Questions tagged [diy]

Questions dealing with handmade (Do It Yourself) radios and radio accessories.

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16
votes
3answers
3k views

SDR sampling bandwidth - do the bits per sample matter?

I'm looking at data converter chips for a homebrew SDR design, and I see that I can choose not just the sampling frequency, but also the bits per sample. Obviously the sampling frequency has to be ...
13
votes
1answer
3k views

Is it a good idea to build your own radio transceiver today? [closed]

With all the advances in the field of electronics, microcontrollers, etc., is it a good option today to build my own amateur radio transceiver (or transmitter/receiver)? Why might one choose to build ...
11
votes
3answers
3k views

How can I add amplitude modulation to this transmitter?

I recently built this circuit, and could hear a nice full quieting signal on my short-wave radio with a 7.2 megahertz crystal for the 40 meter band. What is the simplest way I could Amplitude ...
11
votes
2answers
3k views

How does one read a ferrite datasheet?

Datasheets for ferrite materials are usually filled with incomprehensible graphs with greek letters. For example, Fair-Rite's 73 material: What's a $\mu'_s$ and a $\mu''_s$? What do these numbers ...
10
votes
2answers
4k views

What is the expected microphone input voltage level of a handheld transceiver?

Ok, so I'm looking to inject some computer generated CW into a little handheld rig by wiring direct into the mic input line. What sort of voltage is expected on this input, are we talking uV, mV or ...
9
votes
2answers
334 views

Why do we have to hand wind toroids?

Many, if not most, ham radio kits (transceivers, tuners, ununs, baluns) require the builder to hand wind and tap their own toroids. (example) This is a considerable area of stress for newbie builders ...
9
votes
5answers
8k views

Home-brew 10 meter walkie talkies?

"When I was in high school, we had 8 hams at once. (Probably rare) 4 of us built little 10 meter walkie-talkies and had great fun using them on Field Day, hiking or around town. It was ...
9
votes
1answer
1k views

How do I design a round or square coaxial transmission line to have a specific impedance?

Certain Hex Beam antennas use a coaxial center support post to send the RF to each antenna section, which is superior, in terms of maintenance, to a post with screw terminals connected by short ...
9
votes
2answers
4k views

How can I calibrate a SWR meter?

I would like to build my own HF (1.8 - 30 MHz) SWR meter, however I'm not sure how I can calibrate the meter without an accurate power source. I'm targeting a power capacity of 150 W so I can use it ...
8
votes
5answers
23k views

Is there a simple, DIY, antenna suitable for HF receive only?

So the antenna I'm thinking about doing might be* way too large for my property. Is there another simple, cheap, DIY antenna I could try on my receiver? I know I'm going to want to hook it up and ...
8
votes
5answers
1k views

Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?

I haven't seen this done, (which, after more than a century of amateur and professional radio development, is probably a bad sign), but I had an idea the other day for simplifying the setup and feed ...
8
votes
1answer
93 views

Can two diodes be parallelled in RB to get double the capacitance?

It's a fact of life that air-gang capacitors, are increasingly more difficult to come by - having been superseded by the far more compact varactor diodes. My part of the world components such as the ...
8
votes
4answers
7k views

Building a portable event repeater

How does one go about building a portable repeater for use at events? Preferably at low cost, and with a minimum of bulky parts (so it's travel friendly). Obviously you'd need a pair of radios to ...
8
votes
3answers
2k views

Baofeng low power mod

I have a few baofeng UV5R handhelds sitting around that only transmit, the receiver is damaged. What I would like to do with these is build a foxhunt transmitter. Sure, I could set it to low power (...
7
votes
3answers
3k views

How do I extend broken coaxial cable?

I have a piece of 75 ohm coaxial cable of unknown type (outer diameter is around 7 mm) which has developed a breakage in the center conductor (which is stranded). This cable is an adapter cable which ...
7
votes
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
votes
2answers
595 views

1200 baud packet radio can't communicate

I'm toying with a simple 1200 baud packet radio I built. I'm attempting for it to be compatible with APRS, which uses the Bell 202 signaling, 1200Hz for mark and 2200Hz for space, which I assume map ...
6
votes
2answers
258 views

Why don't monolithic HF transceiver ICs exist?

HAM operators who build their own HF rigs typically do so using discrete components. However, for VHF and UHF rigs, an operator can make use of monolithic transceiver ICs on the market For example,...
6
votes
2answers
1k views

Dummy load construction and heat dissipation

I'm building my own dummy load, consisting of resistors submerged in liquid paraffin (or something similar, not 100% decided). I had some questions around heat dissipation and how I can calculate ...
6
votes
1answer
656 views

Video transmission between ATV and SSTV

I'd like to experiment with amateur video transmission in a setup halfway between ATV and SSTV. 480 lines of B&W image would be sufficient with 10 FPS, and I'm interested in both digital and ...
6
votes
2answers
278 views

Replacing hand-wound inductors with store-bought versions

I'm wading through some schematics for a direct conversion I-Q SDR receiver, and there is an L-C band-pass filter on the input. Each inductor is specified by an inductance, a toroidal core material, a ...
6
votes
2answers
3k views

RF Transceiver for walkie talkie use

I'm close to my EE. BSc finale and I'm looking to play around a little bit with the stuff I've learned. To be honest, I'm a little bit upset that after 4 years of learning communications theory, I'm ...
6
votes
1answer
524 views

Is bending the tips of the antenna wires going to affect the effective length?

I'm looking at designs for low cost DIY yagi antennas for a fox hunt, and pondering coat hanger wire and PVC piping. I'd like them to be built by the youth who will be doing the fox hunt, but that ...
6
votes
2answers
407 views

How to calculate if low-pass filtering is sufficient?

An answer on this question Suggested method for boosting 0.05 watt transmitter up to 10+ watts? suggests putting a filterless 19dB amplifier between the HackRF (or similar general-purpose SDR) and a ...
6
votes
1answer
317 views

Variable phase antenna

I'm thinking about phased antenna arrays, and am wondering if it's possible to have three fixed position antennas, and vary the length of their individual feedlines to the common point through ...
6
votes
3answers
440 views

LoRa radio transceiver for PtP mesh?

I am very new to general RF/radio in general other than basic WiFi, but I'm looking at the feasibility and cost of a long range (>200M between nodes, sometimes probably 500+M) in flat terrain, ...
5
votes
6answers
230 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 ...
5
votes
1answer
1k views

What is homebrew?

My question is the title itself: what is homebrew (or home brewing)? And how do homebrews differ from ordinary ham radios?
5
votes
3answers
167 views

How can I determine/measure power rating of a DIY air capacitor?

I've build an air capacitor like the one described in this article, although I used 1 mm thick single side copper boards (FR4) instead of solid copper sheets. I would like to use such capacitors in my ...
5
votes
2answers
5k views

How to construct a loop antenna for receiving HF?

I have a unused hula-hoop in my garage, and I ran some stranded speaker wire around it once, and attached one side of the wire to the coax shielding, and the other to the coax core wire. Is this the ...
5
votes
5answers
2k views

Simple DIY AM receiver for 25/28 MHz

I'd like to build a simple AM receiver for 25 and/or 28 MHz to receive DCF77-formatted time code. It doesn't have to be extremely sensitive or selective - the local clock oscillator will keep time ...
5
votes
3answers
2k views

What type of solder is best suited for radio and electronic use?

Many types of solder are available today, such as acid-core, silver, rosin-core and aluminum solder. What kind should I use for building antennas and radio equipment? Why? From test question: T7D08
5
votes
1answer
909 views

Can I touch the ground of a PWR/SWR meter?

I'm planning to build a 5W PWR/SWR meter very similar to this design by G3YMC, but with two meters: I'd like to put it in this metal box, and use the box as ground. However, the bottom of the box ...
5
votes
4answers
4k views

How to build a remote control unit that works on amateur radio frequencies?

The only remote control units I have used before was those little cheap 27Mhz puny range cheap units. I would like to build some sort of RC unit, which has a range up to 1km line of sight. I have a ...
5
votes
1answer
38 views

For air coax calculation, what is correct diameter metric vis-à-vis tube stock thickness?

I am interested in creating a square outer-conductor with round inner-conductor air coax post for a hex beam antenna. I found the extremely useful information at: How do I design a round or square ...
5
votes
3answers
257 views

What does a first-time operator need to know when looking for a DIY kit?

When I was growing up, I lived about three blocks from a Heathkit, and envied every device on the shelves. Now that I'm older, am teaching myself electronics and have a background in film and ...
5
votes
1answer
866 views

Are there easier ways to make traps than coax and plastic pipe?

I recently built an antenna for my attic inspired by http://degood.org/coaxtrap/. I found making the coax traps very time consuming and frustrating to tune. I got to thinking about 3D printers, and ...
4
votes
4answers
273 views

Are QRP transceivers only meant for CW communication?

I was just thinking about making a QRP transceiver, but are they only used for CW (Morse code) communication? If it is so, can I modify a QRP for two way audio communication?
4
votes
2answers
330 views

What should I put in a “Go box”, “Go bag”, or “go kit” for emergency communications?

If I wanted to build a mostly-portable-but-still-comprehensive kit to use in emergencies, either my own, or simulated ones through ARES or RACES, what should I put in the kit? I'd prefer responses to ...
4
votes
1answer
93 views

Will I get cleaner keying by keying the oscillator, or interrupting the amplifier B+?

One of my goals as a new ham is to homebrew my own transmitter (using vacuum tubes, aka valves). Initially I'll stick with CW for the transmitter, though over time I might build an AM modulator or ...
4
votes
2answers
101 views

How do homebuilders find an audience to distribute kits to?

Many (QRP) homebuilders offer their projects as kits. A popular series nowadays is the BITX. There are often mailing lists connected to those projects; I am a member of several. I'm wondering how ...
4
votes
3answers
138 views

Testing for 'Bad' Coax

I have a lot of 'donated' coax that has been given to me with unknown provenance. I'm wondering what things I can do that can determine whether I keep it or send to the tip? Some of the things I have ...
4
votes
3answers
465 views

Bridging LAN over ~1-2km distance

A friend of mine and I live across a lake from each other, and recently we thought it'd be fun to try and connect our computers together somehow across that distance. Running cable from either side ...
4
votes
4answers
3k views

Can I listen to hams on a standard AM/FM broadcast receiver?

I am very much out of practice with amateur radio (like many others), so to some, this question may seem obvious. I don't have any specialised amateur radio equipment, but I do have a Sanyo AM/FM ...
4
votes
1answer
154 views

What dielectric strength is required for a variable capacitors in a 100W T-network antenna tuner?

I would like to build a 100W T-network antenna tuner: I have a 12-pole wafer switch, 12.5 meters of enameled copper wire (d=1.5mm) and a pair of 12-365pF variable capacitors rated 200V DC (dielectric ...
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 ...
4
votes
1answer
525 views

Receive Data on Specific Frequency

So if I were to build a simple AM radio transmitter just using say, my Arduino, an oscillator, and wire for an antenna (this is all crude I know, but work with me here) and use it to transmit data ...
4
votes
2answers
1k views

What is an cheap and easy to build kit for a sw ssb transceiver? [closed]

I have a licence since I was 14 which is exactly half of my life, but honestly with the advent of the internet I somehow lost interest and sold my equipment. Now I really start to think, I should ...
4
votes
2answers
788 views

Low parts count CW HF receiver?

I'd like to be able to provide my kids with the opportunity to build something a little better than a passive crystal set, but still very, very simple in terms of individual electronic parts count. ...
4
votes
4answers
293 views

Should the capacitance or inductance be varied to achieve resonance?

A resonant circuit is typically composed of some resistance and reactance, the latter being provided by inductors and capacitors. The resonant frequency being calculated as the inverse square of their ...