Questions tagged [diy]
Questions dealing with handmade (Do It Yourself) radios and radio accessories.
17
questions
16
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2
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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 ...
- 50.8k
9
votes
6
answers
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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 ...
- 12k
19
votes
3
answers
6k
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SDR sampling bandwidth - do the bits per sample matter?
I'm looking at data converter chips for a homebrew SDR design, and I see that I can choose not just the sampling frequency, but also the bits per sample.
Obviously the sampling frequency has to be ...
- 12k
10
votes
2
answers
915
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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 ...
- 794
6
votes
3
answers
7k
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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 ...
- 7,092
4
votes
3
answers
6k
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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, ...
- 319
10
votes
1
answer
2k
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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 ...
- 12k
8
votes
2
answers
665
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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 ...
- 7,092
7
votes
7
answers
1k
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Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka "antenna tuner")?
I will soon need an antenna impedance match (aka "antenna tuner"), because I'll initially only have a single antenna for my HF rig (needs to cover 80m, 40m, 20m, 15m, and 10m). Obviously, in order to ...
- 3,967
6
votes
1
answer
918
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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 ...
- 165
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votes
2
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862
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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 ...
4
votes
2
answers
816
views
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 ...
- 153
4
votes
1
answer
401
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Will I get cleaner keying by keying the oscillator, or interrupting the amplifier B+?
One of my goals as a new ham is to homebrew my own transmitter (using vacuum tubes, aka valves). Initially I'll stick with CW for the transmitter, though over time I might build an AM modulator or ...
- 3,967
4
votes
2
answers
1k
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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 ...
- 12k
3
votes
3
answers
200
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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 ...
3
votes
5
answers
4k
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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 ...
- 51
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vote
3
answers
3k
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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 ...
- 111