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: Hallicrafters HT-4 10m and 15m coils and tuning units
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I'm digging back 50 years, but I recall, at a TV station I worked for in
transmitter operations, that we had an HT-4, crystal controlled on a 26 or
27 mc f...
3 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.
A 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.
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!