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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3answers
612 views

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, ...
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1answer
1k views

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 ...
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1answer
34 views

Handheld VHF Radio Antenna Shorted Signal and Ground Connections

I am not really working in radio circuit design but I am mostly working on embedded systems sides of things. I recently build a system to listen AIS signals. I ordered these telescopic antennas to ...
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4answers
1k views

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. ...
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4answers
771 views

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 ...
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2answers
83 views

VHF/UHF vs 2.4GHz/5GHz

Was curious if you anyone had information as to why 5GHz wifi is more susceptible to walls and floors in buildings (as compared to 2.4Ghz) but the opposite seems to be true for VHF vs UHF. We tend to ...
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1answer
79 views

How the diode in this circuit achieves AM modulation

For the last week, I've been looking for a simple circuit to transmit VHF analogue TV video signals, so that I can transmit my Raspberry Pi output to a TV set. Since I don't have enough experience in ...
3
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1answer
249 views

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 ...
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4answers
280 views

Routing VCC with jumpers?

I'm trying to route a new VHF RF receiver (LO is 151MHz, RF is 162MHz). There's a pair of LC filters on this board, as well as a Si5351 oscillator and a crystal. From what I've read, an uninterrupted ...
3
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1answer
74 views

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 ...
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2answers
901 views

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 &...
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0answers
82 views

Checking for signals above strength threshold over SDR on VHF

So I have a small NooElec Software Defined Radio and I've got it working well with my Raspberry Pi using GQRX as a controller and to visualize the SDR output. My goal though is to use a python script ...
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1answer
3k views

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 ...
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1answer
77 views

How very high frequencies (VHF) are propagated during night over large distances?

I am new in telecomunications and this question just came up today and I coudn't find an explanation. Here is the most common model for the ionosphere: The ionosphere layer E is the main resposible ...
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2answers
1k views

"Old FM" vs. Modern FM radio signal. What's the difference and can I adapt?

I have a vintage radio that I managed to get all circuits and tubes back into original spec. The AM stations tune in fine but I get nothing on FM. I am told this is because it's tuning in "Old FM" - ...
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1answer
740 views

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 ...
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1answer
401 views

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 ...
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0answers
191 views

Considering Transmission Line Effects for Clock Generator

I'm trying to design a clock circuit to convert a 50 MHz 5-volt clock signal down to 3.3 volts without inverting it. The concept is relatively simple, but as I never designed anything like this from ...
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1answer
299 views

How to find input impedance of RA30H1317M1 RF power amplifier module?

I am building an amateur radio VHF transmitter. I want to use off the shelf transmitter module like DRA818V (or similar) as the drive amplifier and RA30H1317M1 as the final amplifier. This is my idea:...
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2answers
695 views

"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 ...
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3answers
924 views

Identify Symbols on Circuit Diagrams for VHF Radio Build

I found these circuit diagrams for VHF transceiver online, and am having trouble recognizing a number of the symbols. Would you please help me identify the boxed symbols? Here's what I've got so far: ...
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4answers
2k views

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) ...
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1answer
831 views

VHF radio - Motorola GM340 - could I have damaged it with too much current? Why would it not be damaged by being connected to a 12v battery? [closed]

I connected a Motorola GM340 VHF radio to the 12v DC converter for another radio, an ICOM IC78, which gives 13.7v at 16 amps. The wiring did not have a fuse. As it did not work, I wonder if the ...
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1answer
1k views

Streaming UHF/VHF/AM/FM over IP

I am working on a project that can stream TV and Radio signals over IP. I found a device to capture the signals and send them over IP realtek-rtl2832u but I am ...
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2answers
2k views

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 ...
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2answers
1k views

UHF RFID reader ability to recognize tags in less than 1 m reading distance

If the UHF RFID reader basic reading distance is up to 5 m, if adjusted to be less than 1 m or to be up to 1 m, can it be able to recognize all the tags? Or since it's for mid range reading, the ...
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1answer
277 views

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 ...