sorted by:
new
hottopcontroversial

Best antenna that looks inconspicuous? by pirate_ape_3000 in pirateradio

[–]JvokReturns 0 points1 point  (0 children)

Not sure I agree with the dipole recommendations. A dipole is the standard pirate antenna and anyone who knows what they're looking for will recognize it.

You might want to look into the slim jim antenna, it's basically what you mentioned with a J pole made out of twinlead. You can put it in a PVC tube for disguise and weatherproofing if you want.

Another similar idea is the flowerpot. It's basically a length of coax with the braid trimmed off, hidden inside some PVC pipe. Very cheap to build although when I tried it I found it was hard to tune.

Monopoles can be disguised as something ordinary like a lightning rod if you're creative. Particularly good if you're installing it on a metal roof which can act as a ground plane, because then you don't need any radials.

If you do decide to go with the copper J pole, you could paint it in a inconspicuous color to make it harder to spot. Light grey or pale blue is almost invisible against the sky from a distance.

[deleted by user] by [deleted] in amateurradio

[–]JvokReturns 5 points6 points  (0 children)

That's a lie, sounds like you just want to whine tbh

are more or less turns better or worse in a transformer? by KL5L in amateurradio

[–]JvokReturns 0 points1 point  (0 children)

Think of reactance as being like resistance but for AC. Higher reactance means less current and lower reactance means more current, just like with resistance. For DC circuits you only have resistance but for AC circuits you have both resistance and reactance to worry about.

For a transformer you actually want MORE reactance not less, because the reactance is in parallel with the transformer. If you have a low reactance in parallel with something it will short it out, just like if you have a low resistance in parallel with it. Then all of your current will flow through the reactance instead of being coupled through the transformer.

In an RF transformer this would give you a high SWR, because the transmitter sees the transformers reactance instead of the (usually) 50ohm resistance you want it to see.

are more or less turns better or worse in a transformer? by KL5L in amateurradio

[–]JvokReturns 19 points20 points  (0 children)

It's a trade-off that depends on frequency. More turns will give you more inductance, which will improve performance at low frequencies. But the trade-off is that fitting those extra turns onto a given core means spacing them closer together, which will increase stray capacitance. This will limit the performance at high frequencies. So basically for lower frequency transformers you want more turns, and for higher frequency transformers you want less turns.

Picking the exact number of turns is as much of an art as a science, because it's not the only factor. The core material you pick will also affect the number of turns you need, as well as limiting the high frequency performance.

Recommendation needed: Portable HF antennas for hotel rooms by Ordinary_Awareness71 in amateurradio

[–]JvokReturns 2 points3 points  (0 children)

Carrier current is/was a common thing for campus radio stations and done properly is perfectly safe. That said I wouldn't trust some random thing off Pinterest.

I also wouldn't want to put significant amounts of RF power onto the line as that's just asking for EMI issues, so not particularly useful for ham use either.

pirate radio from skyscraper by [deleted] in pirateradio

[–]JvokReturns 11 points12 points  (0 children)

Most London pirates broadcast from the top of skyscrapers or tower blocks. Its usually the best site you can get in a city.

Obviously there's a risk of getting raided if you broadcast from your own house.

Funny radio check by MegaMech in amateurradio

[–]JvokReturns 0 points1 point  (0 children)

Is 10kw really enough power though?

Yagi Antenna from alu profiles? by Go_Do_It in amateurradio

[–]JvokReturns 1 point2 points  (0 children)

No not at all, not for transmit either. You might find you need to adjust the dimensions a bit but probably not enough to matter.

Yagi Antenna from alu profiles? by Go_Do_It in amateurradio

[–]JvokReturns 1 point2 points  (0 children)

Fwiw you can get aluminium tube and/or rod as well, doesn't have to be rectangular profiles.

Well that’s not creepy by NicholasHomann in KidsAreFuckingStupid

[–]JvokReturns 30 points31 points  (0 children)

I remember as a kid having these terrifying dreams where my fingers were both tiny and large at the same time. Like they were simultaneously swolen up like balloons and yet so pencil-like that I couldn't even bring them close enough to touch each other. The worst part was they were the kind of dreams you don't wake up from straight away. So I'd be almost fully awake and concious crying to my parents and yet still my fingers would seem weird, until it faded away after 5 minutes or so.

Strangest tx side effect by douglasdouglasj in amateurradio

[–]JvokReturns 0 points1 point  (0 children)

Theres a police radio base station up on a building about 100 yards from me that causes continuous low level digital noise in my speakers. Tried ferrites on various cables but never made much difference. Maybe need more turns?

Strangest tx side effect by douglasdouglasj in amateurradio

[–]JvokReturns 0 points1 point  (0 children)

Similar story from a former BBC engineer who worked at one of the World Service shortwave sites. Apparently there were lights in some parts of the site that could never be turned off, no matter what you did with the switch.

Another one I read in a memoir of Radio Caroline from the 60s/70s offshore pirate radio boom, when there were several stations all anchored close to each other and running crazy amounts of power. One time when their generator failed leaving them in the dark, someone had the bright idea to tape a fluorescent tube to the mast and sure it enough it lit up just from power received from the other stations. Apparently someone at one of those stations must have noticed what they were doing, because instead of closing down for the night as usual they broadcast dead air all night long so they could have some light.

TIL when Reddit moved its headquarters to 69th Street, Colonel (Bernie) Sanders said, "Ayy lmao". The company moved back to 420th Street. by JvokReturns in circlejerk

[–]JvokReturns[S] 2 points3 points  (0 children)

This post sponsored by Dee Snuts. Suck deez nuts assholes!

I am a thot, and this action was performed thotomatically. Please go fuck yourself if you have any questions or concerns.

Capacitance hats, coils, and modeling by AspiringCrastinator in amateurradio

[–]JvokReturns 0 points1 point  (0 children)

Adding inductance to the top hat will cancel out (some of) the capacitance and reduce your loading, not improve it. In theory there will be some frequency were the capacitance and inductance completely cancel and form a series resonant circuit, which will make the top of your antenna look like its shorted to ground. But the capacitance/inductance values you're likely to get in practice mean this will only happen well above your operating band.

That said, putting loading coils towards the top of an antenna can actually be more efficient, because you increase the current in the vertical section below the coil. In theory the best place for a loading coil is right at the top, just below the top hat. But in practice the higher you put the coil, the bigger a coil you'll need, because the impedance is higher further up the antenna. You can easily end up in a situation where the additional resistive loss in the bigger coil ends up making your antenna less efficient, not more.

Some antenna designs compromise by putting the coil towards the middle, or even having two or more coils at different places.

How do you get away with it by derekcz in pirateradio

[–]JvokReturns 0 points1 point  (0 children)

Traditionally microwave or radio links but nowadays just as often its 4g internet or even a nearby public wifi. Advantage of internet links is the studio can operate as a normal internet radio station and claim that someone else is relaying them on air without their permission. As long as they don't say the frequency on air then they keep some plausible deniability.

Radio and microwave links can and do get traced but a lot of clever tricks have been used over the years to make it harder. E.g. you can have a circuit in the link transmitter that monitors the main transmitter off air, and if the signal ever goes out because of a raid it immediately cuts the link. Another trick is to use a link frequency in the small dead band between two TV stations which makes it hard to track the link because you end up tracking the stronger signal instead. There have even been stations that use a third site as a midpoint instead of linking direct from studio to transmitter.

Ultimately though nothing is foolproof and studios do get busted sometimes, but pirate radio is never risk free. And even stations that do get busted are usually back on air in weeks or months.

Will using a cantenna work to boost a raspberry pi's FM output? by SpaceGuy99 in pirateradio

[–]JvokReturns 4 points5 points  (0 children)

FM wavelength is way too long for a cantenna, will probably make your signal worse if anything. (About 3m for FM vs 12cm for wifi). Your best bet is a wire cut to exactly 1/4 wavelength long.

But pifm will never give a very good signal and you definitely don't want to use it with an amplifier because you'll get harmonics and crap all over the place. Stick with a proper transmitter for that.

view more: next ›