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- Date: Thu, 17 Feb 94 18:28:25 PST
- From: Info-Hams Mailing List and Newsgroup <info-hams@ucsd.edu>
- Errors-To: Info-Hams-Errors@UCSD.Edu
- Reply-To: Info-Hams@UCSD.Edu
- Precedence: Bulk
- Subject: Info-Hams Digest V94 #171
- To: Info-Hams
-
-
- Info-Hams Digest Thu, 17 Feb 94 Volume 94 : Issue 171
-
- Today's Topics:
- callsign server info
- Coax minimum-loss impeance
- Hawaiian 2m repeaters?
- Iambic keyer paddles
- John Ramsey
- MINIMUF on HP42S calculators
- Nude QSL cards
- pc.usl.edu more up-to-date than cs.buffalo.edu
- QSL info????
-
- Send Replies or notes for publication to: <Info-Hams@UCSD.Edu>
- Send subscription requests to: <Info-Hams-REQUEST@UCSD.Edu>
- Problems you can't solve otherwise to brian@ucsd.edu.
-
- Archives of past issues of the Info-Hams Digest are available
- (by FTP only) from UCSD.Edu in directory "mailarchives/info-hams".
-
- 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: 17 Feb 94 00:15:44 GMT
- From: yale.edu!noc.near.net!news.delphi.com!BIX.com!hamilton@yale.arpa
- Subject: callsign server info
- To: info-hams@ucsd.edu
-
- ah301@yfn.ysu.edu (Jerry Sy) writes:
-
- >which port do I telnet to get to callsign server on
- >cs.buffalo.edu ?
-
- telnet callsign.cs.buffalo.edu 2000
-
- Regards,
- Doug Hamilton hamilton@bix.com Ph 508-358-5715
- Hamilton Laboratories, 13 Old Farm Road, Wayland, MA 01778-3117
-
- ------------------------------
-
- Date: Fri, 18 Feb 1994 00:29:26 GMT
- From: agate!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!hpscit.sc.hp.com!cupnews0.cup.hp.com!news1.boi.hp.com!hp-pcd!hpcvsnz!tomb@network.ucsd.edu
- Subject: Coax minimum-loss impeance
- To: info-hams@ucsd.edu
-
- Over on sci.electronics, someone was asking about how we
- came to 50 ohms as common for coax impedance. I posted
- the appended followup after some interesting calcs that
- I had not seen previously: I'd seen the "77 ohms for
- min loss" thing, but not the effects of dielectric noted
- here, and I thought folk here might be interested:
-
- ========================================================
-
- Subject: Re: History of 50 ohms standard?
- Newsgroups: sci.electronics
-
- Richard Karlquist (rkarlqu@scd.hp.com) wrote:
- : In article <CLBvpK.7q4@odin.corp.sgi.com>,
- : Dave Chengson <chengson@chengson.mti.sgi.com> wrote:
- : >Does anyone know the background/history of where 50 ohms came from?
- : >Its been suggested that it came from WWII from the antenna folks
- : >and it is rumored it was a relatively arbitrary impedance value.
-
- : I believe this is discussed in the MIT Rad Lab books.
- : With air dielectric, 74 ohms gives the minimum loss for a given
- : outer diameter. 35 ohms give the highest power handling capability
- : assuming air breakdown is the limiting factor. 50 ohms is a compromise
- : about half way in between.
-
- I remembered it as 77 ohms for the minimum loss, and just went thru
- the calcs to figure it out. Turned out to be 76.708 ohms ;-)
- Now this is interesting, because it turned out to depend only on
- the ratio of inner to outer diameter, and expressed that way, was
- independent of dielectric, under the assumption that dielectric
- losses are negligible, which should be the case for practical
- coax cables at HF frequencies. I might add that this also assumes
- perfect surface conditions on the round (not stranded) conductors.
-
- OK, carrying this one step further, the outer-diameter/inner-diameter
- ratio for min loss under these conditions is 3.59112:1. With air
- dielectric, this is the 77 ohm cable. But if the dielectric is
- polyethelene, commonly used in WWII vintage cables, the impedance
- is ... 51.02 ohms! By the way, doing the same thing for solid
- Teflon gives 52.9 ohms, still really close to 50.
-
- For those interested in the calcs:
- Zo=60*ln(D/d) / (e^.5)
-
- where
- Zo is characteristic impedance of coaxial line
- D is inner diameter of outer conductor
- d is outer diameter of inner conductor
- e is dielectric constant of insulation
-
- A100 = 4.34 * Rt / Zo + 2.78*f*Fp*(e^.5)
-
- where
- A100 is dB attenuation for 100 feet of line
- Rt is total effective resistance at operating freq
- f is operating frequency
- Fp is power factor of dielectric at frequency f
- (and the second term is generally negligible at HF,
- leaving 4.34*Rt/Zo, for practical insulations.
- Dissipation in the insulation favors lower impedance
- since the loss goes down with voltage)
-
- Rt = .1 * f^.5 * ( 1/d + 1/D)
-
- You can reduce this: let D/d = x, then
-
- A100*D/(7.233E-3*(e*f)^.5) = ( x + 1 ) / ln(x)
-
- For a constant D, e and f, you want to minimize the right side for
- minimum attenuation. That leads to the D/d mentioned above.
- Substitute e=1 into the Zo formula for air; e=2.26 for polyethelene,
- and e=2.10 for teflon.
-
- 73, K7ITM
-
- ------------------------------
-
- Date: 17 Feb 1994 16:09:44 -0600
- From: library.ucla.edu!agate!howland.reston.ans.net!cs.utexas.edu!not-for-mail@network.ucsd.edu
- Subject: Hawaiian 2m repeaters?
- To: info-hams@ucsd.edu
-
- I'll be in Hawaii (on Maui and in Honolulu) from March 25-April 6 and was
- wondering if anyone could provide some advice as to good 2m repeaters...
-
- Yes, I have a rptr directory, but I was hoping for more specific advice.
-
- Thanks!
-
- ---
- Jason Hanson + 1510 Tripp Cir. #VI309 + (608)264-1079
- U. of Wisconsin + Madison, WI 53706-1294 + Ham Radio:N9LEA (Extra)
- jjhanso1@students.wisc.edu jhanson@macc.wisc.edu undergrad-Political Sci.
-
- ------------------------------
-
- Date: 16 Feb 94 17:30:26
- From: elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!howland.reston.ans.net!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!ub!dsinc!netnews.upenn.edu!mipg.upenn.edu!yee@ames.arpa
- Subject: Iambic keyer paddles
- To: info-hams@ucsd.edu
-
- I am told that in general, right handed operators use the right paddle
- for the dash while the left paddle is used for the dit. OK no problem
- so far.
-
- Is there a rationale behind this convention?
-
- If right handed people use their right hand to send code, why do they
- do this? It seems to me that it would be much more convenient to send
- code with the left hand so that the right hand is kept free to copy
- incoming code. This is the same logic that is used with baseball
- mitts. Is it that strictly right handed people can not do this?
-
-
-
-
-
-
-
-
-
-
-
-
-
- --
- Medical Image Processing Group | Conway Yee, N2JWQ
- 411 Blockley Hall | EMAIL : yee@mipg.upenn.edu
- 418 Service Drive | VOICE : 1 (215) 662-6780
- Philadelphia, PA 19104-6021 (USA) | FAX : 1 (215) 898-9145
-
- ------------------------------
-
- Date: 16 Feb 1994 23:51:01 GMT
- From: koriel!newsworthy.West.Sun.COM!abyss.West.Sun.COM!sunspot!myers@ames.arpa
- Subject: John Ramsey
- To: info-hams@ucsd.edu
-
- In article DCt@news.direct.net, kg7bk@indirect.com (Cecil Moore) writes:
- >Dana Myers (myers@sunspot.West.Sun.COM) wrote:
- >: >But my approach was not, "you idiots don't know your ass from..."
- >
- >: The implication is that Jeff's approach was this. Do you knoe something we
- >: don't?
- >
- >That has been Jeff's approach toward Ramsey for the year that I have been
- >on Internet.
-
- Keep in mind, Jeff's experience with Ramsey appears to pre-date your arrival
- to the Internet.
-
- >: In the 20 or so years I've been building kits, especially Heathkits,
- >: I've had at least 90% of them work from the moment the power was turned on.
- >
- >Your experience has been different from mine. I had 100 times the trouble
- >out of Heathkits that I had with Ramsey kits. You probably weren't around
- >for the '50s when it was a miracle if a Heathkit ever worked.
-
- Sure. Anyone can find from the callsign database my birthdate of 5/3/63. I
- started building kits around the time I was 10.
-
- >: I will say, flat out, that John Ramsey indeed bad-mouthed Jeff Gold by
- >: name during a phone call with me despite the fact I asked him not to do so.
- >: * Dana H. Myers KK6JQ
- >
- >I agree it was probably not a "politically correct" thing to do. But John
- >may (or may not) share my attitude that anyone who calls another person
- >a liar in public is less than human. And John probably doesn't appreciate
- >his name being a line item on Internet so how about us taking this off
- >line?
-
- Hang on, slamming your customers is not only not politcally correct, it is
- bad business. It doesn't matter if they call you a liar. Anyway, why wouldn't
- John appreciate his name being a line item on Internet?
-
- ---
- * Dana H. Myers KK6JQ, DoD 466 | Views expressed here are *
- * (310) 348-6043 | mine and do not necessarily *
- * Dana.Myers@West.Sun.Com | reflect those of my employer *
- * This Extra supports the abolition of the 13 and 20 WPM tests *
-
- ------------------------------
-
- Date: Thu, 17 Feb 94 17:35:00 MST
- From: news.mtholyoke.edu!news.byu.edu!news@uunet.uu.net
- Subject: MINIMUF on HP42S calculators
- To: info-hams@ucsd.edu
-
- Some time ago I ported MINIMUF (a BASIC program for predicting
- MUF's) to my HP42S calculator. If anyone's interested in it, email me
- and I'll send you a copy. (It's free.)
-
- --
- Ed Haymore | AA6EJ
- ed@byu.edu | Live long and prosper.
-
- ------------------------------
-
- Date: Fri, 18 Feb 1994 00:11:19 GMT
- From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!math.ohio-state.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!col.hp.com!csn!server!georgen@network.ucsd.edu
- Subject: Nude QSL cards
- To: info-hams@ucsd.edu
-
- Jim Hollenback (jholly@cup.hp.com) wrote:
- :
- : No, I don't think your out of place. Would one send a nude QSL to a foreign
- : country? I certainly hope not. In some counties they would be banned and
- : could get the recieving ham in trouble. Besides, what sort of image are
- : you presenting for the U.S.? If you would not send one to a foriegn country,
- :
- : Jim, WA6SDM
- : jholly@cup.hp.com
-
- :
- Although correct that some countries would ban nude QSL cards, you will find
- that countries banning the card are relatively few. Not all countries
- are as "Prudish" as this country about nudity.
-
- Nude cards do exist, I've gotten some from Japan. QSLs of this sort
- usually get answered more quickly........
-
- Signed: "Dirty Old Man Amateur"
-
- George, W1XE/0
- email georgen@redwood.stortek.com
-
-
- ------------------------------
-
- Date: 17 Feb 1994 21:05:40 GMT
- From: agate!msuinfo!news.mtu.edu!sol.ctr.columbia.edu!news.cs.columbia.edu!news.boxhill.com!ariel!ken@network.ucsd.edu
- Subject: pc.usl.edu more up-to-date than cs.buffalo.edu
- To: info-hams@ucsd.edu
-
- For what it's worth, the callsign server at
- telnet pc.usl.edu. 2000
- appears to be more up-to-date than the one at
- telnet cs.buffalo.edu. 2000
-
- (the former has my new mailing address, the latter does not!)
-
- Does anyone know if the two servers are related?
- They appear to use the same callsign server software...
-
- 73
-
- Ken (ken@boxhill.com)
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 22:24:20 GMT
- From: mentor.cc.purdue.edu!noose.ecn.purdue.edu!constellation.ecn.purdue.edu!wb9omc@purdue.edu
- Subject: QSL info????
- To: info-hams@ucsd.edu
-
- I'm wondering if anyone out there has a CURRENT WORKING ADDRESS for
-
- 4N7ZZ, Tibi of Yugoslavia
-
- I have no idea if he is dead or alive at this point, alive I certainly
- HOPE, for his sake.
-
- A long time ago I worked him and tried to send a QSL card, but I
- suspect that events in the region probably zorched that one. For
- all I know he might even have a different call by now.....
-
- If anyone has any info, please email to:
-
- wb9omc@harbor.ecn.purdue.edu
-
- posting it here might also be useful on the off chance that anyone
- else also needs QSL for 4N7ZZ.
-
- Thanks,
-
- Duane
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 06:05:44 GMT
- From: news2.uunet.ca!scilink!gts!torsqnt!problem!vigard!mdf@uunet.uu.net
- To: info-hams@ucsd.edu
-
- References <1994Feb11.003343.2956@ke4zv.atl.ga.us>, <bote.760946660@access1>, <1994Feb12.160701.4407@ke4zv.atl.ga.us>
- Subject : Re: Medium range point-to-point digital links
-
- gary@ke4zv.atl.ga.us (Gary Coffman) writes:
-
- >So an 8 bit system would have a SNR of 10*log(2^9)=27 db.
-
- heywaitaminute. isnt the SNR a power ratio? you've
- done a voltage ratio here ...
-
- >per second. That requires a very good brickwall filter, however,
- >so sampling is usually done at a somewhat higher rate, say 3X
- >or 4X the highest audio frequency. Lets pick 3X. So our required
- >bit rate is 16*15,000=240 kb/s.
-
- but after your oversampling and filtering, you don't bother with
- the "in-between" samples anymore ... you still end up transmitting
- 10kbps (in your example).
-
- tho i would say that 8kilosamples/second @ 8bits is quite accepatable.
- 64kbps. using an ADPCM encoder you can chop this in half.
-
- if you have a soundblaster, you can experiment with both sample rate
- and resolution ... 4k samples/sec is too low, 6k is passable. fewer
- than about 5 bits would probably make things very irritating.
-
- >Or we can abandon voice grade radios for the links and use purpose
- >built digital radios with higher baud rates. If we take a 56 kb
- >WA4DSY RF modem (GRAPES), and couple that with an on the fly
-
- or you could just get a pair of gunplexers. pricey, but you also
- get the beginnings of a *very* high speed (>1Mbps) data link. voice/packet/
- whatever.
-
- price/performance/future: how much are gunplexers, how much are
- the WA4DSY modem/radios and compare what both are eventually capable of.
-
- as you might be able to tell, i like spending other people's money. :-)
- --
- Matthew Francey mdf@vigard.mef.org (or mdf%mstype@sq.com)
- AX25: VE3RQX@VE3RZR.#SCON.ON.CAN GPS(NAD27): N43o34.210' W079o34.563' +0093m
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 17:36:32 GMT
- From: psinntp!arrl.org!jbloom@uunet.uu.net
- To: info-hams@ucsd.edu
-
- References <gregCKI0zw.Kuo@netcom.com>, <1994Feb3.190229.8136@arrl.org>, <x8yqthx.jramsey@delphi.com>
- Subject : Re: RAMSEY FX TRANSCEIVER
-
- jramsey@delphi.com wrote:
- : Jon Bloom (KE3Z) <jbloom@arrl.org> writes:
- :
- : >harmonic spectral purity requirements.) They promised to send us one of
- : >the new units as soon as it became available. (Normally, we only
- : >*purchase* Product Review items, but we decided that it would be hard
- : >for them to fine-tune a kit :-)
- : > We waited a couple of months, then called Ramsey. To make a long
- : >story short, we called *every* couple of months, but we never received
- : >the promised radio. Finally, we just bought one (through a third
- : >party). This is the unit we reviewed. In March of 1993, we contacted
- :
- : And one wonders why we don't advertise in QST, it's the attitude of
- : history re-writers such as J.B. I was there, and the facts just ain't so.
- : I'd rather talk on the phone! But I had to respond to such talk. You see, the
- : ARRL couldn't get their kit to work! So we sent them an assembled unit.
-
- No, as I said before, it *did* work, but didn't meet spectral purity
- requirements. *That's* why we requested an assembled unit--which also
- didn't meet the requirements and worked just like the one we built.
-
- By the way, when I was doing the phone calling (eventually I turned it
- over the the Product Review editor), I spoke not to you, but to one of
- your employees. So I'm not sure how you can claim first-hand
- knowledge. Of course, it may be that your employee was telling me one
- thing and telling you something different.
-
- : Yes it did not meet the FCC specs for spurious - missing by about a db or
- : two ( I'm at home and don't have notes handy). The ARRL missed the whole
- : point of the kit which was to promote kit building, etc,etc. Now. I'm
- : sure you are thinking, "but it didn't meet FCC!" True, but for a fascinating
- : contrast, look at the GLOWING review of the MFJ regen receiver! Guess it
- : doesn't spray RF.I do believe that MFJ has been quite a big QST advertiser, too.
-
- As for the MFJ receiver, the RF amplifier in the front end probably
- keeps the radiation down to an insignificant level.
-
- Our obligation in Product Review is to present all the relevant facts
- our members might want to know about a product. The failure to meet
- spectral purity requirements (by more than "a dB or two," by the way)
- certainly falls into the category of "relevant facts," as does the
- demonstrated receiver strong-signal performance. Also in that
- category, for a kit, is information about the quality of the assembly
- instructions and manual, which we said were good. Sure, we covered
- product performance, not only the building itself, because in the end,
- the buyer wants the enjoyment of building *and* the performance.
-
- Whether or not a manufacturer advertises in QST has no bearing on
- whether a product is selected for review. I don't imagine you'll
- believe that, but it's true. To keep it that way is one reason why the
- person who selects what will be reviewed and the person in charge of
- advertising are two different people who work in wholly separate
- branches of the HQ organization.
- --
- Jon Bloom KE3Z jbloom@arrl.org
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 21:09:16 GMT
- From: fluke!chuckb@beaver.cs.washington.edu
- To: info-hams@ucsd.edu
-
- References <9402152045.AA03433@rodgers.rain.com>, <CLAFwp.J8C@cup.hp.com>, <2jrovm$qss@reznor.larc.nasa.gov>lyon1.f
- Subject : Re: Nude QSL cards
-
- I received a QSL card from Japan that had a nude photo of a woman. That one
- always gets comments when people look through my QSL card collection.
-
-
-
- --
- Chuck Bowden / WB7R / chuckb@tc.fluke.com / (206) 356-6228
- Fluke Corporation / MS 232E / PO Box 9090 / Everett WA 98206-9090
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 20:46:44 GMT
- From: elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!oakhill!yosemite.sps.mot.com!ben@ames.arpa
- To: info-hams@ucsd.edu
-
- References <CL2txF.8EJ@srgenprp.sr.hp.com>, <2jqi1t$rer@pegasus.cc.ucf.edu>, <2jt93e$ds9@charm.magnus.acs.ohio-state.edu>
- Subject : Re: Nude amateur radio clubs
-
- In article <2jt93e$ds9@charm.magnus.acs.ohio-state.edu>,
- William VanHorne <wvhorn@magnus.acs.ohio-state.edu> wrote:
- >In article <2jqi1t$rer@pegasus.cc.ucf.edu>,
- >John W. Meaker <jm6033@pegasus> wrote:
- >
- >> I'm curious about nude QSL cards. Would anyone be offended if they
- >>received a QSL card in the mail with nude people on it? Would it be
- >>better to mail the card in an envelope? The envelope increases the
- >>cost of mailing a QSL considerably, and cost a consideration when you
- >>mail many cards.
- >
- >Even the *thought* of receiving a QSL card with a nude picture of the average
- >ham on it is enough to offend me. I mean, seriously, folks. Leaf through
- >any QST of recent (or even ancient) vintage, look at the pictures of the
- >hams and imagine seeing them nude.
-
- So, explain to me just how it is that someone is somehow a different person
- simply because they wear no clothing. The difference is only in the eye
- of the beholder...
-
- --ben
-
- --
- Ben Thornton Amateur call: WD5HLS
- Internet: ben@yosemite.sps.mot.com Motorola Inc., Austin, TX
- Caution: Wearing clothes has been shown to cause permanent psychological
- dependence on textiles. WEAR THEM AT YOUR OWN RISK.
-
- ------------------------------
-
- Date: Fri, 18 Feb 1994 00:29:39 GMT
- From: world!dts@uunet.uu.net
- To: info-hams@ucsd.edu
-
- References <CLCnIn.n3D@news.direct.net>, <2jurkaINNli7@abyss.West.Sun.COM>, <CLDzxC.JBr@news.direct.net>
- Subject : Re: John Ramsey
-
- In article <CLDzxC.JBr@news.direct.net> kg7bk@indirect.com (Cecil Moore) writes:
- >Dana Myers (myers@cypress.West.Sun.COM) wrote:
- >: What other newsgroup should we discuss this in?
- >
- >How about
- >
- >alt.revenge.vendetta.character.assassination.hurt.Ramsey's.business?
- >
- >: a good business does not berate customers in the presence of other
- >: customers. Are you suggesting this is not true? * Dana H. Myers KK6JQ
- >
- >Dana, I will give you the benefit of the doubt and for the sake of this
- >discussion, accept what you have said as true... that John Ramsey berated
- >Jeff Gold in a private telephone conversation with you. Now who is the
- >worst offender of common decency and professional ethics... one who
- >berates an individual in a private telephone conversation or one who
- >berates an individual in public on Internet? Seeking professional revenge
- >for a personal insult seems like extreme overkill to me.
- >
- >I didn't understand until you told me just now that Jeff was
- >complaining about a personal problem rather than a transceiver. In my
- >opinion, the only objective question to be answered here is, does Ramsey
- >make a resonable transceiver for the money? The votes are obviously split
- >and the free market will decide the answer.
- >
- >73, Cecil, kg7bk@indirect.com
- >
-
- The problem is, I think I'd be concerned with buying any more products from
- Ramsey. After all, if I had any problems, he might bad-mouth me all over the
- place too. It is bad business and really just plain unneccesary. Jeff appears
- to be a very nice guy for not filing a slander suit, especially given the
- ample evidence.
-
- --
- ---------------------------------------------------------------
- Daniel Senie Internet: dts@world.std.com
- Daniel Senie Consulting n1jeb@world.std.com
- 508-365-5352 Compuserve: 74176,1347
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 17:31:15 GMT
- From: psinntp!arrl.org!jbloom@uunet.uu.net
- To: info-hams@ucsd.edu
-
- References <1994Feb12.160701.4407@ke4zv.atl.ga.us>, <1994Feb14.131000.8706@arrl.org>, <1994Feb15.160936.23577@ke4zv.atl.ga.us>
- Subject : Re: Medium range point-to-point digital links
-
- Gary Coffman (gary@ke4zv.atl.ga.us) wrote:
- : In article <1994Feb14.131000.8706@arrl.org> jbloom@arrl.org (Jon Bloom (KE3Z)) writes:
- : >Gary Coffman (gary@ke4zv.atl.ga.us) wrote:
- : >: In article <bote.760946660@access1> bote@access1.digex.net (John Boteler) writes:
- : >: >I have gotten a bug up my rear to configure our point-to-point
- : >: >repeater linking system with digital paths ranging 20
- : >: >to 40 miles apart.
- : >[deleted]
- : >: Well lets look at some numbers and see. Lets assume
- : >: you want "broadcast" grade audio. That's a SNR of
- : >: 50 db. Digital transmission regenerates bits so
- : >: that above a certain threshold level the effective
- : >: SNR is only the quantization error of the digital
- : >: equipment itself. A crude way of looking at this
- : >: is to consider this error as bit jitter at the lsb-1.
- : >: So an 8 bit system would have a SNR of 10*log(2^9)=27 db.
- : >: That's obviously not good enough. 16 bits yields a SNR of
- : >: 10*log(2^17)=51 db which is close enough for our purposes.
- : >
- : >Use 20*log(x), since we're talking about a voltage ratio. An easy rule
- : >of thumb is 6 dB of SNR per bit of quantization. It's actually a tad
- : >better than that, since the quantization error is not constant;
- : >sometimes the error is a small fraction of one LSB, sometimes it's up
- : >to half an LSB. 8 bits will give you about 50 or so dB of SNR.
-
- : Well I don't want to get into a big fight about comparing power spectra
- : ratios to voltage ratios, I'll just say that it's the power spectrum that
- : you hear. If you want to use voltage ratios instead, that's fine, but it
- : means I'll have to raise the "broadcast quality" number to the 90-100 db
- : range instead of the 45-50 db range.
-
- Ummm... 50 dB is 50 dB whether expressed as a voltage ratio or a power
- ratio. That's precisely why we use 20 as the coefficient when
- calculating decibels on the basis of voltage ratios. That is:
-
- power ratio = [(V1)^2 / R] / [(V2)^2 / R] = (V1/V2)^2
-
- so, in dB,
-
- dB = 10*log[(V1/V2)^2] = 2*10*log(V1/V2) (by properties of logarithms)
- = 20*log(V1/V2)
-
- To talk about a "power dB" as separate from a "voltage dB" is
- meaningless, *unless* the two voltages you are comparing occur across
- different impedances, which is not the case here. Your statement makes
- no sense.
-
- So, what's enough SNR, 50 dB or 100 dB? I suggest it's 50 dB. A
- compact disk gives you about 90 dB, and I'd hate to think we need
- better than CD quality on our voice links!
-
- Of course, to realize the 50-dB SNR from the 8-bit system, the signals
- have to use all of the available signal range. If you use less, the
- SNR is reduced proportionally, as the signal is closer to the noise
- floor. That probably argues for something on the order of a 12-bit
- converter for "overhead." But with good ALC ahead of the A/D, 8 bits
- might be acceptable.
- --
- Jon Bloom KE3Z jbloom@arrl.org
-
- ------------------------------
-
- Date: Thu, 17 Feb 1994 19:52:01 GMT
- From: agate!howland.reston.ans.net!europa.eng.gtefsd.com!emory!wa4mei.ping.com!nanovx!kd4dts!jcw@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <CLAz5v.Iss@news.direct.net>, <fred-mckenzie-160294172009@k4dii.ksc.nasa.gov>, <1994Feb17.143114.3229@ke4zv.atl.ga.us>│╥
- Subject : Re: John Ramsey
-
- I built the 2m kit, and was I mad when I was done. I could never get the
- radio to produce 5 watts, and I had access to a Motorola spectrum analyzer.
- I talked to a Ramsey 'droid at the hamfest, and said "Oh yea, a tune up is
- about $10." I said, "Cool, I'll send it off." I talked to the service
- department who said "Oh, it's $50 to align a radio." I told them that was
- ridiculous, here's what the other guy told me. They said "Oh, well, if we
- don't have to fix it, there's no charge, except shipping." I told them
- "Fine, you won't have to fix anything, the radios not broke". I later
- find out that I have to pay $50 to get my radio out of hock with these
- BOZO's. I say "Well?" They say "Well, adjusting the coil on the final
- (which isn't in the manual) was a repair". I tell them "F**K you, here's
- $50 give me my damn radio back, I'm never buying another frickin' Ramsey
- product. Your sales people are liars, your technicians are liars, and you
- have my radio that I have to pay 50 bucks for, or I'll never see it again."
- I got it back, and it produces about 4 watts, still under spec. I'll
- never buy any Ramsey crap again.
-
- - John, KD4DTS
- --
- --------------------------------------------------------------------------------
- John C. Wren (kd4dts) | "The UNIX operating system has a command, NICE,
- jcw@kd4dts.atl.ga.us | which allows a user to voluntarily reduce the
- ..!emory!wa4mei!kd4dts!jcw | priority of his process, in order to be nice to
-
- ------------------------------
-
- End of Info-Hams Digest V94 #171
- ******************************
-