Questions tagged [bandwidth]

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3
votes
2answers
123 views

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

I was wondering how the Radio interfaced with a TNC. I thought the computer sent digital data (in a serial format) to the data port on the radio, but from what I read online, it is not a data port. ...
18
votes
5answers
13k views

Why do folded dipoles have greater bandwidth than ordinary resonant dipoles?

This is something I've read in passing, but never encountered an explanation of why. For example, Wikipedia says: Another common place one can see dipoles is as antennas for the FM band; these are ...
1
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4answers
131 views

Determining one exact antenna length for a whole band (e.g. FM/AM broadcast, Bluetooth and others)

How does a single FM antenna length work in the entire FM frequency band range, when there are theories which state that the antenna size should always be close to wavelength/4 for proper reception &...
3
votes
3answers
86 views

NFM and FM compatibility

I read that using narrow band (NFM) when you should be using normal(FM)/wide-band(WFM) can result in the a reduced volume at the receiver. What happens in the opposite situation? (What if you are ...
8
votes
2answers
1k views

Do FCC regulations limit digital data rate?

Are there FCC regulations that specifically limit digital data rate on the amateur bands? Are there any recent or proposed changes? If so, what are they specifically?
1
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2answers
68 views

Power vs. Bandwidth

A 10 watt transmitter is transmitting a 700 hz tone in a 3 kHz wide band. If the power is increased to 1000 watts will that not increase the bandwidth if the data (700Hz tone) remains constant? What ...
3
votes
2answers
156 views

Maximum legal QRQ CW speed?

Computer generated and decoded Morse Code seems to be a not-uncommon operating practice in the HF bands. Given this, and that there's no reason why Morse/CW signals can't be synthesized and decoded ...
1
vote
3answers
362 views

Bandwidth, Q-factor, Radiation Eff calculations

Is it possible to give approximate answers about what an antenna is capable of? There are a lot of formulas out there, but every single one I found is based on actual measurement; input, output, SWR ...
7
votes
1answer
152 views

Why are radio frequency ranges aligned on multiples of 3?

Why are the radio bands organized by multiples of three? For example the HF band is from 3–30MHz and UHF is from 300–3000MHz. Why not multiples of 2? Or plain powers of ten?
10
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1answer
343 views

Why does the FCC put restrictions on symbol rates?

This answer claims that Mostly, on HF, the FCC has chosen to limit modes of transmission and symbol rates rather than bandwidth Why does the FCC limit symbol rates?
3
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1answer
96 views

Is it possible to receive weather satellites with a ham radio rig? (Icom 910)

I would be interested in receiving weather satellites (NOAA and Meteor) with my Icom 910. It has very good filters and could be a better solution than a simple SDR. However, its manual specifies that ...
1
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2answers
109 views
5
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4answers
2k views

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

I am reading about how radio communication works and I have an unanswered question. We have wideband channels with 25kHz of radio spectrum. The transmitter modulates a signal and sends it. The ...
5
votes
4answers
166 views

Do signals have to be more separated on higher frequencies?

Someone told me that 10 meters was the biggest band because you can fit the most channels in it. He said that in higher frequencies like 2 meter etc, you have to separate the signals more apart for ...
3
votes
1answer
1k views

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

I built a fan dipole according to the basic instructions in the SRI publication describing the theory and basic design. My questions is about next steps in tuning for the various bands. I am ...
7
votes
2answers
1k views

How does signal strength relate to bandwidth?

Let's say I have a 25 W transmitter. First I transmit some SSB signal with 2500 Hz bandwidth (no audio compressor is used, etc...). Then I transmit a BPSK31 signal with at most 100 Hz bandwidth using ...
8
votes
2answers
344 views

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

The ham radio frequency allocations tend to comprise a larger frequency range for increasing frequency (also see this plot). For example, the 40 meters band is from 7,0 to 7,2 MHz, thus 200 kHz, while ...
0
votes
1answer
75 views

What is the equation relating maximum data transfer rates for a given EM bandwidth

I was thinking, since visible light has a much higher EM frequency than radio wave light, its bandwidth also has a far higher max data transmission rate, so people have been researching how to use ...
0
votes
1answer
106 views

Ultrasonic FM receiver

I need a FM receiver that is capable of receiving ultrasonic audio frequencies above the standard wide band FM range of 15 KHz. I'd like something that can receive signals up to 60 kHz if possible: I'...
5
votes
1answer
491 views

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

While a normal voice channel is ~10kHz-15kHz in bandwidth, some digital modes can be significantly wider. Are there any legal restrictions on how much bandwidth I could use for amateur radio ...
11
votes
6answers
476 views

Key CW on zero crossings - zero bandwidth?

I remember being surprised to learn that a CW signal has a bandwidth (albeit small), but when I thought it over, it made sense. Essentially, we are modulating the carrier with a low frequency square ...
2
votes
1answer
102 views

Channel Bandwidth & Occupying Frequencies

I have started working on TDMA algorithms for SDR utilizing narrow band waveforms, and I have started reading about narrowband waveforms. But I am confused about the concepts of channel bandwidth and ...
3
votes
2answers
586 views

Sound quality in portable FM radio devices vs dedicated stations

When speaking to a portable radio transmitter the sounds usually gets distorted. However in radio stations that are dedicated to play music the sound is significantly better. First of all, why? And ...
2
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5answers
683 views

Metal for antenna construction?

What do I need to consider when choosing metal for an antenna? How do I determine what thickness to use?
1
vote
1answer
1k views

Do reflector and director widths (wire size) affect Quagi bandwidth?

A 2m Quad antenna made from 1/2" tubing will have a larger bandwidth than the same Quad built with 14 AWG wire. Would the respective bandwidths be maintained if both Quad loops were made into Quagis ...
1
vote
1answer
202 views

How to generate FM narrowband using varactors

I don't really understand how FM narrow band is created, and at the same time I can't figure out how using this simple circuit of varactors (varicap diodes) we narrow the bandwidth. simulate this ...
5
votes
1answer
496 views

Does the wire/conductor size of all the elements affect antenna bandwidth?

Does the wire diameter of the reflector and the directors of a beam antenna affect the bandwidth or is it only the driven element diameter that has this effect?
7
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2answers
1k views

Moon->Earth 433MHz link achievable digital bandwidth

Let's assume we have the following situation: Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz. Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
1
vote
1answer
92 views

overly large bandwith for a FSK signal?

I am trying to recover my 2FSK signal using an SDR. I have centered the SDR modem on the median frequency (the virtual carrier) and captured my signal via some 90 kHz bw modem. THis is the recording ...
2
votes
1answer
439 views

What are the FCC's bandwidth restrictions for the various amateur bands?

Does the FCC restrict how much bandwidth an amateur radio operator can transmit? I've seen restrictions for transmitting data, like packet and ATV, but, for example, could I legally use a huge ...
0
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1answer
51 views

What are the standard bandwidths used on the various amateur bands?

What are the standard bandwidths used on the various amateur bands? For example, FM on 2 meter generally uses about 3kHz, right?
4
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1answer
3k views

How many frequency channels are there in a frequency band?

I've often heard people saying that 4G uses the 1800 MHz band but precisely what all frequencies does it work upon? Does it mean that is just uses one frequency i.e. 1800 MHz, well in that case wouldn'...
5
votes
1answer
206 views

Receiving commercial / public-safety on a general-coverage HAM transceiver

I have an ICOM-7100 that I've installed in my mobile as my primary (nay, only) HAM transceiver; and I'm trying to avoid wasting a ton of space in my vehicle (not to mention money) for a proper scanner,...
3
votes
2answers
1k views

Is it possible to calculate the Q factor for an antenna type, given a frequency?

With only pen and paper, is it possible to calculate the ideal Q-factor for e.g. a dipole antenna, loop etc, given a frequency?
2
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3answers
5k views

Calculating bandwidth of antenna?

Is there a way to calculate bandwidth of an classical dipole antenna having this information: center frequency wire velocity wire diameter I would disregard antenna height, to simplify. I am not ...
12
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3answers
514 views

What are the relative bandwidths of the amateur bands?

While I was operating on 40 m for Field Day, I noticed a higher SWR than when I first set my antenna tuner for the band. This happened, of course, because I was in a different part of the band, but I ...
3
votes
1answer
134 views

What is the proper spacing away from a rare RTTY station?

How far away should I transmit from a rare DX station in RTTY? RTTY itself doesn't take that much bandwidth, but I've heard that I should be spaced 2-3 kHz away. Is that true? Thanks!
2
votes
1answer
148 views

ISM band bandwidth compared to other bands for theoretical WLAN use, performance?

As a purely theoretical question, what would it be like if wireless computer networking equipment was redesigned and allowed to operate at some other band than the unlicensed ISM band which is ...
8
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1answer
2k views

Is the bandwidth of an LCR resonant circuit independent of the capacitance?

Is the bandwidth of an LCR resonant circuit independent of the capacitance, if the inductance and its series resistance are kept the same, and the Q is high? This question and the calculation ...
4
votes
2answers
190 views

What does channel spacing look like in the time domain?

I'm trying to understand how radio works, and the concepts of AM/FM modulation are relatively clear to me. My next hurdle, however, is the following: How does differentiating between signals with ...
7
votes
2answers
145 views

Which band will I be authorized the most bandwidth?

Lets say I want to do a bit of experimenting with some high bandwidth uses for transmitting data, high quality voice, etc. Which Amateur band will give me the maximum bandwidth, and what is the ...