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- Date: Tue, 15 Feb 94 14:11:06 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 #156
- To: Info-Hams
-
-
- Info-Hams Digest Tue, 15 Feb 94 Volume 94 : Issue 156
-
- Today's Topics:
- Boring WWV Programs
- Bosnian Ham Address
- Commercial Radio License Exam Opportunity ** Cambridge MA ** 12 March
- Copying High-Speed CW: Print or Scr
- Daily Summary of Solar Geophysical Activity for 14 February
- GAP DX EAGLE comments?
- Nude QSL cards
- Vision Impaired Ham needs help
-
- 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: Tue, 15 Feb 1994 17:39:57 GMT
- From: agate!howland.reston.ans.net!cs.utexas.edu!news.unt.edu!news.oc.com!convex!constellation!osuunx.ucc.okstate.edu!datacomm.ucc.okstate.edu!martin@network.ucsd.edu
- Subject: Boring WWV Programs
- To: info-hams@ucsd.edu
-
- One day in the late seventies, I was tuned to the 10MHZ output for
- WWV and heard a strong aditional carrier appear on the frequency, almost at
- zero beat. The carrier lasted a few seconds and then was replaced by a
- male voice which said, "Hey! What time is it out there, WWV?" This was
- next followed by half a dozen or so hand-typed RTTY characters which were
- of the 850HZ shift variety. The transmitter, then left the frequency.
-
- The voice and the RTTY were heterodyned against WWV so that the voice
- was audible although I think it was originally SSB. I bet this was a rogue
- operator of a military or commercial avaiation system who was fooling around.
-
- If my memory serves me right, there was a 400HZ power supply whine
- on the audio like one might hear from an aircraft transmitter and the voice
- had that crisp, close-talked sound that usually comes from a headset
- microphone.
-
- Martin McCormick WB5AGZ Stillwater, OK
- O.S.U. Computer Center Data Communications Group
-
- ------------------------------
-
- Date: Sat, 12 Feb 1994 01:50:14 GMT
- From: hearst.acc.Virginia.EDU!murdoch!darwin.clas.Virginia.EDU!jad8e@uunet.uu.net
- Subject: Bosnian Ham Address
- To: info-hams@ucsd.edu
-
- I worked Danny, T93M, on 12 May 1993. He said he was in
- Sarajevo. Unfortunately, I don't know if he is still
- transmitting (or alive, either). We talked on 21.282 SSB at
- 1842 UTC. I didn't get a chance to chew the rag with him since
- he had a big pileup of folks trying to get to him. His QSL
- manager is DL8OBC.
-
- I know this info isn't directly relevant to the number that was
- posted, but if you managed to reach DL8OBC, he/she might be
- able to tell you the current operating situation.
- --
- __________________________________________________
- J. Andrew Dickerson jad8e@virginia.edu
- Amateur Radio KD4UKW 71442,547@compuserve.com
- __________________________________________________
-
- ------------------------------
-
- Date: 14 Feb 1994 09:43:29 GMT
- From: swrinde!cs.utexas.edu!math.ohio-state.edu!sol.ctr.columbia.edu!news.kei.com!bloom-beacon.mit.edu!senator-bedfellow.mit.edu!w1gsl@network.ucsd.edu
- Subject: Commercial Radio License Exam Opportunity ** Cambridge MA ** 12 March
- To: info-hams@ucsd.edu
-
- ** MROP and GROL exams in Cambridge MA ** Sat. March 12th 1994 **
-
- The MIT Radio Exam Team will conduct exams for the General
- Radiotelephone Operators License and the Marine Radio Operators
- Permit. The exams will be held at 10AM Saturday March 12th
- in Cambridge MA at 77 Mass Ave in MIT Room 1-150.
-
- A regular schedule of exams is planned for Cambridge MA. on the
- second Saturday of odd numbered months. For more information call
- Nick at 617 253 3776 (9-5).
-
- There is a $35 examination fee. Bring the ** original ** and a
- copy of any commercial license or proof of passing certificates
- you want to claim credit for. Also bring 2 forms of picture
- ID, a black pen and a pencil.
-
- Copies of the question pool are available from the Government
- Printing office or from W5YI at 1 800 669 9594.
- This is probably the best study guide available for the moment.
- A few copies are available for pickup in Cambridge.
-
- The General Radio Telephone Operators License is required to
- service transmitters in the aviation, maritime and international
- radio services. A Maritime Radio Operators Permit is required to
- operate radiotelephone stations aboard large ships and certain
- aviation and coast stations.
-
- At a later date exams will be available for the Commercial Radio
- Telegraph operators licenses and the Global Maritime Distress and
- Safety Systems (GMDSS) licenses. Amateur Extra Class operators may
- be particularly interested in obtaining a commercial telegraph
- license as they will receive credit for the 20 WPM 2nd class code exam.
-
- The MIT Radio Exam Team operates under the auspices of the
- National Radio Examiners COLEM, part of the W5YI group.
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 18:25:10 GMT
- From: agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!brunix!maxcy2.maxcy.brown.edu!cro@network.ucsd.edu
- Subject: Copying High-Speed CW: Print or Scr
- To: info-hams@ucsd.edu
-
- In article <9402130630592.gilbaronw0mn.DLITE@delphi.com>, gilbaronw0mn@delphi.com (Gilbert Baron) writes:
-
- |> Printing is not feasabile above 25 WPM. You must learn to use cursive.
-
- This is true if you want to copy everything in the QSO. However as you may
- do too, I usually copy in my head the conversation and jot notes on info
- such as report, name, etc. This is even more efficient and in my opinion easier.
-
- Christopher Ogren NM1Z
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 00:09:25 MST
- From: gulfaero.com!vixen.cso.uiuc.edu!howland.reston.ans.net!math.ohio-state.edu!cyber2.cyberstore.ca!nntp.cs.ubc.ca!alberta!ve6mgs!usenet@network.ucsd.edu
- Subject: Daily Summary of Solar Geophysical Activity for 14 February
- To: info-hams@ucsd.edu
-
- /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
-
- DAILY SUMMARY OF SOLAR GEOPHYSICAL ACT
-
- 14 FEBRUARY, 1994
-
- /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
-
- (Based In-Part On SESC Observational Data)
-
-
- SOLAR AND GEOPHYSICAL ACT
- ------------------------------------------------------------
-
- NOTE: Intense stratospheric warming and a strong anticyclone exists over
- the North Atlantic and Europe. Warm air is spreading east.
-
- Please also note the inclusion of greater than 2 MeV electron fluence
- values (useful for monitoring satellite charging activity).
-
- !!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 045, 02/14/94
- 10.7 FLUX=101 90-AVG=106 SSN=059 BKI=4433 3534 BAI=023
- BGND-XRAY=B2.3 FLU1=6.2E+06 FLU10=1.7E+04 PKI=4443 3544 PAI=028
- BOU-DEV=056,052,037,028,022,073,035,044 DEV-AVG=043 NT SWF=00:000
- XRAY-MAX= B7.9 @ 0032UT XRAY-MIN= B2.0 @ 1749UT XRAY-AVG= B2.8
- NEUTN-MAX= +003% @ 0945UT NEUTN-MIN= -001% @ 2105UT NEUTN-AVG= +0.6%
- PCA-MAX= +0.1DB @ 1845UT PCA-MIN= -0.4DB @ 0440UT PCA-AVG= -0.0DB
- BOUTF-MAX=55359NT @ 0416UT BOUTF-MIN=55304NT @ 1608UT BOUTF-AVG=55336NT
- GOES7-MAX=P:+000NT@ 0000UT GOES7-MIN=N:+000NT@ 0000UT G7-AVG=+065,+000,+000
- GOES6-MAX=P:+131NT@ 1727UT GOES6-MIN=N:-084NT@ 0648UT G6-AVG=+088,+040,-034
- FLUXFCST=STD:100,105,105;SESC:100,105,105 BAI/PAI-FCST=020,010,015/020,012,018
- KFCST=0115 5010 0005 5010 27DAY-AP=022,022 27DAY-KP=3333 5533 3553 4233
- WARNINGS=*AURMIDWCH
- ALERTS=
- !!END-DATA!!
-
- NOTE: The Effective Sunspot Number for 13 FEB 94 was 39.6.
- The Full Kp Indices for 13 FEB 94 are: 4+ 3+ 3o 5- 4- 5- 5- 4-
- The 3-Hr Ap Indices for 13 FEB 94 are: 33 19 15 41 21 37 42 24
- Greater than 2 MeV Electron Fluence for 14 FEB is: 3.6E+08
-
-
- SYNOPSIS OF ACT
- --------------------
-
- Solar activity was very low. Region 7671 (N10E65)
- features a large, dark, spot extending over three degrees.
-
- Solar activity forecast: solar activity is expected to be
- very low.
-
- STD: Region 7671 is associated with extremely intense Ca XV
- emissions. The National Solar Observatory reported extremely
- intense emissions as this region rotated around the east limb
- on 12 February. Bad weather has prevented attempts to observe
- emissions since then. C-class flares are possible from this
- region. The threat for possible satellite anomalies may
- continue for the next 2 or 3 days before electrons at greater
- than 2 MeV fall back toward background levels.
-
- The geomagnetic field has been at unsettled to minor storm
- levels at mid-latitudes and major storm levels at high
- latitudes. The storm which began 05 February continues at high
- latitudes, but appears to have receded at mid-latitudes. The
- energetic electron flux is elevated for the seventh day
- in a row.
-
- Geophysical activity forecast: the geomagnetic field is
- expected to range from unsettled to minor storm for day one.
- The field is expected to relax to mostly unsettled levels
- for day two. A new coronal hole may disturb the magnetic field
- on day three.
-
- Event probabilities 15 feb-17 feb
-
- Class M 05/05/05
- Class X 01/01/01
- Proton 01/01/01
- PCAF Green
-
- Geomagnetic activity probabilities 15 feb-17 feb
-
- A. Middle Latitudes
- Active 35/25/30
- Minor Storm 20/15/20
- Major-Severe Storm 05/05/05
-
- B. High Latitudes
- Active 35/25/30
- Minor Storm 25/15/20
- Major-Severe Storm 05/05/05
-
- HF propagation conditions continue to very slowly improve,
- but are still well below normal, particularly on higher
- latitude paths. Conditions are expected to remain below-normal
- for at least the next 3 to 4 days. Another smaller coronal
- hole related disturbance is expected to rejuvenate activity on
- about 17 February, although it should primarily affect the
- higher latitudes.
-
-
- COPIES OF JOINT USAF/NOAA SESC SOLAR GEOPHYSICAL REPORTS
- ========================================================
-
- REGIONS WIT
- -----------------------------------------------------------
- NMBR LOCATION LO AREA Z LL NN MAG TYPE
- 7668 N09W29 283 0050 CSO 09 011 BET
- 7669 N05E32 222 0000 AXX 00 001 ALPHA
- 7670 N08E48 206 0010 BXO 05 004 BET
- 7671 N10E65 189 0450 CHO 06 003 BET
- 7667 S07W80 334 PLAGE
- REGIONS DUE TO RET
- NMBR LAT
- 7659 S13 150
-
-
- LISTING OF SOLAR ENERGETIC EVENTS FOR 14 FEBRUARY, 1994
- -------------------------------------------------------
- A. ENERGETIC EVENTS:
- BEGIN MAX END RGN LOC XRAY OP 245MHZ 10CM SWEEP
- NONE
-
-
- POSSIBLE CORONAL MASS EJECTION EVENTS FOR 14 FEBRUARY, 1994
- -----------------------------------------------------------
- BEGIN MAX END LOCATION TYPE SIZE DUR II IV
- NO EVENTS OBSERVED
-
-
- INFERRED CORONAL HOLES. LOCATIONS VALID AT 14/2400Z
- ---------------------------------------------------
- ISOLATED HOLES AND POLAR EXT
- EAST SOUTH WEST NORTH CAR TYPE POL AREA OBSN
- NO DAT
-
-
- SUMMARY OF FLARE EVENTS FOR THE PREVIOUS UTC DAY
- ------------------------------------------------
-
- Date Begin Max End Xray Op Region Locn 2695 MHz 8800 MHz 15.4 GHz
- ------ ---- ---- ---- ---- -- ------ ------ --------- --------- ---------
- 13 Feb: 0051 0244 0429 C1.3
-
-
- REGION FLARE STATISTICS FOR THE PREVIOUS UTC DAY
- ------------------------------------------------
-
- C M X S 1 2 3 4 Total (%)
- -- -- -- -- -- -- -- -- --- ------
- Uncorrellated: 1 0 0 0 0 0 0 0 001 (100.0)
-
- Total Events: 001 optical and x-ray.
-
-
- EVENTS WIT
- ----------------------------------------------------------------
-
- Date Begin Max End Xray Op Region Locn Sweeps/Optical Observations
- ------ ---- ---- ---- ---- -- ------ ------ ---------------------------
- 13 Feb: 0051 0244 0429 C1.3 IV
-
- NOTES:
- All times are in Universal Time (UT). Characters preceding begin, max,
- and end times are defined as: B = Before, U = Uncertain, A = After.
- All times associated with x-ray flares (ex. flares which produce
- associated x-ray bursts) refer to the begin, max, and end times of the
- x-rays. Flares which are not associated with x-ray signatures use the
- optical observations to determine the begin, max, and end times.
-
- Acronyms used to identify sweeps and optical phenomena include:
-
- II = Type II Sweep Frequency Event
- III = Type III Sweep
- IV = Type IV Sweep
- V = Type V Sweep
- Continuum = Continuum Radio Event
- Loop = Loop Prominence System,
- Spray = Limb Spray,
- Surge = Bright Limb Surge,
- EPL = Eruptive Prominence on the Limb.
-
-
- ** End of Daily Report **
-
- ------------------------------
-
- Date: Sun, 13 Feb 1994 20:55:06 GMT
- From: agate!library.ucla.edu!europa.eng.gtefsd.com!darwin.sura.net!news.Vanderbilt.Edu!news@ames.arpa
- Subject: GAP DX EAGLE comments?
- To: info-hams@ucsd.edu
-
- Hi,
-
- I was wondering if anyone has had any experience with the DX Eagle antenna
- which GAP makes. It is a smaller version which is roughly comparable
- to the R-7. I have a lot of input on the Cushcraft, but not much
- on this particular GAP model. Most of the info I have gotten involves
- experience with the larger low band versions, and is negative.
-
- 73
-
- Alan
-
-
- Recommended
- four
- line
- signature.
-
- ------------------------------
-
- Date: 15 Feb 94 19:33:48 GMT
- From: news-mail-gateway@ucsd.edu
- Subject: Nude QSL cards
- To: info-hams@ucsd.edu
-
- John Meaker (kr4ah) writes:
- |
- | 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.
-
- There has been considerable discussion about the demography of the
- amateur radio community and how we can attract younger people to the
- hobby. Although nude QSL cards may attract teen-age boys to the hobby, I
- hope we don't have to resort to this method.
-
- My son got his novice license when he was 11 and my daughter when she was
- 8. Regardless of what you may think about my moral values and religious
- convictions, I feel it is my responsibility to teach them to my children
- and help guide them through the difficulties of puberty which are before
- them. I would feel extremely offended if someone sent a nude QSL card to
- either of my kids. I do not wish either of my kids to be receiving nude
- photos in sealed envelopes, either.
-
- My opinion is not up for debate here. Remember, the question is whether
- nude qsl cards may be offensive. I suspect that there may be some people
- who preach tolerance but will not tolerate my position on this issue.
- They may even be driven to challenge my beliefs. As this is not the
- issue, their comments are being redirected to /dev/null.
-
-
- Best Wishes. Lowell (kc7dx)
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 02:23:02 GMT
- From: scubed!ihnp4.ucsd.edu!sdd.hp.com!vixen.cso.uiuc.edu!howland.reston.ans.net!agate!library.ucla.edu!csulb.edu!csus.edu!netcom.com!henrys@network.ucsd.edu
- Subject: Vision Impaired Ham needs help
- To: info-hams@ucsd.edu
-
- Today I spoke with Roy, W8SAG who is a vision impaired ham (age 75)
- who lives in Colorado Springs, Colorado.
-
- Roy does not have a computer, so I told him that I would do my best
- to find out everything that I could about *talking* computers and
- programs that can assist the blind ham.
-
- If you know anything about *talking* computers, the software and
- hardware, please Email me. I will pass the info along to Roy.
-
- Thanks,
-
- Smitty, NA5K
-
- --
- -----------------------------------------------------------------------
- | Henry B. Smith - NA5K henrys@netcom.com |
- | Dallas, Texas |
- | |
- | "I'm not sure I understand everything that I know" |
- -----------------------------------------------------------------------
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 16:09:36 GMT
- From: agate!howland.reston.ans.net!gatech!wa4mei.ping.com!ke4zv!gary@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <bote.760946660@access1>, <1994Feb12.160701.4407@ke4zv.atl.ga.us>, <1994Feb14.131000.8706@arrl.org>
- Reply-To : gary@ke4zv.atl.ga.us (Gary Coffman)
- Subject : Re: Medium range point-to-point digital links
-
- 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.
-
- >: Now the Nyquist limit says we have to sample at a minimum
- >: of twice the highest frequency in the audio. If we assume
- >: that's 5 kHz, then our minimum sample rate is 10 kilosamples
- >: 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. That's not going to fit in a
- >: normal FM two way radio bandwidth, so we're going to have to
- >: resort to trickery.
- >
- >Yes, you sample at that higher rate, but then you digitally filter with
- >a near-brick-wall filter and reduce the sample rate to very near the
- >Nyquist rate, via decimation. (Consider compact disks.) At the
- >receiving end you interpolate to raise the sample rate back to
- >something that can use reasonable reconstruction low-pass filters. So,
- >a more realistic analysis gives a transmitted 10 kHz sampling rate at 8
- >bits per sample, for 80 kbit/s.
-
- I'll buy the digital filtering and decimation, and I'll even allow
- that interpolation is acceptable at the Nyquist limit. I won't buy
- into 8 bits, however. Whether you need a power spectrum ratio of
- 50 db, or a voltage ratio of 100 db, 8 bits still doesn't do it.
- So we're back with a 160 kb/s data stream before compression.
-
- >: Codecs use various compression schemes to lower the effective
- >: bit rate. Delta modulation is one such trick, and LPC (linear
- >: predictive coding) is another. These are effective real time
- >: compression methods, but do suffer some artifacts. Or we can
- >: take a page from the newer high speed telephone modems and use
- >: LZW type on the fly lossless compression and complex modem
- >: encodings that use less than one baud per bit. Off the shelf
- >: modems can deliver up to 56 kb effective data throughput over
- >: voice grade channels wsing a base baud rate of 600 baud. That's
- >: not quite good enough though.
- >
- >Even if you could make that degree of m-ary coding work on a radio
- >link, which I have my doubts about.
-
- You can, but it has to be a well engineered full duplex link. Of
- course if you had voice grade links that good to begin with, you
- wouldn't need to be worrying about digital audio to improve SNR. :-)
-
- >: 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
- >: compression scheme like LZW, we can easily get the required 240 kb/s
- >: throughput for broadcast grade audio without dealing with the timing
- >: artifacts of delta modulation or LPC. Occupied bandwidth would be
- >: less than 70 kHz.
- >
- >In my experience, LZW doesn't compress speech all that well. You'll be
- >lucky to get a 2:1 compression; you certainly won't get 4:1. Worse, you
- >won't get that compression consistently. Some parts of the transmission
- >will be compressed more than others, leading to timing/buffering
- >problems. You really want a compression scheme that is tailored to
- >speech.
-
- Yes, LZW is just an example of a compression scheme currently popular
- for on-the-fly use in data modems. However, delta modulation can also
- be "bursty" leading to time distortion of the audio, and a single
- error can propagate for a significant time before the system recovers.
- There are tricks that are helpful, however, if we know the nature of
- speech, and we do. There are band gaps in the speech power spectrum,
- and there are time characteristics to the key sounds that we can use
- to tailor a compression scheme to minimize redundancy in the bit stream
- without going to excessively lossy methods. We can also make use of
- group and run length coding on partial samples of the spectrum before
- merging them into the final bit stream, IE we know that a low frequency
- speech component is going to presist for several milliseconds so we don't
- have to transmit repetitive samples to reproduce it. (This requires a bit
- of tricky DSP, but it's doable.)
-
- >: If we can settle for less than perfection, however, Motorola has
- >: a codec scheme that they claim can fit a digital voice signal in
- >: the same bandwidth as a NBFM voice signal, IE 20 KHz. It won't
- >: work through off the shelf FM radios though, a purpose built
- >: radio is required, and it won't yield "broadcast" SNRs. I have
- >: the write up on it around here somewhere, but can't lay my hands
- >: on it right now. I seem to recall that its an 8 bit system so
- >: the SNR is going to be around 27 db. It should be noted that hams
- >: consider the 20 db quieting level "full quieting" and thus perfectly
- >: acceptable audio quality.
- >
- >8 bits is entirely adequate (see above). I'm not familiar with the
- >Motorola system, but I suggest that it is probably *not* using a
- >lossless compression scheme. That means that you'll experience some
- >additional noise/distortion, beyond quantization noise.
-
- Yes, the compression method is lossy. That, and the limitation of
- 8 bit sampling, is why I don't consider it capable of yielding a
- broadcast SNR.
-
- >I've done some playing with MX-COM's CVSD codec. While I haven't
- >analyzed the SNR, "by ear" it produces reasonable reproduction at 32
- >kbit/s and audio I can stand to listen to (barely) at 16 kbit/s. At 64
- >kbit/s, its audio is entirely acceptable for amateur purposes. IMHO.
-
- The ear is rather easily fooled since most of us have poor sonic memory.
- Rapid A/B testing between the source audio and the reconstitued digital
- audio will quickly show the difference, however. An even better test is
- to feed a pair of headphones such that the original audio is in one
- channel, and the reconstituted signal is in the other. Shifts in the
- sound stage are an immediate clue as to defects in the reconstituted
- signal. We can use poor sonic memory to our advantage in communications
- links, but 8 bits isn't good enough to fool the ear under most conditions.
- 8 bits can fool the eye, 255 grey levels are sufficient for luminance video,
- but anything less than 12 bits is noticable to the ear, and 16 bits are
- required if that ear is trained and discerning.
-
- As I mentioned, most amateurs consider a 20 db quieting, power ratio,
- sufficiently good for a communications channel. That's doable in 8 bits,
- but it won't meet the criteria of this discussion.
-
- Gary
- --
- Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
- Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary
- 534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary
- Lawrenceville, GA 30244 | |
-
- ------------------------------
-
- Date: Mon, 14 Feb 94 22:00:33 -0500
- From: scubed!ihnp4.ucsd.edu!sdd.hp.com!vixen.cso.uiuc.edu!howland.reston.ans.net!noc.near.net!news.delphi.com!usenet@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <1994Jan28.171743.483@arrl.org>, <gregCKI0zw.Kuo@netcom.com>, <1994Feb3.190229.8136@arrl.org>
- Subject : Re: RAMSEY FX TRANSCEIVER
-
- 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.
- 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.
- No, you'll not see a Ramsey ad in QST. It was years ago that I was approached
- by a QST ad director to advertise. He expounded how QST was looking out for the
- amateur, requiring test units before accepting ads. I responded that they had
- plenty of ad pages from DSI, a since defunct freq ctr mfg who sold trash and
- was openly taking $$ for products they had no intention of shipping! Of this is
- the virtue you speak? Well, DSI closed shop, took QST readers for hundreds of
- thousands of dollars and even stuck that nice old ad director too!
- Yes, I'm hot and seeing this kangoroo (sp?) court makes me long for my work-
- bench rather than this CRT. I don't have the luxury of getting paid to
- read and respond to everything here - but I do welcome phone calls to myself
- at the office (716) 924-4560. Just ask for me.
-
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- End of Info-Hams Digest V94 #156
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