Questions tagged [diy]
Questions dealing with handmade (Do It Yourself) radios and radio accessories.
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Is a loading coil antenna better than a whip for HF reception
I would like to know whether a loading coil antenna can be used for receiving HF signals, especially for the SW broadcast?
Usually, any HF resonant antenna would be too long but can a shorter whip ...
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Using a loading coil antenna for HF reception
I would like to know whether a loading coil antenna can be used for receiving HF signals, especially for the SW broadcast?
Usually, any HF resonant antenna would be too long but can a shorter whip ...
user29505
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62
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How does this simple (Class A?) MOSFET amplifier achieve linearity at 70% efficiency?
The KD1JV SSB/CW QRP Transceiver uses a IRF530A MOSFET as its final power amplifier stage, to produce 5 W at 70% efficiency:
The signal comes through the gate, and the IRF530A operates in common ...
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How can I keep a dummy load constant resistance when resistance changes by temperature?
A dummy load by definition converts the energy to heat. Since this raises the loads temperature, which raises the loads resistance, the load will not have a stable resistance. This makes it hard to ...
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Shortwave radio antenna
I came to know that there are shortwave antennas avoidable in the market (Sangean ANT-60) that uses only a single long wire winded inside a case that can be hung inside the room or near the window. ...
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How to test a simple homebrew CW transmitter - can I use an AM radio?
I've built a simple very low power (10-100mW) CW transmitter, and would like to test it over very short distances before working on my amplifier. (For background, please see A first homebrew design: ...
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What are the electrical properties and connectors of a CW key?
I'm working on a simple homebrew design and want to connect a CW key to it. (The basic design can use a simple built in pushbutton key, but I'd like to be able to purchase a proper key and use it as ...
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Budget Open Source and Open Hardware SDRs?
Recently, I've been playing with an RLT-SDR dongle and enjoying it. While I've designed plenty of PCBs and other electronics, I haven't had a chance to work with RF at all, so I wanted to design my ...
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Why do homebrew designs wrap toroids instead of using off the shelf inductors?
Why do homebrew designs wrap toroids instead of using off the shelf inductors?
Off the shelf inductors are easily available in a range of values, including uH and even some mH. And hand wrapping ...
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A first homebrew design: Band, antenna, and ground wave propagation
I'm working on a very simple homebrew transceiver and request review of our selected band, antenna, and power.
Background: A child got very interested in ham radio, as an incentive for to earn his ...
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How is the length of an inverted V affected by being too close to the ground?
In the near future, I'm planning to build an indoor inverted V dipole. However, I won't be able to raise the ends significantly above the floor. I understand that this will adversely affect ...
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How can i convert a modulated DSB-SC signal to a SSB-SC signal?
I am designing a simple transmitter using an SI5351A to generate the carrier, then modulating it with a diode ring modulator to generate a dsb-sc signal, then somehow converting it to ssb modulated ...
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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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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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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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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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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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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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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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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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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 ...
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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 ...
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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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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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145
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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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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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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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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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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 ...
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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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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 ...
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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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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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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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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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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 ...
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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 ...
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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 ...
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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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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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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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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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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 ...
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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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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 ...
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Can these in-band spurs from rpitx be eliminated somehow?
I'm putting together a 2m NBFM transmitter/receiver combo using rpitx and rtl-sdr. During testing my low-pass filter I discovered that rpitx is generating spurious signals within and around the band (...
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Why is my diplexer such a spectacular failure?
I'm trying to create a diplexer for the 2m and 70cm bands so that two antennas can share a feedline to my "shack". My radio is a Yaesu FT60 handheld, 5W max.
I have home made a j-pole for 2m, and a ...
user14945