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Questions tagged [diy]

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

3
votes
1answer
38 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
112 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
votes
3answers
97 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
vote
5answers
79 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 ...
1
vote
3answers
214 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
votes
1answer
82 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
votes
2answers
225 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 ...
3
votes
2answers
152 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
35 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 ...
4
votes
3answers
233 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
votes
2answers
200 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
vote
1answer
78 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 ...
0
votes
2answers
554 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
vote
2answers
169 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
383 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
votes
3answers
113 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
vote
2answers
153 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
174 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
2k 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
119 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?
4
votes
1answer
283 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
319 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 ...
4
votes
3answers
2k 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
vote
1answer
114 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 ...
6
votes
2answers
351 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 ...
2
votes
3answers
953 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
vote
3answers
1k 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
185 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
189 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 ...
4
votes
3answers
408 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
3answers
860 views

Recommended 9:1 unun core type(s)

I would like to construct a 9:1 unun that connects my QRP transceiver to a random-wire antenna. The transceiver's antenna connection is an unbalanced BNC jack and the random-wire antenna is, well, a ...
0
votes
1answer
115 views

Amateur Radio shack/antenna considerations during house construction

We are constructing a house on a tiny 30ft by 55ft plot and the construction uses cement bricks and the roof has embedded iron rods. The house has ground + 2 floors and the top floor mostly has two ...
0
votes
1answer
157 views

Kenwood TS-440SAT Change VFO Resolution?

When I turn the VFO on my Kenwood TS-440 it changes the frequency in 10Hz steps. One full rotation changes it by 1kHz. There is a modification (by cutting a diode lead) to change the frequency ...
2
votes
3answers
367 views

Connecting Wouxun KG-699E to computer sound card audio input/output

I have a Wouxun KG-699E and I am trying to connect it to audio connectors in a PC. Right now, I have connected it by this schematic (it uses Kenwood-type of headset connector) where instead of ...
0
votes
1answer
95 views

List of capturable data services (diy)

Looking for a list of capture-able data services. By browsing some sites I accidentally discovered that it is possible to receive NOAA satellite weather images with DIY receiver (link) or (here), ...
0
votes
1answer
139 views

CW paddle interface wiring problem

I have the MFJ-564B iambic paddle which I need to wire to the MFJ-552 CW interface. The paddle is stereo (dits/dahs) and the interface is mono (when connected to paddle, only gives DITS). How can I ...
1
vote
0answers
240 views

Activities for High School ham radio club [closed]

I just started an Amateur Radio Club at our High School (KE0FXH) Our school is not a technical school (it is an arts school) and I am trying to find activities to get students interested in ham radio ...
2
votes
2answers
266 views

What restrictions exist for non-HAMs in the 5.8 GHz band?

What restrictions exist for non-HAMs in the 5.8 GHz band in the USA? Context: these types of popular video transmitters (600 mW, 25 mW) commonly used for FPV piloting. Any requirements to have a HAM ...
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 (...
6
votes
1answer
576 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 ...
4
votes
1answer
147 views

Help with readings on schematic

I am in a Kenwood TK805D and a Kenwood TM241A to interface some of the hidden inner circuitry with the outside world so I can use the radios to do more than just talk on (ex. AllStar node, cross band ...
1
vote
1answer
187 views

Why are many FHSS / DSSS transcievers limited to 63 mW?

While researching a DIY digital video streaming solution for an outdoor quad-rotor project, I've noticed that a lot of the popular digital transceivers seem to be limited to 63mW transmit power: http:...
3
votes
2answers
647 views

Ideas for a simple VOX circuit for packet?

I want to build a simple circuit, preferably only a few transistors which simply activates when it hears a low level audio, and deactivates when the audio signal does not exist anymore. No pre-delay ...
4
votes
1answer
470 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 ...
2
votes
1answer
713 views

How to measure received signal strength, using DIY circuit

I use 2.4GHz receivers for flying my RC planes via FPV. So i can get best reception i use multiple antennas on multiple video receivers. I have a diversity controller that uses noise in the video ...
1
vote
1answer
71 views

How do I integrate XStream RF modules with any microcomputer (Rasp Pi, Beaglebone)?

I have selected XStream RF modules due to their price and their range (7 miles). I am part of a car team and hence need to transmit and receive data between the car and the ground station (follower);...
5
votes
1answer
777 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 ...
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 ...
7
votes
4answers
5k 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 ...