Questions tagged [diy]

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

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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
218 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
493 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
2k 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
121 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
190 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
406 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
105 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
174 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
266 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
289 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
683 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
148 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
189 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
828 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
536 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
789 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);...
6
votes
1answer
941 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
8k 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
251 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
117 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
950 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
251 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
92 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
279 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 ...
4
votes
4answers
297 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 ...
4
votes
1answer
100 views

Under what circumstance does non-toroid former lend itself to HF?

Many HF circuits posted in my copy of the ARRL manual (1972 edn - Yes, it's a vintage) appear to use a toroidal former with a coil. The same applies to HF circuits posted on the internet. From what I ...
3
votes
1answer
566 views

Kenwood TM-241A direct discriminator out

I am going to do a simple SIMPLEX all-star node, using the URIx USB radio interface, which I just got. I have a Kenwood TM-241A transceiver. I was told the speaker out jack is not sufficient: The ...
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 ...
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 ...
-2
votes
1answer
121 views

multiband mimo ad-hoc wireless connections from different spectrums [closed]

I'd like to create a multiband MIMO ad-hoc wireless network. Can I turn on every GPS, WIFI and Bluetooth radio of a mobile device and synchronize data transfers at extreme speeds between a small, ...
5
votes
2answers
6k 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
2answers
853 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. ...
10
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 ...
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 ...
12
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 ...
5
votes
3answers
258 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 ...
9
votes
5answers
25k 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 ...
4
votes
2answers
843 views

What impedance matching do I need between my 300Ω feedline and Softrock receiver?

I will be assembling a Softrock Ensemble II HF receiver, and I know I'm going to want it on air as soon as I build it, so I'm challenging myself to build an antenna for it first. The plan is to do a ...
7
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
2answers
618 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 ...
7
votes
1answer
332 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
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 ...
8
votes
3answers
4k 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 ...