Questions tagged [diy]
Questions dealing with handmade (Do It Yourself) radios and radio accessories.
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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 ...
2
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0
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How can I key low voltage and still keep a tube VFO running constantly?
I'm interested in building a VFO based single tube CW transmitter.
These devices are known to have issues with frequency drift and chirp; frequency drift can apparently be mitigated by ensuring ...
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1
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Given that transmit "chirp" is mainly thermal related, what parts would need to be temperature regulated to limit chirp?
I'd like to build a Colpitts (or Hartley) oscillator based one-tube CW transmitter, and I'd like to use a VFO circuit rather than crystal control (in part because of the expense and limited ...
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1
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Need some help to design a DIY MW Radio receiver
AM Medium Wave Radio Receiver Design.
First of all, I am a hobbyist and stuff related to electronics are not very strange to me but the chapter of Radio and RF frequency , intermediate frequencies , ...
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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, ...
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4
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Wired RF connection without antenna
I’d like to build a radio system for use in underground caves. Wireless signals are nearly impossible to propagate in this environment, so I’d like to run long coaxial cable between each station. Are ...
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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 ...
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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 ...
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1
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Swapping crystal from HF to VHF in a QRP tranceiver
I am trying to build a short-range QRP weak signal VHF 2m CW transceiver. I found a small circuit that fit my needs, but it was made for use on 40m instead of my target frequency. The circuit included ...
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1
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2
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A question about chassis mount SMPS mounting
I have couple of chassis-mount 75 W, 15 V DC Mean Well switching power supplies (the PDF datasheet is here) and I need to mount them as in a shelf of a 19" rack frame.
I have no prior experience ...
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Why is my homebrew copper sulphate resistor behaving like a capacitor? [closed]
I brewed a CuSO4 resistor in a glass jar. I got the idea from here. This was done by creating a solution of Copper Sulphate in distilled water. The lid on the jar was provided with a BNC socket into ...
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3
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Serial Inductors in Tuned Circuit - Elenco AM780K AM Radio Kit
I'm trying to understand a component of an AM radio kit that I have. (There is a document available here: https://www.elenco.com/wp-content/uploads/2017/10/AM-780K_REV-K-2.pdf describing the build ...
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1
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Is there anything special about 4.9152 MHz intermediate frequency?
I noticed that there are several QRP transceivers that use 4.9152 MHz intermediate frequency. For instance, John Dillon, WA3RNC uses it in Penntek TR-25, TR-35 and TR-45 transceivers. Also a very ...
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How to build the best bang for yhe buck uhf vhf antenna or should i just buy one [closed]
Help with antenna build what makes up a great antenna what can I use for elements and would a dush network dish be good reflector and how to wire the elements like the copper to one side and the ...
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What simple methods are available to test a homebrew SSB transceiver on transmit?
Overview
Before putting my recently completed homebrew single conversion 20m mono-bander on the air, I borrowed another radio to listen to the transmission and make sure everything was OK. It turns ...
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How do I test if three turns are better than 4 turns?
I built a class ab amplifier kit to use with my qrp radio. 2 watts in creates 50+ out.
This was the pa 70 amplifier kit.
It is a kit with no instructions, but a whole suite of internet videos and ...
1
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1
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What is a diode for in a JFET-based audio mute circuit?
I've build the following audio mute circuit:
It works fine. However in many circuits I've seen people add an extra diode on the gate of Q1:
For instance, see "QRP Classics" page 120 / page ...
- 15.5k
2
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1
answer
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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 ...
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5
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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 ...
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14dB insertion loss for bandpass filter acceptable?
I'm busy with a direct conversion receiver for the 20m band, using a VXO and a 14.060 MHz crystal.
I designed a bandpass filter with the following components, using this design calculator.
Someone ...
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1
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915
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How do I wire an external mic and speaker to the Yaesu FT-250R without using their adapter?
I'm trying to wire up an external mic with PTT and a speaker to my Yaesu FT-250R to basically use as a VHF base station when I'm not mobile. Unfortunately, I can't find anywhere a description of how ...
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2
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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 ...
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3
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3
answers
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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 ...
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How to estimate input and output impedance of an amplifier?
I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in ...
CommunityBot
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1
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Looking for criticisms on my VNA-like SWR meter I am designing
I am in the process of building a SWR meter with VNA-like features. I'd be really interested to hear from fellow hams any input, suggestions, or tips they have regarding this before I go get it mass ...
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7
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1
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Simple circuit for acceptably clean CW in homebrew TX?
I'm working on a design for a home-brew 10 metre transmitter for CW. My oscillator is running cleanly, and I need to add a (small, probably 1/2 ~ 1 Watt) power stage to it, and I need to "...
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4
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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 ...
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5
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0
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What is an expected IF level of SA612?
I tried to use SA612 as a frequency mixer. Since it's a Gilbert cell, it has a high input impedance. Thus I added a pair of transformers as "Experimental Methods in RF Design" book suggests:
...
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3
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How to transmit computer audio to a wireless microphone receiver? [closed]
I'm currently trying to broadcast my computer's audio output to a wireless microphone system receiver so that I can accompany my school's coming presentation with music. The frequency range is 480-598 ...
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1
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DIY Triplexer for HF (low), 6m (med), and 2m/440 (high)
I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas ...
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3
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Motorola Microphones
Can a person use moto mic's on all their radios by rewiring the end plugs I have a few mic's and want to change the plugs to work on my Gn300's and Maxtracs and how to do this re Colors and positions ...
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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
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Unknown kit from DK0TV
When my father - who became a ham years after I did - passed away, I found an unstarted project (board + components), which I only re-discovered again years later.
The board is marked DK0TV-001, and ...
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Fractal antenna shapes that work for you? [closed]
I just answered this question, and I wanted to know if any particular shape has been found to be successful for anyone.
There seems to be a lot of research on IEEE that indicates that there should be ...
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2
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How to reduce VFO sensitivity to the hand capacitance?
I got a little tired of Si5351 and decided to build an analog CW transceiver. It's almost done and works pretty well. However, I discovered one problem. When I reach the VFO control with my hand the ...
2
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1
answer
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can i convert an FM coaxial antenna to just speaker wire?
I have a Sony MHC-GX450 compact mini stereo system. The connector for the FM antenna is coaxial, and is labeled 75 Ω. I'm wondering if somehow I can use speaker wire for the FM antenna.
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How to measure quartz crystal motional parameters using a VNA?
I want to measure quartz crystal motional parameters with a VNA. Unfortunately all Google searches I've done have lead me to nothing in concrete. I know how to get an impedance curve and measure the ...
2
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IF derived AGC: how to choose the best block diagram?
I've built several transceivers in the past. I never implemented IF derived AGC, so I decided to give it a try in the next project.
I choose to build a superheterodyne receiver, which will probably ...
4
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4
answers
369
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3D Printed yagi antenna
I'm trying to produce a Yagi antenna for the 2.45 GHz band using a 3D dual extruder printer. The idea is to print the antenna elements using a metal filament and encasing it all in plastic.
The ...
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2
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Is power output or something else to blame for my duplexer failing?
A Ham buddy of mine and I were trying to setup a UHF repeater in our area due to a lack of them. We had two Motorola CDMs, one a 1250 and one a 1550, and we purchased a $200 or so reject only duplexer ...
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What type of omnidirectional antenna gives the most gain for a frequency of 2.4 GHz?
I have a 2.4 GHz transceiver that outputs 4.5 DBm. I wish to amplify the signal using a 15.5 DBi antenna so that the signal reaches 20 DB, the maximum legal limit. Preferably, the antenna would be of ...
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Is the Boom Strictly Necessary in a Vertical Dipole?
I'm planning to build a vertical dipole for 4m and a club member pointed out that my design needs to allow for a boom that should be at least a 1/4 wave long. Why does a vertical dipole need a boom ...
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RF Bridge Problem - K6BEZ Antenna Analyzer
This question regards erroneous SWR measurements of K6BEZ antenna analyzer (links gone from Internet now) design from 2013 using Arduino and AD9850 DDS modules. There have been many variations of it ...
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What causes an AF amplifier to make popping sounds in a superheterodyne receiver?
Recently I've made a simple single IF superheterodyne SSB receiver for 40 meter band. The schematic is available here [PDF]. VFO and BFO are based on Si5351, the AF amplifier is LM386. It works OK but ...
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5
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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?
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Looking for origins of a crystal filter schematic used in uBITX
Here is a crystal filter used in uBITX transceiver:
I've never seen such a topology in any other transceiver and decided to invest some time in exploring it. Turned out it's quite interesting. Eight ...
3
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2
answers
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How do you calculate the number of turns for a common mode choke?
I want to build a common mode choke for my end-fed wire antenna, using turns of coax through an FT140 or FT240 ferrite. I can find various finished products for sale, but I want to make my own. I ...
- 7,864
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1
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How do I connect a homebrew antenna using RX-8 to a Yaesu FT-70DR (SMA)?
I made an 2m / 70cm tape measure antenna using RG-8 coax. That part was quite a bit of fun and went fine. But when I tried to connect the coax to my Yaesu FT-70DR, the copper core of the RG-8 was too ...
- 7,864
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1
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Simple AM Radio Troubleshooting
I just got all the parts to make a simple AM transmitter from Scitoys. I followed the instructions from different websites and they still don't work. I don't know why it's not working. On my ...
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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 ...
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