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I didn't even know that was a thing
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May 20, 2015 20:10
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it' s pretty neat but it' s one of those things where you start out with a $20 SDR stick and keep adding poo poo to make it better and you end up spending enough to have gotten the hackrf in the first place
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May 20, 2015 20:17
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ham it UPPPPPPPP *geico humpday voice*
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May 20, 2015 20:20
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ham it up uP UP
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May 20, 2015 20:20
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Jonny 290 posted:the 2n5109 would probably be good through 400+ mhz but youd need a pretty juicy jfet for vhf/uhf i think. mini whip is kind of useless for anything above HF, the version i've seen has no voltage gain in the cicuit either the principle is the same as an e-field probe used in EMC testing, it picks up whatever voltage fields are in the air, the whip element is tiny so it has some capacitive coupling to the ether/free space impedance since the whip is tiny the capacitive coupling from the fields in the air is also tiny (i.e. high impedance), the JFET acts as a high impedance buffer instead of the normal 50 ohm input of a receiver, the bipolar transistor decreases the output impedance some more to allow it to drive a 50 ohm input this circuit is lossy, but for LF-low band HF the atmospheric noise levels are huge compared to thermal noise, so the loss actually doesn't matter much since the noise floor coming in will also be high the noise factor of the JFET amp used obviously matters a bit, the U310 is a pretty good amp in that respect, substitute at your own risk using the circuit for VHF and up will be much less effective and probably pointless compared to a normal LNA circuit, using a super tiny pickup whip will let the circuit keep working as "normal" but the sensitivity will be poor compared to a piece of wire since at higher frequencies thermal noise is the main limitation additionally the input capacitance of the JFET will start to matter a lot more, a "perfect" JFET might work better but those don't exist. bootstrapping the input to reduce the capacitance might work up to a point but it's a wasted effort in this case the PSA4-5043+ from mini circuits is one of the best low noise MMICs on the market for this sort of thing, that + a small discone or just a straight whip is probably the best way to build a VHF+ receiver antenna. the issue is local FM + cell phone traffic will reduce the sensitivity and cause intermodulation, ideally you want a set of band pass filters on the input to reject the big commercial bands for the extremely lazy, just get a preamped TV antenna, those small flat ones have preamps and dual band bow-tie antenna designs inside that will do low band VHF + UHF i could probably spin up a simple app board for the PSA4-5043+ in an hour or two if no one's done it before?
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May 20, 2015 22:32
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i got the mini-whip up to about 21 feet above ground and i now have blastin' fuckin piles of images all the way up through like 3.4 mhz whatcha think. bcb filter? i love being able to blast in AM broadcast but if it fucks everything lower than 6 mhz it can go i will say in its defense that HOLY poo poo LONGWAVE i can get like a half dozen nav beacons between 250 and 400 khz
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May 21, 2015 02:17
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you replaced the JFET right? could be that you need to tune the drain current a bit if you're seeing second and third harmonics of the stations and not intermod the webSDR guys who built this thing also struggled with FM broadcast intermod, so a low pass is also a good idea issue with making a filter that goes before the JFET is it's very difficult to know the source impedance of the antenna so a 50 ohm filter won't work at all, but if the JFET is operating at a good bias point it shouldn't really struggle that much with AM maybe try checking it for distortion in the LW band using a signal generator and scope?
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May 21, 2015 06:18
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yeah i got no test equipment besides a fluke copy :P I like the drain current idea. ill swap out the resistor and see if maybe i can get it to be a bit more sane. other than that i'm fuckin' tickled with this thing. gonna build sniep one and throw it on his little sw receiver, its got an rf gain iirc so i think he'll be okay
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May 21, 2015 06:21
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hey radio guys I have my scanner streaming if you're interested. I Can't say sometihng interesting will happen though http://www.livestream.com/spleens
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May 21, 2015 06:27
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man nothing is happening tonight
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May 21, 2015 06:51
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 that's what you don't want to see right?
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May 23, 2015 16:03
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PuTTY riot posted:
yeah you're not gonna be able to get to the pins through that resin blob
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May 23, 2015 19:49
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if you wanna go caveman with a hair dryer/heat gun you can get it off without /too/ much trouble. guess what we dont own any more
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May 23, 2015 19:56
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Jonny 290 posted:if you wanna go caveman with a hair dryer/heat gun you can get it off without /too/ much trouble. guess what we dont own any more eyebrows?
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May 23, 2015 20:06
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Jonny 290 posted:if you wanna go caveman with a hair dryer/heat gun you can get it off without /too/ much trouble. guess what we dont own any more note: you may also desolder everything on the board
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May 23, 2015 20:32
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Bloody posted:note: you may also desolder everything on the board and nothing of value was lost but yeah the epoxy is a bitch move. i realllllllly wish i could find a source for these gd usb sound sticks without epoxy on the chip cause it'd be literally $5 to build packet interfaces (instead of $10 lol)
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May 23, 2015 20:35
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whats the chip underneath and does digikey not sell it
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May 23, 2015 20:37
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they do but augh i am not good at pcb fabrication http://www.ebay.com/itm/like/181149857401?lpid=82&chn=ps i would totally do a usb board with this thing and proper ham radio outputs, send it off to oshpark and fab them up and mail them out to you guys if yall can help me lay out a board for this there is a company that has done this but they want bigfuckingmoney for a $2 sound controller and some pcb work
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May 23, 2015 20:42
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which parts of the process
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May 23, 2015 20:43
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if its literally just layout i'd be happy to lay out the yosboard if you give me a diptrace schematic
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May 23, 2015 20:44
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all i know is my Acquired From Dubious Means copy of electronics workbench 10.0 i will start poking thru the suggestions yall have dropped over the past bit
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May 23, 2015 20:48
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in the meantime check this out http://www.crompton.com/hamradio/usb_fob_modification/ http://www.ebay.com/itm/291156304476 lets try these. i'll order 2 and see what the score is
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May 23, 2015 21:07
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it would be way cooler if those had solder mask that said "yospos, bitch" on one side and the goat man on the other.
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May 23, 2015 21:42
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May 23, 2015 21:42
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this is some impressively bad soldering
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May 23, 2015 21:49
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I'm the single not-cold-joint in the whole pic also DALE
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May 23, 2015 21:56
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Dale is good That project isn't
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May 23, 2015 22:02
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spankmeister posted:Dale is good honestly I am not even familiar with parts brands it just was something I'm the
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May 23, 2015 22:04
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I'm the gobs of sticky translucent white substance
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May 23, 2015 22:07
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Bloody posted:I'm the gobs of sticky translucent white substance But enough about your posting
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May 23, 2015 22:12
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hahahah lmao i'm the grommet for the usb cable with zero strain relief on the inside so the cables's gonna pull out anyway DUDE WHY DIDNT YOU JUST USE A USB EXTENSION THERE
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May 23, 2015 22:13
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i'm the wire stripped with human teeth
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May 24, 2015 00:08
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like did he f up the solder joints on that electrolytic by the green jack just out of spite or what
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May 24, 2015 00:21
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AX.25 Murderer
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May 24, 2015 00:42
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Sniep posted:AX.25 Murderer mods pls
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May 24, 2015 00:55
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i think i have now every permutation of 12vdc to powerpole and powerpole to (x) 
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May 24, 2015 03:03
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might flick it on for this coming up in a few last night i had good copy of the CW beacon from HO-68, and listened to a couple hams talking on ao-73. i still need more antenna height and better antennas and coax tho.
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May 24, 2015 19:13
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I didn't realize that so many people were into radio here. Sorta been studying and taking practice questions for a technician license. Some stuff is easier to remember, like announce your callsign every 10m. Other stuff, like what frequencies you're allowed to operate in, and translating 5m, 2m, etc to frequency ranges, more annoying to memorize. Realistically I'd just have a cheat sheet before turning on the radio. How important is it to memorize all the numbers to pass a test? The concepts are easier and common sense.
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May 24, 2015 20:41
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threw a wine-cork-style dipole ads-b antenna (same design as that idiot that doesn't understand the CAP theorem's) together, and it's way way way better than the big-rear end coaxial collinear antenna i built left one is the dipole
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May 24, 2015 22:32
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| # ? May 14, 2024 16:00 |
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SSH IT ZOMBIE posted:I didn't realize that so many people were into radio here. yeah don't sweat the numbers too much. only a couple of questions on your exam will be about that. hamstudy.org is your friend
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May 24, 2015 22:38
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