Questions tagged [electronics]

Questions which involve the properties or applications of individual electronic components.

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4
votes
0answers
56 views

Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

If I'm building a vacuum tube HF transmitter (say, 40 m band), obviously the simplest mode to build is CW; it's common to key the oscillator input to the final (in order to keep the oscillator running ...
1
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0answers
56 views

Are jammers relate to electronics or electrotechnics , why? [closed]

Are jammers relate to electronics or electrotechnics , why ? Please ,tell me the main difference between electronics and electrotechins and why we can classify jammers as electrotechics or ...
7
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1answer
72 views

Double power-handling ability of RF amplifier output transformer

I want to base the output network for a 500W push-pull HF amplifier on "A 250W Broadband Linear Amplifier" described in Chapter 17 of the 2014 ARRL Handbook. I need advice on whether and/or how the 1:...
5
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6answers
231 views

Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka “antenna tuner”)?

I will soon need an antenna impedance match (aka "antenna tuner"), because I'll initially only have a single antenna for my HF rig (needs to cover 80m, 40m, 20m, 15m, and 10m). Obviously, in order to ...
1
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0answers
67 views

How can the output power of a Yaesu FT101E be increased?

I have a Yaesu FT101E which has low output because the final 6JS6C valves are old. If i increase the plate voltage on the final tubes from 600 to 800 VDC by changing the mains transformer tapping ...
1
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2answers
79 views

Is double amplitude modulation useful?

If i amplitude modulate an AM carrier with an audio signal, can i then feed that resultant AM waveform into another modulator and amplitude modulate the AM signal to give a signal which is amplitude ...
2
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1answer
42 views

Attenuator Cascaded Connection

PAT1220-C-10DB-T5 is a 10dB attenuator. (This chip is just an example, it could be any other component as well). Can I simply connect 3 of them in series in a PCB design to make my cheap 30dB ...
1
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3answers
209 views

How to reduce voltage ripple of a linear power supply?

I made a simple linear power supply for my transceiver using 12V 30A transformer, four diodes RHRP3060 forming a rectifier and three 30_000 µF capacitors connected in parallel. I also used a 200 Ω 50W ...
2
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1answer
56 views

Can an indoor antenna damage unshielded electronics?

I have a 25w radio running through a ~4.5db gain antenna. If I use a 4W HT indoors, I can hear a loud buzzing noise emmanating from my computer speakers. If I used the 25w mobile with the 4.5db gain ...
-1
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1answer
43 views

Skin effect for a modified antenna with a high frequency pulsed DC

A direct current will be interrupted by a high frequency switch. It seems , that in a wire, connected to the source (the antenna rod), instead of pushed back- and forwards electrons, the electrons get ...
4
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2answers
246 views

Share wide band antenna with multiple transceivers

I'm trying to incorporate several transceivers on my board design; I need WiFi (2.4 GHz) SatCom (~1.6 GHz) RF (~900 MHz) and GNSS (~1.5 GHz). I need to combine them into one antenna. I found a wide ...
7
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2answers
113 views

Water cooling a GS-35B in lieu of air cooling?

Does anyone know how to --or have any experience with-- water or oil-cooling the anode? Since forced-air cooling is required, the sound from the blower and the exhaust air would be too noisy for my ...
6
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1answer
567 views

How to determine number of turns for a 1:1 balun?

I would like to make a 1:1 balun with М1000НМ ferrite core (magnetic permeability - 1000) and 1 mm thick copper wire using triple bifilar winding. Unfortunately I didn't manage to find a clear ...
1
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2answers
312 views

Why does a Class-C non-linear power amp distort SSB but does not distort AM?

Can someone tell me why exactly a transistor non-linear power amplifier will amplify an AM signal without noticeable distortion, but will distort an SSB signal, giving the familiar scratchy sound ...
6
votes
2answers
518 views

Feed-through Capacitors

I'm in the "information gathering" phase of a RF Power Meter project and the design I fancy (W7ZOI Power Meter) calls for a feed-through capacitor at the output port. I understand that a feed-through ...
5
votes
2answers
110 views

Is there a best ratio of L to C in a resonant circuit?

When designing a resonant circuit, for example as a local oscillator, the product of $L$ and $C$ determine the resonant frequency according to $$f_{res} = \frac{1}{2\pi \sqrt{L C}}.$$ This means that ...
7
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0answers
94 views

UHF FM power amplifier design without expensive software

I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application ...
5
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0answers
107 views

Beyond Maximum Stable Gain of a transistor

I was plotting constant-gain circles on the Smith chart the other day for a potentially unstable RF transistor. I recently read on-line that for a potentially unstable transistor the maximum gain ...
5
votes
2answers
219 views

Learning RF electronics

I've been studying and building test circuit for actually several YEARS now, so far with no success. It sounds ridiculous but it's true. So I feel like I have a good understanding or RLC circuits, I ...
0
votes
1answer
51 views

Reflection Coefficient to Impedance transformation on the Smith Chart

A certain RF transistor has a source - reflection coefficient with a magnitude of .105 and a phase angle of 160°. When plotted on the Smith Chart, the normalized impedance is .825 +j .06 Ω. What is ...
1
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3answers
103 views

I just got this RF equipment but i don't know what's for

I got some RF equipment for free (it was going to the trash and I 'rescued' it). It's almost new, and seems expensive, but i don't know it's purpose. Googling the model numbers yields very little ...
2
votes
2answers
302 views

What's the difference between a Return Loss Bridge and a Circulator?

From my understanding a return loss bridge basically consists of three terminals: an RF input, a DUT output and a RF output which goes to say a spectrum analyzer; I understand that the RF input signal ...
3
votes
1answer
97 views

Series resonant circuit, how to calculate voltage across the capacitor?

This is question a3i3-1 from the practice questions in the book "amateur radio Exam Secrets": A series resonant circuit has 10V peak across it when at resonance. At that frequency the resistance of ...
2
votes
1answer
65 views

Inductors for Impedance Matching

I need to impedance match an IF mixer circuit to a 10.7MHz crystal filter. One of the inductors was calculated to be 44 $\mu$H. So I need a relatively large value inductance in a small package to fit ...
5
votes
2answers
172 views

What is Norton's transform?

This article from Itchen Valley Amateur Radio Club describes an interesting technique called "Norton's transform": This results in a negative capacitor, but in a circuit where there are other ...
1
vote
1answer
93 views

How does this Pixie circuit produce a beat frequency?

I have two Chinese Pixie kits that I've assembled. I think they are pretty interesting, from a QRP / tinkering stand-point. Looking at the schematic below, where is the beat frequency coming from? ...
3
votes
3answers
65 views

Conventional or electron current

I’m reading a radio theory book, Radio Theory Handbook by Ron Bertrand VK2DQ, which suggests that electron flow (ie current flowing from negative to positive) is used in radio theory and design. In ...
8
votes
3answers
476 views

Why are germanium diodes specified in amateur radio designs?

It's somewhat common to find a schematic that calls for a germanium diode in amateur radio contexts. For example: This is a QSK circuit from the Fldigi manual. And yet, purchasing a germanium diode ...
3
votes
2answers
313 views

Can anyone please suggest a substitute for the BFY51 transistor?

I have to replace a faulty BFY51 Transistor. I could not find one in the market since they have been discontinued. What is a suitable replacement?
1
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3answers
175 views

Easy way for an uncertified hiker to broadcast a distress signal

I am wondering whether shortwave can be used as an effective distress call for a hiker who is a non-ham operator. More specifically, Are non-certified operators permitted to broadcast distress calls ...
4
votes
2answers
152 views

Is using a DDS chip directly a viable way to transmit 2FSK and PSK on HF?

I'm thinking of building an HF transmitter for data (AX.25 or PSK31). Rather than using an IF stage, I'm thinking of generating the RF frequencies (or phases) directly with a Direct Digital Synthesis ...
3
votes
2answers
1k views

How to find or derive the maximum safe input power to a receiver?

A number of my RF devices have a specified safe maximum input power, for example: "The maximum RX power of HackRF One is -5 dBm. Exceeding -5 dBm can result in permanent damage!" source "If you look ...
3
votes
3answers
302 views

Why is coax loss logarithmic?

With DC hookup wire, losses are directly proportional to length. If the resistance of 100m of wire is 10 ohms then the resistance of 200m of wire will be 20 ohms. But we measure coax loss in decibels ...
1
vote
1answer
246 views

Old Yaesu FT-470 HT audio feedback with external speaker mic

I have a generic external speaker mic with the two-pin connection (1x 3.5mm, 1x 2.5mm mono jack), which doesn't work with my FT-470 (no real surprise, figured I'd just mod it.) I've started the mod, ...
1
vote
1answer
60 views

WIFI PACKETS AMPLITUDE AND DISTORTION [closed]

How is it that a computer receiving packets through wifi doesn't get those wifi packets distorted often? Wouldn't things like other radio waves interfere with the signal often? How does my computers ...
3
votes
2answers
176 views

In the context of the mixer in my radio, what does balanced and unbalanced mean?

I'm trying to understand how the mixer in a radio actually works, at a physics level. When looking at this article and studying the first schematic I realized I really don't understand what balanced ...
0
votes
2answers
618 views

what are the alternatives to LM387 and SA602AN?

I am building a 20 Mhz RF receiver out of the NASA radio JOVE instruction manual and they have recommended the use of LM387 as an audio amplifier. SA602AN as mixer IC:
2
votes
0answers
98 views

What protocol does the Vertex VX-2200/2100 use for programming?

I have seen a number of programming cable schematics on the internet, but I couldn't understand very much how they worked. From what I picked from all schematics, it appears the protocol uses the <...
5
votes
3answers
2k views

Good FM receiver single-chip IC for simple VHF receiver?

Is there an IC out there that implements all, or most all, of a simple FM receiver in the VHF range? I'm interested in doing some experiments with using DTMF over the air for tele-commands and the ...
2
votes
2answers
319 views

Adapting an antenna tuner for use with a panel meter instead of an LED

I'm building NorCal's / W6JJZ's BLT tuner (pdf) for use on 40m/20m with a 5W transmitter. I would like to remove the LED and use a small panel meter instead. I don't have a 1N34A at hand, but I do ...
3
votes
2answers
140 views

Building an IQ mixer using an in-phase LO splitter

There are many examples of IQ mixers on the internet; all use 90 degree hybrids to split the LO to the mixers with the outputs being combined in-phase. I'm curious, could both mixers be fed an in-...
4
votes
3answers
3k views

How should this SWR meter's directional coupler work?

I'm wrapping up a "home build" of the MFJ-941EK antenna tuner kit and having trouble getting the wattmeter calibrated. I can't use C4 to get the reflected power reading calibrated down to 0 as is ...
1
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0answers
78 views

Practical Resources for the Amateur Radio Student? [closed]

What electrical circuits can be easily build by someone with basic electrical engineering skills that exemplify the fundamental components of radios, antennas and so on?
3
votes
3answers
109 views

Switching 450 Ω window line

I have a very old Harvey Wells Z-Match antenna tuner (transmatch) with two outputs on the back for 450 Ω window line. One output is for “medium frequency” and works for 75 and 40 meters. The other ...
9
votes
3answers
2k views

Why does “high SWR” damage transmitters, instead of “impedance mismatch”?

In the audio realm, where cable lengths are insignificant compared to the signal wavelength, I would understand an impedance mismatch damaging an amplifier as follows: Take an audio amplifier that ...
1
vote
2answers
244 views

RF6886 high power amplifier maximum reverse power

I'm designing a circuit which uses the RF6886 amplifier IC. What is the maximum reverse power that the amplifier can sustain? At what reverse power will the amplifier die?
2
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1answer
189 views

Basic Signal Detector using MOSFETs

I am trying to design and build a basic signal detector using MOSFETs because they are more compact than resistors, capacitors, and inductors. I was wondering if anyone here has any suggestions on how ...
2
votes
1answer
503 views

Adding a panadapter via SDR

I've become very accustomed to the waterfall display on my SDR, especially for digital modes over HF. I'm thinking about tying into the IF on my IC-718 and connecting to an SDR to add a waterfall to ...
1
vote
0answers
40 views

Relay cross reference for 1925-3-2

My amateur radio uses 1925-3-2 relays on the low pass filter board to select bands. This relay is no longer available. Is there an alternative I can use? Or something?
1
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2answers
182 views

I need help identifying what I believe is a military radio

I'm hoping this question is okay to ask here. While this question is not strictly amateur radio related, I think this is the best community to ask. I'm looking for any information on this. ...