Path: agate!spool.mu.edu!umn.edu!uum1!kksys.com!edgar!moron!pillock!stevej From: stevej@pillock.moron.vware.mn.org (Steven Jarosh, KA0VYB) Newsgroups: rec.radio.amateur.homebrew Subject: Old Microwave Ovens > New TV Xmitter Message-ID: Date: Fri, 04 Feb 94 09:10:58 CST Organization: 11th Hour Contest Group (North American Chapter) Lines: 26 A bit of History: In about 1986-88 the British Amateur Television Assoc. published in their newsletter a spoof article about using the magnetron tube in a microwave to create a 2.4ghz FM TV transmitter. I do not remember the author. There was a lot typical british humor thoughout the article but in the end my buddy Chris (G4JEC) and spent weeks arguing whether it could be done. Fast forward to June 1989: I had just received my July issye of 73mag and on the front cover in small letters "Microwave oven ATV is here!". I was ecstatic when I saw the article and I must have laughed for 5 minutes. My oven is still in the garage The title of the article is: ATV Transmitter from a Microwave Oven! Author - David Pacholok KA9BYI Page - 54 73 Amateur Radio - July, 1989 250 Watts - Be careful! Steve KA0VYB ***Microwavers do it with higher frequency*** --------------------------------------------------------------------------- From: Dave Hallidy To: (and many other destinations) Cc: "steve.davies@nmp.nokia.com" Subject: RE: Microwave mobile/base Date: Mon, 10 Feb 1997 09:27:58 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Sender: owner-vhf@w6yx.stanford.edu Precedence: bulk Ron- I read your post and had a couple thoughts. 1. Microwave ovens are designed to work in the ISM band at 2450 MHz. = They use magnetrons as their source of RF, and these are traditionally = incapable of large amounts of retuning (i.e. down to 2304). While they = (one that I know of, actually) have been injection-locked to work in the = upper part of the band somewhere around 2400-2450, the article that was = written a few years ago by the guy who did it suggested that it wasn't = simple. He had to use some kind of tube power amp to get enough = injection to lock the mag on frequency. He used it for ATV in his test, = and yes, he did get 650 W of peak sync power out. BUT, there is no weak = signal activity in the States at this end of the band (it's all down at = 2304), so there wouldn't be anybody to work in that mode. OSCAR 13 had = a downlink at 2401, but we know where OSCAR 13 is and it was a DOWNLINK, = not an UPLINK. There has been some NBFM work at this end of the band- a = few repeaters on the West Coast, mainly. 2. At 50 miles, you don't need 500W on 2400 MHz! My company's 1W = Spread Spectrum radio operating in the same band (and with a 15 MHz = bandwidth- you'd use 5 to 10 kHz for NBFM- read: better S/N ratio) can = go that far easily with a good antenna (4-6 foot diameter). Many hams = operate at 2304 running just a few watts and they regularly communicate = over distances much greater than 50 miles. I suspect that a = well-designed station running 10W mobile should be able to work NBFM = that far IF the path is more or less line of sight. If it's blocked, it = probably doesn't matter how much power you run- it probably won't work, = at least not reliably. 3. You could certainly use a high power inverter in your car to = generate 115VAC to run such a beast (they've got 'em now that will do a = couple kW of 115VAC power), but why bother? 4. Perhaps my biggest concern would be the intensity of the RF field = you'd be generating. Anyone in a vehicle near you might be in serious = jeopardy of getting hurt from all that RF, including yourself. This is = not a joke. 5. As an aside, there was an article in QST sometime last year I think, = that described a repeater group's efforts to put a 2400 MHz repeater on = in California. You might want to check it out if you haven't read it- = they did well with relatively low power and simple stuff (omni antennas = and a few watts mobile, as I recall). Hope this helps. 73 Dave K2DH ---------- ... ------ Submissions: vhf@w6yx.stanford.edu Subscription/removal requests: vhf-request@w6yx.stanford.edu Human list administrator: vhf-approval@w6yx.stanford.edu