Date: Sun, 23 Jan 94 23:40:04 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 #69
To: Info-Hams
Info-Hams Digest Sun, 23 Jan 94 Volume 94 : Issue 69
Today's Topics:
???
Are there any RS232C cards for PCMCIA?
Bird Problems with Yagi Antenna
callsign servers
CW Books
CW filters and DSP-9 (2 msgs)
Daily Summary of Solar Geophysical Activity for 22 January
International Callsign Server
The differences in CW filter performance
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: Thu, 20 Jan 1994 01:32:18 GMT
From: usenet.coe.montana.edu!netnews.nwnet.net!ns1.nodak.edu!plains!drusteba@decwrl.dec.com
Subject: ???
To: info-hams@ucsd.edu
------------------------------
Date: 21 Jan 94 10:00:22 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!sgigate.sgi.com!olivea!koriel!sh.wide!wnoc-tyo-news!aist-nara!ccsparc01!icspub!ce-gw!ee!kitagawa@network.ucsd.
Subject: Are there any RS232C cards for PCMCIA?
To: info-hams@ucsd.edu
Thank you everyone who responded by mail or news.
I> Are there any RS232C cards for PCMCIA slot?
> you may want to consider "dockable" laptops.
Unfortunately I've never heard of the docking station for my favorite
T1950. I am told that there are some serial interface cards for PCMCIA
(by IBM and others) but still don't have specific model numbers.
I> I'm also looking for PCMCIA Ethernet cards for 10base-2 (Coax)
I've got the info that there is one for T1950;
NWETH02 Noteworthy 10base2 PCMCIA type II Ethernet card.
> You could go with the old, yet trusty Xircom 10-Base2 external LAN
> adapter....
Oh, it might be even better if I can save a PCMCIA slot. Thanks!
I> FYI (to Hams only, probably contesters only): Why do I need so many
I> serial ports? Yes, I want to run CT (by K1EA) in multi-multi station.
I am informed that CT ver 8.47 has implemented a single-directional
loop which requires only one serial port per computer. If it works
fine, I don't need a serial port card nor an Ethernet card, i.e. the
best solution for me.
Masahiro Kitagawa <kitagawa@ee.es.osaka-u.ac.jp>
Electrical Engineering, Engineering Science, Osaka University
------------------------------
Date: Sun, 23 Jan 1994 06:28:08 GMT
From: sdd.hp.com!nigel.msen.com!usenet.ins.cwru.edu!ukma!news2.uunet.ca!iceonline!icebox!janc@network.ucsd.edu
Subject: Bird Problems with Yagi Antenna
To: info-hams@ucsd.edu
>This produces a messy roof and a serious hazard to parked cars, cats and
>small children on the ground :-)
>
>Also, however, the elements have been getting torqued seriously out of
>plane by the weight of the lil' chirpers. They seem not to have an eye
>for symmetry and apparently don't understand about balanced loads,
>balanced feed lines, or the like.
>
Some of the local hams in this area have mounted plastic Owls atop the antenna
and tuned to compensate (if and when necessary). It seems to keep the real
feathered fiends at bay.
-----------------------------------------------------------------------------
: If you eat a live toad first thing in the
janc@icebox.iceonline.com : morning, nothing worse will happen to you all
: day.
: To you or the toad.
-----------------------------------------------------------------------------
------------------------------
Date: Fri, 21 Jan 1994 21:34:58 GMT
From: utcsri!newsflash.concordia.ca!sifon!clouso.crim.ca!hobbit.ireq.hydro.qc.ca!barde!vaillan@uunet.uu.net
Subject: callsign servers
To: info-hams@ucsd.edu
In article 7Fy@ucdavis.edu, ez006683@othello.ucdavis.edu (Daniel D. Todd) writes:
>Hi all,
>I was trying to access the buffalo callsign server but I keep getting an
>error. Is this a network problem a local problem or an operator problem.
>
>othello% telnet electra.cs.buffalo.edu 2000
>telnet: service to this port is not available
>othello% telnet callsign.cs.buffalo.edu 2000
>telnet: service to this port is not available
>othello% telnet 128.205.32.2 2000
>telnet: service to this port is not available
>othello%
>
>Thanks for the help,
>Dan
>
>--
>*---------------------------------------------------------------------*
>* Daniel D. Todd Packet: KC6UUD@KE6LW.#nocal.ca.usa *
>* Internet: ddtodd@ucdavis.edu *
>* Snail Mail: 1750 Hanover #102 *
>* Davis CA 95616 *
>*---------------------------------------------------------------------*
>* I do not speak for the University of California.... *
>* and it sure as hell doesn't speak for me!! *
>*---------------------------------------------------------------------*
>
You must have network problems...
Here is what I get:
telnet 128.205.32.2 2000
Trying 128.205.32.2 ...
Connected to 128.205.32.2.
Escape character is '^]'.
Callbook v1.3 Bug reports to bowen@cs.buffalo.edu Type 'help' for help
>> call kc6uud
Call-Sign: KC6UUD Class: TECHNICIAN
Real Name: DANIEL D TODD Birthday: DEC 19, 1966
Mailing Address: 1411 WAKE FOREST 6, DAVIS, CA 95616
Valid From: MAY 7, 1991 To: MAY 7, 2001
>>
73
Clem.
---
Clement Vaillancourt, | Institut de Recherche d'Hydro-Quebec
Analyste, | Varennes, P. Quebec, Canada, J3X 1S1
Informatique scientifique | Tel:+1 514 652 8238 Fax:+1 514 652 8309
vaillan@ireq.hydro.qc.ca | Radio-amateur: VE2HQJ@VE2CRL.PQ.CAN.NA
------------------------------
Date: Thu, 20 Jan 1994 21:57:04 GMT
From: library.ucla.edu!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!pacbell.com!unet!white!johng@network.ucsd.edu
Subject: CW Books
To: info-hams@ucsd.edu
Ok, I've gone though the 200 or so unexpired articles, as well as
the FAQ (probably not closely enough) and below is the
closest my question has come to being answered.
In article <2hebl3$2l9@news.acns.nwu.edu> rdewan@casbah.acns.nwu.edu (Rajiv Dewan) writes:
>In article <CJqtFz.61@wri.com>, Bruce Pea <pea@wri.com> wrote:
>>Can anyone recommend some good books on copying code??
>>
>>Next test date is in March here, and I want to be ready
>>to "ace" the 13wpm general class code test. I'm using
>>SuperMorse and listening to code on my radio. I remember
>
>Noting the lack of a call sign in you sig, I assume that you
>are not a ham yet. So I will not recommend getting on the air
>and using it. ... [delete] ...
My question is:
If I pass the 13 wpm test, do I also have to pass the 5 wpm
test? Or in other words; Can I get a General class license
by passing the written tests for Novice, Technician and
General and then pass ONLY the General CW test?
I am interested in a General class license because of the
privileges it provides but I am not that hot about learning
CW at 5 wpm, then having to bump up to 13 wpm. I've listened
to 5 and 13 wpm and they sound like two different languages!
I'm pretty confident that I can be proficient at 13-15 wpm with
plenty of practice. Any thoughts on how 'practical' this ambition is?
Am I setting myself up for 'too much' work by skipping over the
5 wpm rate?
--
John Gratton | johng@net.com
Hans Christian 33 "Nakia" | (415)780-5774
The last time an informal vote on "should we split rec.boats" was taken, the
motion was defeated 67 to 18. Before you start it again, please consider that.
------------------------------
Date: 21 Jan 1994 22:36:55 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!cs.utexas.edu!geraldo.cc.utexas.edu!astro.as.utexas.edu!oo7@network.ucsd.edu
Subject: CW filters and DSP-9
To: info-hams@ucsd.edu
yee@mipg.upenn.edu (Conway Yee) asks:
>>When I look at CW filters, I see advertised bandwidths of between circa
>>250Hz to 600Hz. What are the difference?
The 250 Hz ones have a bandwidth of 250 Hz and the 600 Hz ones have a
bandwidth of 600 Hz. That are[sic] the difference. What do you mean?
Ref the DSP-9 postings, I have used mine a few times and am still not
sure that it is doing anything for me on CW. It's cute having a 100 Hz
width filter but, as someone mentioned, when it cuts out your sidetone
you think twice about using it. So far, I've found that the fiddling
around adjusting the receiver output for signals of different level as
well as playing with the gain on the DSP-9 is distracting when tuning
the bands. There is a narrow range of signal strengths where the DSP
really helps. If the signal/noise is already 10 I don't need it to be
100, and when it's 1, the DSP doesn't really help. I need to play
with it some more, I'm sure.
It should be useful on phone, when I get around to that. Taking out
the jammers and tuners-up on top of DX stations is useful, but it's
not saying much for the state of amateur radio if the DSP boxes are
primarily of use for removing deliberate human (or quasi-human) QRM.
As far better ops than I have said, sometimes the best filter is the
one between your ears.
Derek "up lid" Wills (AA5BT, G3NMX)
Department of Astronomy, University of Texas,
Austin TX 78712. (512-471-1392)
oo7@astro.as.utexas.edu
------------------------------
Date: 21 Jan 94 18:34:27
From: ucsnews!newshub.sdsu.edu!usc!howland.reston.ans.net!vixen.cso.uiuc.edu!uwm.edu!msuinfo!netnews.upenn.edu!mipg.upenn.edu!yee@network.ucsd.edu
Subject: CW filters and DSP-9
To: info-hams@ucsd.edu
I ask a poorly phrased question:
>When I look at CW filters, I see advertised bandwidths of between circa
>250Hz to 600Hz. What are the difference?
A poster replies:
>The 250 Hz ones have a bandwidth of 250 Hz and the 600 Hz ones have a
>bandwidth of 600 Hz. That are[sic] the difference. What do you mean?
I am asking about the difference in CW performance. Is a narrower
filter easier to copy or a wider one?
--
Medical Image Processing Group | Conway Yee, N2JWQ
411 Blockley Hall | EMAIL : yee@mipg.upenn.edu
418 Service Drive | VOICE : 1 (215) 662-6780
Philadelphia, PA 19104-6021 (USA) | FAX : 1 (215) 898-9145
------------------------------
Date: Sat, 22 Jan 1994 21:40:50 MST
From: sdd.hp.com!cs.utexas.edu!howland.reston.ans.net!sol.ctr.columbia.edu!destroyer!nntp.cs.ubc.ca!alberta!adec23!ve6mgs!usenet@network.ucsd.edu
Subject: Daily Summary of Solar Geophysical Activity for 22 January
To: info-hams@ucsd.edu
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
DAILY SUMMARY OF SOLAR GEOPHYSICAL ACT
22 JANUARY, 1994
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
(Based In-Part On SESC Observational Data)
SOLAR AND GEOPHYSICAL ACT
-----------------------------------------------------------
!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 022, 01/22/94
10.7 FLUX=113.0 90-AVG=103 SSN=102 BKI=3212 0022 BAI=005
BGND-XRAY=B2.1 FLU1=7.1E+05 FLU10=1.0E+04 PKI=3212 2122 PAI=007
BOU-DEV=029,017,008,010,002,002,010,011 DEV-AVG=011 NT SWF=00:000
XRAY-MAX= C1.6 @ 0110UT XRAY-MIN= B1.9 @ 1808UT XRAY-AVG= B2.7
NEUTN-MAX= +002% @ 1205UT NEUTN-MIN= -002% @ 2005UT NEUTN-AVG= +0.0%
PCA-MAX= +0.1DB @ 0745UT PCA-MIN= -0.4DB @ 1500UT PCA-AVG= -0.0DB
BOUTF-MAX=55348NT @ 0446UT BOUTF-MIN=55328NT @ 1925UT BOUTF-AVG=55341NT
GOES7-MAX=P:+000NT@ 0000UT GOES7-MIN=N:+000NT@ 0000UT G7-AVG=+060,+000,+000
GOES6-MAX=P:+127NT@ 1950UT GOES6-MIN=N:-061NT@ 0601UT G6-AVG=+081,+032,-031
FLUXFCST=STD:110,110,110;SESC:110,110,110 BAI/PAI-FCST=005,005,005/010,010,010
KFCST=1111 2111 0101 2111 27DAY-AP=007,005 27DAY-KP=2012 3223 1121 2211
WARNINGS=*SWF
ALERTS=
!!END-DATA!!
NOTE: The Effective Sunspot Number for 21 JAN 94 is not available.
The Full Kp Indices for 21 JAN 94 are: 2o 3- 1+ 1- 1+ 2- 3- 2o
SYNOPSIS OF ACT
--------------------
Solar activity was low during the past 24 hours. Region
7654 (N09W06) produced the only C-class x-ray event observed
but has lost its delta magnetic configuration. Two new regions
were numbered. Region 7658 (N12E16) is a simple bipolar group.
Region 7659 (S13E47) was spotted briefly but is presently only
plage and an arch filament system. Several unassociated Type
III radio sweeps, and discrete radio bursts were reported. A
large, inactive prominence is rotating over the east limb.
Solar activity forecast: solar activity is expected to be
low. Region 7654 retains the potential for occasional eruptive
flares.
The geomagnetic field has been at mostly quiet levels at
middle geomagnetic latitudes for the past 24 hours. Some
periods at active levels were observed at auroral latitudes.
Geophysical activity forecast: the geomagnetic field is
expected to be quiet for the next three days. Active conditions
are possible on 26 Jan in response to disturbed solar wind
associated with a filament disappearance on 21 Jan and an
equatorial coronal hole which will be near central meridian
on 23 Jan.
Event probabilities 23 jan-25 jan
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF Green
Geomagnetic activity probabilities 23 jan-25 jan
A. Middle Latitudes
Active 05/10/10
Minor Storm 01/05/05
Major-Severe Storm 01/01/01
B. High Latitudes
Active 05/10/10
Minor Storm 01/05/05
Major-Severe Storm 01/01/01
HF propagation conditions were normal over all regions.
Near-normal conditions should persist over the next 72 hours.
High latitudes may begin seeing effects of the above-mentioned
disturbance on 25 January. Otherwise, near-normal conditions
are expected to continue.
COPIES OF JOINT USAF/NOAA SESC SOLAR GEOPHYSICAL REPORTS
========================================================
REGIONS WIT
----------------------------------------------------------
NMBR LOCATION LO AREA Z LL NN MAG TYPE
7652 N04W23 220 0090 HSX 02 001 ALPHA
7654 N09W08 205 0610 CKI 09 032 BET
7657 N12W37 234 0080 DAO 06 012 BET
7658 N12E14 183 0010 BXO 05 005 BET
7659 S13E47 150 0010 BXO 02 002 BET
7656 S22W62 259 PLAGE
REGIONS DUE TO RET
NMBR LAT
7647 S15 096
7646 S09 087
7645 N13 085
7649 S19 079
LISTING OF SOLAR ENERGETIC EVENTS FOR 22 JANUARY, 1994
------------------------------------------------------
A. ENERGETIC EVENTS:
BEGIN MAX END RGN LOC XRAY OP 245MHZ 10CM SWEEP
0102 0109 0114 7654 N10W00 C1.6 SF 280
0246 0246 0246 110
0633 0633 0634 310
1911 1919 1926 7654 N08W10 B6.2 SF 290
1928 1928 1928 110
POSSIBLE CORONAL MASS EJECTION EVENTS FOR 22 JANUARY, 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 EXT
EAST SOUTH WEST NORTH CAR TYPE POL AREA OBSN
57 N18W17 S10W57 S10W57 N18W17 250 ISO NEG 008 10830A
58 N20E29 S15E22 N02E07 N30E17 190 ISO POS 016 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 Jan: 0324 0328 0332 B4.5
0758 0802 0809 B3.5
0816 0821 0838 SF 7654 N07E17
1019 1023 1025 B6.6
1140 1146 1155 B4.5
1610 1613 1616 B4.0 SF 7654 N08E12
2059 2103 2106 B4.6 SF 7654 N07E08
2308 2330 2340 B7.8 SF 7654 N06E07
REGION FLARE STATISTICS FOR THE PREVIOUS UTC DAY
------------------------------------------------
C M X S 1 2 3 4 Total (%)
-- -- -- -- -- -- -- -- --- ------
Region 7654: 0 0 0 4 0 0 0 0 004 (50.0)
Uncorrellated: 0 0 0 0 0 0 0 0 004 (50.0)
Total Events: 008 optical and x-ray.
EVENTS WIT
----------------------------------------------------------------
Date Begin Max End Xray Op Region Locn Sweeps/Optical Observations
------ ---- ---- ---- ---- -- ------ ------ ---------------------------
21 Jan: 0758 0802 0809 B3.5 III
2308 2330 2340 B7.8 SF 7654 N06E07 Continuum
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: 24 Jan 94 03:38:02 GMT
From: news-mail-gateway@ucsd.edu
Subject: International Callsign Server
To: info-hams@ucsd.edu
Does anyone know of a server that can be TELNET'd that has a
INTERNATIONAL callsign data base or CD-ROM on it? Whats
the address? Buffalo.edu does not support international
that I know of.
/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\
! JD DELANCY | Lizzie Borden took an axe !
! VM: 1-800-862-4511 Box 9276 | And plunged it deep in to the !
! VOICE: 301-763-4943 or 3474 | VAX.. !
! | Don't you just hate people who !
! Email: k1zat@bah.com | do all the things YOU wanted to !
! AX25: K1ZAT@K3HKI.#SOMD.MD.NA | do ?? !
/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\/*\
------------------------------
Date: 21 Jan 94 17:16:54
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!agate!msuinfo!netnews.upenn.edu!mipg.upenn.edu!yee@network.ucsd.edu
Subject: The differences in CW filter performance
To: info-hams@ucsd.edu
When I look at CW filters, I see advertised bandwidths of between circa
250Hz to 600Hz. What are the difference?
--
Medical Image Processing Group | Conway Yee, N2JWQ
411 Blockley Hall | EMAIL : yee@mipg.upenn.edu
418 Service Drive | VOICE : 1 (215) 662-6780
Philadelphia, PA 19104-6021 (USA) | FAX : 1 (215) 898-9145
------------------------------
Date: 23 Jan 1994 08:28:40 +0200
From: vixen.cso.uiuc.edu!howland.reston.ans.net!xlink.net!zib-berlin.de!netmbx.de!Germany.EU.net!EU.net!sunic!trane.uninett.no!news.eunet.no!nuug!news.eunet.fi!elvis.clinet.fi!@sdd.hp.com
To: info-hams@ucsd.edu
References <1994Jan11.150658.25191@ke4zv.atl.ga.us>, <940118.46856.LEEVANKOTEN@delphi.com>, <2hihn7$1vs@news.u.washington.edu>.unin
Subject : Re: BRAIN CANCER, LEUKEMIA FROM HAM RADIO
Man has a high risk to get at least brain cancer if listening too
much 2m repeater OH2RAA in Helsinki.
--
Jukka Salomaa jukka@clinet.fi OH2BUA
phone +358 400 315 444 puhelin 9400 315 444
------------------------------
Date: 22 Jan 1994 18:26:34 +0200
From: library.ucla.edu!agate!howland.reston.ans.net!pipex!sunic!news.funet.fi!butler.cc.tut.fi!lehtori.cc.tut.fi!not-for-mail@network.ucsd.edu
To: info-hams@ucsd.edu
References <2hple7$ti@geraldo.cc.utexas.edu>, <YEE.94Jan21183427@mipgsun.mipg.upenn.edu>, <2hpqci$m30@safety.ics.uci.edu>ht
Subject : Re: CW filters and DSP-9
Clark Savage Turner (turner@safety.ics.uci.edu) wrote:
> Most IF filters don't have much ring, though some, many audio filters
> (except DSP I understand) can ring pretty badly.
What should the audio filter frequency (and phase response) look like
to avoid ringing. A high-Q single stage bandpass sounds horrible, but
how does a filter with flat passband (eg. Butterworth or elliptic)
sound like or is it really required to use Bessel-response in order
to get rid of the hollow sound produced by noise peaks.
Paul OH3LWR
--------------------------------------------------------------------
Phone : +358-31-213 3657
X.400 : G=Paul S=Keinanen O=Elisa-Tampere A=ELISA C=FI
Internet: Paul.Keinanen@Telebox.tele.fi
Telex : 58-100 1825 (ATTN: Keinanen Paul)
Mail : Hameenpuisto 42 A 26
FIN-33200 TAMPERE
FINLAND
------------------------------
Date: 22 Jan 1994 18:25:41 +0200
From: library.ucla.edu!agate!howland.reston.ans.net!pipex!sunic!news.funet.fi!butler.cc.tut.fi!lehtori.cc.tut.fi!not-for-mail@network.ucsd.edu
To: info-hams@ucsd.edu
References <2hple7$ti@geraldo.cc.utexas.edu>, <YEE.94Jan21183427@mipgsun.mipg.upenn.edu>, <2hpqci$m30@safety.ics.uci.edu>ht
Subject : Re: CW filters and DSP-9
Clark Savage Turner (turner@safety.ics.uci.edu) wrote:
> In <YEE.94Jan21183427@mipgsun.mipg.upenn.edu> yee@mipg.upenn.edu
> (Conway Yee) writes:
> >I am asking about the difference in CW performance. Is a narrower
> >filter easier to copy or a wider one?
> This is a matter of personal taste for many of us.
[deleted]
> The filter can do two things for you :
>
> 1. Eliminate QRM nearby
> 2. Quiet down the background noise.
>
> Reference number 2, some filters don't do so well at this,
The filter bandwidth (which is usually defined as the bandwidth between
the points where the frequency is -6 dB down from the maximum in the pass
band) is not the only figure-of-merrit to look for. Equally important is
the shape of the frequency response above and below the quoted bandwidth.
This is usually specified with the -60 dB bandwidth and it indicates how
much background noise will get through.
There are 250 Hz (at -6 dB) filters with a 1.2 kHz -60 dB bandwidth
and there are 500 Hz filters with a 800 Hz -60 dB bandwidth, so
look carefully at the specifications. Despite broader passband, the latter
filter is more effective to quiet down background noise and interfering
signals a few hundred Hertz or more above or below the passband.
Some manufacturers specify the passband bandwidth and the frequency
offset from the center of the passband where the frequency response is
-60 dB down, in the previous example +/- 600 Hz resp. +/- 400 Hz.
Some even omit the +/- signs so that the figures look better. You
can easily get the impresion that (+/-) 600 Hz is better than 800 Hz
(total) bandwidth, so be carefull.
Instead of the -60 dB bandwidth, sometimes the shape factor is given,
which is simply the ratio of the -60 dB bandwidth to the -6 dB bandwith.
The shape factor for the first example is 4.8 and 1.6 for the latter.
In some cases the shape factor is given at a smaller attenuation e.g.
50 dB/6 dB to get smaller (and better) figures.
Thus, it is very hard to select filters solely on the basis of passband
bandwidth.
As Clark pointed out in the begginning it is also a matter of personal
taste.
Paul OH3LWR
--------------------------------------------------------------------
Phone : +358-31-213 3657
X.400 : G=Paul S=Keinanen O=Elisa-Tampere A=ELISA C=FI
Internet: Paul.Keinanen@Telebox.tele.fi
Telex : 58-100 1825 (ATTN: Keinanen Paul)
Mail : Hameenpuisto 42 A 26
FIN-33200 TAMPERE
FINLAND
------------------------------
Date: 21 Jan 1994 17:21:00 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!agate!linus!linus.mitre.org!mwvm.mitre.org!m14494@network.ucsd.edu
To: info-hams@ucsd.edu
References <2hk4tpINN125@abyss.West.Sun.COM>, <CJwDLy.4wz@news.direct.net>, <2hkd5iINN15h@abyss.West.Sun.COM>
Subject : Re: Ramsey FX Transceivers
Dana Myers writes:
> The difference is that the IC24AT was factory built and then adjusted
> by the factory to specified tolerances.
I don't know about Icom specifically, but this is generally
not true of consumer electronics. The published specs for
most electronics represent an average based on samples
taken from the production run. The statement at the end of
the specs that says "Specifications subject to change without
notice" really means "Your radio may not do this well". Only
a very few manufacturers offer "guarenteed specs", in which
each and every unit is guarenteed to meet the spec. When I
bought a stereo receiver a while back, I went with Tandberg
because unlike almost every other manfacturer, they
guarentee their specs. Check the spec sheet for the radio in
question; if it doesn't say they're guarenteed, they aren't.
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* These are my opinions only*
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End of Info-Hams Digest V94 #69
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