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12
votes
3answers
3k views

How can I add amplitude modulation to this transmitter?

I recently built this circuit, and could hear a nice full quieting signal on my short-wave radio with a 7.2 megahertz crystal for the 40 meter band. What is the simplest way I could Amplitude ...
12
votes
4answers
1k views

What is generally considered “too much” power for JT-65 on HF?

Recently, I have begun experimenting with JT-65A, mostly on 20 meters. I usually run about 5 watts with that mode, since I know that JT-65 is a weak-signal mode. Is that still too much power? What is ...
12
votes
1answer
16k views

What do “QRM” and “QSB” refer to?

An answer on Basic QSO format? mentions things like "QRM" and "QSB". What do those terms mean?
12
votes
1answer
2k views

How would a time-difference-of-arrival receiver with two antennas know which side the signal is from?

An easy TDOA design by Byonics was published with the following schematic: It appears that the antennas are switched at a rate of 640Hz, which allows a 640Hz tone to be heard in the radio when the ...
12
votes
2answers
996 views

Direction finding: How to find a stuck FM transmitter on 70cm?

There's a blank carrier on a 433 MHz FM voice frequency here. How should we go on about finding the transmitter's location? Practical procedure? Could be somewhere downtown.
12
votes
1answer
5k views

How is the IF for a superhet selected?

There seem to be almost as many choices for the intermediate frequency (IF) as there are superheterodyne receivers and transceivers out there. The ones I have come across are 455 kHz, 452 kHz, 1.6 MHz ...
12
votes
4answers
967 views

Amateur radio in an EOC?

Consider a small town's emergency operations center. While there are amateur radio operators involved, they primarily work for government or public safety, and there is no active ARES participation. ...
12
votes
3answers
3k views

Share antenna between receiver and transceiver?

I recently put up a fan dipole for 80/40/20/10. I'm looking for a way to share this antenna with a receive-only SDR and my shack transceiver. Obviously I can just switch this antenna between the two ...
12
votes
2answers
544 views

What are the (US) rules about unlicensed low-power transmissions?

It is common wisdom that transmissions of any sort (perhaps unidentified, encrypted, in the FM broadcast band, etc.) are permitted if they are sufficiently low power. Where are the FCC regulations ...
12
votes
3answers
6k views

Protect rig from static charge on antenna

How can I continuously discharge static from my end-fed antenna? My Electraft K2/100's autotuner (schematics) has an SWR bridge using two 1N5711 pin diodes. These diodes get blown if any static ...
12
votes
3answers
536 views

What is the role of digital data modes in emergency communications?

Emergency operations are typically reliant on voice traffic today. Are digital data modes used at all in emergency operations, and why/ why not? Couldn't data modes be used to pass information more ...
12
votes
2answers
3k views

How does one read a ferrite datasheet?

Datasheets for ferrite materials are usually filled with incomprehensible graphs with greek letters. For example, Fair-Rite's 73 material: What's a $\mu'_s$ and a $\mu''_s$? What do these numbers ...
12
votes
3answers
6k views

Where are the baluns for VHF and higher? How can one be made?

In another question, commenters recommended that I look into adding a 1:1 balun to a dual-band dipole to eliminate the feedline as a radiator. As I understand it, a 1:1 balun also functions as a choke,...
12
votes
2answers
502 views

Is there a KML or similar file that shows all of the CQ Zones?

I'm wanting to view the CQ Zones in Google Earth, and I understand that a KML file will allow me to do so. Is there a place where I can get a KML file that shows all of the CQ Zones?
11
votes
4answers
2k views

Is is possible to operate D-Star from a software-defined radio?

What is preventing a software-defined radio from transmitting the D-Star protocol?
11
votes
2answers
1k views

Why do Amateur Radio organizations in the United States oppose the relaxation of encryption prohibitions?

I saw this question stating that it is illegal to encrypt traffic, at least in the US and UK. I also heard that there was recently an attempt to get the FCC to loosen this restriction, but a lot of ...
11
votes
2answers
12k views

What's the pinout for “Kenwood” 2.5mm TRS/3.5 mm TRS connector?

I've seen many Chinese HTs (Baofeng, Puxing, Wouxun, QuanSheng etc.) using the so-called "Kenwood connector", which has a 2.5 mm TRS connector and a 3.5 mm TRS connector. It looks something like this: ...
11
votes
4answers
207 views

How do I increase my phone intelligibility?

Listening to various operators at different times, I've sometimes noticed, especially during contests, that some operators are easier to understand than others, and it doesn't all seem to be due to ...
11
votes
4answers
7k views

How To Join Packet Radio BBS

I'm a complete newbie here, and on the Southeast Coast of the USA. I don't even own a ham radio yet. Some preppers and I got to talking about a dystopian time of Internet collapse where shortwave ...
11
votes
4answers
1k views

Are antennas circuits?

For an antenna to work, doesn’t charge have to flow through it? A current must be present. To me it indicates it must be a circuit, but how is a dipole a circuit? If they are not circuits, then how ...
11
votes
2answers
670 views

What does a SSB frequency actually indicate?

An SSB signal is an AM signal with the carrier and other sideband filtered out, if I understand correctly. As such, when specifying an SSB frequency do you specify the carrier frequency, then state ...
11
votes
8answers
4k views

What is the best time of day/Band to make a contact with Hawaii from the East Coast?

I need to get Hawaii for Worked All States, and live on the East Coast (Virginia). Furthermore, I have a poor antenna, and thus only the prime times of the day seem to really be opened for me. What ...
11
votes
3answers
1k views

Why can't I hear myself from a second radio when bouncing off a repeater?

I am a relatively new ham, and haven't joined any club yet or participated in any nets. I have, however, hit a repeater just to know I can do it. I was told my sound was scratchy (no surprise there) ...
11
votes
3answers
397 views

Resort FM radio station

I stayed at a resort in the U.S. recently that is located in an unpopulated area with virtually no radio reception. To fill the gap, the resort has its own FM station that can be heard only within ...
11
votes
3answers
185 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 ...
11
votes
2answers
255 views

Why do satellites receive and transmit on different bands?

Most satellites I've found transmit on VHF and receive on UHF or vice versa. Why is this? I would think there's enough space on a single band.
11
votes
1answer
4k views

What do the three-letter modulation codes (emission designators) stand for?

I've seen these weird three-letter modulation codes like J3E, A3F, A1A, F3E and so on. Someone even wrote 2K40J3E or 12K5F3E. What do these codes stand for?
11
votes
6answers
378 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 ...
11
votes
2answers
570 views

Why is an exemption for music given to NASA broadcasts of manned space flight missions?

FCC 97.113 Prohibited transmissions reads: (e) No station shall retransmit programs or signals emanating from any type of radio station other than an amateur station, except propagation and ...
11
votes
2answers
359 views

What kind of antenna is that one?

Yesterday I saw the following antenna: I am very puzzled, at first glance it seems a simple dish but: The mesh is really wide (low frequency?). It is pointing to Zenith. I think that most dish ...
11
votes
2answers
4k views

Conductive boom vs non conductive boom: what's the difference on a Yagi?

I designed a Yagi antenna using 4nec2, assuming that I would use a non conductive boom. If I use an aluminum boom but I insulate the elements from the boom, can I keep the same design? How does it ...
11
votes
2answers
4k views

How do I renew my FCC amateur license?

I have a technician class license, and my license expires in March 2014. How do I renew my license? I received a notification in the mail from W5YI-VEC informing me that I could renew my license ...
11
votes
1answer
746 views

How can I participate on Echolink with my Android phone?

I want to use my Android mobile phone to send and receive over Echolink, like if I was using an amateur radio station. How can I do that? I'm a SWL and only plan to listen until I get my license, and ...
11
votes
2answers
314 views

What would propagation look like on Mars?

If we could get a few HF stations on Mars, what would the propagation look like? Thought shamelessly copied from this blog.
11
votes
4answers
2k views

Does iron ore in the ground affect my signal?

Mineral content in the ground varies from one place to another. I've visited places where the ground & waters were an orange-red shade from the high iron content; not good for trees either. This ...
10
votes
4answers
906 views

What is the highest US amateur license I can get in one sitting?

If I start with no current license, can I take all the exams in one sitting to get to Amateur Extra?
10
votes
5answers
527 views

How did hams manage to tune their antennas before VSWR meters?

In the early 20th century --back when the hobby was still new-- before VSWR meters and antenna analyzers were invented, how did radio operators know whether they were tuned for maximum power out? ...
10
votes
1answer
2k views

Why would you need a signal generator to receive early satellite transmissions?

I recently watched, on You Tube, a NOVA program about the British school masters and students who were the first to publish the news that the Soviets had started launching satellites from a new launch ...
10
votes
3answers
926 views

What does the spark-gap do in a spark-gap transmitter?

I read the Wikipedia article about spark-gap transmitters and I have to admit that I’m even more confused as to what the spark-gap actually did. The article references this simplified circuit ...
10
votes
1answer
1k views

Fastest Speed allowed for CW FM repeater ID in USA

What is the fastest legal WPM I can use for my repeater's Morse code identification? I am in the USA.
10
votes
1answer
9k views

What is a waterfall display?

High-end transceivers apparently come equipped with a water-fall display - something to do with improved spectrum visibility. This is supposed to lead to potentially higher QSO count and rate. What ...
10
votes
4answers
8k views

Is an antenna analyzer necessary for building antennas?

I'd like to try my hand at building a few antennas for VHF/UHF use. I'm going to be going approximately from established designs, but obviously the final result will require some tuning. I don't ...
10
votes
2answers
3k views

How to reduce RF in the shack when using vertical HF antenna (no radials)

What can be done to reduce RF in the shack (riding back along the coax) when using a vertical 10M antenna (without radials due to space constraints)? The antenna is an IMax-2000 at 32' elevation (20' ...
10
votes
1answer
260 views

What is Jamboree on the Air (JOTA)?

What does this term mean? I'm not good with radio terms at all, but I was especially curious about this one...
10
votes
2answers
577 views

Multiple simultaneous tunings with SDR

I just found out about WebSDR, and I was wondering how is it possible that many listeners listen and tune to different stations simultaneously. Which components/technologies allow this, and how does ...
10
votes
3answers
4k views

Why prefer LC oscillators rather than RC oscillators in RF design?

I don't recall ever seeing an RC oscillator driven RF transmitter or receiver. What prevents people from choosing RC oscillators in RF design?
10
votes
2answers
1k views

My neighbor is complaining about my transmissions, what can I do?

My neighbor has indicated that they can hear noise from their computer amplified speakers when I'm transmitting. We've done a few tests and it does appear that it's my transmitter that's causing the ...
10
votes
3answers
374 views

Does modulation affect propagation?

Does the modulation scheme, whether OOK, SSB, AM, FM, a digital mode, etc, affect the propagation of a signal?
10
votes
2answers
263 views

How do I find a frequency to call CQ on during a contest?

I know that in many contests, sitting on a frequency and calling CQ is a very effective strategy to rack up points. However, during very popular contests it can be very difficult to find an open ...
10
votes
1answer
143 views

Dominant speeds of Morse Communications

5 wpm is easy to learn and better than nothing in emergency. Speed Morse Coding is fine for "sport competition" I am trying to find out which is the typical speed for what I call "conversation" and ...

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