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- Date: Thu, 17 Feb 94 11:43:43 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 #169
- To: Info-Hams
-
-
- Info-Hams Digest Thu, 17 Feb 94 Volume 94 : Issue 169
-
- Today's Topics:
- Amateur Radio Newsline #861 11 Feb 94
- Commercial Advertising via Internet?
- Communications links with Sarajevo
- HELP
- Icom2SRA mods?
- kits (2 msgs)
- starting campus radio club faq, need info
- Ten Tec PM2A
-
- 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 20:42:16 GMT
- From: gulfaero.com!vixen.cso.uiuc.edu!howland.reston.ans.net!wupost!csus.edu!netcom.com!dparker@network.ucsd.edu
- Subject: Amateur Radio Newsline #861 11 Feb 94
- To: info-hams@ucsd.edu
-
- "I am concerned that you continue to move forward and keep pace with
- the commercial side, so that the technologies you have on the
- air will in fact provide you all of the kinds of feature rich
- functions that are going to be available to the general public."
- Ralph Haller N4RH, FCC
-
- Dahhh you mean like 20 WPM CW as a requirement?
-
- Dave Parker, KD6RRS
-
- ------------------------------
-
- Date: 17 Feb 94 18:13:36 GMT
- From: news-mail-gateway@ucsd.edu
- Subject: Commercial Advertising via Internet?
- To: info-hams@ucsd.edu
-
- Alexandr writes:
- >
- Hi, world!
- >
- > Anybody know where can I find a few quartz resonators for
- >governmental TV station in Novosibirsk, becouse component plants in
- >^^^^^^^^^^^^ (read commercial)
- >Russia are stay or closed and component distributors demand minimal order
- >in $1000.
-
- What the heck is this? This should have never wound up on the this forum.
- Maybe Alexandr needs to read the FAQ for this group.
-
- I am getting exceedingly annoyed at the folks in the CIS pleading poverty.
- They found it no problem to spend 30% of their GNP for 40 years to "bury us"
- with their commie rhetoric & propoganda. Don't buy this feinged plea for help
- as genuine. Its just another attempt at the CIS apparatchiki trying to extort
- Western merchandise, monies, and/or aid thru pleas that play on our sympathies.
- 73 de Walt - K2WK
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 20:09:41 GMT
- From: world!slm@uunet.uu.net
- Subject: Communications links with Sarajevo
- To: info-hams@ucsd.edu
-
- Even the biggest supporters of ham radio will admit that it can't
- substitute for a conventional telecommunications network;
- hams can't be expected to take the place of regular phone and
- postal service indefinitely.
-
- Yet that is what the hams of Bosnia-Herzegovina have been trying to
- do for almost two years now. Serbian nationalists besieging Sarajevo,
- cut off postal service in April, 1992, and cut off
- telephone lines to the city in July, 1992. Sarajevans have been under
- a communications blockade ever since.
-
- So, for this city of more than 300,000 people, there is
- virtually no way for them to contact loved ones outside. And,
- people in the rest of the world with family and friends in Sarajevo
- have almost no way to find out if their loved ones are OK.
-
- As a result, the few hams able to still operate in Sarajevo are
- overwhelmed with requests to try to pass messages in and out of
- the besieged city. They are doing heroic humanitarian work, but
- this can't substitute for restoration of phone lines. They really
- need our help to try to get their regular phone links back.
-
- It turns out that the telecommunications equipment which could restore
- phone service between Sarajevo and the rest of the world IS SITTING
- IN A WAREHOUSE IN DALLAS, TEXAS, BECAUSE THE UNITED NATIONS HIGH
- COMMISSIONER FOR REFUGEES REFUSES TO ALLOW IT TO BE FLOWN INTO
- SARAJEVO AIRPORT. The reason? U.N.H.C.R. says the equipment isn't
- "humanitarian aid!!!!"
-
- I think hams more than anyone understand that providing communications
- during times of crisis is in fact a great humanitarian issue.
-
- Several U.S. Congressmen, including Rep. Edward Markey, chairman of
- the House Subcommittee on Telecommunications and Finance, are working
- to try to get the U.N.H.C.R. to reverse its decision and allow
- the equipment to be flown into Sarajevo's airport (which is under
- U.N. control).
-
- Markey's office is trying to get as many people as possible to contact
- their senators and congress(wo)men by Tuesday, Feb. 22, and ask them
- to co-sign a letter to the U.N. High Commissioner for Refugees urging
- that the equipment be allowed in.
-
- I am hoping that some hams might consider helping this effort --
- and our colleagues under siege in Sarajevo -- and make a few calls
- to your legislators urging them to sign onto the letter. The text
- of the letter, and Markey's correspondence to other Members of
- Congress, is below (taken from soc.culture.bosna-herzgvna).
- If you know who your representatives are but don't have their
- phone number, you can call the Capitol switchboard at 202-224-3121.
-
- Thank you.
-
- 73, Sharon KC1YR
-
- ---------------------------------------------------------------------
-
-
- This is the letter that Congressman Markey is asking his
- Congressional colleagues to sign (and that you should ask your
- legislators to sign):
-
- Ms. Sadako Ogata
- United Nations High Commissioner for Refugees
- Case Postale 2500
- CH 1211 Geneve 2 Depot
-
- Dear Commissioner Ogata:
-
- We understand that the UNHCR has rejected a request to permit
- transport of telecommunications equipment into Sarajevo submitted
- on behalf of the Bosnian government by Mr. Muhamed Sacirbey, Bosnian
- Ambassador to the United Nations. As concerned Members of the United
- States Congress, we are writing to urge you to reconsider this
- decision and end the communications black out in this besieged city.
-
- Although we respect the need to monitor closely all shipments into
- the Bosnian capital, we firmly believe that the telecommunications
- equipment constitutes humanitarian aid and should be airlifted at
- the earliest possible opportunity. Because telephone links have been
- severed by Serb militants throughout the 22 month siege, those with
- relatives and friends in Sarajevo are left to agonize daily over the
- possibility that their loved ones have been injured or killed by the
- relentless shelling of the city. Additionally, the total lack of
- communications equipment further isolates the residents of Sarajevo
- and prevents rapid access to emergency services. In fact, similar
- equipment is currently supporting humanitarian missions in Somalia
- and other areas. Therefore, we believe that this shipment to Sarajevo
- does constitute humanitarian aid, and lifting the ban on the
- transportation of telecommunicatoins equipment would be a humane action.
-
- We urge you to allow the telecommunications equipment to be shipped
- to Sarajevo. Thank you for your prompt attention to this matter.
-
- Sincerely,
-
- ----------------------------------------------------------------------
- And this is the letter Congressmen Markey and John Dingell are sending
- to their colleagues.
-
- RESTORE SARAJEVO'S LINK TO THE WORLD
- February 14, 1994
-
- Dear Colleague:
-
- Last week, the international community watched in horror as scenes
- from the bombed-out marketplace in Sarajevo were beamed into homes
- around the world. For those with relatives and loved ones in the
- Bosnian capital, these images were even more frightening. Because
- telephone links have been severed by Serb militants throughout the 22
- month siege, relatives and friends were left to agonize for hours and
- even days over the possibility that their loved ones were injured in
- the blast.
-
- While residents of Sarajevo suffer under a total communications blackout,
- the telecommunications equipment needed to lift this informational
- embargo sits, packed and ready to go, in a warehouse in Dallas, Texas.
- The United Nations High Commissioner for Refugees, which controls
- shipments into the Sarajevo airport, has refused to allow the
- equipment to be delivered on the grounds that the materials do not
- constitute humanitarian aid. If relieving the anguish of thousands
- of Bosnians and their loved ones outside of Sarajevo does not qualify
- as humanitarian aid, then we do not know what does.
-
- The U.S. Department of State, which has the authority to recommend
- to UNHCR that the equipment be sent, has refused to intervene because
- it was advised by the Defense Department that the materials could have
- military value. Clearly, the export of materials with a potential dual
- use should be carefully controlled. Within the United States government,
- the Commerce Department strictly regulates the export of American
- products with military applications. The claim that the telecommunications
- equipment bound for the Bosnian capital constitutes military
- assistance, however, is completely groundless. In fact, the
- identical equipment which UNHCR is denying Sarajevo can be
- shipped without a special export license to Iran, Iraq, China,
- Syria, and Pakistan, among others. If this equipment is so
- dangerous, why does the U.S. government allow it to be exported
- so widely while refusing to send it to Sarajevo, a city under siege
- with virtually no means to defend itself?
-
- As NATO prepares for possible airstrikes, further shelling of
- Sarajevo by Serb forces is likely. Unless the UNHCR permits the
- transfer of this telecommunications equipment immediately,
- Sarajevans and their loved ones outside the city will be subjected
- again and again to the agonizing uncertainty resulting from a
- preventable communications embargo. After almost two years of
- bitter siege, Sarajevo's residents have been deprived of all civil,
- personal, and social rights. Everything that makes for regular
- urban living has already been taken away from Sarajevo and its
- citizens, and still the UNHCR continues to deny Sarajevans one
- of the most basic of all rights, the right to talk to each other.
- While we agree that UNHCR must monitor shipments into Sarajevo,
- we find some of their decisions rather curious. For example,
- the UNHCR blocked a shipment of surplus underwear headed for the
- Bosnian capital because of supposed military applications.
-
- Lifting the ban on telecommunications would be a humane action,
- especially considering the inhumane inaction which has characterized
- the international community's response to this bloody conflict up to
- this point. If you are interested in signing the attached letter to the
- United Nations High Commissioner for Refugees, Ms. Sadako Ogata,
- urging her to permit the transfer of the telecommunications
- equipment, please contact Mark Bayer of Representative Markey's
- office at 5-2836 by the close of business on Tuesday, February 22.
-
- Edward J. Markey
- John D. Dingell
-
- --
- electronic address: slm@world.std.com
-
- ------------------------------
-
- Date: 17 Feb 94 17:11:00 GMT
- From: news-mail-gateway@ucsd.edu
- Subject: HELP
- To: info-hams@ucsd.edu
-
- I found some 7062 tubes...what are they...12au7's or what????
-
- Clark Fishman WA2UNN cfishman@pica.army.mil
-
- ------------------------------
-
- Date: Wed, 16 Feb 1994 16:39:44 GMT
- From: loral!hlb@network.ucsd.edu
- Subject: Icom2SRA mods?
- To: info-hams@ucsd.edu
-
- Can someone email me mods for the above or point me to a location
- where I can obtain them via an ftp mail server (as I cannot ftp directly)?
-
- Thanks,
- hlb@li.loral.com
-
- --
- hlb@li.loral.com
-
- ------------------------------
-
- Date: Thu, 17 Feb 1994 17:25:36 GMT
- From: agate!howland.reston.ans.net!usc!news.cerf.net!megatek!jimc@network.ucsd.edu
- Subject: kits
- To: info-hams@ucsd.edu
-
- In article <2jull5$rhc@geraldo.cc.utexas.edu> oo7@astro.as.utexas.edu (Derek Wills) writes:
- >fred-mckenzie@ksc.nasa.gov (Fred McKenzie) says:
- >
- >>>I think the kits [Ramsey] sells are aimed towards people like
- >>>ourselves, who are quite willing to go through the ordeal of
- >>>de-bugging a kit, for the feeling of accomplishment from getting
- >>>it to work! Unfortunately, we are like dinosaurs about to become
- >>>extinct.
- >
- >>>The modern ham seems to think a kit is something you merely plug the parts
- >>>into, like assembling an IBM-clone computer from modules. From that point
- >>>of view, I'll admit that John's kits are not "modern".
- >
- > Something that has not been clear to me from the start of this thread
- > is why the people who are smart enough to de-bug assembled kits that are
- > obviously in dire need of it are not smart enough to assemble the things
- > from their own components in the first place. Is it cheaper buying one
- > of these kits than it is buying the individual components?
- >
- Depends on where you live. The answer is often "yes".
-
- -jim
-
- >
- >Derek Wills (AA5BT, G3NMX)
- >Department of Astronomy, University of Texas,
- >Austin TX 78712. (512-471-1392)
- >oo7@astro.as.utexas.edu
-
-
- --
- Jim Campbell "The Tye-Dye Guy" | "Remember to tweet!"
- jimc@megatek.com | When in doubt, you're probably
- WB6ZPB NSS ASA TNS | unsure about something
-
- ------------------------------
-
- Date: Thu, 17 Feb 1994 15:59:09 GMT
- From: agate!howland.reston.ans.net!europa.eng.gtefsd.com!emory!wa4mei.ping.com!ke4zv!gary@network.ucsd.edu
- Subject: kits
- To: info-hams@ucsd.edu
-
- In article <2jull5$rhc@geraldo.cc.utexas.edu> oo7@astro.as.utexas.edu (Derek Wills) writes:
- >
- > Something that has not been clear to me from the start of this thread
- > is why the people who are smart enough to de-bug assembled kits that are
- > obviously in dire need of it are not smart enough to assemble the things
- > from their own components in the first place. Is it cheaper buying one
- > of these kits than it is buying the individual components?
-
- It can be, but mostly it's *easier* to buy from one source instead of
- chasing down components from a bunch of different vendors, all of whom
- seem to have minimum orders well above the price of the components you
- need from them. I hate having to deal with vendors who are geared to
- PO numbers and 1000 unit pricing for my little onesy twosy purchases.
- I can easily run up a *phone* bill as high as the kit cost just tracking
- down vendors who will sell me the parts.
-
- So I'm willing to pay a premium to the kitmaker because he provides a
- real service by acting as my purchasing agent for project components.
- Where some of them fall down is in the *design* of their projects. Their
- services are rather useless if they supply you with the wrong parts for
- the wrong circuitry to do the job properly. I think the kit designer has
- a responsibility to produce a kit that can meet it's claimed specifications
- when assembled by someone competent to follow instructions. If a lab full
- of test equipment and ad hoc circuit changes are required for the project
- to successfully meet FCC specs, that should be stated up front in the
- advertising.
-
- My main gripe with the Ransey transceiver kit is that the builder is
- led to believe that he can successfully complete the project with only
- a frequency counter, power meter, and DVM. That's not true. If you follow
- the instructions to the letter, you'll have a radio that won't meet
- advertised specs, and will have an output spectrum that looks like a
- comb on the spectrum analyzer. You *cannot* just peak that PA for maximum
- output and have a clean spectrum.
-
- Note: Ramsey isn't the only offender here. Hamtronics kits are at least
- as bad. In fact, just getting a clean oscillator that will start reliably
- in their 70cm converter is just short of impossible with the circuitry
- they provide. You can either get an easy starting comb generator, or
- you can get a clean spectrum on an oscillator that won't start. Sheesh!
- A simple design change fixes the problem, but you shouldn't be expected
- to have to do that.
-
- 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: 15 Feb 94 20:40:18 GMT
- From: gulfaero.com!vixen.cso.uiuc.edu!howland.reston.ans.net!gatech!prism!gt0265d@network.ucsd.edu
- Subject: starting campus radio club faq, need info
- To: info-hams@ucsd.edu
-
- jrl2@cornell.edu (Jeffrey Luszcz) writes:
- >Hello,
- > I would like to start a FAQ for Collage Amateur Radio Clubs. If you know
- >of a radio club on campus could you send me some info about it. IUm looking
- >for
-
- << INFO DELETED >>
-
-
- Well, I'd like to start with my own club, The Georgia Tech Amateur Radio Club
- (W4AQL). We are at Georgia Tech in Atlanta, and have undergrads, graduates,
- alumni, faculty and staff, and a few others as members. Our officials are:
-
- Sponsor: Dr. Paul Steffes (paul.steffes@ee.gatech.edu)
- President: Dave Kunkee K0DI (gt5830b@prism.gatech.edu)
- VP: Jeff Tucker N9HZQ (tucker@eedsp.gatech.edu)
- Treasurer: Dave Huggins N4RMM (david.huggins@gtri.gatech.edu)
- Secretary: Carrie Carter N9JSR (carter@magnolia.gatech.edu)
- Shack Steward: Mike Whaley KD4UGI (whaley@hibiscus.gatech.edu) (that's me!)
- Shack phone: (404) 894-2971
- Shack Address: Room E-180, Electrical Engineering Bldg, Georgia Tech
-
- We have a repeater on 145.15 (input 144.55) located on the GT campus,
- with a remote site on 145.05 in Duluth, GA. Our shack is very well equipped,
- with 2 Kenwood TS-940S's, an icom and a Yaesu VHF rig (ferget the numbers)
- two Alpha 77 amps on the Kenwoods, and the following antennas: TH-6, 10,15,and
- 20 meter beams, 2m and 70cm satellite antennas, and 80 and 160 meter dipoles.
- We probably have more up there, but between the 3 towers I can't remember
- all of it :-)
-
- GTARC was started by 1927 for sure, and we believe that it may have existed as
- early as 1911- we're still trying to corroborate that info. We have approxi-
- mately 50 members or so, who operate on all bands and all modes, especially
- while contesting! The club has an email server at listserv@gitvm1.gatech.edu,
- or you can send mail to the club account at eew4aql@prism.gatech.edu. We
- would be very happy to hear from any interested folks out there, especially
- those who are or have been associated with Tech or the club.
-
-
- >Even if you canUt answer all the questions, oh well, its a start. I will
- >put the
- >info on a ftp site and/or post if people are interested.
- >Thanks,
-
- >-Jeff Luszcz N2TIQ
- >jrl2@cornell.edu
- >Cornell Amateur Radio Club W2CXM
-
- Well, there's the Rambling Wreck contribution. Good luck to you on this
- project--- and if anyone else out there wants to organize some sort of get-
- together between Tech and some other school (UGA excepted ;-) let us know!
-
- 73 de KD4UGI
-
-
- *******************************************************************************
- * Mike "Gator" Whaley K Chief of Aerospace Engineering *
- * whaley@hibiscus.gatech.edu D George P. Burdell Engineering Inc. *
- * gt0265d@prism.gatech.edu 4 *
- * Georgia Tech Box 40265 U "Ipecac- isn't that a Genesis album?" *
- * Atlanta, GA 30332 G --- Joel, MST 3K *
- * (404) 206-0958 I *
- *******************************************************************************
- * I absolutely refuse to put a disclaimer here: All opinions expressed above *
- * are EXACTLY what Georgia Tech would tell you, VERBATIM, with NO DIFFERENCES.*
- *******************************************************************************
-
- --
-
- *******************************************************************************
- * Mike "Gator" Whaley K V.P. of Aerospace Engineering *
- * whaley@hibiscus.gatech.edu D George P. Burdell Engineering Inc. *
-
- ------------------------------
-
- Date: 16 Feb 1994 14:26:20 -0600
- From: elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!not-for-mail@ames.arpa
- Subject: Ten Tec PM2A
- To: info-hams@ucsd.edu
-
- Anyone have a Ten Tec PM2A manual they could copy? I will pay
- duplication and shipping.
-
- thanks
-
- 73
-
- Jeff, AC4HF
-
- ------------------------------
-
- Date: Tue, 15 Feb 1994 20:30:16 GMT
- From: gulfaero.com!vixen.cso.uiuc.edu!howland.reston.ans.net!wupost!csus.edu!netcom.com!wy1z@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <1994Feb11.030138.403@megatek.com>, <CL2txF.8EJ@srgenprp.sr.hp.com>, <2jqi1t$rer@pegasus.cc.ucf.edu>
- Subject : Re: Nude amateur radio clubs
-
- In article <2jqi1t$rer@pegasus.cc.ucf.edu>,
- John W. Meaker <jm6033@pegasus> wrote:
- >Alan Bloom (alanb@sr.hp.com) wrote:
- >
- >: How many people have received their free QSL card from K4NBN "No Bad News"?
- >: (He used to have a monthly ham ad in QST.) The nude lady in the QSL photo
- >: was indeed a kind of centerfold, although not the type you might expect.
- >: It was done as a promotion for a nudist colony in Georgia or somewhere.
- >
- >: AL N1AL
- >
- > 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
-
- It would depend on who received it. Some people would feel offended,
- others not.
-
- >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.
- >
- > John Meaker -=- kr4ah
- >
- > Disclaimer - I am not responsible for the actions of
- > any Alpha-Hotels other than myself.
- >
- >
- >
-
-
- --
- ===============================================================================
- | Scott Ehrlich Internet: wy1z@neu.edu BITNET: wy1z@NUHUB |
- | Amateur Radio: wy1z AX.25: wy1z@k1ugm.ma.usa.na |
- |-----------------------------------------------------------------------------|
- | Maintainer of the Boston Amateur Radio Club hamradio FTP area on |
- | the World - world.std.com pub/hamradio |
- ===============================================================================
-
- ------------------------------
-
- Date: Thu, 17 Feb 1994 17:03:09 GMT
- From: agate!howland.reston.ans.net!europa.eng.gtefsd.com!emory!wa4mei.ping.com!ke4zv!gary@network.ucsd.edu
- To: info-hams@ucsd.edu
-
- References <bote.760946660@access1>, <1994Feb12.160701.4407@ke4zv.atl.ga.us>, <1994Feb15.060544.8419@vigard.mef.org>
- Reply-To : gary@ke4zv.atl.ga.us (Gary Coffman)
- Subject : Re: Medium range point-to-point digital links
-
- In article <1994Feb15.060544.8419@vigard.mef.org> mdf@vigard.mef.org (Matthew Francey) writes:
- >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 ...
-
- Heh, no, I did a power ratio when I was dealing with voltage ratios.
- As Jon noted, I should have used 20*log(2^9)=54.18 db.
-
- >>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).
-
- No. The best we can do is cut the number of samples down to the
- Nyquist limit of 2xFcutoff by decimation and multiply by the
- number of bits per sample. So we're down to 10 kilosamples/sec
- times 8 bits per sample or a 80 kb/s digital bit stream. (But
- I think you meant that.)
-
- >tho i would say that 8kilosamples/second @ 8bits is quite accepatable.
- >64kbps. using an ADPCM encoder you can chop this in half.
-
- Yes, data compression can reduce the required transmission bit rate.
- I've been dealing with only the raw sample data so far.
-
- >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.
-
- Yeah. If you further reduce Fcutoff, you can lower the sample rate,
- and if you reduce the SNR, you can use fewer bits per sample. But
- we were trying for "broadcast grade" transmission here. And we didn't
- even make that because we restricted Fcutoff to 5 kHz. If we'd insisted
- on a 15 kHz Fcutoff, the required bit rate would be 3x more, or 240 kb/s.
- Applying the *correct* formula, 5 bit samples would give a SNR of
- 20log(2^6)=36 db. That actually looks fairly acceptable for ham grade
- channels. But there's another effect we haven't discussed. That's
- intermodulation distortion. With a 5 bit sample, we have products
- at 5 times the sample rate mulitiplied by each frequency in the sampled
- waveform. If our D/A isn't linear out to a fairly high frequency, we can
- get mixing products, or beats, between the various sample products that
- can wind up down in the audio passband. That'll give us harsh buzzing
- artifacts in our audio that simple filtering can't remove. The higher
- the sample rate, the less these step products become noticable. They
- tend to converge to an infrasonic frequency that's easily filtered.
-
- >>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.
-
- Well the WA4DSY modem is $250, and then you need a transverter. That
- can run from $150 to over $300, and you need the digital driver to
- generate and control the bits to the modem. Say the total is $500-$600
- per end for the package. That means a link is going to cost $1000-$1200
- plus feedline and antennas. Paths of 30-40 miles are fairly routine,
- barring major terrain blockage, and good high sites can do much better
- than that.
-
- M/Acom 10mw gunnplexer transceivers are available for on the order of
- $350 from SI, or raw gunnplexers can be found for $30-$70 on the surplus
- market. But you have to design an AFC system, and the high speed digital
- modulator/demodulators for them. Find dishes for them, and find line of
- sight paths for the links. Costs could be similar, around $1000 per
- link, but site selection would be much more restricted, and likely
- range as well (only a couple of miles for reasonable sized dishes
- and average terrain). Ten watts and 4 foot dishes can give 50+ mile
- paths at video bandwidths under good conditions, but that's serious money.
- It could be worth it for the higher throughput in some cases.
-
- 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 | |
-
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- End of Info-Hams Digest V94 #169
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