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- Date: Mon, 17 Oct 94 01:42:47 PDT
- 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: List
- Subject: Info-Hams Digest V94 #1129
- To: Info-Hams
-
-
- Info-Hams Digest Mon, 17 Oct 94 Volume 94 : Issue 1129
-
- Today's Topics:
- anyone know anything about hallicrafters
- Code practice on san fran
- Ham Tests in MD/NoVA/DC area?
- IPS Daily Report - 16 October 94
- New HDN Releases
- Ohio/Penn DX Bulletin #179
- Sound Operated Phones
- strange things in the cleveland national forest
- TUTORIAL: dB & dBm
- WTB: HP608D VHF sig gen
-
- 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: Mon, 17 Oct 1994 04:06:24 GMT
- From: Mike Lyon <mlyon@rahul.net>
- Subject: anyone know anything about hallicrafters
-
- i recently picked up a old hallicrafters shortwave reciever. i would like
- to see if i can get some schematics,information or anything on it. on the
- tune dial it says "Skyrider jr." and i can barely make out the model no.
- it says model "h" in a white circle and after that it says either one of
- these, i can't tell it's a little rusty, but it's either a s-416,
- s-116,s-110, s-410. it's about a foot long and about 9 inches tall and
- about 9 inches wide. and also does hallicrafters still exist? if it does
- could anyone give me the any information on how to contact them.
-
- thank you,
- mlyon@rahul.net
- --
- ///////////////////////
- | Mike Lyon |
- | KE6MRE |
- | mlyon@rahul.net |
-
- ------------------------------
-
- Date: Sun, 16 Oct 94 22:47:38
- From: buddy.sohl@shivasys.com
- Subject: Code practice on san fran
-
- Ne> From: david_b3@sfov1.verifone.com
- Ne> Newsgroups: rec.radio.amateur.misc
- Ne> Subject: Code Practice on San Francisco Peninsula
- Ne> Date: Mon, 10 Oct 94 02:16:52 GMT
- Ne> Organization: VeriFone Inc.
-
- Ne> David Barnes KD6DMS
- Ne> david_b3@verifone.com
-
- Hi David.
-
- I tried a direct internet response but the server kicked the message back
- as denied so I'll go this route. If you got my original reply let me know.
-
- W1AW sends text from QST. The schedule is published in QST and is also
- available from info@arrl.org. Send in the body of the message
-
- reply your internet add
- help
- index
- quit
-
-
-
- You should get a response within a few hours. This is machine to machine so
- as often as your system checks the internet is how fast your response.
-
- 73
- BS KC4WQ
-
- ... Tried everything and it still says C:
- ___ Blue Wave/QWK v2.12
-
- ------------------------------
-
- Date: Fri, 14 Oct 1994 09:00:23 UNDEFINED
- From: dalbert@pbs.org (David Albert)
- Subject: Ham Tests in MD/NoVA/DC area?
-
- I would like to take my No-Code Tech test...does anyone know of tests being
- given in the Washington DC., Suburban MD or VA area?
- Thanks!
-
- ------------------------------
-
- Date: Mon, 17 Oct 1994 02:06:46 GMT
- From: rwc@flare.syd.ips.oz.au (Regional Warning Centre)
- Subject: IPS Daily Report - 16 October 94
-
- SUBJ: IPS DAILY SOLAR AND GEOPHYSICAL REPORT
- ISSUED AT 16/2330Z OCTOBER 1994 BY IPS RADIO AND SPACE SERVICES
- FROM THE REGIONAL WARNING CENTRE (RWC), SYDNEY.
- SUMMARY FOR 16 OCTOBER AND FORECAST FOR 17 OCTOBER - 19 OCTOBER
- -----------------------------------------------------------
- 1A. SOLAR SUMMARY
- Activity: very low
-
- Flares: none.
-
- Observed 10.7 cm flux/Equivalent Sunspot Number : 91/36
-
- GOES satellite data for 15 Oct
- Daily Proton Fluence >1 MeV: 8.2E+05
- Daily Proton Fluence >10 MeV: 9.8E+03
- Daily Electron Fluence >2 MeV: 1.2E+07 (normal)
- X-ray background: B1.3
- Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
-
- 1B. SOLAR FORECAST
- 17 Oct 18 Oct 19 Oct
- Activity Low Low Low
- Fadeouts None expected None expected None expected
-
- Forecast 10.7 cm flux/Equivalent Sunspot Number for 17 Oct: 90/34
-
- -----------------------------------------------------------
- 2A. MAGNETIC SUMMARY
- Geomagnetic field at Learmonth: quiet to unsettled
-
- Estimated Indices : A K Observed A Index 15 Oct
- Learmonth 7 2313 2111
- Fredericksburg 6 9
- Planetary 7 11
-
- Observed Kp for 15 Oct: 3333 3122
- 2B. MAGNETIC FORECAST
- DATE Ap CONDITIONS
- 17 Oct 8 Quiet
- 18 Oct 10 Quiet to unsettled
- 19 Oct 8 Quiet
-
- -----------------------------------------------------------
- 3A. GLOBAL HF PROPAGATION SUMMARY
- LATITUDE BAND
- DATE LOW MIDDLE HIGH
- 16 Oct normal normal normal
- PCA Event : None.
-
- 3B. GLOBAL HF PROPAGATION FORECAST
- LATITUDE BAND
- DATE LOW MIDDLE HIGH
- 17 Oct normal normal normal
- 18 Oct normal normal normal
- 19 Oct normal normal normal
-
- -----------------------------------------------------------
- 4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
- Observed
- DATE T-index MUFs at Sydney
- 16 Oct 18 near predicted monthly values
-
- Predicted Monthly T-index for October: 20
-
- 4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
- DATE T-index MUFs
- 17 Oct 18 Near predicted monthly values
- 18 Oct 20 Near predicted monthly values
- 19 Oct 20 Near predicted monthly values
-
- --
- IPS Regional Warning Centre, Sydney |IPS Radio and Space Services
- RWC Duty Forecaster tel: +61 2 4148329 |PO Box 5606
- Recorded Message tel: +61 2 4148330 |West Chatswood NSW 2057
- email: rwc@ips.oz.au fax: +61 2 4148331 |AUSTRALIA
-
- ------------------------------
-
- Date: Fri, 14 Oct 1994 07:06:04
- From: Lee.Laird@f7009.n124.z1.fidonet.org (Lee Laird)
- Subject: New HDN Releases
-
- The following files were processed Friday 10-14-94 by the Ham Dist Net
- Please allow 48 hours for files to arrive at the HDN Anonymous FTP Site.
-
- HAMEQUIP HAM: Radio and equipment modification distribution
- -----------------------------------------------------------------------------
- RM.ZIP 563,844 Radio Manager V2.01 ICOM R-7000 controller for windows
- -----------------------------------------------------------------------------
- 563,844 bytes in 1 file(s)
-
-
- HAMNEWS HAM: Ham Bulletins and Newsletters
- -----------------------------------------------------------------------------
- ARLB077.ZIP 2,014 10/03/94 - Morse exemption denied
- ARLB078.ZIP 1,991 10/03/94 - Tech license renewals
- ARLB079.ZIP 2,005 10/10/94 - Congress resolution passes
- ARLD060.ZIP 1,886 10/06/94 Committee vote results
- ARLP041.ZIP 2,099 ARRL Propagation Bulletin 10/07/94
- BARTG022.ZIP 4,767 BARTG Bulletin 022 October, 1994
- IRTS1002.ZIP 3,751 IRTS Bulletin 10/02/94
- IRTS1009.ZIP 3,996 IRTS Bulletin 10/09/94
- NEWS0930.ZIP 8,327 NewsLine #894 09/30/94
- NEWS1007.ZIP 8,971 NewsLine #895 10/07/94
- -----------------------------------------------------------------------------
- 39,807 bytes in 10 file(s)
-
-
- HAMSAT HAM: Satellite tracking and finding programs
- -----------------------------------------------------------------------------
- ARLK044.ZIP 3,232 ARRL Keplerian Bulletin 10/04/94
- ARLK045.ZIP 3,231 ARRL Keplerian Bulletin 10/08/94
- -----------------------------------------------------------------------------
- 6,463 bytes in 2 file(s)
-
-
- HAMSRC HAM: Source to Amateur Radio Programs
- -----------------------------------------------------------------------------
- WN940930.ZIP 547,840 Turbo C source WNOS940930 of KA9Q TCP/IP for P
- -----------------------------------------------------------------------------
- 547,840 bytes in 1 file(s)
-
-
- Total of 1,157,954 in 14 file(s)
-
-
- Official Ham Distribution Net FTP Server : ftp.iea.com /pub/borg/hdn
- Official Ham Distribution Net E-mail : ab5sm@netcom.com
-
- Official U.S. Postal Service Address : Ham Distribution Net
- P.O. Box 50003
- Dallas, Texas 75250-0003
-
- Official Ham Distribution Net BBS' : (214) 226-1181 8N1 16.8k v32b
- (214) 226-1182 8N1 14.4k v32b
- Logon: Guest;guest
-
- * Origin: Africa-Asia-Australia-Europe-USA/Canada-S.America (1:124/7009)
-
- ------------------------------
-
- Date: Sun, 16 Oct 1994 16:21:00 EST
- From: kb8nw@barf80.nshore.org (Tedd Mirgliotta)
- Subject: Ohio/Penn DX Bulletin #179
-
- SB DX @ ALLBBS $OPDX.179
- Ohio/Penn DX Bulletin No. 179
-
- The Ohio/Penn Dx PacketCluster
- DX Bulletin No. 179
- BID: $OPDX.179
- October 17, 1994
- Editor Tedd Mirgliotta, KB8NW
- Provided by BARF-80 BBS Cleveland, Ohio
- Online at 216-237-8208 14400/9600/2400/1200/300 8/N/1
-
- Thanks to the Northern Ohio Amateur Radio Society, Northern Ohio DX
- Association, Ohio/Penn PacketCluster Network, DF4RD, DL7VEE & DX NEWS
- Letter, K4CEF & Southeastern Cluster Group, WA1G, NA2M, K3DI, N4VZ,
- KG4ML/WB6VGI, KJ4VH, W6CF, KK6EK, N6SS, N7VEW, F8RU, G0MRF, VA3CW,
- VU2SMN and YU1AB for the following DX information.
-
- 5V, TOGO. Adam, N7VEW, states he has a sked with Dave, 5V7MD, on October
- 19th, on 14165 kHz at 2200z. After their sked, Dave will stick around for
- about 1 to 1 1/2 hours to work stations either from a list or freestyle.
- There is a possibility that Adam may become 5V7MD's QSL Manager.
-
- 8R, GUYANA. Marko, OH6DO/AB6NJ (and now VR2NJ), will be active in the
- CQWW SSB DX Contest as 8R1K. He is planning a serious Single Op/All
- Band effort. His length of stay is unknown at this time. QSLs go to
- OH6DO CBA only. Marko says, "please don't use other addresses."
-
- 9U, BURUNDI. Ted, F8RU, heard from Paul, 9Q5EXV, that he and a few
- others would be active during the CQWW Contest as 4U9U.
-
- BS7H CARDS. Jim, W6CF, the QSL Manager for this operation, has announced
- that all replies went into the mail, October 15th. Card requests for
- BS7H/MM did not go out because the logs have not been received as of yet.
- The logs are expected to arrive sometime next week.
-
- C5, THE GAMBIA. In late October-November, the Whitton Amateur Radio
- Group from South West London will be mounting a DXpedition from C5-land.
- There will be activity on 13 amateur bands from 160 meters to 2.3GHz.
- This will include 6 meters and satellite via OSCAR 13 mode B and S. The
- Gambia is very rare on satellite and this will be the first operation on
- mode "S" from this location. Operating dates will be between October 23rd
- and November 10th, which will include activity in the CQWW SSB DX Contest.
- Look for C56/G0MRF and C56DX during the contest. QSL via G0MRF direct or
- via bureau. Note: In callbooks prior to 1994, G0MRF is listed under G8PDW.
-
- CT3/CR9, MADEIRA ISLANDS. Frank, DL8KWS, was orginally signing DL8KWS/CT3
- from here but is now using the call CR9WAG. Another German operator is
- also active signing DL3KUD/CT3. Both stations are very active on CW and
- on all bands (including the WARC bands). They will be there until October
- 27th. QSL via their CBA.
-
- IOTA NA-066, CALIFORNIA SOUTHERN GROUP. Bob, KK6EK (one the operators
- from the 3Y0PI DXpedition) will be here November 25-27th. His plans are
- to make a special effort on 40 meters. During the operation, he will tie
- into InterNet (intermittantly) and post operating skeds (on the DX
- Reflector).
-
- KG4, GUANTANAMO BAY. Jeff, WI2T, will be active in the CQWW SSB Contest
- as a Single Op (work sked permitting) signing KG4JO. He will be using
- the TS-530 and antenna system at the KG4AN club station in Guantanamo.
- QSL via WI2T.
-
- LX, LUXEMBOURG. A group of Dutch operators will be active from October
- 26-30th. They will be using the callsign LX/PA3DKC on HF (including the
- WARC bands) and LX/PA3CDI on 6 meters.
-
- S7, SEYCHELLES. Andres, EA4EGZ, will be on Mahe Island from October
- 21-28th. Activity will be on CW, 40-10 meters.
-
- V2, ANTIGUA. Ratko, YU1NR, will be active for 20 days starting October
- 26th. His activities will include participation in the CQWW DX SSB
- Contest, he will be on all bands and CW/SSB/SSTV/Packet. Look for him
- to sign V29NR. QSL via YU1NR, Novakovic Ratko, P.O. Box 145, YU-34000
- Kragujevac.
-
- VP9, BERMUDA. Dick, K3DI, informed OPDX that he will be active as
- K3DI/VP9 in Warwick, Bermuda from November 6-12th. QSL via his CBA or
- the W3 QSL bureau.
-
- VR, PITCAIRN ISLAND. It is reported that VR6MW and other VR6-stations
- are active around 0600z on 40 meters SSB (e.g. on 7083 kHz in a net).
-
- VQ9, CHAGOS ISLANDS. This one is for the 160 meter DXers! The operations
- of VQ9SS and VQ8QM have ceased effective October 12th until further
- notice. In the meantime, look for limited operations by VQ9KC and new
- arrival VQ9ZX.
-
- VU4/VU7, ANDAMAN AND LACCADIVE ISLANDS. Bruce, WA1G, received a letter
- from Suhas, VU2SMN, stating there are continuing plans to activate VU4
- and VU7. Suhas reports that they have filed huge amounts of paperwork
- with the Ministry of Telecommunications over the last two years in hopes
- to receive a licence. They still hope to be active sometime this October,
- but the group cannot announce the details like exact dates of operation,
- call signs, QSL info, etc.... until they get the official licence in hand.
-
- XU, KAMPUCHEA. N4VZ reports that European stations were working XU1MF on
- 18138 at 1515z on October 11th, but he was unable to copy him. One of
- the Europeans repeated back his QSL manager as JA1JTU. We've seen no
- mention of this station in recent bulletins or on the air.
-
- FAX YOUR DX INFORMATION NOW! Faxing is available Monday/Wednesday/Friday
- from 0430 to 2330z only. The number is 216-237-8208 and the FAX card is
- sharing the same phone line as BARF-80 BBS using a data/fax/phone switch.
-
- Excerpts and distribution of The OPDX Bulletin are granted as long as
- KB8NW/OPDX/BARF80 receive credit. To contribute DX info, call BARF-80 BBS
- online at 216-237-8208 14400/9600/2400/1200/300 and leave a message with
- the Sysop or send InterNet Mail to: aq474@cleveland.freenet.edu or send
- BitNet Mail to: aq474%cleveland.freenet@cunyvm or send PRODIGY Mail to:
- DFJH48A or send a message via packet to KB8NW @ WA8BXN.OH.USA.NA
-
- /EXIT
-
- ----------------------------
- Tedd Mirgliotta KB8NW
- InterNet: kb8nw@barf80.nshore.org
- Basic Amateur Radio Frequency BBS (BARF-80) +1 216/237-8208
- "Totally devoted to Amateur Radio" - 24 Hrs a day 8/N/1 14.4k-300 baud
-
- ------------------------------
-
- Date: Sun, 16 Oct 1994 21:39:42
- From: vaughnwt@olympus.net (Bill Vaughn)
- Subject: Sound Operated Phones
-
- In article <1994Oct16.174029.26739@ke4zv.atl.ga.us> gary@ke4zv.atl.ga.us (Gary Coffman) writes:
- >From: gary@ke4zv.atl.ga.us (Gary Coffman)
- >Subject: Re: Sound Operated Phones
- >Date: Sun, 16 Oct 1994 17:40:29 GMT
-
- >In article <1994Oct15.191140.5782@egreen.wednet.edu> jmollan@egreen.iclnet.org
- >(John Mollan - Harm) writes:
- >>Recently I have read several books about the US Navy in WWII using
- >>sound-operated phone systems.
- >>
- >>How do these systems operate? What is the electronic theory behnd it?
-
- >They work on the dynamo principle. A dynamic microphone is used that
- >generates a voltage when sound waves vibrate a coil in a magnetic
- >field (or a magnet vibrates next to a fixed coil). That voltage then
- >drives a sensitive set of headphones at the other end of the wires.
- >Gary
-
- And it might interest you to know that sound powered phones as they are
- referred to in the navy and coast guard are alive and well and used every day
- for intership communication.
-
- ------------------------------
-
- Date: 17 Oct 1994 04:58:52 GMT
- From: dr261@cleveland.Freenet.Edu (Tobin T Fricke)
- Subject: strange things in the cleveland national forest
-
- I have heard about Marijuana plantations, Military
- installations, Missile silo's, and Laser and bomb
- testing areas in the Cleveland National Forest. Can
- anyone provide any addittional information?
-
- Specifically, I've heard of a VLF radio antenna that
- is suspended in a culvert below a station on Pleasant
- Peak. Anyone know about his?
-
- Other than that, I'm interested in any nifty and/or
- little known places to explore in the vicinity of
- Orange County, California.
-
- Please reply via Email to dr261@cleveland.freenet.edu
- and not to this newsgroup, since I do not often check
- the usenet newsgroups.
-
- Thanks
- --
- Tobin Fricke dr261@cleveland.freenet.edu
- Duct tape is like the force; it has a light side and a dark
- side, and it holds the world together.
-
- ------------------------------
-
- Date: Sat, 15 Oct 94 21:56:18 -0500
- From: pschleck@gonix.gonix.com (Paul W Schleck KD3FU)
- Subject: TUTORIAL: dB & dBm
-
- USING AND UNDERSTANDING DECIBELS
-
- by
-
- Paul H. Bock, Jr. K4MSG
-
- Author's Note: This tutorial was originally written for the use of
- non-RF/analog engineers (digital, software) and non-engineers who
- needed an easy-to-follow reference on the general use of the decibel.
- I hope that some amateur operators may find it useful as well.
-
- While the historical accuracy of the comments relating to the
- telephone company and telephone company engineers may be open to
- question (the information as supplied to me was anecdotal), the
- technical points made should be valid regardless of the exact turn
- of history.
-
-
- *General*
-
- The decibel, or dB, is a means of expressing either the gain
- of an active device (such as an amplifier) or the loss in a passive
- device (such as an attenuator or length of cable). The decibel was
- developed by the telephone company to conveniently express the gain
- or loss in telephone transmission systems. The decibel is best
- understood by first discussing the rationale for its development.
-
- If we have two cascaded amplifiers as shown below, with power
- gain factors A1 and A2 as indicted, the total gain is the product
- of the individual gains, or A1 x A2.
-
- Input >-------- Amp #1 --------- Amp #2 ------> Output
-
- A1 = 275 A2 = 55
-
- In the example, the total gain factor At = 275 x 55 = 15,125.
- Now, imagine for a moment what it would be like to calculate the
- total gain of a string of amplifiers. It would be a cumbersome
- task at best, and especially so if there were portions of the
- cascade which were lossy and reduced the total gain, thereby
- requiring division as well as multiplication.
-
- It was for the reason stated above that Bell Telephone
- developed the decibel. Thinking back to the rules for logarithms,
- we recall that rather than multiplying two numbers we can add their
- logarithms and then take the antilogarithm of this sum to find the
- product we would have gotten had we multiplied the two numbers.
- Mathematically,
- log (A x B) = log A + log B
-
- If we want to divide one number into another, we subtract the
- logarithm of the divisor from the logarithm of the dividend, or in
- other words
- log (A/B) = log A - log B
-
- The telephone company decided that it might be convenient to
- handle gains and losses this way, so they invented a unit of gain
- measurement called a "Bel," named after Alexander Graham Bell.
- They defined the Bel as
-
- Gain in Bels = log A
-
- where A = Power amplification factor
-
- Going back to our example, we find that log 275 = 2.439 and
- log 55 = 1.740, so the total gain in our cascade is
-
- 2.439 + 1.74 = 4.179 Bels
-
- It quickly occurred to the telephone company engineers that
- using Bels meant they would be working to at least two decimal
- places. They couldn't just round things off to one decimal place,
- since 4.179 bels is a power gain of 15,101 while 4.2 bels is a
- power gain of 15,849, yielding an error of about 5%. At that point
- it was decided to express power gain in units which were equal to
- one-tenth of a Bel, or in deci-Bels. This simply meant that the
- gain in Bels would be multiplied by 10, since there would be ten
- times more decibels than Bels. This changes the formula to
-
- Gain in decibels (dB) = 10 log A (Eq. 1)
-
- Again using our example, the gain in the cascade is now
-
- 24.39 + 17.40 = 41.79 decibels
-
- The answer above is accurate, convenient to work with, and can
- be rounded off to the first decimal place will little loss in
- accuracy; 41.79 dB is a power gain of 15,101, while 41.8 dB is a
- power gain of 15,136, so the error is only 0.23%.
-
- What if the power gain factor is less than one, indicating an
- actual power loss? The calculation is performed as shown above
- using Equation 1, but the result will be different. Suppose we
- have a device whose power gain factor is 0.25, which means that it
- only outputs one-fourth of the power fed into it? Using Equation
- 1, we find
- G = 10 log (0.25)
-
- G = 10 (-0.60)
-
- G = -6.0 dB
-
- The minus sign occurs because the logarithm of any number less
- than 1 is always negative. This is convenient, since a power loss
- expressed in dB will always be negative.
-
- There are two common methods of using the decibel. The first
- is to express a known power gain factor in dB, as just described.
- The second is to determine the power gain factor and convert it to
- dB, which can all be done in one calculation. The formula for this
- operation is as follows:
- Po
- G = 10 log ---- (Eq. 2)
- Pi
-
- where G = Gain in dB
- Po = Power output from the device
- Pi = Power input to the device
-
- Both Po and Pi should be in the same units; i.e., watts,
- milliwatts, etc. Note that Equation 2 deals with power, not
- voltage or current; these are handled differently when converted
- to dB, and are not relevant to this discussion. Below are two
- examples of the correct application of Equation 2:
-
- Ex. 1: An amplifier supplies 3.5 watts of output with an
- input of 20 milliwatts. What is the gain in dB?
-
- 3.5 watts
- G = 10 log ----
- 0.02 watts
-
- G = 10 log (175)
-
- G = 10 (2.24)
-
- G = 22.4 dB
-
-
- Ex. 2: A length of coaxial transmission line is being fed
- with 150 watts from a transmitter, but the power
- measured at the output end of the line is only 112
- watts. What is the line loss in dB?
-
- 112 watts
- G = 10 log ---
- 150 watts
-
- G = 10 log 0.747
-
- G = 10 (-0.127)
-
- G = -1.27 dB
-
-
- *Non-relative (Absolute) Uses of the Decibel*
-
- The most common non-relative, or absolute, use of the decibel
- is the dBm, or decibel relative to one milliwatt. It is different
- from the dB because it represents, in physical terms, an absolute
- amount of power which can be measured.
-
- The difference between "relative" and "absolute" can be
- understood easily by considering temperature. For example, if I
- say that it is "20 degrees colder now than it was this morning,"
- it's a relative measurement; unless the listener knows how cold it
- was this morning, it doesn't mean anything in absolute terms. If,
- however, I say, "It was 20 degrees C this morning, but it's 20
- degrees colder now," then the listener knows exactly what is meant;
- it is now 0 degrees C. This can be measured on a thermometer and
- is referenced to an absolute temperature scale.
-
- So it is with dB and dBm. A dB is merely a relative
- measurement, while a dBm is referenced to an absolute quantity:
- the milliwatt (1/1000 of a watt). We can apply this concept to
- Equation 1 as follows:
-
- dBm = 10 log (P) (1000 mW/watt)
-
- where dBm = Power in dB referenced to 1 milliwatt
- P = Power in watts
-
- For example, take the case where we have a power level of 1
- milliwatt:
-
- dBm = 10 log (0.001 watt) (1000 mW/watt)
-
- dBm = 10 log (1)
-
- dBm = 10 (0)
-
- dBm = 0
-
- Thus, we see that a power level of 1 milliwatt is 0 dBm. This
- makes sense intuitively, since our reference power level is also
- 1 milliwatt. If the power level was 1 watt, however, we find that
-
- dBm = 10 log (1 watt) (1000 mW/watt)
-
- dBm = 10 (3)
-
- dBm = 30
-
- The dBm can also be negative, just like the dB; if our power
- level is 1 microwatt, we find that
-
- dBm = 10 log (1 x 10E-6 watt) (1000 mW/watt)
-
- dBm = -30 dBm
-
- Since the dBm is an absolute amount of power, it can be
- converted back to watts if desired. Since it is in logarithmic
- form it may also be conveniently combined with other dB terms,
- making system analysis easier. For example, suppose we have a
- signal source with an output power of -70 dBm, which we wish to
- connect to an amplifier having 22 dB gain through a cable having
- 8.5 dB loss. What is the output level from the amplifier? To find
- the answer, we just add the gains and losses as follows:
-
- Output = -70 dBm + 22 dB + (-8.5 dB)
-
- Output = -70 dBm + 22 dB - 8.5 dB
-
- Output = -56.5 dBm
-
- As a final note, power level may be referenced to other
- quantities and expressed in dB form. Below are some examples:
-
- dBW = Power level referenced to 1 watt
-
- dBk = Power level referenced to 1 kilowatt (1000 watts)
-
- One other common usage is dBc, which is a relative term like
- dB alone. It means "dB referenced to a carrier level" and is most
- commonly seen in receiver specifications regarding spurious signals
- or images. For example, "Spurious signals shall not exceed -50
- dBc" means that spurious signals will always be at least 50 dB less
- than some specified carrier level present (which could mean "50 dB
- less than the desired signal").
-
- * Paul H. Bock, Jr. K4MSG * Principal Systems Engineer
- (|_|) * E-Systems/Melpar Div. * Telephone: (703) 560-5000 x2062
- | |) * 7700 Arlington Blvd. * Internet: pbock@melpar.esys.com
- * Falls Church, VA 22046 * Mailstop: N203
-
- "Imagination is more important than knowledge." - Albert Einstein
-
- ------------------------------
-
- Date: 17 Oct 1994 01:04:03 -0400
- From: nx7u@aol.com (NX7U)
- Subject: WTB: HP608D VHF sig gen
-
- Do you have a boatanchor yearning to be free?
- Let it take up space in my apartment instead! Give the wife an early
- Christmas present!
- WTB: HP608D. Not 'E', not 'C', only 'D'. with manual nice but not
- necessary. Please respond directly with desired reward.
- scott
- nx7u@aol.com
-
- ------------------------------
-
- Date: 17 Oct 1994 04:25:34 GMT
- From: cradek@herbie.unl.edu (Chris Radek)
-
- References<1994Oct13.020457.4212@walter.cray.com> <37jh0l$8ck@eugene.convex.com>, <1994Oct14.041541.6006@ultb.isc.rit.edu>
- Subject: Re: ARRL And Gay Hams Settle Complaint
-
- >On a more serious note, most homosexual organizations exist to
- >promote acceptance of homosexual behavior as 'normal' and even
- >a Good Thing.
-
- >73...Jim N2VNO
-
- No, actually most "homosexual" (try gay sometime - it's less clinical)
- organizations exist to promote the fact that we're human, just like everyone
- else, and just like everyone else we want and deserve to be treated as such.
- Nobody is trying to "sell" you on being gay; God knows gay people have
- enough trouble without folks like you on our side of the fence... I had
- hoped that technology might help bridge gaps in understanding between people
- with different feelings and beliefs, but it looks like misunderstanding is
- still alive and well here.
-
- ------------------------------
-
- End of Info-Hams Digest V94 #1129
- ******************************
-