The Milradio bug has come out of remission!
Half my old boatanchor collection (easily by weight, probably by volume too) is military stuff, mainly from WWII.
At the moment, very little of it works, none of it transmits! Projects are being re-prioritized to change that. Initially, I had thought I'd get my TCS set going, but the proper cable connectors will be a challenge. Instead, I got out my BC-454 ARC-5 receiver and did a quick alignment on it.
On a hunch, I wondered if it would play nicely running off of a stock dynamotor, ( http://en.wikipedia.org/wiki/Motor-generator ) at the reduced voltage of 12 to 13.8V. (These are most always 24V sets, often "ham-hacked" to run off of 12V by rewiring the filaments.) It was already running well at reduced B+, 160V vs 250V, so the 126V that the freshly re-greased dynomotor worked out well, I can barely tell it isn't as loud playing through a speaker. Its just fine, if not TOO loud with standard 8 ohm contemporary headphones, as there's no AVC.
Next, I'm going to gather up all the other dynamotors, grease their bearings, and see if I can't put together a "rotating" transmitter power supply.
Thats the BC-454 ARC-5 receiver, running in the dynamotor with the end bells removed, I heard that this was necessary to do to cook out any moisture that might be inside the unit. I sorta doubt that, but its good to give the thing a listen to see how its running. The TCS receiver is in the background.
So, I've got a couple of TCS pairs, a GRC-9 that needs a power supply, a Wireless set 19 that needs a power cable, scads of ARC-5 TX's and RX's, a BC-610 that likely needs a restoration, a BC-342... Heck, there's more, I just can't think of it at the moment. ;)
The only W6ATN ATV repeater I have a semi-clear shot to is Oat Mountain. It has an output on 919.25 Mhz. I have an old analog TV that goes up to cable channel 125, which is right around 800.25 Mhz . How convenient!
So, with a 900 Mhz yagi on the roof fed with heliax, I plugged in an SMA mixer (that I'm supposed to be building a 1296 transverter with) and dialed up my K5BCQ DDS signal generator up to 119.0 Mhz, and connected it to the TV.
Didn't quite work. I could tell there was something there that said W6ATN if I stared long and hard at the snowy screen. ;)
Made the following improvements.
1.) Moved the antenna higher. ;)
2.) I connected a cavity bandpass filter. Used my 8924c (and a mini-circuits directional coupler as an improvised return loss bridge) to put the "dip" right at 919.25. Dunno how much gain/loss/rejection it came out to, I'm still learning in that dept. ;) Either way, inserting this helped, noticeably.
3.) fished out a DEMI MMIC kit (10 bucks!!) from the bin, this one had a MAR-6. Soldered together and installed SMA connectors, and inserted between the Bandpass filter and the mixer.
Pretty good:
Here you can see the components: The water heater-lookin' thing is the BPF, MAR-6 preamp is floating in front of it with the green cable connected, and the mixer is floating off to the right with the three SMA's in a row. DDS VFO is on the bottom with the knob and the LCD that you can't read in this picture. Thats it!
Antenna: You can see I have my DVB-T dongle connected, used that to aim and peak.
I've been doing a little bit with Linksys WRT54G's that I've gotten for <$6 from neighborhood thrift stores.
I've been re-flashing them with OPenWRT. Here I have one with an analog temperature sensor, which is on top of an Arduino (Diavolino kit!) which is sending text to one of the WRT's serial ports. I've since added one additional wire, and the Arduino is running happily (and reporting temperature quite accurately) from the WRT's 3.3v supply.
This whole thing could be made much, much smaller, though I'm presently more interested in the ambient room temperature out there, vs. the internal temp of the WRT.
So, I can ssh into the WRT from inside the house, cat /dev/tts/1, and read the temp out in the shack. In addition, functioning as as a wireless network bridge is fairly useful as well!
Perhaps someday I'll connect a real teletype to that tty. ;)
No more borrowing gear for 10 Ghz contests! I'm well on my way to having my own working X-band station.
Thursday evening at the SBMS meeting, I got my hands on a completed Qualcomm lambchop conversion, a waveguide switch, a nice "whitebox" dish, and a few other goodies. Friday evening I hooked some of it up and shot the video below.
Its a few KC's off, and you can hear some drift in there. It was cold that evening (probably below 60F!!!) and I was using an uncalibrated 10Mhz txco. A rubidium disciplined oscillator would be much better, a lot more accurate. Combined with a few other goodies I already have, including a rubidium unit, I hope to have a rugged, portable transverter built up soon.
Spent a couple of hours Sunday on the Beach 40. ( The new commonly accepted name for VK3YE's 40M DSB transmitter/ receiver.)
I got the Receive audio section installed, and a few immediate problems debugged. I had absolutely no audio out, except for when I touched my finger or signal tracer to the input of the audio chain.
Further probing revealed:
1) The transistor in the VFO buffer amplifier was bad. Replaced it.
2) A 500 ohm bournes trim pot is not a satisfactory substitution for the required 200 Ohm part. I tacked in to 100 ohm resistors for now, need to get out to All Electronics soon.
3.) "Trying to be cool" and using surface mount diodes in the mixer ring failed. ;) There was poor gain, and things "looked funny" on the scope. Tore a few jumpers out, but left the SMD diodes as a lesson to myself, and then installed a new diode ring with proper through-hole diodes. MUCH better.
Once it was working in hard-wired receive mode:
4.) For my tastes (listening with a speaker, not headphones) this thing needs an additional audio amplifier stage. Using the good old Radio Shack amplified speaker cranked all the way up, I found that my perceived MDS was down below -110 dBm on my HP sig gen. Yeah, that won't occur in real life, but its a usability enhancement worth adding. I'm not excited about using the ubiquitous LM386, instead I'm going to try a TDA7052, (perhaps like SPRAT 142) which I have on hand but have never played with.
5.) I started building it "Drilled Island Manhattan" style, then for my attempted SMD mixer stage, I went crazy with the dremel. Made some mistakes. At that point, I found it much easier to switch to "Super Glued Island Manhattan." That's how I think I'll finish it.
And speaking of G3XBM, his "tenbox" project is ramping up, and sounds intriguing!
You can see a 10 Meter theme here! I'm also gearing up to put an old Stancor ST-203a 10m AM mobile transmitter (See Electric Radio, #280, September 2012) on the air, with a to-be-determined receiver.
Next, I've shaken awake the Homebrew Dual Sideband group, and announced my intent to build VK3YE's simple 40 meter dual sideband transceiver.
7.200 Mhz crystals (from N4ESS) should show up in the next couple of days. Meanwhile, I've been recently randomly calling CQ on 7200 with the "store bought rig."
Schematics below, thanks to WB6TNL!
12/10/12 PLEASE NOTE!!! The schematics are being frequently updated, please check the files section of either the Homebrew Dual Sideband, or Minimalist QRP Transceivers for the latest. Also, The name of this project has changed to the "Beach 40" transceiver.
Yes, you heard right, not MHz, not kHz... but Hz. Yeah, and I bet trying to get actual work done on such a contraption just plain hurts too. ;) Sorry.
I was pretty floored to find this simple NOP tester circuit at http://www.z80.info/z80test0.htm Slight change to the circuit, I used a 555 in an Astable mode for the clock source. By changing capacitors I can run at either 6.8 Hz, or a crazy-fast 68 Hz.
I've been on quite the inexplicable retro-computing kick, likely from the NSL Assembly Language class. Its bringing back memories of the Z80 asm class I took at Mt. Sac long ago, and before that, of the weird PC-looking device I bought at a government warehouse back at the dawn of the Internet age when I was in College. I had hoped my $7 was buying a PC that I could get on the (test-based) Internet with, instead my nerdy dorm-neighbors informed me that it was some sort of gubmint data terminal, and even though it looked sorta like a PC, there was no way in hell it'd run MS-DOS, due to the Zilog Z80 CPU it had.
Going waaay farther back in time... In 5th grade we got to play with the Commodore PETS at school, and later that year I got my own C=64 for my birthday. Oh, how rich I'd be today if I would have only learned machine language back then! ;) Sure...
Anyway, I had always thought building a computer from discrete components, though a total waste of time from a practical standpoint today, would still be cool as hell.
The other day I found this site, http://n8vem-sbc.pbworks.com/w/page/4200908/FrontPage
The guy sells blank boards for his single board computer for $20, and I likely have all of the other pieces in my junk box, so I think I'll order one.
And yes, I have seen http://www.brielcomputers.com , I'm trying to justify the expense. ;)
I do want to cobble a dumb terminal together with a pair of Arduinos and and old trash-day CRT TV, to re-create the carppy video experience of those old Commodore 64 days. Maybe even snip the driver wires to the Blue and Red guns so I get that awesome Green-a-chrome screen.Would be the perfect thing to use with the Z80 single board computer. Or, I could use my Teletype, hmm... ;)
Video of the NOP tester running. The video clearly shows a wiring error I made... Its in the still picture above, too, can you find it?
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Thats the BC-454 ARC-5 receiver, running in the dynamotor with the end bells removed, I heard that this was necessary to do to cook out any moisture that might be inside the unit. I sorta doubt that, but its good to give the thing a listen to see how its running. The TCS receiver is in the background.
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