Questions tagged [ham-radio]

Ham radio (also called amateur radio) is a licensed form of radio communications for private and non-commercial use. Frequency allocations are made available specifically for ham radio and power levels allowed are typically much higher than available in unlicensed areas of the spectrum.

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Triode Regenerative Receiver Circuit - room for improvement and possible errors

I've designed this radio circuit, it's made to work on the 80m and maybe 40m band. Regen is controlled using a pot in the tickler coil. Tube is ECF82, coil is air cored on a 30mm former. Will it be ...
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1 answer
129 views

What is the name of this antenna?

I compared RSSI of several antennas including this one I found laying around: It performed from all angles about 10 dB better than for example the quarter wave ANT-433-CW-HD-SMA (Mouser Link). Tests ...
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2 answers
43 views

Datasheets, dimensioning questions

I have a problem reading this datasheet. This one is very weird, does 3-1.5 mean that pin is 3 mm wide, and 1.5 mm is meant to be a radius, or does it mean 1.5 mm and that that 3 means three pins? ...
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71 views

Buying a variable inductor

I need a variable inductor of about 70 nH. I found one at Mouser. As you can see, it says that its inductance is 70 nH, but when I open the datasheet it says that inductance is from 9 to over 280 nH. ...
1 vote
1 answer
132 views

Oscillators-completely new approach

I found this link about high frequency VCOs. Although I don't work with such high frequencies, I gave it a try. So I designed this circuit: As you can see, I replaced BC547B (in previous post) ...
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1 answer
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What kind of relay is used for high-power RF front-end applications?

My son and I are designing an RF frontend at 146MHz with a 300W amplifier on the TX side an an LNA on the RX side to be placed near an antenna feedpoint. The frontend will be inline to an existing ...
2 votes
4 answers
2k views

Why does this transistor oscillator not work at 100 MHz?

I tried to simulate this oscillator in Multisim, but it doesn't work, I get just DC voltage from it. With the same biasing I got to make it work, but on lower frequency (around 1 MHz), while I want to ...
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57 views

Estimating the range of an antenna and determining what the best option is?

I'm very new to radio communication so I apologize for the lack of knowledge about this subject. That being said, I'm looking for a directional antenna imagine a situation as follows, I'm in a rural ...
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1 answer
229 views

Automatic Audio Source Switching

I was unable to find an answer to this question, but feel free to link any additional threads I may have missed. In my car, I have an aftermarket amp, and multiple HAM and public service radios. I ...
4 votes
1 answer
90 views

Building a personal RF anechoic chamber in a large walk-in closet?

What would one need (besides many foam absorbers) to build an in-home small anechoic chamber for transmissions in the UHF to L-bands (specifically 500Mhz - 2 Ghz), and what resources would you point ...
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2 answers
79 views

Getting started with Radio design [closed]

For a while now, I have been exploring many RF, communication protocol and radio etc. I am kind of looking for a way where i can implement the software stack for a particular open Radio. Means like ...
2 votes
1 answer
178 views

RF PCBs on 2 layer FR4

I deigning a PCB for an open-source RadioSonde with 403Mhz transmissions using Si4063 ic. Now, these radiosondes are supposed to be inexpensive since there is quite tough competition in the market ...
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2 answers
85 views

Can an antenna be modeled as a 2-port passive network?

I've been using xnec2c to model antenna characteristics in Linux and the latest version is able to create a CSV by frequency of SWR, Zr/Zi, dB gain, and other metrics. I was thinking it would be neat ...
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1 answer
57 views

Can you measure or estimate antenna reflection back into freespace caused by a freespace impedance mismatch?

Consider an antenna as a 2-port reciprocal network such that you may have S11 reflection at the feedpoint, but also S22 reflection back into freespace. S11 is well understood and measured because that ...
1 vote
2 answers
109 views

Help with the error K2_A2 Coupling to shorted-out inductor L5 and looking for pointers for better modelling SWR

I have an RF linear amplifier kit that I am trying to better understand. The problem I am having is that my driver/transmitter is seeing a non matching impedance. To better understand the amplifier ...
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65 views

Test Input Transformer with Signal Generator

I have an RF Amplifier kit that is not working. The main problem is that the input transformer presents the radio with a high, unexpected SWR. It does amplify, so something works. The transformer is ...
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1 answer
139 views

What is this binocular transformer and how do I model it in LTSPice, Have High SWR In Ham Radio

I purchased this 70 Watt Amplifier Kit and built it. Unfortunately, the kits do not come with any instructions. I have managed to find a variety of web sites where people built the amp and offered ...
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1 answer
70 views

Difference between various 955 electron tubes

From the operational point of view, is there a notable difference between the following electron tubes? Jan 955 JRC 955 Jan 955 VT121 JHY 955 VT121 I'm asking broadly about the main points (e.g.: ...
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77 views

Understanding RF MOSFET Bias Circuit

A faulty in vehicle DCDC charger has fed 16V or so into a brand new radio and I'm stuck with a non-transmitting transmitter. This particular circuit has multiple amplification stages with two preamps ...
6 votes
1 answer
94 views

Ham Transceiver to computer Interface design question

I am building a Ham transceiver to computer interface, which has the RS232 port controlling the PTT on the radio. The circuit currently calls out for a 1.2K resistor in series with the RTS line and ...
0 votes
2 answers
456 views

QUCS simulation radio transistor amplifier

I'm trying to design a small amplifier for AM signals to use before the usual diode-C-R detection (the reception in my area is very poor). I devised a QUCS simulation as below: The diode and ...
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4 answers
98 views

Building an FM transceiver

As an electronics hobbyist, I've already built a thing or two so this didn't seem like a complicated thing to do, but I was terribly mistaken. I wanted to build an FM modulated radio transceiver ...
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1 answer
75 views

What's the maximum possible power output of this RF CATV amp?

please tell me what is the maximum possible output wattage that this RF CATV distribution amp (see below for specifications) would likely output with maximum possible input before damage? ~13 mW is ...
2 votes
2 answers
1k views

Tube Transmitter Issues

I'm back working on my friend's 807 tube transmitter. I've had some previous posts on this and I'd like to thank all the people who responded for your help! I bought an oscilloscope and a dummy load ...
2 votes
4 answers
4k views

Designing a simple CW transmitter/receiver

I'm interested in building my own radios for use on the air. I'm still rather new to electronics so I'm looking for simpler projects that I can build to learn on the way, and I'm thinking that a CW ...
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3 answers
247 views

Final transistor in VOX circuit design is saturated even when no audio is supplied

Background: I have a μBITx v6 HF transceiver. It has an audio input and output, and a mechanism where the transmitter is keyed up when the ring connector (called PTT, push-to-talk) from the audio ...
1 vote
2 answers
62 views

Radio Waves: Spark gaps vs general wireless radio antennas?

I was recently told by a friend who teaches college physics that "in reality radio waves are only generated when an electric current is made to move violently through a conductor". He went ...
3 votes
1 answer
3k views

How to DIY BaoFeng radio-to-soundcard cable?

I've got a cheopo BaoFeng UV-5RE that I'd like to try as packet radio. I've snipped the plug off of the headset that came with the handheld, soldered it onto some breadboard cables, and did the same ...
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2 answers
190 views

Radio Waves propagation (Intuitive Understanding of Wave propagation)

I have few similar questions regarding Radio waves communication particularly FM and AM type of Radio wave communication. Please bear with the naivety of the questions. Questions: Radio waves in FM ...
2 votes
1 answer
164 views

Does this crystal circuit work?

I need a tiny oscillator circuit for testing an application. Now I haven't much experience in creating oscillators so I would like to use this Collpits-circuit: I only need the carrier wave so I ...
1 vote
1 answer
222 views

How to add a simple ESD protection to RDA5807M FM tuner antenna pin?

I am using an i2c controlled FM tuner IC (RDA5807M) in a DIY fm radio, but I am a little bit worried about ESD protection on the Antenna line (A headphone lead being used for this). Can i add standard ...
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1 answer
118 views

What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave-length long?

What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave long? I have been told that this the the basis of what is known as a wave guide &...
1 vote
3 answers
232 views

How would you combine DC power, bi-directional serial data, and an RF signal on a single 50-Ohm coax feedline?

I would like to power a remote device and communicate with it over some serial protocol on the far-end of a 50-Ohm coax feedline (RS232, i2c, SPI, etc), while at the same time sending/receiving an RF ...
2 votes
1 answer
128 views

L-C-L vs Pi network

I am playing with a simple high-pass phase shifter implemented as a Pi network in Sonnet Lite with a center of 146MHz and discovered something by accident that I would like to understand: By mistake, ...
1 vote
1 answer
519 views

Can I replace a 101 ceramic capacitor with a close value one?

I'm kind of new to electronics and sorry if this is a bad question. I am trying to repair my father's old radio transmitter and I noticed that the PTT won't pick up your voice. I opened it up and ...
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111 views

How to connect a 4:1 balun to a a log periodic antenna?

I'm following a plan for a home made LTE/4G UHF antenna here: https://www.thingiverse.com/thing:3221812 ...because it looks to be of a very similar to design to a very expensive 4G anntenna I know ...
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2 answers
136 views

How, exactly, does the 'input signal' wave(s) modify the carrier-wave of a radio signal? [closed]

I cannot find a simple (or really, not-so-simple) explanation of how mixing the high-frequency carrier wave with the lower-frequency input signal works... Is it entirely due to constructive and ...
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4 answers
433 views

Different antenna lengths for different frequencies?

I just want to understand a few things which I couldn't get clarity from a lot of websites searched through google as I could see differing information. My questions : How does a single FM antenna ...
3 votes
5 answers
1k views

Troubleshoot Crystal Radio

Alright, I'm totally confused. I have built the following circuit with absolutely no result, not even a click. Even after reading through several other similar questions on the board, I haven't ...
2 votes
1 answer
121 views

What to look for when selecting an RF detector diode

I'm currently diving into the topic of RF detectors and I ask myself which are the key criteria when choosing a diode for a given frequency range. I have a simple detector using a 1N916, which works ...
1 vote
1 answer
103 views

What causes 100Hz spuriour emissions on AD9850 WSPR transmitter?

I've built WSPR transmitter based on AD9850. AD9850 is driven by 125 MHz crystal. TX frequency is 14 Mhz. On the receive side there is upconverter (+125 MHZ crystal) and SDR (both RTL-SDR and AirSpy). ...
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2 answers
94 views

Understanding Dipole vs Commercially available antennas

I'm working on a project involving RF. I have a pretty good understanding of "HAM Radio" style RF engineering, but not at a professional level. I'm trying to find a commercially available dipole ...
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1 answer
135 views

What's a good ferrite material for broadband transformers in the UHF band?

I need a single hole tube shape, that I can use up around 500 MHz. I've not found anything beyond 300MHz on Magnetics Inc, Fair-Rite etc. I need a cylinder shape with single central hole, OD <7mm, ...
4 votes
3 answers
36k views

How do I estimate the transmission distance of a 50 watt 2m radio?

Can anyone point me to a reference for calculating (estimating) the transmission distance of a 50-watt, 2-meter radio? The transmitting antenna will probably be 5-7 meters above ground. Probably the ...
-1 votes
1 answer
81 views

Tech help with story: Will my radio signal be blocked by a mountain? [closed]

Hoping I can get some help with a technology question for my novel. My protagonist is being pursued, and they have put a tracker in his arm he cannot remove, lest it blow up and kill him. Pretty ...
0 votes
1 answer
119 views

Does a pcb as patch antenna isolate itself?

I'm currently working on a prototype patch antenna for UHF. Since I'm out of copper at the moment, I used empty PCB's as base material (don't mind the PCB in between, it's only a spacer): So now my ...
3 votes
0 answers
140 views

RFI protection for a stepper motor controller

I'm building a remote tuning device for a magnetic loop antenna. It will use a stepper motor to turn the shaft on the mag loop's variable capacitor. The electronics will consist primarily of a ...
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2 answers
1k views

JFET colpitts oscillator - very unstable

I've designed, simulated and build this simple JFET colpitts oscillator and I couldn't get it to work with real parts. I didn't have BF256B jfet model so I simulated it using some generic one. The ...
7 votes
3 answers
2k views

Why does the ionosphere reflect HF but allow VHF signals to penetrate through?

Wikipedia says: ... Unlike high frequencies (HF), the ionosphere does not usually reflect VHF waves (called skywave propagation) so transmissions are restricted to the local radio horizon less ...
5 votes
1 answer
376 views

BJT Clapp Oscilator for 3-6MHz

I designed a Clapp VFO to aid in my Ham Radio projects (Non-superhet SSB and CW recievers for 80M and hopefuly 40M). I chose the clapp topology for it's frequency stability. I want it to tune at least ...