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 ...
- 3,054
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 ...
- 13k
14
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 ...
- 14.7k
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 ...
- 50.8k
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 ...
- 669
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 ...
- 50.8k
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 ...
- 9,599
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 ...
- 23.7k
9
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 ...
- 131
8
votes
Why can't VHF / UHF be used with ionosphere reflection?
The ionosphere typically neither reflects nor absorbs waves with VHF or higher frequencies, but passes them through to space. There are no reflections back to the ground, so there is no useful ...
- 23.7k
8
votes
Accepted
Tuning/trimming a ground plane antenna
My trick is instead of cutting, rather extend the whip first, and see if the SWR gets better or worse. Extend it 1/2" with a bit of wire wrapped around it and sticking out. If the SWR gets better, ...
- 9,599
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 ...
- 50.8k
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 ...
- 18.3k
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, ...
- 14.7k
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 ...
- 14.7k
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 ...
- 10.7k
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, ...
- 23.7k
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 ...
- 10.7k
7
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:
$...
- 50.8k
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 ...
- 50.8k
6
votes
Marine VHF whip antennae - what are they?
Without having one of these antennas to disassemble (perhaps destructively), I can't tell you exactly how they are constructed. But maybe I can address some of your underlying concerns.
Firstly, ...
- 50.8k
6
votes
Accepted
Is a modded Yaesu FT-270r acceptable to use on MURS frequencies?
I am not a lawyer, and this is not legal advice. I'm also not particularly familiar with MURS, and generalizing from other information.
According to Wikipedia, MURS (as many other US unlicensed radio ...
- 23.7k
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 ...
- 50.8k
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 ...
- 783
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 ...
- 276
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 ...
- 9,599
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 ...
- 9,599
5
votes
Tuning/trimming a ground plane antenna
If you take SWR measurements at a range of frequencies and plot them (or just watch the SWR reading as you change frequency), you should get a graph with one or more valleys of low SWR.
Ideally, if ...
- 23.7k
5
votes
Weather Imaging with NOAA satellites - legal?
Here in the US, it is perfectly legal for you to listen and "download" the satellite data. Since the data is created by a public agency, it is considered to be in the public domain and not subject to ...
- 69
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