrum with a SDR USB dongle, I found something that sounded like an old 56k modem (at around 160MHz, FM modulation, Europe region). After some research, I found out that is relatively common to broadcast digital messages…
Dino
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Analyze My Homebrew Diplexer

I'm in need of a diplexer that'll separate RF signals from a single feedline to two antennas. What I designed and built was a diplexer that would allow ~38 Mhz and below out port 1, with ~38 MHz and above out port 2. This is primarily to use a…
MarkSchoonover
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Wrong Sign in the Output of 80MHz Transimpedance Amplifier

I have recently built the following circuit for (homodyne) differential detection of optical laser pulses. In fact, I rebuilt the circuit from this paper with small deviations: simulate this circuit – Schematic created using CircuitLab You can find…
tozero
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Why does this JFET buffer perform so poorly at 82 MHz?

I made a Colpitts oscillator that worked well first time. Frequency about 82 MHz. (nb. corrected diagram adding ground between series 68 pFcaps and corrected Vout) I wanted to add a buffer and chose to use a JFET 2N3819 from the circuit described…
Dabbo
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Duplexer for portable VHF repeater

For my undergrad EE capstone project I'm designing and building a 2m band analog amateur radio repeater. Our design goal is to build a solar-powered low power repeater (something like 5-20 watts) which can be carried in a backpack and easily…
Synchrondyne
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How to connect antenna to oscilloscope?

I have zero experience with antennas and little experience with electronics. I need to detect weak radio signals in the range ~100MHz - 1.3GHz and analyze them with an oscilloscope. I bought a large, broad-band log-periodic dipole antenna. I also…
Adomas Baliuka
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How to deal with ground in VCCed-chassis device?

I'm restoring old USSR radio receiver ("Okean-209"). I've already resoldered all electrolytic capacitors so audio amplifier works great again (there was very low sound before that). However, there are still some problems all related to the…
Drobot Viktor
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Can long-range radio waves from an RTV tower penetrate thin plastic composite material next to its source?

We are currently developing a conceptual design for the renovation of Croatia's main RTV tower located on 1033 meter tall peak Sljeme at the Medvednica mountain north of Zagreb. The idea is to renovate and reopen its upper gondola for touristic…
Ivan Tahlin
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Is it possible to use a YIG tuned filter to make a YIG tuned oscillator?

My application requires an oscillator continuously tunable between 1GHZ and 10GHZ (or a wider range). The output (somewhere between 1mW-15mW) has to be coupled to an ultrawide band antenna. No PLL allowed. Generous phase noise and frequency…
MikeTeX
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Designing a VHF Colpitts oscillator using BJT

I am trying to design an oscillator circuit which can produce a good sine wave with a frequency of at least 500 MHz and oscillating voltage of around 10 - 15 volts. The output of this oscillator will be just connected to a two conducting plates of…
Pradeep G
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Can a composite video line doubler be made using simple hardware components? (composite -> progressive scan)

I have a lot of old analog video equipment and my trusty Apple IIe Color Monitor is finally dying. Since CRT's aren't produced anymore, and because I just am interested in how it is done, I obtained a decent plasma monitor (I can't get enough of…
Wyatt Ward
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Choosing capacitor for RF coupling

I want to couple 10W at 150MHz, 50 Ohms (before and after an RF switch). The PA is a RA08H1317M powered by 14V DC. How do I choose an RF coupling capacitor? I have found this answer, but it only applies to the frequency, not power. What power rating…
filo
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Time to digital converter (TDC) for time of flight (TOF) applications. 66.6 picosecond sample

My question is in regards to dynamic range of short time period TDCs, or alternative solutions to a time to digital application. If further information is required, please ask. TDC datasheet Question. TDC7200 datasheet says, Measurement Range: –…
Lars Olof Lundh
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Voice and data through TDMA in VHF systems

In a VHF radio system using TDMA can a time slot be used to carry both voice and data bits together or is it necessary that both be transmitted in two different time slots. Also while reading an article on channel size, I read channel size=12.5Khz…
sk1
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How can this 160MHz VHF locator tag work with such small antenna?

I recently came across a VHF locator tag used to find animals in the field. It operates on the 160MHz band. According to the user the locator range is some km line of sight (using Yagi antenna) and some hundred meters "in the jungle". I disassembled…
optronik
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