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14 votes

Why do we have to hand wind toroids?

I suspect the primary reason that the kit supplier does not ship the kit with prewound toroids is that there is insufficient volume to make it economical to have them commercially wound. A second ...
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12 votes
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What is homebrew?

Homebrew is (as the name suggests) when you make your equipment yourself, as opposed to buying it. An amateur setup consists of many components - the largest and most complicated of which are a radio ...
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9 votes
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Why do we have to hand wind toroids?

Some things are best answered in Song. I don't want to encourage you, but you might hum along to the tune of Eye Of The Tiger: It's the wind of the donut It's the thrill of the built Rising up ...
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9 votes
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Are QRP transceivers only meant for CW communication?

QRP only means low power, often 1W or less. While you could technically have a 1W SSB transceiver and call it QRP, the practical range of such a radio would be limited. It is much easier to hear a ...
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9 votes
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Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?

The results depend on the two bands you choose. Frequency ratios of 2:1 are a good choice because the longer dipole, which is a full wavelength at the higher frequency band, will show high impedance ...
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8 votes
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Why don't monolithic HF transceiver ICs exist?

Why aren't there monolithic HF ICs. There are, in the shape of actual (broadcast) AM receiver ICs, which can most likely with minimal effort be also used to transmit. However, are there technical ...
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7 votes
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1200 baud packet radio can't communicate

If you're used to dealing with protocols between chips, like UART, SPI and I2C, then APRS will feel quite strange. Whereas if you've been involved with CAN, Ethernet, USB at the low level, then APRS ...
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7 votes
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Does a paint-can dummy load have high voltage on the metal can? Would an insulated container be better?

Assuming you are using coaxial cable and connectors, the case of the dummy load is contiguous with the shield of the cable and the usually-metal case of your radio. So touching the dummy load is not ...
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7 votes

Water cooling a GS-35B in lieu of air cooling?

The GS-35A tube is the liquid cooled version of the same tube. Some hams have fabricated their own version of a liquid cooling jacket to replace the fins on the GS-35B: The designer of this jacket ...
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7 votes

Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?

What you describe is not far off from a common fan dipole. This is a multiband antenna consisting of several dipoles in parallel, each cut to a different length. Only instead of orienting each dipole ...
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7 votes

RF Bridge Problem - K6BEZ Antenna Analyzer

(See updated information further down) I found an article to address the problems all in one place in QST, September 2019. The author addresses the same problems in the question, and explains his ...
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7 votes
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Unknown kit from DK0TV

This kit is a FM receiver built in 1977 by DK0TV. The receiver works on a single fixed frequency 30.000 MHz FM and has a very good sensitivity. It is used with a 10 GHz Gunnplexer to listen to the 3 ...
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7 votes
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Can these in-band spurs from rpitx be eliminated somehow?

I can't dig up my source for this, but I'm pretty sure these spurs are just the result of rpitx using a fractional-N PLL (that isn't in any way optimized for phase noise) to generate a square wave. ...
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7 votes
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How to measure quartz crystal motional parameters using a VNA?

I don't know if this counts as "easy", but: Find the series resonant frequency. Multiply this frequency by $2\pi$ to convert it to an angular frequency, and call that $\omega_s$. Note the ...
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7 votes
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What type of omnidirectional antenna gives the most gain for a frequency of 2.4 GHz?

An antenna can't "amplify" a signal, it can only concentrate it in certain directions. If you want a peak gain of 15 dB (about 30x the power density of an isotropic radiator), you can only ...
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  • 8,730
6 votes
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Effect of paint / uv coating on velocity factor of PVC

No. Even if the electromagnetic material properties of the paint were drastically different than that of air, the few microns of coating won't be even measurable. (Unless that coating really is ...
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6 votes

Does a paint-can dummy load have high voltage on the metal can? Would an insulated container be better?

The metal exterior enclosure is an important component for a dummy load. The metal acts as a shield, containing any electromagnetic energy inside the can. Getting a shock is not an issue since the ...
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6 votes

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? If you are active in ...
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6 votes
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How can I determine/measure power rating of a DIY air capacitor?

Congratulations on your home brew project! It is great to see experimentation of this type. The two primary parameters for a capacitor are working voltage and ESR (effective series resistance), with ...
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  • 18.1k
6 votes

Will I get cleaner keying by keying the oscillator, or interrupting the amplifier B+?

Highest frequency stability is generally achieved when the oscillator is kept running while some following stage (or stages) is (are) keyed. However, the very high Q of a crystal-controlled oscillator ...
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  • 7,685
6 votes
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How to design constant impedance tracks on PCB?

Besides not knowing about the dimensions, substrate relative permittivity $e_r$ and backside ground yes/no my guess from the picture is that the transmission line is a microstrip line and not a ...
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  • 326
6 votes
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How to reduce VFO sensitivity to the hand capacitance?

As mentioned in the comment by henryflower, make sure that the shaft (and thus the frame) of the variable capacitor are grounded. You need to use rubber mounting grommets around the screws which bolt ...
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  • 3,321
5 votes
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Can I touch the ground of a PWR/SWR meter?

There's no problem with what you're proposing, usually. Most of your other equipment probably has exposed metal connected to “ground”. If it's not causing trouble, this won't either. But if you have ...
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  • 22.7k
5 votes
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AN762 Amplifier Transistors

The tests they are referring to are for amplification characteristics like linearity and stability, not continuous thermal dissipation. That said, unless you've constructed the thing in such a way ...
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  • 1,814
5 votes

MW AM reception improvements?

That's a lot of questions! Would there be any SNR advantage if each sideband was detected seperately? Would the correlation of the LSB and the USB be usefull because the noise in general is not ...
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5 votes

Antenna experimentation

The main risk is damaging the radio with a high SWR. You can buy a meter that will measure the SWR, or your radio may have such a meter built-in. Or you can take precautions like reducing the transmit ...
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5 votes

Are QRP transceivers only meant for CW communication?

A QRP transceiver is just a transceiver that operates on low power (usually less than 5 watts). If you look at the international Q Code, you will see that QRP simply means 'low power', and QRO means '...
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  • 4,281
5 votes

Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka "antenna tuner")?

...variable caps are ... no longer manufactured in the old "interleaved plates, air spaced" form, and the tiny plastic dielectric ones that are still available can't take much voltage (and are ...
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  • 7,685
5 votes

Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka "antenna tuner")?

Fair-Rite makes ferrite rods which would be suitable for HF applications. It should be possible to create or repurpose a screw-operated mechanism to move the rod into and out of a cylindrical coil. ...
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  • 7,685
5 votes

Why is my diplexer such a spectacular failure?

You have soldered a 68nH inductor instead of 100nH! Maybe the layout and the wiring also play a key role. Here's a vintage commercial one. It's quite compact. The size, inclusive of the coaxial ...
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