New answers tagged hf
-1
Well this is my first answer on Amateur Radio Beta, so be gentle. While I'm a new ham and liable to be ignorant on some subjects, I'm also a 10 year veteran software developer. However, if I'm wrong about something, please enlighten me. :-)
I might be off-base here in that I interpret "not ham" to mean "not necessarily ham".
HamNet might be what you are ...
5
What if I wanted to run a radio broadcast station on a commercial SW band? Say, I am on a boat in international waters.
What you're suggesting is known as pirate radio. That Wikipedia page provides plenty of examples of unlicensed stations, many of which operated for years before either being shut down or getting licensed. Many of those stations operated ...
1
You might find it more cost effective to buy a relatively inexpensive, lower power radio (even QRP class), and couple it with an amplifier to get your desired power level. There is a fairly broad selection of lower power "all-band" portable/mobile HF rigs available, some in "some assembly" form for under US$200.
For only 100W output, you ought to be able ...
2
I don't know that commercial class HF transmitters are still being built, but it shouldn't be very difficult to put one together. You'd need the audio mixing and control equipment that goes with any radio broadcasting station (this would be the same as a commercial MW AM or FM broadcast station), an HF transmitter that can be tuned to your chosen/assigned ...
0
The DXLab Suite includes PropView, a convenient front-end to VOACAP, which makes current and near-term propagation predictions. PropView works in conjunction with the other components of the DXLab Suite, so it works best when you use DXLab for all of your logging and operating functions.
You can download N6BV's Propagation Prediction Files with the purchase ...
0
Growing up in Europe and hanging on the SW dial, there were lots of stations received in cities without even any special antenna gear. At a maximum a totally non-tuned wire thrown anywhere along an inner wall was all that was had. Lots of stuff was received even so. But that was Europe, Europe is crowded and small, and the stations were perhaps less than 500 ...
1
As for the USA, the FCC has a database of enforcement actions here: https://www.fcc.gov/reports-research/maps/fcc-enforcement-actions-against-pirate-radio-location/. Casual sampling of this information leaves the impression that the majority of the enforcement actions concern the commercial FM band and are generally initiated not by any systematic FCC ...
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I'm looking to buy a shortwave to listen to
If you want to listen only I would use an SDR box on the computer. It is a total game changer. Seeing the waterfall visualization you can survey the bands at a glance and zoom in quickly where you find interesting action.
either solely at home or perhaps if possible in a vehicle when traveling.
Again, for ...
1
The Band Activity chart at DX Heat is a good way to evaluate propagation from the standpoint of "who is working whom, right now." Combining the color coded activity depiction with your general knowledge of when bands are more likely to be open can guide you as to what bands are opening and which are closing. The filtering tools allow you to target specific ...
1
You can do quite a lot with the RTL-SDR as a "spectrum analyzer". A proper spectrum analyzer will be accurately calibrated to measure absolute power, but if you can fix the gain of the RTL-SDR and the receiving software you can use it to make relative power measurements which are sufficient if you only want to roughly quantify linearity.
You could dump the ...
2
Super-Light intro to nonlinearities
Amplifier model
Ideally, an amplifier has this output function $f(x)$, where $x$ is the input amplitude:
$$f_\text{ideal}(x) = a_1 x\text,$$
and we call $a_1$ the amplitude gain (which is inherently the square root of the power gain).
Sadly, real amplifiers don't have ideal behaviour, instead they have:
$$f(x) = a_1 ...
3
These are just conventions. Back in the day of wavelengths determining the band you are in, the “highest” (i.e. the longest wavelength) band was the 160m band. This is of course not true any more, with many countries having access to bands with much longer wavelengths. But the 160m band is still known as “top band”.
Since then, it has become the convention ...
1
If you rely on detecting RF output to activate the T/R relay, you will be switching it while there is already RF output (obvious, I know...) this leads to two problems: the switching can cause a transient high SWR that may damage the exciter, and switching under power can cause arcing which damages the T/R relay itself. Even if it doesn't cause an immediate ...
0
As I understand you, your amplifier looks for a certain level of RF power at the input. If it is there, then the amplifier switches to active mode; if the RF power isn't at the input, then the amplifier switches to standby/bypass mode.
The advantage of using that switching method must be that no secondary connection for a switching signal between the ...
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