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5
votes
1answer
2k views

What is the difference between a scanner and a receiver?

What is the difference between a scanner and a receiver?
4
votes
3answers
5k views

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, ...
4
votes
1answer
204 views

How does a higher antenna reduce rain static on a lower antenna?

I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
4
votes
1answer
361 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
3
votes
2answers
407 views

How can I know over what distance or at what speed I can communicate? [closed]

Given some description of some parameters like: transmitter power frequency antenna location time of day how can I know over what distance communication is possible? Can I know the limits to these ...
3
votes
2answers
20k views

Can a Baofeng UV-5R+ be used on FRS, GMRS, and MURS?

Is this secure if I was talking to another Baofeng UV-5R+?
3
votes
1answer
619 views

Idea for better reception in crowded city

I am living in crowed area of a city. It is impossible for me to set up an antenna outside the apartment. I receive signal inside the room. I have a funcube dongle pro+ and some RTLSDR, the picture ...
3
votes
2answers
649 views

How to make a “you're getting warm/cold”/“fox hunting” game based on RF signals

I would like to build a system in which the emitter emits omnidirectional RF signals, and the receiver gets a stronger signal (it does not have to be accurate) with a) closer distance from the emitter ...
3
votes
3answers
2k views

Convert maidenhead grid square to lat/long in Excel?

I have a list of maidenhead grid squares in an Excel sheet that I want to convert to latitude and longitude. I want to keep it as simple as possible. Does anyone know of a formula to convert from ...
3
votes
5answers
3k views

Balun and tuner configuration for multiband dipole

I'm putting up a multiband dipole in some tall trees. (Perhaps it's more correct to call it a "dipole-doublet"). The situation I'm imagining looks like this: The legs of the antenna are each 100 ...
2
votes
2answers
2k views

How do you calculate the field strength at a given distance?

Given this question from the full license exam in the UK: What is the field strength at a distance of 7m from an antenna with an effective radiated power of 100W? in which the answer is: 10 V/m ...
2
votes
8answers
2k views

What kind of 2 meter antenna is this?

At first glance this appears to be a simple ground plane but there is far more going on. The ham who built this back in the '80s is now SK and I can't find anything else like this anywhere. The ...
24
votes
7answers
3k views

Encrypted traffic and amateur radio

Am I allowed to send encrypted traffic via any medium or any frequency, or is this completely barred (and thus everything has to be open with no exceptions?)
16
votes
5answers
3k views

Can a licensed ham use or modify CB equipment to work the 10 Meter Amateur bands?

Can a licensed ham use or modify CB equipment to work the 10 Meter Amateur bands? If so, are there any advantages/disadvantages to this?
16
votes
4answers
24k views

What bands and modes will give me voice at 3,000 miles?

I pursued Amateur Radio primarily for local emergency communications and as part of my electronics education. My only radio right now is an inexpensive 2m/70cm HT which is good for local weather ...
14
votes
12answers
15k views

How can I safely transmit without an antenna tuner or SWR meter?

Just what the title says. An Antenna Tuner, henceforth AT, is almost a de facto piece of equipment in a shack; working the bands without one is tantamount to leaping off the diving board into a ...
14
votes
3answers
2k views

WWV, WWVH, and WWVL may be shut down. Are there any alternatives?

The US government is proposing to shut down the NIST standard time and frequency stations WWV, WWVH, and WWVB in Colorado and Hawaii. If that actually happens, are there any free or inexpensive ...
12
votes
7answers
1k views

Can I transmit anything inside a Faraday cage?

Can I perform any transmission regardless of my license as long as I'm inside an RF sealed enclosure, such that no RF will be detectable from my transmissions off my property? I imagine the answer is ...
11
votes
3answers
196 views

What skills will I learn from contesting?

I got into Amateur Radio for emergency preparation and to allow me to expand my electronics hobby. My needs are being met, but I'm wondering if I'm missing out on increasing my skills by avoiding ...
10
votes
2answers
12k views

How does the baofeng radio eliminate squelch tail?

All tests are performed in Carrier Squelch mode on all radios without any sub-audible tone or digital squelch involved. Scenario 1: The Baofeng handheld radio Keys up. Another Baofeng is listening. ...
9
votes
1answer
621 views

Antenna tuning while receiving

I've built AA5TB's antenna coupler for a 5W 20m transceiver. Tuning was kind of difficult because my transceiver has buttons for sending a dot and a dash, but no tuning mode, so I couldn't have the ...
9
votes
2answers
642 views

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 ...
9
votes
3answers
769 views

What gain do I need to talk to SO-50 with my HT?

My HT has 5 W of power, a sensitivity of about 0.2 µV, and I would like to talk to the SO-50 with it. How much gain do I need in my antenna to make this work?
8
votes
3answers
764 views

What happens in a low loss feed-line with a high SWR

I was recently reading an interesting article from the ARRL to get a better understanding of the SWR. The following case is still unclear: A low loss feed-line with an impedance that doesn't match ...
7
votes
1answer
2k views

How to determine number of turns for a 1:1 balun?

I would like to make a 1:1 balun with М1000НМ ferrite core (magnetic permeability - 1000) and 1 mm thick copper wire using triple bifilar winding. Unfortunately I didn't manage to find a clear ...
7
votes
1answer
724 views

Coherent CW synchronization?

When using coherent CW, how is the receiver frequency and/or Morse Code dot clock synchronized to the transmission precisely enough to allow for synchronous decoding?
6
votes
2answers
1k views

Does a tube based HF transmitter need an antenna tuner?

With the adjustments on a transmitter such as a Yaesu FT-101E, is there any purpose for an antenna tuner, or can you accomplish the same thing by adjusting the loading and other controls?
6
votes
3answers
9k views

How do I power my radio in a vehicle mobile install?

I want to install a 30W mobile UHF radio in my car. I already have an antenna and mounting bracket - but how do I get power to this radio? It has an SAE bullet connector on the back - do I just need a ...
6
votes
3answers
754 views

Can an antenna be too powerful for certain receivers?

I'm brand new to shortwave radio and have been researching what kind of a receiver to get. I'll use it on the antenna I'll build (longwire, 50-100 feet) for shortwave listening; no transmitting. Right ...
6
votes
1answer
7k views

Noise bridge use in antenna construction?

How does a noise bridge work? And how can a noise bridge be useful in building, testing, and/or tuning an antenna?
5
votes
1answer
137 views

How to prevent cracking the capacitors in my diplexer?

Just made my first 2m/70cm diplexer. Important: I aim to be able to use this up to 50 Watts. S21 from the LP section: Having access to regular distributors such as Farnell/Element14, Mouser, Digikey,...
5
votes
2answers
1k views

Can antennas have reverse harmonics

I know antennas can have 1/4 wavelength, 1/8th etc. but if you are operating from UHF bands, can the antenna be lets say twice as long?
5
votes
2answers
7k views

Where year 2016 falls in the sun spot cycle for HF propagation?

Are we now at the good or bad portion of the 11 years cycle? What effect are we seeing now? How large (strong/deep) is the effect during the peak and bottom of cycle? What will change in coming years?
5
votes
2answers
2k views

How to find or derive the maximum safe input power to a receiver?

A number of my RF devices have a specified safe maximum input power, for example: "The maximum RX power of HackRF One is -5 dBm. Exceeding -5 dBm can result in permanent damage!" source "If you look ...
5
votes
3answers
7k views

What is the velocity factor of a wire?

This is Belden 9223. It is a 50-ohm coaxial cable, velocity factor 0.56 This is Belden 8524. It is a 22 AWG hookup wire. No velocity factor in the datasheet. Why does the coax datasheet have a ...
4
votes
1answer
374 views

Where exactly is the Morse code character “;” defined?

I've seen that quite often in Morse code tables (for example here), under punctuation, a semicolon ";"character is listed. However, the ITU-R M.1677-1 doesn't specify that character as a part of ...
4
votes
2answers
130 views

What is the impedance of an off-center fed resonant dipole?

Given a dipole approximately 0.48 wavelengths long, such that when fed in the center the feedpoint impedance has zero reactance, how does the complex impedance change as the feedpoint is moved away ...
4
votes
1answer
751 views

FM Receiver on GNU Radio with RTL-SDR fails to produce any output sound

Here is how the FM Receiver I made using the GNU Radio Companion. (Basically, I was following this tutorial by VYE6Y on youtube.) FM Receiver Problem: Unfortunately for me, the GNU Radio gives no ...
4
votes
1answer
488 views

Dipole Center Spacing

I have a question about dipole construction. I am working with a turnstile, but building dipoles to validate my system with linearly polarized transmission before moving on to circular. My design has ...
4
votes
1answer
73 views

Voltages in a beam antenna's passive elements?

This question has good answers for the voltages reached in portions of a dipole antenna during transmit. In a beam (Yagi or Yagi-Uda) antenna, do points along passive or parasitic elements (...
3
votes
2answers
402 views

Can two FM radios transmit two separate PL tones at the same time, and be received by two radios with matching PL tones?

Can two FM radios transmit two separate PL tones, and be received by two radios with matching PL tones? Or will the receivers hear a mix of the two, or nothing at all?
3
votes
2answers
135 views

Accounting for feedlines in noise temperature calculations

In writing an answer to "Use noise figure and gain to calculate weakest signal radio can receive?" I've managed to confuse myself. I believe this much is true: $$ T_\text{eq} =T_1 +{T_2 \over G_1} +{...
3
votes
1answer
320 views

Is it possible to make a shield that blocks time-varying electric fields, but not time-varying magnetic fields?

Take, for example, a shielded loop antenna. It is often claimed that the antenna is inside the shield, and the shield blocks electric fields from reaching the antenna, while allowing magnetic fields ...
3
votes
2answers
520 views

Are used PolyPhaser IS-50 RF surge protectors likely to work?

I'm looking at buying a used IS-50NX-C0: The listings usually say something like "Used, pulled from working equipment." While I'd believe they still work as far as normal operation is concerned, I ...
3
votes
2answers
598 views

Can left-hand and right-hand circular polarizations exist at the same time?

I read in a comment: it doesn't matter which circular polarization you choose, because they are both present, and the whole point here is to select one of them instead of receiving both and getting ...
3
votes
2answers
2k views

Longest achievable ground wave range on 40-meter bands [closed]

What is the longest possible range on the 40-meter band by ground wave? A reference said we can achieve 150 miles at 8 MHz with only a 100 watt transmitter. It also says on 160 meters, the ground ...
3
votes
2answers
924 views

What is Circular Polarization?

So I just learned that a satellite does not send out a circularly polarized signal, it just switches orientation slowly when it topples through space. I thought that because they were spinning, the ...
3
votes
2answers
189 views

How do blind hams operate?

In an earlier question, there seemed to be some surprise when I (indirectly) asked about radio modes accessible to a blind operator. First question: So how do blind hams operate? If I were to be ...
3
votes
3answers
1k views

What happens to a vertical Yagi when you mount it on a vertical metal pole?

How much difference does a metal pole make when it's sitting in the middle of all the lower elements of my beautiful new highly optimized to the max YO.EXE 10 m yagi ? I get it that the closeness of ...
2
votes
4answers
116 views

Which 10 m antenna will give the most rejection in one direction for received signals which are vertically polarized?

I want to null out a particular direction so that i can't receive some vertically polarized interference on 10 m coming from that direction. Which 10 m antenna will give the most rejection in one ...

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