Date: Mon, 15 Nov 93 04:30:34 PST From: Ham-Homebrew Mailing List and Newsgroup Errors-To: Ham-Homebrew-Errors@UCSD.Edu Reply-To: Ham-Homebrew@UCSD.Edu Precedence: Bulk Subject: Ham-Homebrew Digest V93 #103 To: Ham-Homebrew Ham-Homebrew Digest Mon, 15 Nov 93 Volume 93 : Issue 103 Today's Topics: Electronic Keyer Kit remote switch single sideband What's RG-22? Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Ham-Homebrew Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-homebrew". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: 12 Nov 1993 22:46:33 GMT From: news.service.uci.edu!paris.ics.uci.edu!csulb.edu!library.ucla.edu!europa.eng.gtefsd.com!gatech!swrinde!dptspd!TAMUTS.TAMU.EDU!eemips.tamu.edu!sanjesh@network.ucsd.edu Subject: Electronic Keyer Kit To: ham-homebrew@ucsd.edu there is a keyer construction based on microprocessor, which is very flexible and user friendly. pl look into ARRL handbook. -mallik mallik@aisg.com ------------------------------ Date: Wed, 10 Nov 1993 23:42:31 GMT From: amd!amdcl2!brian@decwrl.dec.com Subject: remote switch To: ham-homebrew@ucsd.edu Steve Bass writes: > As part of a project of mine, I would like to construct a remote > control switch that operates on principles used by garage door > openers and car alarm systems. > > Steve Bass > sbass@fc.hp.com I just finished playing around with one of these and wanted to post what I'd learned to the net but wasn't sure whether anyone would be interested. Obviously, someone is, so here's the garage door info file: I recently reverse-engineered the transmitter half of a simple garage door opener. My intent was to increase it's range beyond the current 30 foot maximum. I didn't figure out how to crank the power, but I did learn a lot about how they work. I haven't studied the receiver box yet. Clock: The circuit derives a simple 50% duty cycle clock from an RC based oscillator. Most of this logic is contained in the single IC. There are two external resistors and one external capacitor used to set the clock frequency. (Note that this clock is a digital clock and has nothing to do with producing the actual RF.) This clock has a period of approximately 1.15 milliseconds. Coding: The code for this unit is a 9 digit base 3 number. It is set via a 9 place dip switch with 3 positions per switch. The 3 positions are labeled minus zero and plus. The switch labeled 1 is sent first. Here are the waveforms associated with each "digit": _ _ _ _ _ _ _ _ clock: / \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_ _ _ -: / \_____________/ \_____________ (ie. short short) _____________ _ 0: / \_/ \_____________ (ie. long short) _____________ _____________ +: / \_/ \_ (ie. long long) The IC reads the switch positions and produces a digital signal which is a sequence of nine of the above waveforms (one for each switch) strung end to end followed by a long period of zero output. The key is sent repeatedly while the button is held down. Keying: There are only two connections between the IC and the RF oscillator. One of them carries the above "key" waveform and is apparently used to power the oscillator! I don't really understand the function of the second connection. Oscillator: The RF oscillator is composed of a single n-channel JFET transistor (type 2n5486) and several passive components. It appears that the oscillator tank circuit and the antenna have been combined into a single unit made of a loop on the circuit board with an adjustable capacitor across it. By adjusting the capacitor, I could change the oscillation frequency from 275MHz (max cap) to 335MHz (min cap). Note that most common remote units operate at 390MHz, so this obviously isn't one of them! At the risk of producing a monster, here is an ASCII drawing of the RF oscillator circuit: +9V pin15 | | R7=150K D1 0.62V | 6.7V | +-----+------+----pin14 L1 | | | 4.8V | L3 R9=1K D2 +--------------+ R8=1K | | | | + | | s +--switch--GND | +--------+-----C5----+----g JFET | | d | 10pF | | LOOP | | both diodes are | 16x12mm +-+--+ | cathode "down" | | | | L1=L3=2.2uH | var 4.7pF | | | | | +--------------+----+-----------------------+ The voltages shown are during oscillation. I had some real difficulty measuring the frequency of this circuit because there isn't any point on the circuit that is a pure RF with no AC component due to the switching waveform. I finally just coupled to probe into the loop with a small loop on the oscilloscope probe. Pin 15 is the switching waveform. When it's high, the circuit oscillates. I don't know the function of pin 14. The switch is the button that activates the whole circuit. Anyone with ideas for how to increase the power of this unit? The receiver is in a weather sealed box and I haven't gotten brave enough to open it yet. Brian McMinn N5PSS brian.mcminn@amd.com ------------------------------ Date: Sun, 14 Nov 1993 02:01:54 GMT From: library.ucla.edu!europa.eng.gtefsd.com!emory!kd4nc!ke4zv!gary@network.ucsd.edu Subject: single sideband To: ham-homebrew@ucsd.edu In article <1993Nov13.164257.15906@cs.rit.edu> atd@cs.rit.edu (Albert T Davis) writes: > >I have been out of this for a while.... > >Is the filter method still the most common for SSB generation? >Why? > >It seems to me that the phasing method is far superior with today's technology. > >al. It remains difficult to achieve a precise 90 degree phase shift over 3 octaves of audio frequencies. DSP offers the potential to solve that problem though. Gary -- Gary Coffman KE4ZV | Life's a journey, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | not a destination. | uunet!rsiatl!ke4zv!gary 534 Shannon Way | Live it. | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | | ------------------------------ Date: 10 Nov 1993 20:51:22 +0200 From: dog.ee.lbl.gov!agate!spool.mu.edu!olivea!inews.intel.com!ilx018-bb.intel.com!ilx049.intel.com!not-for-mail@network.ucsd.edu Subject: What's RG-22? To: ham-homebrew@ucsd.edu I was at this surplus electronic junk place, and they had a big spool of "RG-22" coax cable. I couldn't tell much about it, except that it seemed to resemble RG-8. None of my references (ARRL Handbook, Antenna Book, etc.) mention this type of cable. Anyone ever heard of it? Thanx in advance, ------------------------------------------------------------------- Doug Braun Intel Israel, Ltd. M/S: IDC1-41 4X/N1OWU Tel: 011-972-4-655069 dbraun@inside.intel.com ------------------------------ End of Ham-Homebrew Digest V93 #103 ****************************** ******************************