A question this morning from Scott KQ4AOP caused me to Google this old book On page 59 I found the article about my first transmitter. Someone has put a copy of the entire book on the interenet. Here it is:
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Re: Parasitic Suppressors?
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L = 6 turns. winding diameter 10 mm. winding length 15 mm PEV-2 1.6 mm
R=50 ohm. C=68 pf
4 hours ago
A favorite book. I think you meant page 59 of the book/ page 66 of the pdf. Back when Bob, KU7G called me about including the MOuSeFET, I mentioned that improvements were made to the VFO section, some suggested by Zack, W1VT. Bob said he couldn't accept any changes, as he had to meet a deadline. Would have been nice, but my website did document the mods and improvements anyway.
ReplyDeleteThis probably explains the many errors in the ARRL publications. "Sorry, no changes, we have a deadline!"
DeleteDeadlines pretty-much explain everyone's errors.
DeleteI think it is worse than that. It is more: "We know there is an error in the schematic that will cause this rig not to work. But we are going to publish it anyway. And we won't even do an errata. Who cares?"
DeleteOh my! Such disaffection . . . a man after my own heart.
DeleteCouldn't publish with my Google account, because I'm blocking 3rd party cookies. Oh, well.
ReplyDeleteI have the print copy of this book on my bookshelf, along with W1FB's QRP Notebook and other good bocks, like SSDRA and EMRFD.
73,
-- Dave, N8SBE
I'd like to see ARRL themselves make PDFs of out-of-print publications available. It may not be standard for-profit publishing practice, but it's entirely consistent with the non-profit character of the League. To recoup costs, it could even charge $5 or $10 for a download.
ReplyDeleteIn the alternative, they could grant official permission for private individuals to scan and post PDFs. Again, not standard business practice, but then ARRL isn't a business. Its stated "mission" is "[t]o advance the art, science, and enjoyment of Amateur Radio," and one of its "vision" statements is that is "[e]ncourages radio experimentation and, through its members, advances radio technology and education." This mission and vision is not advanced by keeping out-of-print (but not currently commercially-viable) under rigid copyright protection. Perhaps the ARRL already turns a blind eye to private uploads, but this is hardly encouraging.
I completely agree.
DeleteA problem with older texts is that many parts used are unobtainable. A bigger problem is also that so of the theory or design principles are out dated or even held wrong.
ReplyDeleteFoe instance, we now know the reason for thr hum in direct conversion radios to be the vfo leakage. This was never addressed and many older designs continued to used unbalanced mixers eith fets or bipolars. The apprpach to add a simple rf amplifier or use a diode mixer makes for simpler and better DC radios.
The greatest value of these older publications is that they offer examples of design principles and circuit topologies that, however "obsolete," still shed light on basic RF electronics and practice. As such they serve as learning resources and points-of-departure rather than as paint-by-number recipes (to mix metaphors) for inexperienced (and sometimes indolent) homebrewers.
DeleteIt *is* true that many of the parts they call out are unavailable, but knowing how to find substitutes (and change biasing and other circuit provisions accordingly) is extremely valuable for both practical application *and* for the learning value of doing so.
I have PDF copies of Doug DeMaw's _W1FB's Design Notebook_ (1990) and his _W1FB's QRP Notebook_ (1991). These have proven just as valuable to me as EMRFD and some of the better recent editions of the ARRL Handbook (none of them as valuable as older editions). I'm never going to use any of the active mixers (using dual-gate MOSFETS, etc.) that DeMaw shows, but knowing how they work helps to understand mixing mechanisms in general. There are more examples of practices and topologies no longer in favor but still have conceptual and education value.
There's no doubt some of these older publications could frustrate the uninitiated or casual builder, but they are--to mix metaphors again--nurishing food and golden nuggets for homebrewers on whom nothing is lost.
Actually QST did publish (in May '87) a few feedback items to the original Dec '86 QST article. They were minor items. When we go to the QRP Classics ('90) version of that article, the feedback items, except for one, did get corrected--Aaaarg! Well, I have been through that with IEEE papers too,so.....
ReplyDeleteFarhan's point about DC receiver hum sure bring back memories of common-mode chokes, running off batteries, turning off the house power, and trying to figure out if the neighbor's fish tank heater was doing it. Wrong on all counts. As Farhan said, add a simple RF amplifier, use diode (presumably DBM) mixer. That solved DC hum elegantly- a distant memory!
Regarding Farhan's note: We had no hum problems with the DC RX we built for the high school students. The VFO was a PTO (of Farhan's inspiration!) and was completely unshielded. There was no RF stage. A BP filter went right into a homebrew diode ring mixer, followed by a simple W7EL diplexer and on to an audio amp. We powered it with 9 volt batteries. Never had any hum. I wonder if the secret of our success might have been the diode ring. 73 Bill HI7/N2CQR
DeleteThe Diode Ring (DBM) certainly helps as well as the battery. The battery might let you get some distance from the AC lines, too. It brings up a few more questions: What band was that for? Describe the antenna system used, that might be a clue.
ReplyDeleteMy goal is LO Leakage <-70dBm on my 80M DCR's, so I can operate with any antenna, anywhere I go. You may not need this low an LO leakage, it depends if your antenna system can couple into a re-radiator, especially one like someone's AC power supply with unbypassed rectifiers. Plenty of these around!
Mike: It was for 40 meters. I used it with a coax fed dipole (no problems). We also recommended a 1/4 wave end-fed with 1/4 wave counterpoise (again, no problems).
ReplyDeleteI note that Wes's original solid-state DC recevier used this topology: https://soldersmoke.blogspot.com/2018/11/w7zoi-direct-conversion-receivers-some.html
Our high school receiver project is here:
https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver
73 Bill N2CQR