Date: Fri, 1 Apr 94 23:07:49 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 #364
To: Info-Hams
Info-Hams Digest Fri, 1 Apr 94 Volume 94 : Issue 364
Today's Topics:
Hamfest List - Mid Atlantic States
How phasing SSB Exciters Work (Was: RF and AF speech processors)
passive satellites
Repeater Voter Questions
RF and AF speech processors. Was: FT-990 vs TS-850
Time to lighten up.....
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: 31 Mar 1994 19:43:38 -0500
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!news.intercon.com!news1.digex.net!access.digex.net!not-for-mail@network.ucsd.edu
Subject: Hamfest List - Mid Atlantic States
To: info-hams@ucsd.edu
MID-ATLANTIC HAMFEST LISTING March 31, 1994
The following is a listing of known hamfests in the MD/NJ/PA/VA area.
I will update this list as necessary. Please send any additions or
corrections to me at cps@access.digex.net so that others may benefit.
Thanks,
Chris Smolinski, N3JLY
April 10, 1994:
HAMCOMP '94 8AM-1PM, $5 adm, $12 tailgating, $20 table.
Trenton State College, Rt 31, Ewing Township.
Talk-In 146.67-, 146.52 simplex.
Contact Don Write AA2F (609) 737-1723.
May 15, 1994:
HAMFEST '94, 7AM-2PM, $5 adm, $8 tailgating, $12 tables.
Middletown Grange Fairgrounds, Penns Park Rd, Wrightstown, PA
Talk-In 147.09/R, 146.52 simplex
Contact: George Brechman N3HBT (215) 443-5656
May 21, 1994:
Cherryville Hamfest, 8AM-2PM, $6 admission, $10 tailgating, $15 tables
Warren County Farmers Fairgrounds, Rt 518 North, Harmony, NJ I78-exit 3.
Contact Keith Burt, KF5FK, (908) 788-4080 before 10PM
VE Test Session Contact Marty Grozinski, NS2K, (908) 806-6944 before 9PM
Talk-In 147.375+ & 146.820-
May 22, 1994:
Great Hagerstown Hamfest, 8AM-3:30PM, $5 adm, $5 tailgating, $20 tables
Hagerstown Jr COllege Rec Center, Exit 32B from I-70, right at Edgewood Rd
Contact Page Pyne or Fred Bailey (301) 714-0688
VE Exams 9AM contact Pat KQ8E at (304) 289-3576
Talk-In 146.34+
June 5, 1994:
Ole Virgina Hamfest, 8AM-3PM
Prince William County Fairgrounds, Manassas, VA
June 19, 1994:
Father's Day Hamfest, 8AM-3PM, $5 adm, $5 tailgating
Walkersville Fire Co, Walkersville, MD, rt 15 to rt 26 to rt 194
Frederick Amateur Radio Club, PO Box 1260, Frederick, MD 21702
Talk-In 146.52, 147.06+, 448.425-
July 10, 1994:
Maryland Hamfest, 8AM-?, tailgating opens at 6AM
Timonium Fairgrounds, York Rd, I-695 to I-83 to Timonium Rd
BRATS, PO BOx 5915, Baltimore, MD 21208
VE Exams 10AM, Pre-registration required
Talk-In 147.03+, 224.96-
July 16, 1994:
Red Rose Repeater Assn, 9AM-3PM $5 adm, $5 tailgating, $20 tables
McCaskey High School, Reservoir & N Franklin Streets, Lancaster, PA
Red Rose Repeater Assn, PO Box 8316, Lancaster, PA 17604
Talk-In 147.015+
August 7, 1994:
Southern Patuxent Hamfest, 7AM-2PM, $5 adm, $5 tailgating, $25 tables
Prince George County Equestrian Center, Upper Marlboro, MD
Rt 301/ Rt 4, exit 11-A (Rt 4 Pennsylvania Ave) from DC Beltway I-495
Contact: Southern Patuxent ARC, PO Box 399, St Leonard, MD 20685
(410) 586-2177
Talk-In 147.15
Hamfest 94, 8AM-?, $5 adm, $3 tailgating
Bucks County Drive In Theater, rt 611, 6mi N of Pa Turnpike exit 27
Mid Atlantic Radio Club, PO Box 352, Villanova, PA 19085
Talk-In 147.06, 145.13
August 14, 1994:
SARA Carroll County Hamfest, 8AM-?, $5 adm, $5 tailgating, $8 tables
Carroll County Ag Center, Smith Ave, Westminster, MD
Contact: Alan Parker, KS3L, (410) 859-1475
SARA Hamfest, 607 Brentwood Rd, Linthicum, MD 21090
Talk-In 146.52, 224.68, 224.64
Hamfest & Computerfest, 8AM-?, $4 adm, $7 tailgating, $25 tables
Career Institute of Technology, Easton, PA
Delaware-Lehigh ARC, RR 4 Greystone Bldg, Nazareth, PA 18064-9211
(610) 820-9110
Talk-In 146.70
September 9 & 10, 1994:
Queen Wilhelmina State Park, Mena, Arkansas. $2 park entrance fee, $5 adm.
Contact Gerald Wallis, N5KKD, (501) 524-3094
September 17&18, 1994:
Virginia Beach Hamfest $6 adm, $15 tailgating, $30 tables, $125 booths
Virginia BEach Pavillion
Manny Steiner, K4DOR, 3512 Olympia Lane, Virginia Beach, VA 23452
(804) HAM-FEST
September 18,1994
South Jersey Radio Assn, 8AM-3PM, $5 admission, $5 tailgating
Pennsauken High School Parking Lot, near US rt 130 / NJ rt 73
Contact Diane Nafis, N2LCQ, (609) 227-6281, (609) 228-8088
VEC Test Session registration at 9:30 AM
Talk-In 145.290-
October 30, 1994:
Mason Dixon Hamfest 8AM-?, $5 adm, $5 tailgating, $15 tables
Carroll County Ag Center, Westminster, MD
Mason Dixon Hamfest, PO Box 763, Hanover, PA 17331
VE exams $5.60, 9AM, reg 8AM, Page Evans NE3P, (717) 359-7610
Talk-In 145.410-
------------------------------
Date: Fri, 1 Apr 1994 03:21:38 GMT
From: lerc.nasa.gov!magnus.acs.ohio-state.edu!csn!col.hp.com!srgenprp!alanb@purdue.edu
Subject: How phasing SSB Exciters Work (Was: RF and AF speech processors)
To: info-hams@ucsd.edu
Tom Bruhns (tomb@lsid.hp.com) wrote:
: But what if it was a design goal to come up with a quadrature phase
: network with flat frequency response and linear phase? Would that be
: possible? I think so, and I offer comments below in support of that
: idea. If I don't get to it, maybe someone else can check out the
: suggestion at the end to see if it really can work.
: ...
: 10. It _should_ be possible to find a pair of MFD filters with overlapped
: passbands (either two bandpass filters or a lowpass and a bandpass)
: which have equal d(phi)/df and a 90 (or 45--see paragraph 11) degree
: phase difference between the channels in the shared passband.
: Actually finding such a pair is the exercise remaining to be done!
: Any volunteers?
Tom: Your logic seems impeccable. The only possible fly in the ointment
I can see is that it may not be possible to find the required band-pass
filters such that the overlap region covers a 10:1 frequency range
(300 Hz - 3 kHz). It may have to be done at an "IF" frequency so the
band-pass filters cover a smaller percentage bandwidth.
: As a simple feasibility check, I asked a curvefitter to fit to a couple
: linear phase ramps with constant amplitude, offset by 90 degrees, in the
: range from 300Hz to 3.5kHz, and it didn't have any trouble getting
: within a tenth dB and under a degree, with about 14 poles and 14 zeros
: for each. None of the poles was particularly high Q: max about 8.
Did the curvefitter use an equation in the form of a ratio of
polynomials? If so, then all that's required is to derive the poles
and zeros and we're practically done!
I seem to recall that a conventional phase-shift network can be implemented
with around 4 all-pass filters (per output), each of which has a pole-zero
pair on the real axis (Q of 1/2). Each filter can be built with a single
op-amp, one capacitor and 3 resistors. Tom's idea is basically to use more
all-pass filters and to allow them to have higher Q.
As a further complication, one could intentionally design the phase-shift
network to have slightly non-linear phase to compensate for the unflat
group delay of the audio filter.
Of course, all this assumes that achieving linear phase (as opposed
to a small, smoothly-varying phase error) is worth the extra work.
Sounds like making the phase response "perfect" would more than
triple the network complexity. (10 to 14 high-Q poles versus 4
low-Q poles.)
AL N1AL
------------------------------
Date: Thu, 31 Mar 1994 15:49:59 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!pipex!sunic!EU.net!julienas!nenuphar.saclay.cea.fr!avocette!parnoul@network.ucsd.edu
Subject: passive satellites
To: info-hams@ucsd.edu
Hi there,
A colleague just realized that the news posting outside the company is
up again and running, we have been quiet for some reason for more than
one year... Reading the news was fine though.
Following is an idea I'd like to have some feedback from the EME'ers
for instance.
Do you think the big telecom satellites operating geosynchonously(sp?)
above the equator could be used as passive satellites for ham contacts ?
The reflecting surface should not be neglectable considering the huge
solar panels, at least the satellite body should provide echos back
to earth.
I heard that the first ham "satellites" were aluminium covered ballons,
reflecting some of the VHF power.
The geosync. satellites are much further away, maybe the big guns in EME
have a chance to hear something back ?
The input stages of the mentionned satellites operating on whatever freq.
might not appreciate the strong field shooting at them... Any regulations
on that point ?
What do you think ?
73 de f5hnk/Patrick
RYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRY
Patrick Arnoul F5HNK Email: parnoul@gaap.saclay.cea.fr
French Atomic Commission (C.E.A)
Centre d'Etudes de Saclay Phone: (33) 1 69 08 82 91
DTA/LETI/DEIN Bat 528
F-91191 GIF SUR YVETTE CEDEX Fax: (33) 1 69 08 83 95
THE QUICK BROWN FOX JUMPED OVER THE LAZY DOG'S BACK THE QUICK BRWON FOX JUMPED O
------------------------------
Date: 1 Apr 1994 05:06:43 -0600
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!news.uh.edu!uuneo.neosoft.com!sugar.NeoSoft.COM!not-for-mail@network.ucsd.edu
Subject: Repeater Voter Questions
To: info-hams@ucsd.edu
In article <2nf4iu$dn6@news.udel.edu>,
Dave Dabell <dave@diusys.cms.udel.edu> wrote:
>
> What voter should we use?
> I've heard good things about Doug Hall products.
> Are there others that should be considered?
If you're going to buy one, the Hall voter is the best value. I've used it
in a commercial application and it's a fine product. Works great and I'd
highly recommend it. You can sometimes find surplus Motorola and GE voters
on the used market. They're a bit tricky to use compared to the Hall, but
all work basically the same.
>
> Anyone have suggestions on how to preserve audio
> fidelity over the UHF link?
> One thought I had was to route remote receiver
> detector audio directly to the link xmit modulator.
> This would bypass receiver de-emphasis and link xmit
> pre-emphasis circuitry. Comments?
You have the right idea. One other comment--make sure you feed the audio into
the link transmitter past the audio limiter. This will make sure the audio
doesn't get clipped by the link transmitter. Since you have control over the
deviation of the links, you can get away with no limiter. The audio can be
made flat from below 100 Hz to above 3 kHz with normal narrow-band FM
equipment. I usually feed my audio into the PL input on the transmitter. This
is usually after the limiter and pre-emphasis.
>
> What is the best way to match the remote receiver
> audio to the main receiver?
> I assume that audio level and frequency response
> characteristics should be closely matched to make
> the voting process transparent.
This is the most important aspect of a voted system. If the receivers don't
match, the voter will tend to favor one receiver over another. The Hall voter
has adjustments which allow the user to "fool" it into thinking one receiver
is noisier than another, but this won't make up for the audio being close to
start with. I've never used equalization, but it's pretty easy to get it
right by just taking discriminator (non de-emphasized) audio from the receiver
and feeding the link transmitter past the audio processing.
>
>I'd also welcome any general advice or experiences folks
>have had with remotes that might be of help to us.
What you'll find most impressive is that a voted system will cover better
than the sum of the receiver sites. Because you have diversity reception, much
of the mobile flutter heard on single site receiver systems will disappear.
I think you'll be pretty happy with it. The only down side is the additional
maintenance of the link equipment and voter.
Good luck.
--
Jim Reese, WD5IYT | "Reality is for those with no imagination."
jreese@sugar.neosoft.com | --Jim McClellan
------------------------------
Date: Fri, 1 Apr 1994 08:22:10 GMT
From: lerc.nasa.gov!magnus.acs.ohio-state.edu!csn!col.hp.com!news.dtc.hp.com!hplextra!hplb!hpwin052!hpqmoea!dstock@purdue.edu
Subject: RF and AF speech processors. Was: FT-990 vs TS-850
To: info-hams@ucsd.edu
Alan Bloom (alanb@sr.hp.com) wrote:
: Crystal filters designed for receive filtering are not optimum
: for a transmitter SSB generator.
: AL N1AL
Yippeee ! Thanks, Alan. That one little fact is always a shock
to everyone I explain it to.
Think of two expensive-grade Japanese rigs in QSO. The transmitting
rig will have an SSB generator with crystal IF filter, an RF clipper (Tx
IF would be a better adjective) and another SSB crystal filter. For
economy, the radio will use SSB filters designed for Rx selectivity as
the same filters are switched into the receive path. Serious Dxers will,
of course, have changed them for especially narrow ones. At the
receiving end, the posh radio on receive will have two SSB crystal
filters in use, one in its 9-ish MHz IF, and one in its 455 kHz IF.
The sound that reaches the listener's ears can have passed through
FOUR receiving-spec crystal filters, some or all of which could be
special extra-narrow ones.
We are talking of up to 32 poles of crystal filtering, as four sets
of 8-pole 2.4kHz wide sections. Just look in Zverev to see the group
delay and ringing characteristics.
Those filters are important in the receiver, but quite inappropriate
in the transmitter, we could halve the damage done to the sound quality.
My thoughts for a home-brew ultimate rig are running towards phasing
SSB generation, IF speech processing and then a >3kHz wide crystal
filter as a post-clipper clean-up. Carrier and opposite sideband
suppression will be the sum of the performance of the phasing system and
the crystal filter, so neither need produce spectacular performance.
Experiments have shown a good, clean, controlled output spectrum,
limited by power amp intermod products, and the audio quality was
outstanding.
Here in the 1990s I'm daydreaming about DSP'ing a similar scheme,
Hilbert-transform based SSB generation, arithmetic clipping, and a
digital SSB filter feeding a DAC producing a low IF to make a cheap and
excellent SSB generator/speech processor.
Multiband audio processing looks attractive, but it is the peak of
the sum of all the bands that is what has to be controlled, so I think
this may not be the best technique. There is, of course no technique
that is RIGHT, but some are better than others....
Amusingly, some of the fancy DSP based speech processor techniques
turn out to be "RF processors" in digital form.
Cheers,
David
(It's refreshing to have a decent technical debate going in place of
the code wars and hand-held questions...)
------------------------------
Date: Fri, 01 Apr 94 08:23:32 GMT
From: netcomsv!netcomsv!skyld!jangus@decwrl.dec.com
Subject: Time to lighten up.....
To: info-hams@ucsd.edu
Time to interject some humor here. I spotted this in the Yucks digest and
just knew it belonged here....
I was toying with using search and replace to insert Jeff Herman's name in
this, but figured that the rest of you would figure it out on your own.
73 es GE from Jeff
Date: Thu, 10 Mar 1994 16:05:21 -0600
From: skip@cy.cs.olemiss.edu (Skip Sauls) (by way of werner@cs.utexas.edu (Werne
r Uhrig))
Subject: [yucky stuff] Zsolt Szabo is DEAD!!!
To: Gene Spafford <spaf>
JOHNS HOPKINS (ANP) - Zsolt Szabo, the self-proclaimed genius who has
gained notoriety for his absurd net postings, was found dead today
at his terminal. Cause of death is unknown, but police detectives
believe that he may have suffered from an overdose of EGO, a new
and highly addictive narcotic. An autopsy has been ordered, but
there is little chance of finding anything as the brain is usually
consumed. Amazingly, the drug allows the person to continue to
live, although admittedly in a severly reduced capacity, for up to
2 days after the last traces of the brain have degenerated.
Police have been perusing the last few articles posted by the
late Mr. Szabo on a computer bulletin board, referred to only as
"that advocacy thing" by the detectives. A search of his apartment
also turned up several photographs of a fashion model that he has
apparently been stalking for the past few months. The only other
evidence that the press was allowed access to was a series of words
drawn in human feces on the wall of the deceased's apartment. Most
of the words suggest an anal-fixation and are not printable here, but
there were several that appear to be code words, including "730",
"mbyte", and others. Police speculate that the former was the time
that the deceased finally expired and that the latter was in reference
to some sort of sado-masochistic sexual implement.
Although very little information can be found about EGO, there is
increasing speculation that it may have been around longer than some
suspect. Each canister of EGO, which is a gas, has the letters "JY"
engraved on it, along with the picture of what appears to be some
sort of bird, perhaps a falcon. Unlike some narcotic gases, EGO is
not an inhalant, at least in the traditional sense. The nozzle is
acutally inserted into the anus and the gas is release into the
intestines for absorption. This admitttedly bizzare method may be
the cause of the intense anal-fixation exhibited by users in the
final stages of the addiction.
Amateur: WA6FWI@WA6FWI.#SOCA.CA.USA.NOAM | "You have a flair for adding
Internet: jangus@skyld.grendel.com | a fanciful dimension to any
US Mail: PO Box 4425 Carson, CA 90749 | story."
Phone: 1 (310) 324-6080 | Peking Noodle Co.
------------------------------
Date: Fri, 1 Apr 1994 06:31:44 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!vixen.cso.uiuc.edu!news.uoregon.edu!engineer.mrg.uswest.com!cherokee!walter!thumper!cotton@network.ucsd.edu
To: info-hams@ucsd.edu
References <slayCnEC6z.KDF@netcom.com>, <2nca7d$hf2@network.ucsd.edu>, <dsharpCnHu0x.IDp@netcom.com>cheroke
Reply-To : cotton@thumper.bellcore.com (Chase Cotton)
Subject : QRMers ... (was Re: Obscenity on ham bands)
hey folks, just saw this on the net ... sounds neat!
a cure for the garbage mouths too?
Chase
-----
Chase Cotton cotton@thumper.bellcore.com
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
============================================================
============================================================
PRODUCT PRESS RELEASE NET POLICE INC.
APRIL, 1994 DISTRIBUTE ALL FEEDS
Are you like me? You sit down for a few hours to listen to
a ham net and just relax. You tune up on 40 or 80 meters,
everything is going great, not a thunderstorm in earshot,
and then just as you begin writing down the phone number of
the fellow selling the mint Collins tx/rx pair for $200, the
numbers fade and are replaced by a 2000+ watt
"belchhhhhhhhhhh", "burppppppp", or "yawnnnnnnnnn". The
repeat is similarly stomped. You only get the area code.
You curse under your breath. Hoping for a "recheck", you
listen carefully only to be deafened by a 40 over 9 carrier
and then you begin to moan and cry softly. Later you toss
and turn all night dreaming about a QRM-seeking missile.
Well, soon your prayers will be answered ...
You've heard about "voice printing" and recently the FCC's
use of "transmitter signatures", and now YOU will have some
help fighting the most fearsome of all amateur radio
monsters, the dreaded "QRMer" ...
NET POLICE INC. is happy to announce the introduction of a
new high-tech tool which will become the QRMer's worst
nighmare ...
THE BELCHprinter (tm)
---------------------
The BELCHprinter (tm) is NET POLICE INC.'s triple threat
answer to this age old problem. Using modern DSP and RISC
microprocessor technology, the BELCHprinter unit is
connected to the audio and IF feeds of your receiver. When
the console unit's trigger is depressed, the BELCHprinter
takes an IF and audio sample and extracts a unique numeric
print of the QRMer and his transmitter (when using the
optional high accuracy clock unit). The number is compared
with other existing prints and duplicates are merged. Then
a unique numeric ID is shown in the BELCHprinter's display.
The unit stores 2048 prints in nonvolatile memory. With the
optional RS-232 interface and software package, the unit can
be combined with your PC to form a complete QRMer
identification system with almost unlimited storage. To
help further ID the QRMer, the BELCHprinter can be
instructed to sample the signals of a known
transmitter/operator and thus unknown QRMer prints can be
identified. The built-in database in the BELCHprinter
software can of course hold call and name information.
A follow-on packet radio product is expected to be ready
soon which will allow the exchange of QRMer print records
between BELCHprinter owners so national and global databases
can be constructed. NET POLICE INC. will also be serving as
a repository for print records and will be distributing a CD
version of the entire BELCHprinter Database (tm) as soon as
sufficient prints have been collected.
Hang in there. You'll get that Collins or Kenwood yet ...
And coming soon ...
BELCHsquelch (tm)
------------------------------------------------------------
------------------------------------------------------------
The first production BELCHprinter units are currently
undergoing alpha tests around the country and orders will be
accepted shortly. Prices have yet to be determined, but
should be in line with other modern amateur radio
accessories. You may contact NET POLICE INC. for further
information on the product and associated accessories.
Discounts are being considered for sales to recognized net
control stations as a courtesy to the amateur radio
community.
model# description MSRP
------ ---------------------------------------------- ----
BLCH1 BELCHprinter unit, manual, patch cords TBD
BLCH1a RS-232 control, software for IBM compatible PC TBD
BLCH1b high accuracy clock unit for BLCH1 TBD
BLCHcd CDRom print database (requires BLCH1a) TBD
Distributor inquiries are encouraged.
NET POLICE INC. call 1-800-BAD-HAMS
2611 Indiana Ave., Suite 390A
Chicago, IL 60019
------------------------------
Date: Thu, 31 Mar 1994 20:07:12 +0000
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!pipex!demon!llondel.demon.co.uk!dave@network.ucsd.edu
To: info-hams@ucsd.edu
References <CnG3Jt.Htw@srgenprp.sr.hp.com>, <CnI0t1.DJ@seastar.org>, <1994Mar31.140529.6602@arrl.org>
Subject : Re: How phasing SSB Exciters Work (Was: RF and AF speech pr
Why not use a Weaver (Third Method) exciter? It is easy to generate a couple
of 1800Hz carriers which are 90 degrees out of phase, and fairly easy to
generate a couple of 10.7MHz carriers which are 90 degrees out of phase, and
the rest is reasonably straightforward without any expensive bits. SBL1 mixers
are cheap, so the fact that you need four shouldn't be prohibitive.
Dave
--
*****************************************************************************
* G4WRW @ GB7WRW.#41.GBR.EU AX25 * Start at the beginning. Go on *
* dave@llondel.demon.co.uk Internet * until the end. Then stop. *
* g4wrw@g4wrw.ampr.org Amprnet * (the king to the white rabbit) *
*****************************************************************************
------------------------------
Date: Fri, 1 Apr 1994 00:47:31 GMT
From: ihnp4.ucsd.edu!swrinde!sgiblab!wetware!spunky.RedBrick.COM!psinntp!psinntp!arrl.org!zlau@network.ucsd.edu
To: info-hams@ucsd.edu
References <1994Mar23.162557.7558@arrl.org>, <2msav8$8f9@vixen.cso.uiuc.edu>, <1994Mar25.135851.5580@arrl.org>
Subject : Re: RF and AF speech processors. Was: FT-990 vs TS-850
Zack Lau (KH6CP) (zlau@arrl.org) wrote:
: Ignacy Misztal (ignacy@ux2.cso.uiuc.edu) wrote:
: :
: : Cheap AF processors use AF clippers. DSP-based processors are not only
: : novelties now, but they are more xepnsive to built than RF processors.
: : Why AF clippers are worse than RF (IF) clippers? Consider a 500Hz
: : tone test. With AF processor you will get extra 1000,1500,2000,2500
: : Hz tones. With RF (SSB and DSB) processor 500Hz will be the only
: : output. Please note that some older rigs have "implicit" RF
: : processors. For instance, SWAN 500 has 7360, a beam deflection tube,
: : as a DSB modulator. By clipping peaks, it acts with the following XTAL
: : filter as a DSP processor.
: :
: If you clip an ideal DSB waveform (1 kHz modulation), aren't there
Oops, this should be 500 Hz modulation, not 1 KHz modulation in the
parenthesis.
: two tones spaced 1 kHz apart that could generate IMD products at
: 1.5 kHz and 1.5 kHz (receiver output)? What if you had a significant
: amount of carrier leakthrough that was cleaned up by the crystal
: filter? Couldn't this give you extra tones at 1, 1.5, 2, and 2.5
: kHz (at the receiver)?
What this means is that having two crystal filters, one before and
after the clipper, results in less distortion on your transmitted
signal. The extra filter can also be useful on receive, since IF
amplifiers typically reintroduce noise on the unwanted sideband
detected by most product detectors. It isn't difficult to obtain
matched sets of crystal filters, if you have enough $$$.
--
Zack Lau KH6CP/1 2 way QRP WAS
8 States on 10 GHz
Internet: zlau@arrl.org 10 grids on 2304 MHz
------------------------------
End of Info-Hams Digest V94 #364
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