Walter Underwood K6WRU
  • Member for 8 years, 3 months
  • Last seen more than a month ago
How do I report an emergency using ham radio?
Accepted answer
36 votes

On voice, use "Mayday Mayday Mayday" at the beginning and end of the transmission. This is only for life-threatening emergencies. http://en.wikipedia.org/wiki/Mayday_(distress_signal) For ...

View answer
Calculating Antenna Length on the FCC Exam vs. in Reality
Accepted answer
18 votes

The $492/f$ formula is for an ideal antenna in free space, the $468/f$ is an estimate for real antennas at a reasonable height over ground. The $492/f$ formula is a conversion from metric units to ...

View answer
What is Jamboree on the Air (JOTA)?
13 votes

The Jamboree-on-the-Air, or JOTA, is an annual Scouting event that uses amateur radio to link Scouts around the world. Held on the third full weekend of October each year since 1958, this worldwide ...

View answer
What is the purpose of a balun and a unun in a feed line?
Accepted answer
10 votes

A balun matches a balanced load to an unbalanced line, but it can also do other useful things. A current balun can present a high impedance to common-mode signals, which will help reject noise. Common ...

View answer
Using a balun with a resonant dipole
9 votes

Another answer mentions the paper by K9YC, Jim Brown. This is the best reference on baluns in amateur radio. See: http://audiosystemsgroup.com/RFI-Ham.pdf Chapter 6 is about baluns and antennas. He ...

View answer
Why do concurrent FM signals not mix together?
9 votes

This is called the "FM capture effect" and is mostly a characteristic of the demodulator design. Demodulators with a strong capture effect detect the zero crossings of the signal. The zero crossings ...

View answer
PL tone removal?
Accepted answer
8 votes

I would expect some low-frequency roll-off in the amp and the speaker. You could check by putting headphones on the speaker output. Wikipedia says that a 300 Hz cutoff high-pass filter is common. ...

View answer
Can I have multiple inverted-vee antenna fed by a single coax?
Accepted answer
8 votes

Yes, this works fine. It is often called a "fan dipole". There are separate resonant dipoles for each band, all fed from a common point. The wires should be separated by a foot or more. If you have ...

View answer
How can one convert from Lat/Long to Grid Square?
8 votes

If you'd like to do it yourself, you can use this Python program I wrote. # -*- coding: utf-8 -*- import sys # Convert latitude and longitude to Maidenhead grid locators. # # Arguments are in ...

View answer
Pros/cons of the PL259/SO239 connector (M type)?
8 votes

UHF connectors are cheap and easy to install. In all other respects, they are inferior to more modern designs like BNC or N connectors. The major uses of UHF connectors are amateur and CB equipment in ...

View answer
What is the largest gauge (thinnest diametre) wire I may use as an antenna?
5 votes

The "rule of thumb" for keeping the skin effect at bay is to use conductors that have a diameter greater the twice 3-5 skin depths. Twice the depth because if you can envision the wire having RF ...

View answer
How is a "Generally Inactive" ham determined for Field Day GOTA?
Accepted answer
5 votes

For the 2013 Field Day rules, this is answered in the FAQ in the information packet. Emphasis is in the original document. Q. What is considered a generally inactive licensee? A. The GOTA ...

View answer
Basic QSO format?
5 votes

The IARU has adopted a document titled "Ethics and Operating Procedures for the Radio Amateur". This is an excellent guide to the basics of on-air behavior and the fine points of polite DX'ing. You ...

View answer
Is there any downside to consolidating on BNC connectors for HF?
4 votes

I avoid UHF connectors as much as possible. My shack is all Type N outdoors (weatherproof) and all BNC indoors. UHF connectors work fine for HF and even above that. But I hate connectors where you ...

View answer
If I receive an SOS signal, what is the proper response?
3 votes

First, let's be very clear that making a false distress call is a federal crime carrying sanctions of up to six years imprisonment, and a fine of $250,000. Second, there is no commercial or maritime ...

View answer
High SWR on a Jeep with Spare Tire Mount
3 votes

The metal wheel and the steel-belted tire are big chunks of metal. Those add capacitance between the antenna and ground, so they lower the resonant frequency of the antenna. A shorter whip or a ...

View answer
Are there ways for people with receivers to participate in contests?
Accepted answer
3 votes

Summits on the Air (SOTA) is not a contest, but an ongoing activity with awards. You can participate as an activator (transmitting from summits), a chaser (working those on summits), or an SWL (...

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

For long range voice contacts that work all the time, day or night, you need a satellite phone. Especially if you are considering emergency use, that is your best bet. If you want to do the same ...

View answer
How slow is slow telegraphy?
2 votes

This may be a hold-over from when amateur licenses required Morse code. In the US, the entry level license (Novice) required 5 words per minute, and the next two levels required 13 wpm and 20 wpm. ...

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

Start with the ARRL propagation forecasts. These are updated every month and there is a specific forecast for the path from the East coast to Hawaii. http://www.arrl.org/propagation For a customized ...

View answer
Is it safe to monitor a channel while charging my handheld?
1 votes

The charging cradle is an external power supply that can power the radio and charge the battery at the same time. Yes, that is safe.

View answer
Are there famous radio frequencies?
Accepted answer
1 votes

The International Amateur Radio Union (IARU) has established a small set of emergency frequencies. Some of these are global and some are for one of the three IARU regions. The IARU calls these ...

View answer
Can I listen to hams on a standard AM/FM broadcast receiver?
1 votes

No. Even if you modified it to tune amateur radio frequencies, it won't receive the modulation schemes used. Broadcast FM is wideband FM, which is not legal for amateurs on most frequencies. AM is ...

View answer
Adequate lightning protection for sloped dipole or G5RV?
1 votes

That will not help enough. Lightning spreads out as it gets near to the ground. It also doesn't really conduct along the ground rod, it can jump back and forth to other objects. So you would get a lot ...

View answer
Can I ignore the radial elements of a 2m/70cm antenna if it's on a metal roof?
1 votes

Those radials look too small to be a ground plane for 2m. They may be a capacity hat to decouple the coax feedline from the antenna. That would be true if the antenna inside the radome is a vertical ...

View answer
Why have knife switch storm grounds for antennas vanished?
0 votes

A regular household light switch is actually an enclosed knife switch. Those are spring-loaded so they close completely every time. If you want to ground your antenna, put a SPDT light switch in a ...

View answer
Is double amplitude modulation useful?
0 votes

This would be much less efficient, because the carrier is sent as part of the modulated signal. It also creates a very wide signal with no additional information, so it wastes bandwidth. Lets assume ...

View answer
House wiring as an antenna on HF and 2 meters?
0 votes

For 2 m, get an Ed Fong dual-band J pole. It looks like a short length of PVC pipe because it is a short length of PVC pipe with an antenna inside. It has performance similar to a 1/4 wave ground ...

View answer
Doublet with ladder line vs coax w.r.t. noise
0 votes

Coax with a good 1:1 current balun at the antenna feedpoint could reduce your received noise. The function of that balun is to provide a high impedance to common mode signal (mostly nearby noise) and ...

View answer