31 votes
Accepted

Why do people say, "get a nickel," on repeaters?

"Getting a nickel" is a reference to how metered pay phones work (worked?). You'd put in some coins, make your call, and when the time you'd payed for expired, the phone operator would ...
webmarc's user avatar
  • 4,105
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 do operators mention the band when calling CQ on phone?

I have a scanner capable of HF receive, multiple HF receivers, and several HF SDR transceivers capable of receiving on more than one amateur band slice simultaneously. Lots of contest stations run ...
hotpaw2's user avatar
  • 13.3k
11 votes
Accepted

Is my low-power VHF transmitter dangerous?

Electromagnetic hypersensitivity does not exist. There is no confusion. It has been rigorously refuted by science. One watt is orders of magnitude below safe exposure limits, and indeed probably less ...
Phil Frost - W8II's user avatar
11 votes

Why do operators mention the band when calling CQ on phone?

It may have served a purpose in the past, with less filtering in transmitters and receivers, no digital frequency displays &c, e.g. to avoid mistaking a harmonic on a higher band for the ...
henryflower's user avatar
10 votes
Accepted

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

Let's clarify some terminology: a balun is any device used to convert between a balanced system (ladder line, dipoles) and an unbalanced one (coax, vertical monopoles). There are a lot of ways to make ...
Phil Frost - W8II's user avatar
10 votes
Accepted

What is proper procedure for asking for "distant" contacts on 2m FM on simplex?

One would usually call CQ DX, but on 2 m FM that would sound a bit odd. Also FM will be heard by many people close by, who will find CQ DX quite funny. You could simply call and explain what you're ...
tomnexus's user avatar
  • 11.2k
10 votes

Why do operators mention the band when calling CQ on phone?

Apart from historical reasons it's also a filler. When calling CQ on SSB you probably want to stretch out your transmission a bit because that's what you need to get heard. In theory you could just ...
Stefan I's user avatar
  • 141
9 votes
Accepted

Why aren’t emergency services using callsigns?

… Why don’t these unencrypted FM emergency services seem to use any call signs … ? They aren't required to and don't find it useful in their procedures. Also, they don't have call signs in the sense ...
Kevin Reid AG6YO's user avatar
  • 24.5k
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

Why is VHF better than UHF in this situation?

This is an ill-posed question, since "best" could mean so many things. If VHF is so plainly best, why does anyone bother with UHF at all? If you mean what option has a lower path loss, then sure VHF ...
Phil Frost - W8II's user avatar
8 votes

If i connect two antennas to one radio using a t connector will it work?

Assuming that both antennas are 50 Ω resistive, they will combine in parallel for a 25 Ω load impedance when transmitting. This will cause the transmitter to see a 2:1 SWR. This is a 0.333 voltage ...
Glenn W9IQ's user avatar
  • 18.6k
8 votes

If i connect two antennas to one radio using a t connector will it work?

If I connect two antennas to one radio using a t connector will it work? That depends on your t-connector. If your tee really is just a branch in the inner conductor and connected outer conducters, ...
Marcus Müller's user avatar
8 votes

Better explanation for beyond-line-of-sight VHF signal reach than "lower curvature to radio waves"

Please accept Phil's answer. It's the sanest one. Now, however to answer: what would be a better answer to this question? Why do VHF/UHF signals usually travel somewhat farther than ...
Marcus Müller's user avatar
8 votes
Accepted

Kenwood TH-D72A: what's the difference between Tone and CTCSS?

"Tone", displayed as "T" on the main screen, selects tone encoder + carrier squelch (your HT will send a tone, selected by the TONE Freq menu, and receive any strong-enough signal, regardless of ...
hobbs - KC2G's user avatar
  • 12.4k
8 votes
Accepted

VHF 50 Ω Antenna Over 75 Ω TV Coax

I will need a UHF/VHF diplexer on either end to suitably merge/split the signals from each antenna Yes, this is correct. A tangent: If you wanted to save some money by using mass-market parts, ...
Kevin Reid AG6YO's user avatar
  • 24.5k
8 votes

How do antennas over 1/2 wavelength work?

It's not a single long element, it's a collinear antenna, which is an array of several dipole elements stacked "end to end", connected in such a way that the current on each element has a ...
hobbs - KC2G's user avatar
  • 12.4k
7 votes

Better explanation for beyond-line-of-sight VHF signal reach than "lower curvature to radio waves"

The full question, and possible answers: T3 C11 Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations? A. Radio signals ...
Phil Frost - W8II's user avatar
6 votes

What would be the easiest and most cost effective ground system for a startup UHF/VHF station

That statement is wrong on several levels. The antenna is DC grounded so no lighting arrestor is needed. A lightning arrester is needed, even if the antenna is DC ground. The arrester's job is to ...
Phil Frost - W8II's user avatar
6 votes

If i connect two antennas to one radio using a t connector will it work?

For receiving it should work up to a certain level. However, the impedance will be completely different from that of a single antenna. So the SWR will be too high for transmitting and reception will ...
ON5MF Jurgen's user avatar
6 votes

Is a copper J-Pole antenna better than a Slim Jim for transmitting?

The slim jim antenna has no more or less gain than a J pole antenna - despite many Internet claims to the contrary. Any perceived difference in gain is likely due to CMC (common mode current) since ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes

RTL-SDR dongle - what antenna should I use for APRS receive only?

Here are the fundamentals of improving VHF antennas from what you've got: "Rubber ducky" (loading coil shortened) antennas are less efficient and more frequency-selective than un-shortened antennas. ...
Kevin Reid AG6YO's user avatar
  • 24.5k
6 votes

Why aren’t emergency services using callsigns?

Why don’t these unencrypted FM emergency services seem to use any call signs or ham codes? They are required to identify periodically and they do. That is the Morse code you heard. Emergency ...
WA9ZZZ's user avatar
  • 286
6 votes
Accepted

Use (TV?) Log-Periodic antenna for VHF

I'm sorry to say that's not a simple log-periodic antenna, it's a hybrid monstrosity to meet some particular need. Guessing from the element lengths: 136 cm each side would work at about 50 MHz, so ...
tomnexus's user avatar
  • 11.2k
6 votes
Accepted

Is testing SWR *practically* less important for 2m/70cm than HF bands?

I would say in practice it is less important because hams use different types of antennas for HF and for VUHF. At HF, the same antenna is often used for many bands. The bands have large fractional ...
tomnexus's user avatar
  • 11.2k
6 votes
Accepted

ISS repeater on a Baofeng?

Absolutely. In fact, 8W may even be overkill. VHF/UHF is far more dependant upon line of sight than on transmit power. Since the ISS is a relatively low orbit station, as long as you have a good pass (...
Nilpo's user avatar
  • 176
5 votes
Accepted

Antenna for a cramped attic

Your attic is pretty low but not quite low enough to be a problem for installing a vertically polarized 144 MHz antenna. There are two common antenna designs that would suit your case: Ground plane ...
Kevin Reid AG6YO's user avatar
  • 24.5k
5 votes
Accepted

What is pinout for headphone FM radio antenna?

The “pinout” for this purpose could be anything. Considering the perspective of the equipment designer: If you have a multi-conductor cable of any sort and you want to use it as an antenna element, ...
Kevin Reid AG6YO's user avatar
  • 24.5k
5 votes

Weird Harmonic Issue on Raspberry PI FM Transmitter

There are many articles which describe how to use a R-Pi to emit (=transmit) a signal. However what most, if not all, articles fail to describe is that this signal is a very rough signal, usually not ...
Edwin van Mierlo's user avatar

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