|
new sats: https://mailman.amsat.org/hyperkitty/list/amsat-bb@amsat.org/thread/UYTSWHRNVO3OREOQMUI62N7T2N3AWAKJ/quote:JAXA announced four CubeSats deploy from ISS at 6th Oct with J-SSOD.
|
# ? Oct 6, 2021 02:37 |
|
|
# ? Mar 29, 2024 08:22 |
|
with aviation radios, when two people try to transmit at the same time you hear a distinctive kind of interference. sometimes it sounds like a high-pitched squeal or beep, but it can also be a warbling noise or a rapid series of pulses. you can hear one type here at 1:35: https://www.youtube.com/watch?v=jTPnGMxdlPo&t=95s I assume you get it on ham radios too. what causes this? like from a physical or mathematical standpoint? my best guess is that we're hearing the beat frequency created by two radios that are just a teeny bit out of tune, like one is transmitting at 118 200 000 Hz and the other is at 118 200 005 Hz and that's why we hear a 5 Hz warbling -- but i don't know if the electronics would allow that sort of thing. does that make sense? Sagebrush fucked around with this message at 06:54 on Oct 11, 2021 |
# ? Oct 11, 2021 06:48 |
|
Your explanation makes perfect sense for AM but AM phone isn't super popular in ham these days and I've never heard beating like that, but I've only ever done FM or SSB. E: like check out this plot if a(t) is a 1MHz sine wave and b(t) is 1.001MHz. You can see a clear 1kHz beat between them at the receiver if it's picking up any linear combination of these 2 signals. This won't happen in SSB because in SSB there is no carrier to beat (and you'll just get the two audio signals superimposed maybe with a little pitch shift). I have no idea what happens in FM, so it might be possible but it seems like I'd've heard this when two folks key up on the repeater input at the same time by now if it does beat, and I never have. Stack Machine fucked around with this message at 15:22 on Oct 11, 2021 |
# ? Oct 11, 2021 15:06 |
|
yeah thats carriers smashing. you dont hear it when you're tuned to say, AM broadcast radio, because those transmitters all have super accurate oscillators so there's no heterodyning. (and yes there is a homodyne) anyways its more common in aviation radios because those arent gonna be gps locked oscillators or anything so there's a good chance one plane's radio is gonna be a kilohertz off or whatever.. when there are several hams on the AM voice frequencies (we set 10-20 khz aside in most of the shortwave bands for the AM folks - their audio sounds great and they are running enormous transmitters full of sizzling tubes usually) sometimes they'll transmit over one another accidentally and you'll hear the difference freq as there is generally no such thing as 'channels' in ham radio. put the dial where you want and transmit. usually people use even khz numbers but not always. VHF and UHF ham stuff as well as all analog modulation public service poo poo is all frequency modulated. That works differently with multiple signals, with a phenomenon called "capture effect". if there's a weak signal and a stronger one keys up, you'll only hear the stronger one. If they're roughly equal strength, you'll hear both signals as they fight it out in your receiver and it's super distorted. AM does not suffer from capture effect. That's why your aviation radios are amplitude modulated! You can basically DoS an FM receiver by keying up a strong dead (no audio) carrier. With AM, you could be transmitting a million watt dead carrier signal and if another AM transmitter starts talking, the receiver will still hear them. it's an air safety thing
|
# ? Oct 12, 2021 07:23 |
|
neat! i remember reading that part about FM radios blocking each other in the FAA manuals, yeah. you often have multiple stations not that far apart operating on the same frequency, and if it were FM the stronger signals could completely wipe out your attempt to listen to the weaker station. for instance i regularly pick up calls meant for watsonville when i'm tuned in to half moon bay, with about 50 miles between those airports. also this is why aviation hasn't gone to digital radios apparently. a human can sometimes pick out some key words through the noise where a digital signal would just suddenly crap out. it's considered safer that way. they never explained why it happens, though. how does capture effect work on an electronic level?
|
# ? Oct 12, 2021 07:36 |
|
maybe different in the real world, but back in school we used a phase locked loop to build an FM demodulator. it would lock on to the carrier frequency and the feedback signal that adjusted the PLL frequency higher or lower to track the modulation was tapped off as the recovered audio signal. the PLL characteristics dictate which signal the receiver prefers. the low pass filter in the PLL causes it to prefer small adjustments, continuing tracking the current signal and ignoring a big change to track an interfering signal.
|
# ? Oct 12, 2021 08:09 |
|
exactly. new radios do that in code but same idea
|
# ? Oct 12, 2021 12:46 |
|
this is your periodic reminder that there are 2-3 goon nets on the Brandmeister DMR network a week. I attend most of them and they are actually a really good time. You can chat about radios or just whatever's going on. If there is a brandmeister DMR repeater in your area with a second timeslot that allows you to connect to whatever you want, you just need a DMR radio (usually a handheld) that can hit it. If there isn't, you will also need a DMR 'hotspot' (this is a raspberry pi zero with a tiny little radio stapled to it and put in a box with a little OLED display). Then you run that in your house and connect it to wifi and it'll let you listen to and talk on any DMR talkgroup in the world. the first approach is more 'Real Radio' but who gives a gently caress. Hotspots are super flexible and fun and you basically have your own tiny repeater. I, of course, an am rear end in a top hat, and have mine hooked to a good outdoor antenna through LMR coax, and during a test walk around my neighborhood determined that I can get almost a mile radius from it. not bad for 10 milliwatts
|
# ? Oct 16, 2021 16:53 |
|
thanks for reminding me to check my hotspot range! and for the great effort post on the nets - I sometimes am very lazy with them and assume more knowledge. very naughty of me
|
# ? Oct 16, 2021 17:47 |
|
it's all good, i forget too haha https://twitter.com/jonny290/status/1449417188121612290
|
# ? Oct 16, 2021 17:55 |
|
Jonny 290 posted:it's all good, i forget too haha Heeyyyyyy I got that one in Tennessee! I left my SSTV receiver going while I was out running errands saw that, then wondered if it was a SAARS Goon.
|
# ? Oct 16, 2021 19:31 |
|
yeah i've only got one contact today but i'm hittin a lot of receivers well, it seems
|
# ? Oct 16, 2021 23:57 |
|
the next net is *today* at 7pm U.K. time! I am solidly sticking with this Sunday slot now for a weekly thing since I can never make the late ones - we still need some more Europeans involved though. I know you’re out there and I want to make our side of the pond have just as strong a community as the guys here do in the US
|
# ? Oct 17, 2021 14:36 |
|
i'm so sorry! i slept in heh. Time Zones! anyways I did a fair bit of hamming today, dialed in a few more SSTV templates and had a nice QSO with a fella with extreme design skillz. always a joy to see a fellow dork on the air versus yet another old man posting bikini girls Then i had a nice 30 minute PSK31 ragchew with a fella out of Tennessee - talked motorcycles and such.
|
# ? Oct 18, 2021 00:42 |
|
c radio s: finally spent some time loving with the ssd1306 library to get my lil display working. turns out the big thing was setting Sequential: true. I think, maybe false. whatever the opposite of all the examples was anyway now i display multiple pages on a cadence and it owns. the full project is back on track! now i just need to set up a rotary encoder to physically change channels. i'm also considering some other physical controls, a bigger display, etc but well see - first the encoder
|
# ? Oct 23, 2021 16:59 |
|
are you using the full library or the cutdown ones? i got ssd1306ascii going for my CW/WSPR beacon and it’s really nice
|
# ? Oct 23, 2021 19:31 |
|
its this golang library. the idea is a webui that controls pi_fm_rds on a pi zero. id like to eventually have a nice little box that integrates unobtrusively(-ish) with my vintage radios and rebroadcasts somafm (and other stuff) to them
|
# ? Oct 23, 2021 22:30 |
|
so one of the radios i broadcast to is a game gear with a tv tuner. does anybody know what kind of software id need to broadcast TV signals? iirc the normal amateur tv bands don't cover broadcast channels, but i'm doing a part 15 thing not a ham band thing. i'm mostly just looking for what software to use to put ds9 into a tv (or game gear) with an analogue antenna - the tv equivalent of pi_fm_rds
|
# ? Nov 5, 2021 03:56 |
|
it's straight up NTSC. I don't think there's a code-only project to do that out there, but if you had an old pi with the yellow RCA jack you could get a $10 RF modulator, build a simple antenna for it and have your own tiny station on channel 3 or 4
|
# ? Nov 5, 2021 03:58 |
|
oh wow. dumb question, but im not quite seeing how the transmission work to get across the air. seems like an output that is expecting to direct connect to input wouldn't put out enough power to radiate. am i horribly misunderstanding something (almost certainly yes)?
|
# ? Nov 5, 2021 04:05 |
|
oh i just found thison aliexpress. that oughta just let normal "play a video over video out" poo poo work it'd be cooler to figure it out with just the modulator tho
|
# ? Nov 5, 2021 04:09 |
|
Yeah, my theory is the modulators basically probably poo poo out a milliwatt or so, not much at all, but it's the exact same signal that your local TV NEWS 4 would broadcast back in the day. You could make a simple dipole antenna (about 4 feet per side), string that up, and probably get 50 feet if not more of range.
|
# ? Nov 5, 2021 04:20 |
|
gently caress yeah that's perfect! i'll give it a shot and if i can't figure it out i'll hit up aliexpress thanks man! SNOTEL HAMWAN WINS AGAIN
|
# ? Nov 5, 2021 04:37 |
|
Achmed Jones posted:gently caress yeah that's perfect! i'll give it a shot and if i can't figure it out i'll hit up aliexpress Just tx some Trek
|
# ? Nov 5, 2021 04:46 |
|
mycomancy posted:Just tx some Trek i mean i originally watched ds9 on air on my brother's 19" tv and...yeah
|
# ? Nov 5, 2021 04:57 |
|
important things to transmit: * ds9 * shaw bros * godzilla * probably farscape or smth but once i have trek and kung fi i'm p happy
|
# ? Nov 5, 2021 04:59 |
|
so im lookin on amazon for rf modulators and lol
|
# ? Nov 5, 2021 17:58 |
|
Achmed Jones posted:so im lookin on amazon for rf modulators and lol
|
# ? Nov 6, 2021 01:01 |
|
ok so i'm about to move and buy an ic-7300 and a fat bioenno lifepo battery (as opposed to a power supply). i'm gonna obviously gently caress around with building antennas, but i also want to have a nice multi band HF permanently mounted on the roof. i would expect either a fan dipole or a vertical. no HOA, but i'm also not looking to put a big mast up or to break my neck on the ladder i just want something easy that'll work well. i'd rather not spend an arm and a leg but i'm ok paying for quality. any recommendations?
|
# ? Nov 10, 2021 02:34 |
|
were it me i'd buy a hustler 4btv and have a roof guy install a nice mount for it. the tricky thing is that it'd need some radials to work properly but you can run those along various eave lines or tuck them under shingles. Or even run them on the underside of the roof inside the attic. <200 bucks, 21 feet tall, gets you going on 40, 20, 15 and 10m. The thing is....it's a trapped vertical. So install would consist of adjusting the traps and testing and there'd be a fair amount of put-it-up-measure-the-swr-take-it-down-and-move-a-clamp-an-inch. But after that's done, it's good for a long time. very proven design, iirc they were first sold in the early 70s and have been unchanged since then. e: to clarify...i recommend hiring somebody to get a roof tripod installed just to keep everything clean and watertight. i know how to run 2x10 braces on the underside of the roof and bolt it all together and pour the tar to seal, but it's a pain in the rear end
|
# ? Nov 10, 2021 17:52 |
|
awesome, thank you! that also helps clarify some questions i have/had around "how the gently caress do i attach this to the roof without messing up my chimney"
|
# ? Nov 11, 2021 00:17 |
|
yeah do not use chimney mounts. chimneys were usually built for static vertical load, adding some lateral wind load can result in a very sad, expensive month after a wind gust
|
# ? Nov 11, 2021 00:29 |
|
Achmed Jones posted:awesome, thank you! that also helps clarify some questions i have/had around "how the gently caress do i attach this to the roof without messing up my chimney" my neighborhood, the only one in Copenhagen filled with hams, is any indication you build a huge steel structure next to your house to put your antenna on
|
# ? Nov 11, 2021 08:03 |
|
rip to our silent key may he post in hell
|
# ? Nov 11, 2021 08:18 |
|
grateful that we found this idiot hideout so we could all play beep boops and deedles with magic waves
|
# ? Nov 11, 2021 08:19 |
|
Jonny 290 posted:grateful that we found this idiot hideout so we could all play beep boops and deedles with magic waves
|
# ? Nov 11, 2021 08:54 |
|
speaking of: https://www.youtube.com/watch?v=laYpGB1pWAc traveling wave tubes are wack
|
# ? Nov 11, 2021 08:55 |
|
champagne posting posted:my neighborhood, the only one in Copenhagen filled with hams, is any indication you build a huge steel structure next to your house to put your antenna on in the US there's an FCC rule that you're allowed to build whatever tower you want on your own property for the purposes of amateur radio, and you get to ignore local regulations to the contrary. every few years ARRL tries to get Congress pass a bill that allows people to also ignore HOA regs but it never goes anywhere
|
# ? Nov 11, 2021 18:56 |
|
Jimmy Carter posted:in the US there's an FCC rule that you're allowed to build whatever tower you want on your own property for the purposes of amateur radio, and you get to ignore local regulations to the contrary. haha, that is actually awesome. i am not sure why the us is as good as it is (was) at federal regulation
|
# ? Nov 11, 2021 19:00 |
|
|
# ? Mar 29, 2024 08:22 |
|
Jimmy Carter posted:in the US there's an FCC rule that you're allowed to build whatever tower you want on your own property for the purposes of amateur radio, and you get to ignore local regulations to the contrary. Does federal law not supersede your local hoa?
|
# ? Nov 11, 2021 19:23 |