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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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151 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 ...
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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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62 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
590 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
332 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
247 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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105 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
810 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
204 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
513 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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542 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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3answers
733 views

(TDC) Time to Digital Converter for (TOF) Time of Flight Applications. 66.6Picosecond sample

Hello. My question is in regards to dynamic range of short time period TDC's. or alternative solutions to a time to digital application. if further information is required, please ask. Notes ...
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2answers
645 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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1answer
633 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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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
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
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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2answers
1k 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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1answer
251 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 ...
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1answer
2k 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 ...