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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2answers
98 views

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

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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1answer
47 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, ...
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4answers
107 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 ...
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1answer
46 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 ...
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1answer
66 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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48 views

RIT design: math isn't adding up!

I am building a 7 MHz morse transceiver. It has a Hartley VFO and uses the capacitance of a reverse-biased diode to shift the frequency when transmitting. However, I'm struggling with this offset. ...
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243 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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2answers
57 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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1answer
47 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, ...
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62 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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1answer
75 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 ...
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1answer
93 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 ...
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1answer
406 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 ...
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66 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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1answer
265 views

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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1answer
195 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 ...
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2answers
799 views

Tube transmitter tuning

I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be. The diagram says ...
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3answers
84 views

Wire size question

I am trying to figure out AWG from a European/German schematic. The wire is listed as 0,3mm. (That's 0 (comma) 3mm.) I can find wire for sale in this diameter, but I need a reference to AWG. Is ...
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30 views

Using TWS-BS-6 and RWS-374-3 for analog audio transmission?

I'm really new to electronics and thought I'd build a simple walkie-talkie as a hobby and education project. A friend suggested I consider using the TWS-BS-6 and RWS-374-3 for the radio transmission ...
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2answers
308 views

3.5 MHz 2W AM vaccum tube transmitter [closed]

What do you think of my 80m band radio transmitter I designed? Originally I though about using an Armstrong oscillator, due to its simplicity and sine wavyness, but I heard that crystals are better, ...
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2answers
548 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 ...
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2answers
86 views

Wanting attic antenna for LF and HF receiving

I know next to nothing about antennas and am hoping someone can tell me what antenna I need to pick up ham radio and FM signals on an attic mount antenna. I will have no need to transmit. My attic ...
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1answer
116 views

Amateur radio practice exam question

The question is as follows: An interfering signal from a transmitter is found to have a frequency of 57 MHz (TV Channel 2 is 54 - 60 MHz). This signal could be the: And the options are as follows: ...
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2answers
77 views

Signal Strength to ADC quantisation levels

According to the excellent site of AB4OJ, the Icom 7300 in summary has a 14bit analogue to digital converter with a 1.5 volt peak to peak input (LTC2208-14). I make this to be 91.5uV per quantisation ...
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1answer
1k views

Amateur radio practice exam question about voltage drop

So the question is as follows: ...
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52 views

Why is it difficult to localize shortwave transmissions?

I have read that it is difficult to localize shortwave transmissions, but I don't understand why that is. I know that localizing the bounced transmission is obviously difficult, but when the antenna ...
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1answer
126 views

Purpose of L2,L3 & C6 in the following CW transmitter circuit

I have been trying really hard to understand the purpose of L2, L3 and C6 in this CW transmitter, especially L3 and C6. I have received many conflicting answers such as that L3 is acting as a ...
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1answer
364 views

Transmission Line open and short analysis

I have a transmission line with the following given parameters: Characteristic impedance at 50 ohms, phase as measured using VNA or PNA and frequency. (I can get S parameters as well) Other ...
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4answers
234 views

Can I combine a PLL and a DDS?

I need a controllable frequency for use in a radio transceiver with a range of 3–50MHz (i.e., 80m–6m). The frequency needs to be selectable using a microcontroller. Because chips like the Si5351 tend ...
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1answer
619 views

Coaxial cable for the DC-10GHZ range

I am trying to understand how to choose a coaxial cable (for my current application, I need a 50Ohm coaxial cable that works reasonably well in the DC-10GHZ range). According to the table in section "...
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53 views

Feeding an antenna with a YIG oscillator

Assume I have a YIG tuned oscillator (2-10GHZ), output power 10-20mW, and an ultra wideband antenna corresponding to this range. Is there a problem with feeding the antenna directly with the ...
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1answer
353 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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1answer
91 views

grid dip AN/PRM10: Is the normal operating distance so small?

I recently bought an AN/PRM-10 multifunction grid dip. After I replaced some electron tubes by new ones, most of the functions seem to work fine, but in the grid dip mode, I get no dip unless I place ...
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1answer
277 views

an/prm-10 grid dip question - how the voltage can be negative at the grid? [duplicate]

I am trying to repair a recently bought AN/PRM-10 grid dip. I have replaced some electron tubes by new ones and (almost?) everything seems to be OK regarding the voltages at the pins of the electron ...
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1answer
669 views

Antenna for qrp pixie 2 [closed]

I recently set up a qrp pixie 2 transceiver i purchased from Aliexpress.I want to use it for sending morse code,and listening to the shortwave transmissions.and i want to learn more about it.so i ...
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2answers
1k views

Determining Power in a VSWR Bridge

I have recently been trying to build an Arduino based VSWR bridge. The final goal is to make it feature rich but right now im having trouble calculating the forward and reverse voltage from the ADC ...
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1answer
375 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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1answer
249 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
428 views

What is the purpose of diodes after RF power amplifier and before LPF?

I am planning to build an RF transmitter using an integrated PA module (RA30H1317M1). While studying schematics of similar transceivers, for example IC-2200H (that also has a PA module) I see all ...
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3answers
765 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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1answer
134 views

Decreasing sensitivity of a touch paddle

I made a simple touch paddle using the circuit here. It is too sensitive and also triggers when my finger is only near one of the sides. How can I decrease sensitivity?
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2answers
593 views

Turn on transistor with output from sound card

I want to turn on a transistor by playing sound through my computer's soundcard. I thought that this simple circuit with a diode to rectify the AC, capacitor to smooth it out, and a transistor to ...
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1answer
350 views

Skew planar wheel antenna - is it circularly polarised or not?

'Skew planar wheel' antennas are popular for uhf. They are often described as circularly polarised, but I don't see how they would be. Are they instead just a mixed polarisation omnidirectional ...
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3answers
618 views

Frequency Synthesis from 1MHz to 800MHz

I've been trying to plan out a new project for a while. It's a wideband antenna anaylyzer for radio applications. I've figured out most of the details, but the most important part - the frequency ...
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3answers
4k views

Are there any open / unrestricted radio frequencies that are free for any use?

The only 'free radio frequency' that I could think of are the HAM radio bands. But they really aren't free, for they are regulated by laws that require you to hold a license, restrict what purpose you ...
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4answers
5k views

Can I only use a crystal earpiece for my crystal radio?

I am building a crystal radio for my science fair project, and I am having some issues. For my earpiece, I am using a telephone receiver which may be the issue. For my ground, I am using a water ...
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84 views

Dispersal of radio energy as it moves further away from the source

I apologise for the wording of my question, it will no doubt come across as confusing. If there is anything you are unsure about please feel free to ask me. Question As a radio wave moves further ...
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2answers
125 views

How might this RF double pole switch be constructed and perform?

So I'm aware that there are some high speed RF SPDT switches e.g. Single-Pole Double-Throw (SPDT) switch offering 20nS switching time. I'm interested in a switch like the following picture. This is ...
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3answers
449 views

Commnication between mobiles which are in range of 100 meters without using any mobile tower for free [duplicate]

Every mobile radiates its signal to its nearest tower during phone call.Then is it possible for two mobiles to communicate with out using any tower with in range of 100 meters or more .If it is ...
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1answer
304 views

How does this oscillator work?

I am trying to understand the following oscillator from a Cyclone 40 transceiver (http://www.4sqrp.com/cyclone.php). Here the the VFO (in the actual device, the inductor has a bolt through it to tune ...