Questions tagged [diy]

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

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1answer
60 views

Help understanding transmission loss of trivial circuit

I was trying to DIY a VHF/UHF diplexer, and got some weird readings from the VNA. By debugging I reached this trivial circuit: Which has the following frequency response: I'm trying to figure out ...
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2answers
53 views

How should i go about building my first transceiver?

So i want to build my very own transceiver, not looking for anything worldwide, just local but i do have a background in arduino and some electrical engineering, what tutorials would you recommend?
2
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3answers
74 views

Will a “crystal set” work with an untuned RF amp stage?

In my ongoing process of building up to a homebrewed general coverage receiver/transceiver, a first step might reasonably be a crystal set, where a tuned circuit and simple, or even improvised, ...
1
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1answer
84 views

Design/Build a DIY Audio Attenuator and Splitter

I’m trying to be less of an appliance operator. To that end, I recently came up with a simple project that I thought I could figure out and build entirely on my own. I was wrong. My goal was to ...
1
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1answer
28 views

Can the transmit and receive functions of a boat anchor transceiver share the tank circuit?

I'm starting design work on a two-tube (two-valve, for those who prefer that term) reflex-regen receiver that I hope will cover AM broadcast through 160m-10m -- both amateur bands and those "in ...
2
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0answers
74 views

Has this regeneration control been done?

I'm planning to build a two-tube reflexed RF regen receiver soon. I'm examining methods of controlling the regeneration — it needs to be possible to both initiate and halt oscillation in all bands (I ...
3
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3answers
127 views

Why have knife switch storm grounds for antennas vanished?

Long ago, it was fairly standard to provide lightning protection for outdoor radio antennas by installing a large double-throw knife switch -- antenna leads to the center, radio on one side, ground on ...
1
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0answers
52 views

Microwave kiln for glass [closed]

I am building a 1000W microwave kiln for glass jewelry. The internal capacity needs to be around 5 litres. What internal dimensions of the cavity should I avoid, or strive for, to ensure even heating....
2
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1answer
63 views

Frequency Display for Old Tube Radio

I have a Hallicrafters S-120 1960s vintage vacuum tube receiver (an "All American Five" superhet with solid state rectifier replacing one of the "five" tubes). It works well, doesn't have excessive ...
9
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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 ...
1
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2answers
67 views

Will close-loop metal hangers affect antenna radiation?

I'm working on a kite-supported antenna for an 80m QRP rig -- to be flown at beaches, on mountaintops, and possibly other places where I want to work HF but don't want to lug poles or give up ...
6
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6answers
295 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
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4answers
324 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?
1
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2answers
133 views

How to convert a crystal controlled tranceiver to VFO (aka Unbinding from the Rock)?

If you look at the circuit diagram for a Colpitts crystal oscillator, it's pretty simple -- a crystal, load resistor, and capacitive voltage divider, with the positive supply feeding the control ...
5
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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?
2
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4answers
342 views

What is a simple kind of amateur radio transceiver I could try to build, as a beginner?

I am new to amateur radio, and I'm trying to learn the basics of the hobby. I would like to build a simple radio transceiver from scratch (i.e. not from a kit). I have searched the Internet for ...
4
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1answer
161 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
1answer
108 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
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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 ...
7
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2answers
126 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 ...
3
votes
1answer
266 views

Air Coil AM & Shortwave Crystal Radio Using 1/4" Copper Tubing

Looking to build a crystal radio, need help with the coil. I'm looking to get something to work with 1/4" thin wall copper tubing. Already have some nice diodes and whatever capacitors/resistors I ...
5
votes
3answers
183 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 ...
4
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3answers
153 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 ...
1
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5answers
174 views

Are cold temperatures harmful for ham radio equipment?

I'm getting ready to build an HF / CW kit and just finished setting up a workbench in my garage. While I was wrapping up, I started wondering if the cold temperatures this winter might be harmful to ...
2
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4answers
458 views

Amateur Radio Long Distance Data Communication

My friends and I are going off to college ~180 miles/290 kilometres apart. As a project, we are looking into creating a data communication connection between our two schools. Our requirements would be:...
0
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1answer
91 views

Ultrasonic FM receiver

I need a FM receiver that is capable of receiving ultrasonic audio frequencies above the standard wide band FM range of 15 KHz. I'd like something that can receive signals up to 60 kHz if possible: I'...
9
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2answers
371 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 ...
5
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2answers
398 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 ...
5
votes
1answer
41 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 ...
7
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3answers
491 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, ...
6
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2answers
292 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,...
1
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1answer
113 views

Parts for a 915 MHz low power transmitter

I'm interested in doing some experimentation with custom modulation in the 915 ISM band. Off-the-shelf radio modules use specific known modulations (FSK, QAM, etc.) so those won't work for my ...
1
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3answers
2k views

Slot antenna for 2 meter mobile

My primary vehicle is a Smart car, with a roof that's a piece of plastic(100% moon roof). Not the most awesome of cars to use for grounds. I'm building a bumper mounted antenna tower, EMT with some ...
1
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2answers
244 views

What is the optimal antenna for a high altitude weather balloon?

I was thinking of creating a 2.4 GHz WiFi wireless link with a directional, circular polarized antenna but I am not sure if that would work for such a long distance. The antenna cant weigh more than 1 ...
2
votes
1answer
739 views

What parts / procedure do I need to build a UHF receiver that can connect to a standard pair of headphones

I have a low power wireless microphone (10 - 50 mW) with a large receiver designed to connect to a mixer/sound system. The mic transmits in the UHF band between 530 and 860 depending on the band (see ...
2
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3answers
130 views

Does a paint-can dummy load have high voltage on the metal can? Would an insulated container be better?

I've seen many plans for 50 Ohm dummy loads in paint cans, such as the one here: https://www.nonstopsystems.com/radio/frank_radio_antenna_dummy.htm. I've already assembled a functional dummy load, but ...
1
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2answers
196 views

Section 15.23 “Home-built devices” No license required… to build? Just to Transmit. But…?

Title 47 › Chapter I › Subchapter A › Part 15 › Subpart A › Section 15.23 Home-built devices §15.23 Home-built devices. (a) Equipment authorization is not required for devices that are not ...
2
votes
1answer
262 views

Effect of paint / uv coating on velocity factor of PVC

I own an Ed Fong TBJ-1 antenna, which is like a twin-lead J-Pole with a coax stub and some inductors added. It's enclosed in an unfinished PVC pipe. I'm tempted to paint the PVC with non-conductive ...
2
votes
2answers
3k views

Antenna tuner design

In a related question about a broadband antenna for SDR it was suggested me to build or buy an antenna tuner. Since maybe it was not clear to everybody, I'm designing an antenna tuner for reception, ...
2
votes
2answers
127 views

Antenna experimentation

I want to make a DIY antenna for my Kenwood TH-F6A. Is there any danger of damaging the radio (i.e. by trying an antenna that is unsuitable), or is it safe to experiment?
3
votes
1answer
336 views

Building a headset for a Yaesu FT-270r

I'm trying to build a headset for my Yaesu FT-270r, which replaced a FT-250r. I had a working setup with the FT-250r. An electret microphone element connected to the MIC/PTT pin of the four-way ...
2
votes
1answer
101 views

MW AM reception improvements?

Most AM receivers use Envelope detection. Historically this was simple. PLL-based systems are slightly better at low carrier-to-noise levels. Would there be any SNR advantage if each sideband was ...
1
vote
1answer
394 views

Best way to make a selfmade Long-Range WiFi Link

What needs to be considered? Which type of antenna(only self-made or reused parts, for example satellite dish) is the best for a long range, high throughput WiFi? How to calculate Antenna size and ...
5
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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1answer
121 views

Frequency divider in premix oscillator (PMO)

In his book "Crystal Sets to Sideband", Frank Harris K0IYE describes using premix oscillators (PMOs) to convert signal from low-frequency LO to a particular ham band. Many ham bands are harmonically ...
7
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2answers
425 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 ...
3
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3answers
1k views

Would retrofitting an external antenna to a smartphone be feasible?

I'm not sure if this is the proper StackExchange site, but you guys know RF and I don't know who else would know better. I take the commuter rail to work every day. I have 60-70% cell phone coverage. ...
1
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3answers
2k views

Can I build a mini passive repeater to improve my WIFI reception at home?

The problem There's a concrete wall between my computer and my router (Linksys E900) which affects my WIFI reception pretty harshly, computer receives signal is at -65 dBm, at this rate i get around ...
2
votes
1answer
191 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
215 views

AN762 Amplifier Transistors

According to the MRF421 or MRF454 transistor datasheets, used in the AN762 HF amplifiers say that the transistors are "100% tested for load mismatch at all phase angles with 30:1 VSWR". Further, in ...