# Tag Info

16

No, your oven does not have a dangerous leak. It is designed to only contain only the frequency used by the magnetron (2.45 GHz). The frequency bands used by cell phones are very different. In particular, the door "seals" are rather frequency-selective. Instead of trying to maintain a good electrical contact between the door and the rest of the oven box, ...

9

I'm going to make an educated guess and say no. Here's my reasoning: Consider the difficulty in just communicating with a satellite. See What is a link budget, and how do I make one? or What gain do I need to talk to SO-50 with my HT? Geostationary orbit is much farther away than SO-50 and thus requires more gain, or more power. Now if we are using this ...

8

You can simulate. The idea is to model your RF channel(s) numerically by adding things like AWGN, multipath, clock skew, and so on. And, you want a way to model a lot of these channels, and twiddle the parameters and see how the system responds. There are many software libraries out there that will make this easier. I'd suggest GNU Radio. It has blocks that ...

8

I haven't built one of these myself, but one of the best resources I know of for the theory is antenna-theory. The second page mostly discusses gain. There it talks about optimizing the distance between the feed antenna and the dish, given a fixed pattern for the feed antenna, but basically the same thing applies to narrowing or widening the pattern of the ...

7

So, there's a bit of disappointment I'll have to spread here: Building microwave circuits like the one you need isn't per se as easy as just scaling up a circuit for, say 3 MHz or 100 MHz. Let's assume we start with CW and hence just need an oscillator (and a switch). So, let's do, say, a Colpitts, right? Well, sure, but the problem is that it's ...

7

I'm sorry if this answer doesn't answer your literal questions – it's just that these questions aren't strictly answerable. it is commonly known that electromagnetic radiation from an antenna is polarized; the electric field is parallel to the rod and the magnetic component is perpendicular to it. It is commonly known that antennas come in more shapes than ...

7

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 get it over a very small portion of the sphere (about 3% or less). When we talk about "omnidirectional" antennas, usually we mean that the antenna ...

6

Microwave technology isn't superior. That's why it's abandoned. Optical links are much faster. A single, inexpensive fiber optic cable easily delivers a bitrate of 1000 Mb/s, while a bundle of fibers designed for telecommunications can deliver over 10,000,000 Mb/s. For comparison, a modern high-speed microwave link like AirFiber manages a maximum of about ...

6

It might be a good idea to start by trying to make a block diagram of what you have inside of each of those controllers... Namely, the drone controller is most likely some sort of a system on a chip, which on its own chip, in addition to having a microcontroller also has the radio interface built in. Those are two separate things, but in one package. ...

6

A wire will pick up a GHz signal, as well as a ton of other RF signals, all mixed together. Some sort of filtering is required to separate out your desired radio signals. An Arduino has none of filtering required. Sampling a 2.4 GHz signal requires a sample rate above 5 billion samples per second. The A/D on an Arduino samples at a rate of about 9000 ...

5

After a long time pondering about this, I realized the trick. The first problem is that I had a version 3v of the router, and I installed the 3g version of the software. That doesn't work at all. I should have used the file bbhn-1.1.2-wrt54g-2.4-squashfs.bin instead of bbhn-1.1.2-wrt54g3g-2.4-squashfs.bin (For the latest, probably something different for the ...

5

Antenna efficiency over 130% would mean a perpetual motion machine, so probably not.

5

The sawbird H+ looks like a nice LNA, do you have the H+ H1 version? The plan version seems to be for 1542 MHz, "center frequency of the module is 1.542GHz with approximately 80MHz of bandwidth (-6dB rolloff). As such, it should be used for reception of frequencies between 1.50GHz-1.58GHz" but the H+ H1 has "65MHz bandpass region, centered ...

4

(Sorry about the long delay) An antenna that might meet your requirements is called the HB9CV. It's an array with two dipoles about 1/4 wave apart, driven with the correct current that they add in-phase in the forward direction, and completely out of phase in the backward direction. Getting the currents to do this isn't trivial, because they interact with ...

4

There was a conversation that I saw once about what it would take to bounce a signal off of the ISS, which is much closer and larger than GEO satellites. The area is approximately $400\,\mathrm{m}^2$, but varies significantly depending on the orientation of the arrays. That figure should be good enough for now. Let's assume a distance of between 400 and ...

4

Use a map and a compass. Really. It doesn't have to be more involved than that. As long as we are talking about line of sight propagation, that should be close enough to get you well within the ballpark unless this is about hugely directional antennas (as in, beam widths of perhaps 10° or narrower in the horizontal plane), and even if that's the case, it ...

4

The waves (to be correct: the signals) are exactly as suspectable to noise for both modulations! What's different is the receiver: As the name suggests, Amplitude Modulation (AM) works by taking the input (audio) signal, and using its strength, to modify the amplitude of your carrier wave. The AM receiver hence only has the amplitude of the received signal ...

4

Assuming the systems have no internal loss. Reflected power ratio for system 1 is 0.1, for system 2 is 0.01. $= \Gamma^2 = 10^{-RL/10}$ Power transmitted ratio for system 1 is 0.9, for system 2 is 0.99 $= 1-\Gamma^2$ The first reflection back from each system will be the largest and subsequent reflections will be heavily attenuated, so we approximate by ...

4

Troposcatter is the common mode for beyond line of sight on the 10 GHz ham band when the band is not otherwise open, good for 100's of miles. A radio with just a few watts output power and a moderate sized dish (60cm or more) gets enough ERP for troposcatter. For a few random references, check out: Pages 64-70 of http://www.mike-willis.com/Tutorial/RT%...

4

Aside from what Zeiss Ikon wrote, these high frequencies are indeed also interesting for communications technology, for very high-rate and typically narrow-range links. For example, in cellular mobile communications ("phones"), 5G specifies the "New Radio", which includes using several mmWave bands, the highest among them spanning 37 – 40 GHz. The ...

4

Some general hints from my experience: Use wires not printed metal. You could stop the print for a while to drop in the wires, then finish it, or push them in later. For sanity's sake, design your yagi to use identical directors, and make or buy a wire cutting machine to produce lots of wires of the same length. Plastic will have an effect on tuning - the ...

4

Lumped elements are theoretical constructs from the lumped element model. So you can't really build a filter from lumped elements at any frequency. But, you can ask at what frequency discrete components stop being approximated by the lumped element model. As a rule of thumb, anything that is physically bigger than 1/10th of a wavelength is definitely not ...

3

I'm no expert on sheet metal fabrication and hopefully someone will come along with a more confident one, but in general I would expect that soldering/brazing is the correct answer. (solder in reality would be hard to do, it running all over the place or being lumpy.) From what I have seen of soldering large metal parts (with a torch, not an iron), with ...

3

The biggest issue between stages is that wifi doesn't penetrate metal well. Engine bells and plumbing are generally metal, even if tanks and exterior airframe skin aren't. Since cables are highly reliable, it's worth having the weight to avoid dropouts when flight conditions add enough interference on top of the signal blockage to cut off your guidance at ...

3

You might be able to use this mechanical drawing, from the ARRL's monthly QST magazine for August 1974, to determine whether the available units are appropriate to your needs:

3

Some time as passed since the original posting and I suppose the student has lost interest in this problem. But for the sake of completeness, I offer the following. It must be said (as other commentators mentioned) that the problem as stated lacks sufficient information to give an exact result. Given more scattering parameters of each system, a conversion ...

3

For very narrow gauge, as in the sheet metal used for the waveguide in a microwave oven I think it's a process involving a roller disc inside the waveguide making spot welds at the closest interval possible and doing multiple passes until it's continuous. People reviewing TIG welders on YouTube routinely weld razor blades together. Any thin steel that's ...

3

Two datapoints that might help: A previous company we had a 20-6000 MHz diplexer with a changeover at about 900 MHz, using 0402 parts. Some trial and error to get it to match the simulated design. A current bandpass (highpass+lowpass) filter for 570-1050 MHz is made entirely from discrete parts, including hand-wound wire inductors instead of chip inductors....

2

Martin Ewing AA6E got it right in his comments on the question, which he hasn't posted as an answer yet himself so I'm copying here for the record: Can't verify the dimensions, but is it possible this is a diode detector? Maybe you can gently pull out the gold piece and find that it's the base of a 1N23 or similar. I'm guessing it's not really a connector, ...

2

A frequency of 100 GHz is equivalent to a 3 mm wavelength; these "millimeter waves" have been used for decades in airborne radars. The short wavelength allows a narrow beam and excellent gain from a dish that can fit inside the nose of a fighter aircraft, allowing a forward-looking radar with mechanical sweep to be used without disturbing the aerodynamics ...

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