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- Date: Thu, 24 Mar 94 03:41:12 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 #323
- To: Info-Hams
-
-
- Info-Hams Digest Thu, 24 Mar 94 Volume 94 : Issue 323
-
- Today's Topics:
- Daily Summary of Solar Geophysical Activity for 22 March
- Grid Squares & Lat/Long
- Grounding and lightning protection--KE4ZV (2 msgs)
- Kenwood (TS-850) Computer Interface Info Wanted
- Latest FCC issued call signs
- Parts for Heathkit???
- software-general exam
- Who Brian is
-
- 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, 22 Mar 1994 21:09:29 MST
- From: ihnp4.ucsd.edu!usc!yeshua.marcam.com!zip.eecs.umich.edu!newsxfer.itd.umich.edu!nntp.cs.ubc.ca!alberta!ve6mgs!usenet@network.ucsd.edu
- Subject: Daily Summary of Solar Geophysical Activity for 22 March
- To: info-hams@ucsd.edu
-
- /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
-
- DAILY SUMMARY OF SOLAR GEOPHYSICAL ACTIVITY
-
- 22 MARCH, 1994
-
- /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
-
- (Based In-Part On SESC Observational Data)
-
-
- SOLAR AND GEOPHYSICAL ACTIVITY INDICES FOR 22 MARCH, 1994
- ---------------------------------------------------------
-
- NOTE: A large region of stratospheric warming exists from southern to eastern
- Europe and southwestern Siberia, and is strengthening. Warm air is
- spreading north and northeastwards.
-
- !!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 081, 03/22/94
- 10.7 FLUX=091.1 90-AVG=106 SSN=035 BKI=4222 4322 BAI=013
- BGND-XRAY=A7.7 FLU1=7.1E+06 FLU10=1.8E+04 PKI=4323 5333 PAI=018
- BOU-DEV=067,017,011,018,066,028,017,016 DEV-AVG=030 NT SWF=00:000
- XRAY-MAX= B3.0 @ 0644UT XRAY-MIN= A6.8 @ 0935UT XRAY-AVG= B1.0
- NEUTN-MAX= +003% @ 0005UT NEUTN-MIN= -002% @ 1350UT NEUTN-AVG= +0.2%
- PCA-MAX= +0.1DB @ 2350UT PCA-MIN= -0.2DB @ 2315UT PCA-AVG= -NANDB
- BOUTF-MAX=55344NT @ 0126UT BOUTF-MIN=55306NT @ 1803UT BOUTF-AVG=55330NT
- GOES7-MAX=P:+000NT@ 0000UT GOES7-MIN=N:+000NT@ 0000UT G7-AVG=+072,+000,+000
- GOES6-MAX=P:+126NT@ 1735UT GOES6-MIN=N:-088NT@ 0449UT G6-AVG=+091,+021,-042
- FLUXFCST=STD:090,090,085;SESC:090,090,085 BAI/PAI-FCST=015,010,010/020,015,015
- KFCST=3223 2111 3223 4111 27DAY-AP=011,005 27DAY-KP=2333 2232 1112 2121
- WARNINGS=
- ALERTS=
- !!END-DATA!!
-
- NOTE: The Effective Sunspot Number for 21 MAR 94 is not available.
- The Full Kp Indices for 21 MAR 94 are: 3o 6- 4o 4o 4- 4o 4- 3-
- The 3-Hr Ap Indices for 21 MAR 94 are: 15 65 26 30 21 28 21 13
- Greater than 2 MeV Electron Fluence for 22 MAR is: 1.6E+08
-
-
- SYNOPSIS OF ACTIVITY
- --------------------
-
- Solar activity was very low. Region 7693 (N08W56) showed
- some growth early in the period but was quiet and stable. A
- hedge-row prominence was visible on east limb throughout the
- day.
-
- Solar activity forecast: solar activity is expected to be
- very low to low.
-
- The geomagnetic field ranged from quiet to minor storm levels.
- The more disturbed periods were 0000-0300Z and 0900-1800Z, and
- the other times were typically quiet to unsettled.
-
- Geophysical activity forecast: the geomagnetic field is
- expected to be unsettled to active for the next 24 hours. Con-
- ditions should be predominantly unsettled for the second and
- third days although there may be occasional brief periods of
- active levels.
-
- Event probabilities 23 mar-25 mar
-
- Class M 01/01/01
- Class X 01/01/01
- Proton 01/01/01
- PCAF Green
-
- Geomagnetic activity probabilities 23 mar-25 mar
-
- A. Middle Latitudes
- Active 25/25/10
- Minor Storm 25/10/05
- Major-Severe Storm 10/05/01
-
- B. High Latitudes
- Active 25/25/10
- Minor Storm 30/10/05
- Major-Severe Storm 10/05/01
-
- HF propagation conditions were slightly below normal over
- the high and polar latitude regions for the first half of the
- UTC day, but improved to near normal by the end of the day.
- Near-normal propagation conditions are expected over all
- regions during the next 72 hours through 25 March inclusive
- although a few periods of night-sector high-latitude minor
- signal degradation will remain possible.
-
-
- COPIES OF JOINT USAF/NOAA SESC SOLAR GEOPHYSICAL REPORTS
- ========================================================
-
- REGIONS WITH SUNSPOTS. LOCATIONS VALID AT 22/2400Z MARCH
- --------------------------------------------------------
- NMBR LOCATION LO AREA Z LL NN MAG TYPE
- 7692 N18W19 159 0030 CSO 04 003 BETA
- 7693 N08W56 196 0070 CSO 06 012 BETA
- 7688 N19W88 228 PLAGE
- REGIONS DUE TO RETURN 23 MARCH TO 25 MARCH
- NMBR LAT LO
- 7686 N08 037
-
-
- LISTING OF SOLAR ENERGETIC EVENTS FOR 22 MARCH, 1994
- ----------------------------------------------------
- BEGIN MAX END RGN LOC XRAY OP 245MHZ 10CM SWEEP
- NONE
-
-
- POSSIBLE CORONAL MASS EJECTION EVENTS FOR 22 MARCH, 1994
- --------------------------------------------------------
- BEGIN MAX END LOCATION TYPE SIZE DUR II IV
- NO EVENTS OBSERVED
-
-
- INFERRED CORONAL HOLES. LOCATIONS VALID AT 22/2400Z
- ---------------------------------------------------
- ISOLATED HOLES AND POLAR EXTENSIONS
- EAST SOUTH WEST NORTH CAR TYPE POL AREA OBSN
- 70 N40W12 S26W34 S04W62 N48W14 175 ISO POS 023 10830A
- 71 S14E38 S20E28 S10E26 S10E26 106 ISO POS 002 10830A
-
-
- SUMMARY OF FLARE EVENTS FOR THE PREVIOUS UTC DAY
- ------------------------------------------------
-
- Date Begin Max End Xray Op Region Locn 2695 MHz 8800 MHz 15.4 GHz
- ------ ---- ---- ---- ---- -- ------ ------ --------- --------- ---------
- 21 Mar: 1056 1114 1126 SF 7693 N07W36
- 1130 1130 1134 SF 7693 N07W36
- 1548 1625 1703 B8.2 SF 7688 N21W68
- 1755 1758 1803 B3.1 SF 7693 N10W39
- 1906 1913 1926 B3.6 SF 7693 N08W40
- 2138 2150 2204 B3.2
-
-
- REGION FLARE STATISTICS FOR THE PREVIOUS UTC DAY
- ------------------------------------------------
-
- C M X S 1 2 3 4 Total (%)
- -- -- -- -- -- -- -- -- --- ------
- Region 7688: 0 0 0 1 0 0 0 0 001 (16.7)
- Region 7693: 0 0 0 4 0 0 0 0 004 (66.7)
- Uncorrellated: 0 0 0 0 0 0 0 0 001 (16.7)
-
- Total Events: 006 optical and x-ray.
-
-
- EVENTS WITH SWEEPS AND/OR OPTICAL PHENOMENA FOR THE LAST UTC DAY
- ----------------------------------------------------------------
-
- Date Begin Max End Xray Op Region Locn Sweeps/Optical Observations
- ------ ---- ---- ---- ---- -- ------ ------ ---------------------------
- NO EVENTS OBSERVED.
-
- 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: Wed, 23 Mar 1994 22:46:04 GMT
- From: world!drt@uunet.uu.net
- Subject: Grid Squares & Lat/Long
- To: info-hams@ucsd.edu
-
- Jay Sissom (JAY@medicine.dmed.iupui.edu) wrote:
- : Hello!
-
- : I recently borrowed a GPS device to calculate my Latitude & Longitude. I
- : found a couple of basic programs on Compuserve to calculate my grid square
- : from this info. Either something is wrong with the program, or something is
- : wrong with the ARRL map in one of their books. Here is my lat/long:
-
- : Lattitude: 39' 39.303 N
- : Longatude: 89' 10.550 W
-
- : When I feed these numbers into the programs, I get EM59JP. When I look on the
- : map, EM59 is in Illinois and I live in Indianapolis, IN. Is the map wrong, or
- : is the basic program wrong?
-
- : Thanks
- : Jay
- : KA9OKT
-
- Well, the World Almanac says the coordinates for Indianapolis are
-
- 39.7678 N
- 86.1628 W
-
- So I'd say that, gadget or no gadget, your Lat/Long figures are wrong.
-
- -drt
-
- ------------------------------------------------------------------------
- |David R. Tucker KG2S drt@world.std.com|
- ------------------------------------------------------------------------
-
- ------------------------------
-
- Date: Wed, 23 Mar 1994 18:51:39 GMT
- From: ihnp4.ucsd.edu!pacbell.com!uop!csus.edu!netcom.com!wa2ise@network.ucsd.edu
- Subject: Grounding and lightning protection--KE4ZV
- To: info-hams@ucsd.edu
-
- In article <Cn41oy.L6@hpqmoea.sqf.hp.com> dstock@hpqmoca.sqf.hp.com (David Stockton) writes:
- >: or 5.11 kW-hr. That's 18.396 Megajoules.
- >
- >: Gary
- >
- > That sounds much more like the kind of numbers I wouldn't want to be
- >anywhere near !
- >
- > The ground rod itself will be a small fraction of the resistance and
- >so get a small fraction of the energy, it will be the ground around the
- >rod that takes the brunt. Instant steam explosion?
- >
- About 30 years ago, lightning hit a tree in my parent's house's
- backyard. Boom! Wooden schrapnel all over the backyard! Good
- thing we were all inside the house. Probably a steam explosion in
- the tree.
-
- ------
- A day without netnews is like a day without sunshine!
-
- ------------------------------
-
- Date: Thu, 24 Mar 1994 00:34:03 GMT
- From: ihnp4.ucsd.edu!swrinde!gatech!wa4mei!ke4zv!gary@network.ucsd.edu
- Subject: Grounding and lightning protection--KE4ZV
- To: info-hams@ucsd.edu
-
- In article <Cn4ywC.62s@hpcvsnz.cv.hp.com> tomb@lsid.hp.com (Tom Bruhns) writes:
- >Re: lightening strikes to ground rods, etc.
- >
- >Gotta be a little careful assuming things stay linear at power levels
- >like lightening can deliver. 4000 amps * 200 ohms is 800kV, and
- >that's got a pretty good probability of ionizing the surrounding
- >material, yielding a dynamic resistance that could be a small fraction
- >of an ohm (or even negative), disallowing such a high potential drop.
-
- That's true, at least to an extent. The main mechanism for conduction
- in soil is sparking from soil grain to soil grain. The biggest current
- limiter in soil is the charge saturation that occurs in the vicinity
- of the rod. The mechanisms can be complex, and dependent on soil
- characteristics and soil moisture. 230 ohms is just a typical value
- for the mythical typical conditions, sort of like the typical American
- family with 2.3 kids. :-)
-
- 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: 23 Mar 1994 20:02:50 -0500
- From: ihnp4.ucsd.edu!galaxy.ucr.edu!library.ucla.edu!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!ddsw1!panix!not-for-mail@network.ucsd.edu
- Subject: Kenwood (TS-850) Computer Interface Info Wanted
- To: info-hams@ucsd.edu
-
- A friend is interested in getting details about the computer
- interface "box" used with the Kenwood TS-850. Has anybody built one
- for themselves (rather than buying Kenwood's)? Does anybody have
- schematics? I'm sure that recommendations of commercially available
- software and other hints and kinks would be appreciated as well.
- Email to me (adam@panix.com) and I'll forward your replies.
-
- -Thanx
- -Adam (N2DHH)
-
- ------------------------------
-
- Date: Wed, 23 Mar 1994 19:25:17 GMT
- From: ihnp4.ucsd.edu!swrinde!emory!europa.eng.gtefsd.com!howland.reston.ans.net!news.intercon.com!psinntp!psinntp!psinntp!arrl.org!gswanson@network.ucsd.edu
- Subject: Latest FCC issued call signs
- To: info-hams@ucsd.edu
-
- List of the last call sign issued AS OF MARCH 1, 1994
- Per the FCC:
-
- Note: "-----" = out of calls in that group, default to next Group
- to the right. Example: In Radio District 0, they are out of
- Group C calls, so they are issuing from Group D for Tech/Gen.
-
-
- Radio District Group A Group B Group C Group D
- (Extra) (Advanced) (Tech/Gen) (Novice)
-
- 0 AA0QI KG0LO ----- KB0LYV
- 1 AA1IV KD1TZ N1RMF KB1BGS
- 2 AA2RH KF2UA N2YBR KB2QXD
- 3 AA3HG KE3MC N3RPA KB3BBC
- 4 AD4QG KR4NY ----- KE4KAL
- 5 AB5TB KJ5VI ----- KC5FON
- 6 AC6AP KN6YT ----- KE6FTE
- 7 AB7BL KI7WH ----- KC7BDO
- 8 AA8OI KG8HH ----- KB8RSM
- 9 AA9KI KF9UM N9WHC KB9IXF
- Hawaii ----- AH6NF WH6SV WH6CRD
- Alaska ----- AL7PO WL7QW WL7CHL
- Puerto Rico ----- KP4WM ----- WP4MNW
- Guam WH2D AH2CU KH2JB WH2ANK
- Virgin Islands WP2G KP2CC NP2HG WP2AHU
- Amer. Samoa AH8I AH8AG KH8BB WH8ABB
-
- For more information about call sign assignment in the Amateur Radio
- Service see Section 97.17(f) of the FCC Rules.
-
- 73, Glenn KB1GW (ARRL/VEC)
-
- ------------------------------
-
- Date: 23 Mar 94 04:21:00 GMT
- From: ihnp4.ucsd.edu!swrinde!gatech!concert!news.duke.edu!duke!wolves!psybbs!fredmail@network.ucsd.edu
- Subject: Parts for Heathkit???
- To: info-hams@ucsd.edu
-
- MA>From my understanding of things, Heatkit as we knew is is out
- MA>of business. Is there a source where I can pick up replacement
- MA>parts for one of their kits? Specifically the 51-120 Audio
- MA>Transformer.
- MA>Thanks!
- MA>Matt Adair
-
- Hi Matt! What is this xfmr in?? 73 de WB4IUY
-
- ___
- X OLX 2.2 X ...As I said before, I never repeat myself.
-
- ------------------------------
-
- Date: Wed, 23 Mar 1994 05:11:12 GMT
- From: ihnp4.ucsd.edu!agate!msuinfo!netnews.upenn.edu!iat.holonet.net!pubcon!joe.coles@network.ucsd.edu
- Subject: software-general exam
- To: info-hams@ucsd.edu
-
- IF anyone knows of the existance of a shareware/freeware program that
- presents random questions from the current General exam (a practive exam
- program), please let me know where I might download a copy.
- Thanks,
- Joe Coles
- jcoles@pubcon.fort-worth.tx.us
- KC5BSK
-
- ------------------------------
-
- Date: Thu, 24 Mar 1994 02:58:58 GMT
- From: ihnp4.ucsd.edu!galaxy.ucr.edu!library.ucla.edu!news.ucdavis.edu!chip.ucdavis.edu!ez006683@network.ucsd.edu
- Subject: Who Brian is
- To: info-hams@ucsd.edu
-
- alan v. cook (alan_v._cook@smtpgty.anatcp.rockwell.COM) wrote:
-
- : Perhaps someone should explain to Jeff who Brian is, what Brian stands
- : for, and why, if Brian decides it should be so, almost no one will be
- : able to hear him. I'd do it, but it might be more fun to watch Jeff
- : squirm a little...
-
- I don't know if Jeff knows who Brian is or not. I don't think that being
- eliminated from the digests will cause one to be heard by "almost no one"
- though. It is an interesting point though. I never thought about the
- fact that the digests were censored. Have they been previously? I always
- thought the digests on QRZ? were unadulteraated from their news origin,
- except headers etc. I know that the readership numbers are occasionally
- posted but I've never seen anything regarding the size of the digest
- subscription list.
-
- cheers,
- Dan
- --
- *---------------------------------------------------------------------*
- * Daniel D. Todd Packet: KC6UUD@KE6LW.#nocal.ca.usa *
- * Internet: ddtodd@ucdavis.edu *
- * Snail Mail: 1750 Hanover #102 *
- * Davis CA 95616 *
- *---------------------------------------------------------------------*
- * All opinions expressed herein are completely ficticious any *
- * resemblence to actual opinions of persons living or dead is *
- * completely coincidental. *
- *---------------------------------------------------------------------*
-
-
- ------------------------------
-
- Date: Wed, 23 Mar 1994 23:40:07 GMT
- From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!gatech!wa4mei!ke4zv!gary@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <1994Mar23.000101.38868@rs6000.cmp.ilstu.edu>, <1994Mar23.125211.19448@ke4zv.atl.ga.us>, <1994Mar23.174258.8681@arrl.org>
- Reply-To : gary@ke4zv.atl.ga.us (Gary Coffman)
- Subject : Re: Telecom and Meteors
-
- In article <1994Mar23.174258.8681@arrl.org> zlau@arrl.org (Zack Lau (KH6CP)) writes:
- >Gary Coffman (gary@ke4zv.atl.ga.us) wrote:
- >
- >: We're talking about the constant rain of micrometeoroids here, not the
- >: big visible ones. Individual "pings" are short, but there's a constant
- >: source of them. Hams who work meteor scatter tend to wait for the big
- >: meteor storms and use the longer, and rarer, pings off the larger trails,
- >: but that's not necessary. Only if you use analog voice or hand keyed
- >: Morse are the longer pings needed. If you use digital burst communications,
- >: and good FEC, you can take advantage of the constant supply of short pings
- >: available from micrometeoriods.
- >
- >Long bursts are also needed for AX.25 packet. I don't believe amateurs
- >have actually developed an optimized data system to take advantage of
- >meteor scatter. I'd estimate that there are approximately 0 data
- >links in the amateur service that rely on meteor scatter right now.
- >I suspect that amateurs are still busy working on other options that
- >seem offer more capability.
-
- It's certainly true that typical amateur grade packet is not suited
- to meteor burst communications. Ralph Wallio conducted some tests at
- 1200 baud a few years ago. With short packets (<40 char) some complete
- packets make it, but the trail dies before the ACK can be sent, except
- during showers. Higher speeds would be helpful, but the FCC limits us
- to 19.6 kb on 50 MHz, and really fast TR turnarounds are needed. AMTOR
- sort of works, but it doesn't utilize the pings very effectively.
-
- What we really need, however, is a different approach. In the first
- place, we need to be operating full duplex. With both ends transmitting
- continously, any path is immediately obvious to both ends, and as much
- data can be pushed through as possible during each ping. We also need
- to use a selective broadcast protocol rather than a stop and wait
- protocol. Each side pushes their message through to it's end, and
- repeats only those parts unacknowledged until no unacknowledged
- data remains. The receivers then assemble the messages from the
- received fragments.
-
- Using FEC may or may not be a win here. I think it may, Paul seems to
- think it won't. But I want to apply it somewhat differently than the
- usual case. I want to use the method used in D2 digital videotape. This
- technique "smears" errors across the matrix such that no long burst errors
- are contained in any single FEC protected block. The way this is done is
- to read a frame into a matrix by rows, calculate FEC values by column
- and store them in the last row, calculate a cross FEC by row and store
- it in the last column, and then read out the data for transmission in
- reverse order by columns. If we keep the frame size such that a frame can
- be sent in under a second, about 1500 characters if we use 19.6 kb, then
- on average we should get a frame through per ping. Since the pings are
- generally underdense, and have some doppler, I think the block encoded
- FEC frames will have a much better chance of being reconstructed whole
- than would unprotected blocks.
-
- 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: Thu, 24 Mar 1994 01:55:56 GMT
- From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!emory!wa4mei!ke4zv!gary@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <1994Mar23.000101.38868@rs6000.cmp.ilstu.edu>, <1994Mar23.125211.19448@ke4zv.atl.ga.us>, <paulf.764453359@abercrombie.Stanford.EDU>
- Reply-To : gary@ke4zv.atl.ga.us (Gary Coffman)
- Subject : Re: Telecom and Meteors
-
- In article <paulf.764453359@abercrombie.Stanford.EDU> paulf@abercrombie.Stanford.EDU (Paul Flaherty) writes:
- >gary@ke4zv.atl.ga.us (Gary Coffman) writes:
- >
- >>If you use digital burst communications, and good FEC, you can take advantage
- >>of the constant supply of short pings available from micrometeoriods.
- >
- >Actually, there's some question as to the utility of FEC for MBC systems.
- >Since trail dissipation is a rapid exponential process, signals tend to
- >fall below threshold, on average, in the middle of packets; the required
- >overhead to correct half a packet is quite large, and since one could
- >potentially use those overhead bits to send real information, you're much
- >better off with some sort of a selective retransmission system.
-
- If the system is falling below threshold in the middle of packets, your
- packets are too long. :-)
-
- Seriously, I think what you're trying to say is that on average the
- last frame of a series is lost in the middle. But what that actually
- means is that for any given last frame, *some* of the frame is lost,
- in a range from 99% to 1%, that averages over time to 50%. That means
- in turn that some frames can be recovered with minor overhead, some
- can be recovered with major overhead, and a few are too far gone to
- recover at all.
-
- If the last of a series of frames sent during a burst were all that
- were lost, then I'd agree that FEC is probably not worth the effort.
- But with the underdense pings we're discussing, that's not the case.
- The channel will be noisy, and subjected to doppler throughout. What
- FEC buys us is a good chance to salvage those frames that are sent
- *before* the trail decays beyond recovery.
-
- 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: Thu, 24 Mar 1994 03:00:16 GMT
- From: ihnp4.ucsd.edu!swrinde!gatech!wa4mei!ke4zv!gary@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <2ml9q1$25h@hplvec.lvld.hp.com>, <2mn2rd$ol0@vixen.cso.uiuc.edu>, <1994Mar23.162557.7558@arrl.org>
- Reply-To : gary@ke4zv.atl.ga.us (Gary Coffman)
- Subject : Re: RF and AF speech processors. Was: FT-990 vs TS-850
-
- In article <1994Mar23.162557.7558@arrl.org> zlau@arrl.org (Zack Lau (KH6CP)) writes:
- >Ignacy Misztal (ignacy@ux2.cso.uiuc.edu) wrote:
- >
- >: I am wondering why the QST reviews do not mention the type of processing,
- >: which has a large effect on signal quality. Signals with audio processing
- >: have higher content of AF harmonics, and are subsequently less efficient
- >
- >I don't understand why audio processing has to result in more audio
- >harmonics. Aren't there digital signal processing algorithms that
- >could prevent this effect? Even before DSP, didn't people use split
- >band audio processing to reduce the content of harmonics?
-
- Sure, and still do in broadcasting, but it isn't either easy or cheap,
- and the results still aren't that great. You have to process in 1/3
- octave bands, and there are a lot of them at the lower end of the
- voice spectrum. You also have to adopt a control strategy that doesn't
- alter the amplitude relationships between octaves too much, or the
- time relationships *at all*, otherwise you screw up the frequency
- and phase response on a dynamic basis. That sounds *really* bad,
- worse than just harmonic distortion. Broadcast engineers seem to
- spend half their lives tinkering with the audio processing equipment.
- It's really easier to modulate, limit at RF, filter, and demodulate
- again rather than process properly at AF.
-
- Gary
- --
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-
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- End of Info-Hams Digest V94 #323
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