Questions tagged [diy]

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

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7
votes
4answers
810 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, ...
7
votes
2answers
412 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
123 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 ...
3
votes
5answers
3k 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
303 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
1k 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
174 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 ...
2
votes
2answers
224 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 marketed,...
2
votes
1answer
400 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 ...
4
votes
3answers
4k 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
137 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
382 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
104 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
547 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 ...
6
votes
3answers
4k 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
140 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
votes
2answers
532 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
votes
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
vote
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
204 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
244 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
633 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
3k 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
133 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
249 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
475 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
116 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
202 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
290 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
312 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
765 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
152 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
197 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
1k 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 ...
5
votes
1answer
590 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
851 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
72 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);...
6
votes
1answer
1k 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
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 ...
9
votes
4answers
10k 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 ...
3
votes
2answers
1k views

Where does one find high-voltage variable capacitors and inductors for RF? [closed]

I'm looking to start building various antenna tuning circuits, but I'm limited by my parts inventory. I have pots and mag wire for winding inductors and a nice spectrum of fixed-value capacitors, but ...
3
votes
1answer
1k views

Simple FM low power UHF transmitter circuit

I want to build an low power transceiver on 33cm or 23cm (or 2 meters, but not recommended because of all the other activity interfering with my stuff) I would like to use FM and just have enough ...
3
votes
2answers
1k views

Will I harm batteries by only trickle charging them, or connecting them to a power supply?

I have some 12V, 12Ah Enercell batteries from RadioShack, RS part number 2301219. As far as I can tell these are AGM SLA batteries. I picked up this 3-stage charger from Harbor Freight and as far as ...
2
votes
2answers
267 views

Using square loop VHF antenna for two different stations/frequency?

I'm using a square loop antenna on the rooftop of approximately 15 square meter area. I use it to communicate with a group of mobile VHF radios using a station room. Right now I'm planning to build ...
4
votes
1answer
122 views

How can I establish a wireless link between my PC and TenTec 506 / chipKIT UNO32 using USB port?

I have a TenTec 506 HF transceiver that uses a Digilent chipKIT UNO32 microcontroller. My PC running Teraterm (serial connection) or the MPIDE monitor is connected to the microcontroller's mini B USB ...
3
votes
2answers
1k views

2m Homebrew Receiver - Chip for frequency [closed]

I am a new HAM trying to design a small, cheap 2m receiver. I've been looking up different circuits and homebrew tutorials, but the closest I seem to find to what I'm looking for seems to always use ...
1
vote
2answers
254 views

KN-Q7A - A good place to start? [closed]

I have decent circuit knowledge and would like to get into some homebrew operating, specifically voice. Would the KN-Q7A be a good place to start? If so can I just get the parts and do the circuit ...
1
vote
2answers
94 views

Where can I find HAM forum, newsgroup, etc? [closed]

Where can I find HAM forum, newsgroup, discussion, chat room, etc., either formal or light hearted, apart from this one?
6
votes
2answers
290 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 ...