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On Mar 17, 8:44�pm, wrote:
The advice to study an "All American Five" receiver, OTOH, is very bad, for a number of reasons: 1) You want to build, not take apart. In theory you could take an AA5 all apart and put it back together again, but that's not the same as building something new. As a LEARNING experience it costs (almost always) nothing. There must be tens of thousands still sitting around, doing nothing. 2) There is a good chance that if you can find an AA5, it will need to be fixed to make it work. While you can learn a lot that way, it's still not the same as building something new. I disagree. The only one I've seen "not working" was already damaged beyond repair. :-) I will repeat...it is a LEARNING experience. Since it is working, one can work backwards from that to see what makes it (or a stage within) NOT work. 3) The end result of any such effort is going to be a basic receiver for AM broadcast. Not a transmitter or transceiver, and not a piece of amateur radio or SW equipment. If amateur radio/SW is your interest, it seems to me that your projects should be for amateur radio and SW, not AM BC. True enough, but such receivers still work by the same principles that apply to HF or VHF or LF or VLF. An advantage to using AM BC is the known "signal sources" in the area. One doesn't absolutely need a signal generator to check or compare its performance. 4) AA5 receivers are of transformerless, "AC-DC" design. Usually one side of the AC line is directly connected to the chassis. I have yet to see one that is so "directly connected to one side of the AC line." They may exist, but all the ones I've handled (maybe two dozen all told, different makes and models) have always used a capacitor to chassis from one side of the AC mains. As I recall, they all had UL stickers on them. ... But in order to work on one, you want it out of the cabinet and powered up. Yes, but that applies to ALL such things, yes? :-) Working on one requires a lot of extra precautions to avoid getting a shock. *Better to focus on transformer-operated equipment whose chassis can be directly grounded to minimize the shock hazard. Tens of thousands of tinkerers have gone before you and still survived without being "shocked." :-) Electricians seem to survive just fine and some of them work directly with "hot" circuits...at higher voltages than a nominal 115 VAC. TV repair folks face 24 KV from picture tube ultors (the final accelerating anode)...even when the power is off and disconnected. If all else is troublesome, a cheap 1:1 isolation transformer can eliminate all those "hazards." Cost in the neighborhood of $15-$20 for 50 VA. However, even if used, the "B+" is still at 140 to 100 VDC and is always there when working. Precautions are fine but let us use a little realism on "advice" - tube based devices nearly ALL have lethal- potential voltages present. The average solid-state device tops out at +/-15 VDC or thereabouts, NOT a lethal potential. 73, Len AF6AY |
#12
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This is the HOMEBREW newsgroup and is about BUILDING at home.
I was trying to focus on the LEARNING aspect of getting acquainted with the various stages of radios. I picked the ordinary old table model radio as a representative of such a LEARNING device for several reasons: There are thousands ....[snip].... And if you can find a copy of "Elements of Radio Servicing" by Marcus and Levy, you'll learn even more! I have the 1967 version, and it covers EVERY aspect of an AA5 down to the last details! It also includes a little bit about transistor, auto, and FM radios. -- --Myron A. Calhoun; W0PBV; 2001 Dunbar Road; Manhattan, KS 66502-3907 Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge NRA Life Member & Certified Instructor for Rifle, Pistol, & Home Firearm Safety Also Certified Instructor for the Kansas Concealed-Carry Handgun (CCH) license |
#13
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Interesting..
Well, I'll let you know how I go about this. Greg |
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