15 votes

Moon->Earth 433MHz link achievable digital bandwidth

Short answer: Math says max link rate is 2Mb/s if you knew the perfect channel coding. Which is still an unsolved puzzle. Long answer: You're calculating a link rate. That is fine, and can be ...
Marcus Müller's user avatar
15 votes

Why are radio frequency ranges aligned on multiples of 3?

The ITU bands are actually delineated along plain powers of ten! They're just hiding a bit. From the description above a table of all the bands on Wikipedia: As a matter of convention, the ITU ...
natevw - AF7TB's user avatar
12 votes
Accepted

How does signal strength relate to bandwidth?

It depends on what you mean by "stronger". Ignoring actual limitations of your hardware and just considering the theory of communications, if you have 25 W of transmit power, then you can spread that ...
Kevin Reid AG6YO's user avatar
  • 24.5k
11 votes
Accepted

Why does the FCC put restrictions on symbol rates?

That's a good question---and one that is heavily under debate currently. The FCC originally limited symbol rates as a way of limiting bandwidth for data modes indirectly (it made sense at the time). ...
ruhnet's user avatar
  • 314
11 votes
Accepted

Do FCC regulations limit digital data rate?

The Current FCC Regulations (as of July 2018) Parts 97.305(c) and 97.307(f) regulate digital modes primarily by symbol rate. The table in 97.305(c) maps bands/frequencies to specific symbol rate ...
Glenn W9IQ's user avatar
  • 18.6k
10 votes

Is there a legal limit to the bandwidth of a signal used in the amateur bands?

Summary: In all cases, no more bandwidth than necessary. §97.307(a), (b) In data portions of LF, MF, and HF bands, 500 Hz. §97.3(c)(2) In the phone portions of LF, MF, and HF bands, no more than &...
Phil Frost - W8II's user avatar
9 votes
Accepted

How does a receiver know the exact frequency in the channel to "listen to"?

The signal is not at exactly one frequency. The only signal that exists exactly at one frequency is an unmodulated carrier, and such a signal contains no information. As soon as the carrier is ...
Phil Frost - W8II's user avatar
8 votes

Moon->Earth 433MHz link achievable digital bandwidth

Summary: Theoretical maximum in the neighborhood of 10s of megabits per second. Less than that in practice, perhaps a lot less depending on budget. Let's start with the Friis transmission equation: $...
Phil Frost - W8II's user avatar
8 votes
Accepted

Why do the ham radio bands get broader with increasing frequency?

There's more space at higher frequencies so the allocations can be bigger. Consider the difference between 15 MHz and 30 MHz, and the difference between 5,015 MHz and 5,030 MHz. It's a 15 MHz change ...
Phil Frost - W8II's user avatar
7 votes
Accepted

Key CW on zero crossings - zero bandwidth?

You raise an excellent question and your thought processes are indeed on the right track. First some background. An ideal, uninterrupted sinusoidal carrier has zero bandwidth. Real world factors such ...
Glenn W9IQ's user avatar
  • 18.6k
7 votes
Accepted

Sound quality in portable FM radio devices vs dedicated stations

Bandwidth: Broadcast FM stations are spaced 200 KHz apart, with the intention of allowing this kind of signal structure without interference: The FM broadcast bandwidth of just more than 50 KHz is ...
SDsolar's user avatar
  • 2,089
7 votes

Why do the ham radio bands get broader with increasing frequency?

There are some straightforward reasons I can think of which apply to all spectrum allocations, not just amateur radio: In a lot of cases, the bandwidth of a RF device is relative; if you are using ...
Kevin Reid AG6YO's user avatar
  • 24.5k
7 votes
Accepted

3 Band (80-40-20 Meter) Fan Dipole Tuning Question

Before getting to the questions you asked, an observation: the design doesn't appear to include a balun. Adding one is probably a good idea. Is there a way to flatten the SWR in this range [80m] or ...
Phil Frost - W8II's user avatar
6 votes

How does a receiver know the exact frequency in the channel to "listen to"?

It may be easier to think of the receiver as receiving all frequencies. The job of the receiver is not to tune to a single frequency. Its job is to filter out everything that's not at that frequency, ...
user3486184's user avatar
  • 1,902
6 votes
Accepted

What does antenna frequency range mean in practice?

It means the range of frequencies in which the antenna is designed to operate. Operated outside that range, the antenna may not meet its specifications. This particular antenna is a telescopic whip, a ...
Phil Frost - W8II's user avatar
6 votes

How do 'plumber's delight' type Yagi antennas have a bandwidth?

The elements of a Yagi are dipoles. If you look at a dipole at any instant, the voltage at one tip will be some value, and the voltage at the other tip has the same magnitude, but opposite polarity. ...
Phil Frost - W8II's user avatar
6 votes
Accepted

Why do PSK modes have "bandwidth"?

Binary PSK with instantaneous phase shifts would be equivalent to multiplying a sine wave (the carrier) with a square wave with values at 1 or -1. When two signals are multiplied, this forms a ...
Phil Frost - W8II's user avatar
5 votes

How does a receiver know the exact frequency in the channel to "listen to"?

The receiver "listens" to any and all signals in its receive bandwidth (talking about AM, CW, or sideband here, FM handles everything differently). Generally, there will be only one strong signal ...
Zeiss Ikon's user avatar
  • 4,097
5 votes
Accepted

If the data port on a Yaesu FT-7800R only communicates FM signals, why does the manual mention the port having a bit rate?

The data port does not carry FM signals: it carries demodulated audio. The radio performs FM demodulation and de-emphasis, and the output is heard on the speaker and is also present on the 1200 baud ...
Phil Frost - W8II's user avatar
5 votes

How to increase the bandwidth of half-wave dipole antenna?

Marcus and Richard have answered the question that you asked, how to triple the bandwidth of a dipole, with the correct answer that it can't be done. I suggest that you edit your question to give us ...
rclocher3's user avatar
  • 9,192
5 votes
Accepted

Gnuradio bandwidth of sink cause signal frequency changed?

Gnu Radio doesn't really know anything about frequency in cycles per second (Hz), only cycles per sample. The left of the chart is -0.5 cycles per sample, the middle is 0 cycles per sample, and the ...
Phil Frost - W8II's user avatar
4 votes

Metal for antenna construction?

The type and thickness (up to a point) of the metal plays a key role in the efficiency of the antenna. Efficiency is important because it is efficiency times directivity that determines the gain of ...
Glenn W9IQ's user avatar
  • 18.6k
4 votes
Accepted

Calculating bandwidth of antenna?

Assuming the antenna is in free space, you only need to know the length and diameter of the wire used to construct the dipole. The math is hairy but I wrote a program to do the calculations. Here is ...
Phil Frost - W8II's user avatar
4 votes

Key CW on zero crossings - zero bandwidth?

There is no way to transmit information in a signal with zero bandwidth. Switching the carrier at the zero crossings would reduce bandwidth but not take it to zero. There's a mathematical explanation ...
Phil Frost - W8II's user avatar
4 votes
Accepted

Maximum legal QRQ CW speed?

I have noticed that hams using CW, PSK31, RTTY, etc, use different equations to describe their bandwidth requirements. Over the years, I have used an equation which combines the "k" and the "baud" ...
Glen Ellis K4KKQ's user avatar
4 votes

NFM and FM compatibility

A wide FM transmission in a narrow FM receiver is effectively overmodulation: the excessive deviation of the transmitter results in the instantaneous frequency of the transmission deviating outside ...
Phil Frost - W8II's user avatar
4 votes

Power vs. Bandwidth

Unless there is a defect in the transmitting station, the transmitted bandwidth always stays the same when the power is increased. That is true even if the power is increased from 1 microwatt to 1 ...
Mike Waters's user avatar
  • 7,958
4 votes

How to increase the bandwidth of half-wave dipole antenna?

You might experiment with increasing the diameter of the conductors of the dipole to improve its SWR bandwidth, along with optimizing the physical lengths of those conductors (equally) to center the ...
Richard Fry's user avatar
  • 2,922
4 votes

How to increase the bandwidth of half-wave dipole antenna?

You can increase the bandwidth of a dipole by adding capacitive hats (you may have to shorten the dipole to maintain a given resonant frequency). Conical hats, hemispherical hats, or hats with a ...
hotpaw2's user avatar
  • 13.3k
4 votes

Why ferrite-core transformers are wideband while air-core are not?

"Why ferrite-core transformers are wideband while air-core are not?" Air-core "transformer" is composed of 2 inductors "TUNED" with a magnetic coupling slightly less than ...
Antonio51's user avatar
  • 161

Only top scored, non community-wiki answers of a minimum length are eligible