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also its not the etching, its the drilling *breaks another bit*
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Sep 4, 2016 01:04
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i wonder how 3d printing a thin layer for etch resist would turn out?
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Sep 4, 2016 01:10
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Jonny 290 posted:i wonder how 3d printing a thin layer for etch resist would turn out? plotter with a sharpie?
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Sep 4, 2016 02:32
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haha yes
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Sep 4, 2016 02:33
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so my friend recently switched everything over to SDR rigs and tossed me some of his old gear what's the best route to go down for an antenna tuner? Next HamFest that isn't out in NJ isn't until October, and the only thing I have at the moment is a 10/6/2M magmount whip that's on the fire escape
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Sep 4, 2016 04:26
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The best route: johnson kilowatt matchbox the cheapest route: wind a coil on PVC pipe and find a variable cap or two from an old rig the route most people take at your point: something like an MFJ-941 or MFJ-949 Personally i have two tuners: a kenwood AT-230 with a decent built in meter and lots of antenna switching, and then this big homebrew thing that i posted a bit ago. it's basically an enormous L network with a roller inductor and shitloads of capacitance, it tunes up my 85 foot long wire on 160m with like 3/4 of its capacity to spare. I have no doubt i could use it at 1,000 watts on broadcast AM as a matching network 24/7 until the end of time I end up using the 230 90% of the time still, the meter is really nice as i don't have an external HF watt/swr meter right now
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Sep 4, 2016 04:30
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Lol I just noticed the cat photos section on universal-radio.com
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Sep 4, 2016 09:45
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Progressive JPEG posted:Lol I just noticed the cat photos section on universal-radio.com look at the product images for the Icom IC-7600
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Sep 4, 2016 19:26
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lol, cat view
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Sep 4, 2016 19:30
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new antenna going up in the AM (half up now) I got sick of having poo poo 40m so i started figuring out what i could do. i think elevating my feedpoint would help as there is a ~15-20 foot rise right at our back lot, but i don't want to lose local coverage the plan is vertical dipole bottom half shortened with capacity hat and loading coil top is bent inverted L style oh the short vertical part is the boom from my old 6m yagi and the capacity hat on the bottom is the reflector, remounted to be connected to the boom. i just sledgehammered a 2x4 into the ground, the bottom of the ant will be about 3 ft off the ground wound a 10 turn 7" diameter coil out of copper 1/4" fridge tubing, made a shorting jumper feed at the top of that via coax + balun in theory it should get below 1.2:1 pretty readily and the fact that it's sort of a dipole with one leg vert and one horizontal means it has a near perfect mix of low angle DX and straight-up NVIS cloudburnin' model antenna height is 7.5m tall 7.5m across 
Jonny 290 fucked around with this message at 06:27 on Sep 5, 2016 |
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Sep 5, 2016 06:23
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i made a practice keyer last night from parts lying around. for some reason i thought you could cut that proto board with wire cutters but apparently not. at least it broke along an acceptable line that i was able to trim up. the sound is very buzzy and rough, but that's what you get for building the absolute basic 2 transistor+1cap+1resistor oscillator. 
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Sep 7, 2016 15:38
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my mod version of a modifed PA0RDT antenna is ready for testing nice piece of cast/turned alu. for the base with o-rings, a shielding tube covers the PCB and the flat metal piece at the end of the PCB is a spring contact which connects to a stub in the black plastic over cover, the antenna is a standard 3/8" threaded type so i can swap that out depending on the signal strength in the area. right here in the city I use a 6" whip, but i also have a 20" whip which should work better in a quieter area this version is based on a PA0NHC circuit that's similar to the original mini-whip design except it uses a dual gate RF mosfet (BF998) instead of the JFET for the front end the mosfet has lower input capacitance, which gives higher sensitivity and better LF response for receiving long wave time-stations i modified that version, so mine has an active biasing circuit on the gate (DC-servo integrator keeps the FET biased at the optimal current instead of a trimpot), a lower capacitance+faster ESD protection network, a 10x low noise high bandwidth opamp output buffer instead of the transistor solution, and it uses a transformer for output coupling the low pass filter to get rid of FM broadcast is a combo 10µH input inductor (forms a LPF around 30 MHz with the transistor+diode capacitance) and a feedback cap around the output buffer to further kill the VHF noise before i installed the low pass cap near the buffer i had a strong response all the way up to 200 MHz it's biased with 12-24V DC on the coax (regulated to 10V with a LM1117), there's 1mH + 1µH between the coax shield and ground + center and positive to provide common mode isolation at most frequencies of interest, that should improve the common mode rejection of the antenna compared to the russian made whip (which i think is the PA0NHC design) it seems to perform around as good, but the slight voltage gain helps a fair bit
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Sep 7, 2016 21:01
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I had to put mine back in a box. Never figured out how to knock down the MW images all the way through 5-6 mhz Nice work
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Sep 8, 2016 00:34
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current attempt an Icom band control voltage driven antenna switch to run two antennas no-tune on one radio. Or it will switch a tuner inline one band and switch it out on the other. Super simple, havent added proper psu bypassing yet but i think this should work fine
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Sep 8, 2016 02:08
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add a series diode and a generic electrolytic and you'll be fine pro mode is obviously to use a voltage reference instead of dividing the supply down, and might be worth it to make it a window comparator + use double connectors in case you want to extend the system in the future here's the AP mini-whip installed with the short whip  ap was a danish radio manufacturer specializing in cheap two way VHF systems and some VHF mobile telephony stuff, this antenna was originally a 77.5 kHz DCF timecode antenna using a philips tuned preamp and presumably a similar whip arrangement. no idea what kind of installation this was used in, but the design suggests 70s-80s so a lot of people might have had use for those receivers before GPS was available
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Sep 8, 2016 15:38
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Yeah this one's just a thing to see if it works, i was thinking of doing one that remotely switches via bias tee. can i do a deece voltage ref that'll go rail to rail though? or should I use the 12v for power? the rig offers both 12v tapped-off-the-power-cord and regulated reference 8V, the band voltage goes 0-8, i was just gonna use the +8 line here but no big deal to change now
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Sep 9, 2016 00:08
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Hooked up the rtlsdr hf mode to my vhf discone because that was the best I had and was pleasantly surprised at my shortwave reception. Was able to pick up a decent number of the usuals, Cuba, North Korea on the west coast. bunch of preachers too obviously. Got my 9:1 ready to go now so I'm going to do some random long wire tonight
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Sep 9, 2016 00:19
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the AM/FM collection grows with a sobering addition  Sangean WR-1. It sounds SO GOOD.
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Sep 9, 2016 01:55
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Jonny 290 posted:Yeah this one's just a thing to see if it works, i was thinking of doing one that remotely switches via bias tee. i'd power the relay off 12V and use the 8V as the opamp/reference then
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Sep 9, 2016 08:08
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sounds good 2 me e: been testing this WR-1 all night, the AM is on the good side of average to be sure, but the FM is poo poo hot. i made a dipole and put it up on the kitchen cabinet and it is wall to wall signals, i'm picking up 10kw public radio from 60 miles away. has AM screw terminal inputs as well as the FM F connector so i kinda want to string a wire in the yard and see how it does oh it has 12v in too, neat Jonny 290 fucked around with this message at 08:20 on Sep 9, 2016 |
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Sep 9, 2016 08:16
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a word of warning: not all opamps work as comparators, several types have antiparallel diodes between the inputs and may do strange things if you put a large differential voltage across the inputs LM358 definitely works as a comparator, don't know about the NE5532 but it's probably fine also the only acceptable transistor for driving a relay is the 2n2222A in TO-18 tin can package
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Sep 9, 2016 09:04
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actually it's 3904/6's by the 100 bag i gotta get rid of these things (though i agree with you on aesthetic matters)
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Sep 9, 2016 10:00
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i mostly use 2n7002s or bc847/857cs, since i have 1000 and 3000 of them respectively so drat cheap, it's be insane NOT to buy them by the reel!
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Sep 9, 2016 10:16
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jonny do you have a tivoli model one/two? id love to hear your thoughts about it apparently it has a pretty sophisticated tuner (derived from cellphone tech) but i have no idea if its just marketing fluff or not
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Sep 9, 2016 21:07
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Jonny 290 posted:the AM/FM collection grows with a sobering addition is that a prison radio?
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Sep 9, 2016 23:22
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sure is. the mystery right now is how i have this in my hands when the inmate records show he's up for parole in Oct 2016
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Sep 9, 2016 23:25
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Olivil posted:jonny do you have a tivoli model one/two? id love to hear your thoughts about it i had a model two about 10 years ago (no idea where it went...) and "everyone" had a model one, my grandma still uses one sound is ok, kind of boomy to match the typical radio announcer voice. not enough power to actually play at any real volume though. tuner, never tested it extensively but apparently pretty sensitive for FM. i have my doubts it's derived from anything cellphone in any meaningful way since it's the only FM radio i've seen since the early 2000s that actually has a problem with GSM transmitters. it's real bad where my grandma has hers since there's no 3G coverage "this is the evening news DADIDATDADIDATDIDAT DAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" - oh sorry just checking my facebook it's not even hard to avoid that kind of problem, just use FET/MOS audio opamps and maybe a tiny about of shielding and most of the work's done. never tried it for AM if that's your thing, i doubt it's any better than average e: http://la3za.blogspot.no/2013/12/scratchy-tivoli-audio-model-one.html found a partial teardown of the model two, it seems to basically be designed and built like a 70s receiver with slightly more modern parts. if you want fancy high end receivers, take a look at later model tandberg receivers, in the final years they managed some amazing quality FM receivers. they were often built almost entirely from discretes or discrete building blocks instead of using a standard IC for the job, just to get the best performance longview fucked around with this message at 07:28 on Sep 10, 2016 |
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Sep 10, 2016 07:13
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Yeah i don't have the privilege of having found a random hundo to light on fire on a Tivoli, i know some friends that swear by them but i just have never felt the fire right now my top guns are a realistic GE superadio 3 clone (sorta, some of the circuitry is different, but it's 90% there and I'm satisfied with it) and this sangean jailrig audio is pretty big on bass due to the ported enclosure and there is no lack of it, 3.5" speaker with a pretty heavy magnet and 7w of power (repurposed car audio amp chip) and theres no 3.5 jack for the line in as opposed to the wood cased consumer model cause in jail you could plug headphones into the line in and turn this into a PA system, factory chassis plug still in place
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Sep 10, 2016 07:27
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Hey does anyone have some recommendations for a starter receiver? I'm not really sure what I want since I don't know much about radios in any variety but I kinda like the idea of just being able to scan through the radio waves in London as I'm sure theres all sorts of nerds and pirate radio poo poo being broadcast all over the place. Or is this a dumb idea? maybe it sucks in the UK or a large city like London, anyway it would be cool if someone could give some recommendations or point me towards a good guide or something.
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Sep 10, 2016 15:28
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just go check the last few pages in the DIY ham thread, a lot of discussion of SDR receivers to pick up stuff in town a $5 dongle and maybe $10 in antenna is all you need -- so i ordered some 14.4 MHz TCXOs (guy in florida is selling them by the 50s), 400 TCXOs actually ($100!), and just now i won 250 MC3374 low voltage FM single conversion discriminator ICs ($12!) figure i need to build a radio with the parts i have laying around, otherwise this strategic stockpiling is just collector mania, the design goal for this project will be: no new parts damnit concept will be a fairly simple small assembly for half duplex, starting with VHF but potentially other bands in the future. should be small enough to fit in a small square box near an antenna or for mobile use, a mobile whip should be possible to mount directly on the RF unit. communication will be RS-485 for control and balanced TX/RX audio over a waterproof ethernet cable. some kind of operator console will have to be built later, i'm also deliberately skipping putting in any squelching circuitry or complicated data filters etc. in this module, the modulator and discriminator will have a reasonable flat 10-4000 Hz response suitable for data traffic. two board stack, main board will use a 14.4 MHz TCXO as the time base, SA601 mixer (not fantastic linearity, but i have over 200 of them), 21.4 MHz 1. IF (since i have a few hundred +-7.5 kHz filters), MC3374 discriminator with selectable 2nd IF filter BW (455 kHz) a lot of the RX board is drawn out now, i've decided to build all the trimmable parts like in the VXR9000 repeater series, using varactor diodes under MCU control to tune the assembly. this will also allow temperature compensation, the PCA9685 LED driver is a good choice since it's cheap and has 16 channels of 12 bit PWM. transmit board should mount to the receiver board, and needs to have a modulation response that's fairly flat down to around 10 Hz to support data modes like d-star. i figure 2-3W is a sufficient amount of power for this application. already have a block diagram but no schematic yet. if i can get this working it'd be relatively simple to do a 70cm and 23cm version (23cm would probably require a third IF, or just a higher 1st IF like 110.5 instead of 21.4) and finally start testing my idea for a triplex ad-hoc cross band repeater system.
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Sep 10, 2016 18:18
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really nice! i think my fall project is going to be a direct conversion receiver or something but im not dumb enough to try to build rf stuff w/o a scope so i gotta start that hunt again *prepares for literal torrent of buy-a-rigol*
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Sep 11, 2016 01:22
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buy an 80s tek
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Sep 11, 2016 03:21
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see thats what i wanna do i go round and round on this every year :|
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Sep 11, 2016 04:33
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buy an 80s tek or you'll get a semi-broken rackmount one in the mail 
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Sep 11, 2016 04:45
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atomicthumbs posted:buy an 80s tek 80s tek in the streets, rigol in the sheets
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Sep 11, 2016 05:22
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Jonny 290 posted:*prepares for literal torrent of buy-a-rigol* buy a rigol spectrum analyzer
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Sep 11, 2016 09:03
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longview posted:just go check the last few pages in the DIY ham thread, a lot of discussion of SDR receivers thanks for the heads up I'm going to buy a RTL-SDR and gently caress around with that for a bit.
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Sep 11, 2016 12:40
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80's tek best tek
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Sep 11, 2016 13:27
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spankmeister posted:80's tek best tek that's not a 465B??
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Sep 12, 2016 03:03
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2225 worth a hundred? or do i want a cheap used storage scope im just checking sine waves on qrp oscillators and poo poo, maybe aligning radios
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Sep 12, 2016 03:20
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