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OH MY GOD a verticalvid by one jonny twoninety in which i get cockblocked on a net checkin by two guys that take literally two minutes to communicate a phone number HAM RADIO https://www.youtube.com/watch?v=39yklDzaypw ~fin~
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Mar 19, 2014 01:45
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| # ? Apr 27, 2024 10:14 |
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ah need tah talk ta yew in a baaaaaad way
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Mar 19, 2014 03:38
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that's how amateur radio operators coordinate a phone JO sesh by the way
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Mar 19, 2014 03:39
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ah'm touchin mah ham right now
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Mar 19, 2014 04:05
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gotta check intew tha net tah see if i can sked a landline QSO wid mose
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Mar 19, 2014 16:20
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atomicthumbs posted:ah need tah talk ta yew i literally don't even notice anymore lol
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Mar 19, 2014 16:26
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i didnt realize how much my twang shows up, good lord
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Mar 19, 2014 16:39
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Jonny 290 posted:i didnt realize how much my twang shows up, good lord u seem to have the same minor transplant twang i do w/o the texasisms i also sometimes let slip out
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Mar 19, 2014 17:02
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now i want to check into the Alaska IRLP reflector and see how i sound when i'm talking to them i have one of those weird moving accents.
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Mar 19, 2014 17:25
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how feasible is it to build a wideband RF power amplifier with some sort of SDR IF > amp > IF thing is there a book on radio and amplifier design I could read
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Mar 19, 2014 22:46
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It's extremely easy to build a wideband RF power amp, it's hard to make one that doesn't poo poo out harmonics and spurious signals everywhere. let me see if i can dig up some microwave notes, they like wideband stuffs
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Mar 19, 2014 23:11
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I guess if you wanted to do it my way you'd have to have one hell of an output IF generator
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Mar 20, 2014 00:48
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put down the chocolate covered banana and step away from the european currency system what's yer angle, whatcha thinkin cause i mean we can glue parts together in many ways but only some of them will make sense.
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Mar 20, 2014 01:02
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I recently finished a class on RF and microwave circuits and thought that it was very enjoyable. Real interesting topic. When Jonny 290 mentioned that he was thinking of making a bandstop filter to get rid of 103.9 MHz from messing with his old man signals, I thought it would be the prefect chance to try my hand at some design and make some cool graphs. Grab your soldering iron and your third arm (not that third arm) cause we're about to make ourselves a bandstop filter. Those pesky FM bands won't mess with your VHF enjoyment any more. We are going to use the low pass filter prototype method of designing this filter. This method uses transformations for each of the four types of filters to replace the logical L or C in the prototype circuit. I've attached my work and some pics of the book below so you can follow along. Link to the notes with plots First, we are going to find the center frequency that we want our filter at. For FM broadcast, this roughly means 88 - 108 MHz, so our center frequency is going to be at the geometric mean of this range, 97.3 MHz. Our bandwidth will cover this range, 20% just to work with some round numbers. In reality, this means that 88 and 108 are going to be at 3dB lower than our band. We can estimate what 103.9 MHz is going to be at and compare it to some charts. For this design, we will use a Butterworth or maximally flat filter. Is says that we should see a dB loss of about 11dB with a three element filter. Not bad but not great. It's good enough. Next, we use the values for n=3 to start calculating the values of our components. Now, this is where we use our filter transformations. So, instead of having an series L first, it's an L and C in parallel for that component. For the shunt C, it is a series L and C. From the work, you can find the values. * L1' = 16.35 nH * C1' = 163.5 pF * L2' = 204.5 nH * C2' = 13.09 pF Why not calculate L3' and C3'? Cause in a Butterworth filter, these values are repeated! So we can be lazy and cheap by using the same parts. In class, we used Agilent ADS to simulate our lab designs so let's do the same. Here's our schematic and plot from ADS.   Nice! 97.0 MHz is at -89dB and 104.0 is at -10.98dB! But that's not reality. Reality doesn't have 16.35 nH coils or 16.35 pF caps. But we can get close and simulate. Again * L1' = 16.35 nH = 16 nH * C1' = 163.5 pF = 150 pF * L2' = 204.5 nH = 200 nH * C2' = 13.09 pF = 12 pF  Whoa! It shifted on us, but in a good way. 97.0 MHz is at -14.6dB and 104.0 MHz is now at -54.99dB. We can see that we're close. So, I calculated out the values to set 103.9 MHz as the center frequency and tweaked our values. The only thing that changed was L1' and L3' * L1' = L3' = 15.31 nH = 15 nH * C1' = C3' = 153.1 pF = 150 pF * L2' = 191.5 nH = 200 nH * C2' = 12.25 pF = 12 pF  Eh, 16 nH is probably better for L1' and L3'. Our drop at 104.0 MHz is now -46.4dB.
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Mar 20, 2014 01:38
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Jonny 290 posted:welcome and i hope you are enjoying the thread Forgot I made this post way back when. Definitely enjoying the thread, lots of cool stuff. Now I want to buy a dongle and play with SDR. Here's the breakdown on the APRS setup, most of it I got from googling guides people have written: On the pi: - install soundmodem and the ax25 stack. these were available as packages on the raspbian distro - add some stuff to config files in /etc/ax25 to set up a device for your sound card. google has good examples you can tweak for your use. lets you configure things like txdelay and slot time for sending packets - download and compile aprx. this has a pretty good manual on how to configure it. it can do rx/tx igate and digipeating as well as some cool stuff with multiple radios for cross band and other things. there's other software that'll do aprs too, but I picked this one since it seemed to be actively developed and designed to run on computers with limited resources - run the soundmodem daemon to create the ax25 device and interpret packets from the sound card, then start aprx you'll need to get a cheap usb sound card since the pi doesn't have audio input built in. some loving with the sound levels in alsamixer is required so things don't get distorted you can also use aprx with a TNC. these guys have made one that plugs right into the pins on the pi. a sound card interface allows more flexibility though For the interface to the radio I bought this "easy digi" pcb kit from a ham that sells them on ebay for $10 he also sells pre-assembled ones with enclosures and connectors. You could also just design one yourself. This one has isolation transformers for audio input/output and an optocoupler to trigger the PTT. It's designed to hook up to a RS-232 serial port for PTT triggering via the RTS or DTR pins. You could probably use one of the pins on the Raspberry Pi for this, but I wasn't sure if it would have enough voltage for the RS-232 levels the optocoupler was designed for so I used a usb-serial adapter. The radio I had was an Icom IC-2100H which uses a RJ45 connector for the mic and a 3.5mm plug for audio out, so I just wired up an spare ethernet cable for the PTT and mic input and a regular 3.5mm audio cable for audio out from the radio. There are plenty of other sound card interfaces which I'm sure you're familiar with from doing PSK31. I got the easy digi since it seemed like a fun, easy way to get some soldering experience without loving up anything expensive. The cool thing with soundmodem is it sets up an ax25 device for your sound card and then you can do any kind of packet stuff you want. In the soundmodem config file you can specify an IP address for the interface and then send out packets with the standard ping command, for example, over the sound card (which was useful for testing) Other cool stuff I did was set up an echo link node using the same sound card interface with a program called svxlink. This was actually useful to get the audio levels right by testing with a second radio, since it has an echo module that will retransmit anything it hears. Really anything that uses the sound card should work, so you could probably do digital modes like psk31 with the right software.
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Mar 20, 2014 01:40
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Jonny 290 posted:put down the chocolate covered banana and step away from the european currency system I only know 66% of what I'm talking about, but my idea was a broadband amplifier for the bladeRF's transmitter bit, since it only outputs 3 mw i actually have no idea how an RF amplifier is constructed or works but I was thinking transmitter > IF down to a fixed frequency, like a receiver's IF stage > power amp designed for that frequency > back up to transmit frequency???
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Mar 20, 2014 02:25
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okay, gotcha. alright, so i am going to state that i am not a professional RF engineer. i do not know all the tricks and only know a bit of the math in general, frequency conversion is best done at low signal levels. yes what you are wanting to do is in the realm of a broadband power amplifier. but before we begin, i want to yap about construction practices. As your frequency goes up, two things happen - physical dimensions start to becomes bigger fractions of a wavelength, and circuits become more sensitive to the trace inductance and capacitance provided by the construction materials and methods. So if you're building a 3.5 mhz amplifier for a little bitty CW transmitter you can just make it in a pie tin or altoids can or whatever the gently caress, manhattan/dead-bug it, who cares it'll work fine. But if you're building a 2 meter amp, you need to at least keep your leads short, don't run wires parallel, etc. gigahertz range amplifiers use the PCB themselves as capacitances, inductances and transmission lines. think of it as macro-scale chip fabrication techniques, manipulating the substrate and layers to create circuit elements. long story short, an amp to cover say 300 -3800 MHz (bladeRF range) is going to need to be constructed on par with any other 3.8 GHz amplifier. careful, careful attention to detail is gonna be needed. The upside is that some very cool chips exist that can make this almost as easy as can be. we've mentioned them before, but Monolithic Microwave Integrated Circuits are what you're looking for here. Get out your 15 watt iron and the brightest LED lamp you can because this is surface mount territory. No devices with leads allowed. Basically small all-in-one amplifiers on a chip, they are usually built to take 50 ohms input and output, can be regarded as pretty idiot-proof gain blocks and have a design that lends them to fairlystraightforward construction at microwave frequencies. One of their signature traits is that they usually take their DC power input as a bias on the amplifier output - this seems backwards and wrong, but if you consider the case of an MMIC preamp mounted at the antenna at the top of a long coax run (to help combat cable loss for receiving) it means that you can literally just shoot DC up the line with a little tee in the shack and be done with it. If you want to power it via a separate line, you just hang an RF choke off the output line and feed DC through the other end of that. That's what you'll be doing for your TX amp project. Now, as far as I know, you're going to be able to get somewhere between 500 mW and 2 watts with the biggest common MMIC that you can get off ebay or whatever. But you only have +6 dbm power output, and you're trying to get to +27 to +33 dbm. getting a wide band single mmic with that much gain is going to be tough. it'd be much smarter to find a PCB kit for a two stage mmic amp (these are on ebay for like 10 bucks, add two chips and a couple SMD caps/inductors and you're done) or even the full chassis+pcb kit that comes with SMAs and everything. Then just pick two MMICs - both of them should have the frequency range you care about, the bigger one should be speced for high power output, and the first stage selected should make up however much gain you want. say you find a device with +27 dBm max output (500 mw) and 16 db gain. you need to find another 6 dB gain to get to 27 dB, but what would be nicer is if you had, say, a stage with 10-12 dB gain. Then you could back the bladeRF down to 1 dBm output (one mW), lowering the heat on the radio itself and keeping things more stable. then you have one stage of mmic that takes your signal up to like 10, 20 mW, and that signal drives your final MMIC to crank out five hundred milliwatts of sperm-destroying, pizza-reheating microwave power words words words. i hope this has helped more than confused. i believe for your project it would be an excellent direction to take, as long as you are comfortable with a little bit of basic surface mount soldering.
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Mar 20, 2014 04:53
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Jonny 290 posted:okay, gotcha. I have never soldered anything on a surface before, but yes this definitely helps. i must do research and probably also buy a soldering station and LEARN 2 SMD IN 30 MINUTES kit and also decide whether I really want to spend $420-$650, plus equipment, plus a good antenna, plus transverter (maybe) on a radio at this point in my life
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Mar 20, 2014 05:34
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holy poo poo you find the weirdest things on ebay. look at this thing i want it http://www.ebay.com/itm/Poldhu-Radi...=item461b9e20b4  i think that's a fuse holder
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Mar 20, 2014 05:56
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lolquote:Only certain sites on the crystal surface functioned as rectifying junctions. The device was very sensitive to the exact geometry and pressure of contact between wire and crystal. Therefore it was made adjustable, and a usable point of contact was found by trial and error before each use. The wire was suspended from a moveable arm and was dragged across the crystal face by the operator until the device began functioning.
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Mar 20, 2014 06:00
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i bet you could embed a radio receiver in and around your diaphram at this point so you could be a cyborg ham radio station
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Mar 20, 2014 06:02
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i am a computer
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Mar 20, 2014 06:13
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You need to stop all the downloading
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Mar 20, 2014 06:15
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CamH posted:i am a computer im unsure
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Mar 20, 2014 06:58
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went out for smoke break tried to catch saudisat kinda got some rly weak signals man i gotta get a better antenna
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Mar 20, 2014 16:00
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just placed an order for some RF stuff, mostly connectors and cables but also the PSA4-5403 4 GHz MMIC, some RG-405 semi rigid cable to use in construction and assorted SMA connectors to solder to the 405 cable my SDR solution will look like this: ScanKing ~Royal Discone~ (25-2000 MHz), N-SMA M adapter, RG-405 patch cable to just below the mast, small shielded box with the MMIC amp, RG-174 or RG-58 coax, SMA into shielded box, at first a borrowed bias-tee from work, later a home-made one, SMA output to the SDR dongle/whatever else needs it will probably put a 7805 and some broad-band line filters in the bias-tee box to allow me to use a normal 12V switch mode supply also ordered a WSP80 pen so I'll have a real soldering station at home soon too if i try my hand at that FM-filter posted earlier I'll put it between the bias-box and the SDR dongle longview fucked around with this message at 16:25 on Mar 20, 2014 |
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Mar 20, 2014 16:23
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so i got the dongle a shitload faster than i ever thought possible and now i'm screwing around before dinner, and i think i may have hosed something sideways with this thing right now i'm located in south eastern germany and i swear i'm picking up a local station (N1 or N-Eins) which is supposed to be at 92.9 mHz on 26.6 mHz. FWIW i can also grab it on 92.9 completely clear, and on 26.6 it's fuzzy but definitely there. a few cursory google searches don't show anything about low-frequency stations in germany so I have no idea if this is my dongle not working or if this is some weird science poo poo i don't understand. also in before "lol ur dongle has never worked"
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Mar 20, 2014 18:51
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Ripoff posted:so i got the dongle a shitload faster than i ever thought possible and now i'm screwing around before dinner, and i think i may have hosed something sideways with this thing do u have the correct iq or w/e thing checked? also is there constantly a signal line going down ur waterfall thing? idk thats all i can think of other than the broadcast just overpowering ur dongle
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Mar 20, 2014 18:56
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Ripoff posted:so i got the dongle a shitload faster than i ever thought possible and now i'm screwing around before dinner, and i think i may have hosed something sideways with this thing Unless you got a magic sdr stick that tunes low, you're likely picking up the baseband signal after it's downconverted. thats definitely some sort of image or overload issue. There's a hack where you can literally solder an antenna straight to the ADC input pin and tune the HF bands; my suspicion is that your dongle is picking enough signal up at the ADC pin to hear the signal there. i could also be way off on this, i'm still figuring out how these things work longview posted:just placed an order for some RF stuff, mostly connectors and cables but also the PSA4-5403 4 GHz MMIC, some RG-405 semi rigid cable to use in construction and assorted SMA connectors to solder to the 405 cable hey nice! that sounds like a pretty nice setup. i'm down on cash right now so my sdr in a tree project is going to have to wait but i'm thinking: -raspi -2x dongle -1x hfupconverter -mini-whip for hf, my new little 420 mhz (yes i cut it for 420 mhz) discone design for vhf/uhf -ghetto POE using an 18v laptop adapter up the line, buck converter at the raspi to drop it to 5v i figure i can fit all of this in a rougly 2 foot chunk of 4" ID PVC with tons of room to spare. cap the top and put the discone on top of that, mini whip in the middle, electronics at the bottom. maybe shield the raspi and sticks, not 100% sure yet. thinking its a good idea tho
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Mar 20, 2014 19:03
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Ripoff posted:so i got the dongle a shitload faster than i ever thought possible and now i'm screwing around before dinner, and i think i may have hosed something sideways with this thing  could be the signal from the broadcast station is getting into the PA section of another transmitter somewhere nearby and mixing and producing an image do you have another receiver you can listen on?
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Mar 20, 2014 19:06
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surface mount soldering is seriously not that tough. get good pcbs built (eg oshpark/dorkbotpdx), get some good flux (avoid the thick/resiny poo poo, its useless), and don't freak out. having any access to decent optics to inspect your work more thoroughly will be a huge ++. you don't really need stenciling, paste, etc. absolutely avoid BGA packages, try to avoid no-leads packages (eg QFN). TQFP/similar are easy with flux - just think of it as "im gonna solder down this entire side of the package". flux/surface tension magic will wick the solder to the pads/pins and hlep keep the chip aligned. get some solder wick for when you accidentally put on a shitload too much solder. 0805 and 0603 passives aren't too bad to do by hand. 0402 are borderline. 0201 are great if you're overwhelmed by self-loathing. lots of alcohol for cleaning when you're done (and then drinking when youre actually done) is recommended. you don't need super steady hands or high end equipment to solder smd by hand. i think smd is actually easier than through-hole/leaded. the parts are small, but whatever, surface tension and flux are magic.
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Mar 20, 2014 19:10
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Dijkstra posted:
go in the configure menu and turn off all the AGC stuff, turn down the gain until you can just see the noise floor start to rise, and turn on correct IQ in the radio section, it's just an intermod product that happens when the gain is set too high and there's no band pass filter on the input
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Mar 20, 2014 19:26
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using the power of one of the many webpages that will calculate intermodulation products i discovered that the 3rd order product of 59.750 mhz and 92.9mhz is 26.6 mhz. Ripoff, Does the TV brodacast band in germany go down to 59 mhz? It does in the US however there could be more than two signals mixing too edit: longview has the better answer
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Mar 20, 2014 19:26
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Jonny 290 posted:
i'd still have an option for separating the whip and the discone stuff, but it could work out, fortunately for you electrical fields are far easier to shield than magnetic fields so an aluminium box for the power stuff could be enough you might still have problems with cable-bound noise, in that case try adding common-mode chokes with symmetrical caps to chassis (and don't use the chassis as power return, ever) im actually gonna try some of TIs 2W isolated DC/DC bricks for both the active discone and the mini-whip, I suspect the feed-line plus the power shielding is acting as a big loop since it picks up 15 MHz signals just as well with no power, getting more isolation might help, and i have some tricks i can do with the power shield then quote:however there could be more than two signals mixing too i discovered that the first time i found a wide-band FM signal right in the air-band, I usually adjust the gain slightly differently based on what band im in but there's usually a point where it distorts hard and a bunch of extra signals pop up out of nowhere
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Mar 20, 2014 19:34
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I like how the "UHF connector" is one of the worst choices for UHF applicationsJonny 290 posted:hey nice! that sounds like a pretty nice setup. i'm down on cash right now so my sdr in a tree project is going to have to wait but i'm thinking: my plan: drive to the top of a mountain w/ laptop, dongle, and car whip
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Mar 20, 2014 19:58
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my plan: put a guerilla box on the top of the roof of my apt building. 13 storeys, highest for at least a mile. e: should probably put an gps tracker in it in case someone steals it.
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Mar 20, 2014 20:00
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atomicthumbs posted:I like how the "UHF connector" is one of the worst choices for UHF applications if you want a lovely UHF connector i present to you the gold standard of crap connectors:  just looking at it you can tell it's a piece of poo poo, the belling lee connector, known in all of europe as "that TV connector" you might be able to tell it's a 50 ohm connector by the size of the center conductor, it also uses an outdated gender system where you need a gender changer cable to connect TVs instead of a more sensible male cable female device/wall socket that modern equipment tends to follow it's used for CATV systems up to UHF frequencies, the maximum usable frequency is 100 MHz fortunately the far superior (and over all not too bad considering the price) F connector is replacing it for cable modems and satellite, i still refuse to install TV cables with those connectors, I always put F connectors and then use adapters
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Mar 20, 2014 20:05
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longview posted:it also uses an outdated gender system where you need a gender changer cable to connect TVs instead of a more sensible male cable female device/wall socket that modern equipment tends to follow hmm? here we use those connectors but our outlets have a male for tv and female for radio, so you can use the same regular cable for both, no gender changer needed.
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Mar 20, 2014 20:08
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yeah but the TV has a female connector, this is a bad design
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Mar 20, 2014 20:19
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| # ? Apr 27, 2024 10:14 |
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longview posted:yeah but the TV has a female connector, this is a bad design that connector is a bad design but why is it bad that the tv has a female connector?
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Mar 20, 2014 20:20
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