BE IT KNOWN by all contesters and DXers that amateur radio
station A61AF will be active in the CQ Worldwide CW contest
in the Multi-multi category. Operators will be Paul, K1XM
and Charlotte, KQ1F.
FURTHERMORE, equipment is expected to consist of two radios,
two computers, one CW paddle, a small tribander, a multiband
vertical, and a few dipoles. There is no amplifier at the
present time.
THEREFORE, it is likely that at least one of the stations
will be be operating "search and pounce" for much of the
contest. Stations calling CQ are advised to listen carefully
for a call from A61AF if the band is open.
NOTE that before and after the contest A61AF will be active
giving QSOs on the new bands, on CW, and also YL QSOs.
QSL is via N1QMM.
>From mai@iquest.net (Pat Croft) Mon Nov 13 15:37:00 1995
From: mai@iquest.net (Pat Croft) (Pat Croft)
Subject: Alpha 374A
Message-ID: <m0tF0x1-00032JC@dorite1.iquest.net>
At 12:27 PM 11/12/95 -0500, KK5EP@aol.com wrote:
>I have a chance to purchase an Alpha 374A. Does anyone out there in contest
>land have one & how do you like it? 73, Mike
>
Dear Mike - Have Alpha 374 that is like the little bunny - just keeps going
and going! I think you'll find that to be the case with most Alpha amps.
The "A" model was brought out to comply with the FCC rule changes to halt
(HA-HA!) CB amps- thus no ten meters out of the box. Remember the 8874's
are not a cheap tube and getting in shorter supply. GL Patrick/WB9IQI
>From Pete Smith <n4zr@ix.netcom.com> Mon Nov 13 16:42:28 1995
From: Pete Smith <n4zr@ix.netcom.com> (Pete Smith)
Subject: Noise Reduction...
Message-ID: <199511131642.IAA08429@ix8.ix.netcom.com>
My fairly high inverted vees seem to be extraordinarily susceptible to line
noise and related awfuls - such as a bad electric fence charger somewhere
nearby. This is causing me to revisit the question of low-noise receiving
antennas or other noise-reduction approaches before we get any further into
the *contest* season. I'd appreciate any advice on the following:
1. Best way to connect a receiving antenna to a TS-930S (the manual is a bit
confusing), and best protective circuitry to use.
2. Relative merits of the low-noise antenna approach vs outboard audio DSP
for combatting this kind of noise (assuming the latter will work at all).
Direct E-mail please, and I'll summarize if there's interest.
Thanks!!!
73,
Pete N4ZR (n4zr@ix.netcom.com)
>From Pete Smith <n4zr@ix.netcom.com> Mon Nov 13 16:42:30 1995
From: Pete Smith <n4zr@ix.netcom.com> (Pete Smith)
Subject: Summary - CW Speed in SS
Message-ID: <199511131642.IAA08438@ix8.ix.netcom.com>
Well, I got about 35 responses, all from non-top-ten SS ops. Though I asked
the question in general terms, given both the timing and the examples I
used, most folks focused on SS. As one commented, its long, complicated
exchange makes it a different problem than something like CQWW.
Four operators said they preferred to CQ at relatively high speed - around
30-32 WPM, and then QRS to the speed of those answering. One, a QRP
specialist, said that he felt it was easy to lose a CQ frequency if you went
too slow.
Of the rest, many either said they CQed slowly all the time (in the 18-28
WPM range) or that they would start at 28-30 but slow down any time the rate
diminished. Several agreed with my observation that this worked even in the
Extra Class portion. One said that he would start at 26-28, accelerate to
32-35 on Saturday evening, then drop back to 26 or even lower on Sunday.
Several also said they slowed down on Sunday in an effort to "lure" more
casual ops into QSOs. And not suprisingly, a relatively large number of
casual contesters, or ones whose CW skills aren't (yet) well developed,
checked in with pleas for slower CW and appreciation for a willingness to
QRS. Some of them told of skipping QSOs they would otherwise have made
because of being intimidated by fast CW.
As I said, SS is different. However, one well-known contester and
dxpeditioner responded to the question in a more generic sense, saying:
"It always amazes me to hear folks CQing continuously at 40wpm with no
replies. Makes no sense - I guess they're just hitting the memory button or
CT function key and have switched off their brains. There's no doubt that
slowing down the speed can elicit contacts that would not otherwise have
come along. In fact I find that my code speed is directly proportionate to
pile-up size, up to a maximum of about 35wpm in DXpedition pile-ups and
perhaps 40wpm in contests. Faster than that and it can be counter-productive
on accuracy. If the rate slows down or stops I drop the speed right down to
maybe 20wpm and then let it creep up as the pile-up grows again.
Keyer speed is yet one more variable in the mix that can help increase
contesting performance. Yet it seems that few operators realise it.
Thanks for making the point - it's worthwhile spreading the good word on this."
73,
Pete N4ZR (n4zr@ix.netcom.com)
>From Pete Smith <n4zr@ix.netcom.com> Mon Nov 13 16:42:32 1995
From: Pete Smith <n4zr@ix.netcom.com> (Pete Smith)
Subject: Summary - Grounding (pretty long)
Message-ID: <199511131642.IAA08444@ix8.ix.netcom.com>
I had asked what to do about grounding my second-floor contest station,
given what appeared to be the conflicting requirements of lightning
protection and good RF grounding. Quite a number of replies were received,
and as often seems to be the case with this subject, there was a lot of
scattering among the replies. A number of them contributed ideas that
addressed part of the problem, and that squared with Polyphaser's excellent
book "Grounds." One, however, was particularly comprehensive and seemed to
summarize the thrust of the responses based on specific engineering
knowledge, and he's given me permission to "reprint" it here. Actually, the
text below was posted last summer on a usenet newsgroup in response to a
query very like mine, but I can't improve on it:
Begin huge quote
Ok, this isn't a simple issue, or a single issue. There are several
related concepts and factors involved. Bear with me and I'll try to
touch on most of them.
There are three general reasons given for grounding a station.
1. Improved RF performance.
2. Elimination of stray RF in the shack.
3. Electrical safety.
Of these three reasons, only the latter has merit except under
special conditions. Let's look at them one by one and see where
the truth lies.
1. Improved RF performance.
This is usually a reason claimed for needing a good ground. It is
actually false except with antennas that must work against ground,
and even then the ground needs to be at the antenna feedpoint and
not at the transmitter (unless the transmitter *is* the feedpoint,
as can be true with some random longwire antennas). A balanced antenna,
such as a dipole, yagi, quad, etc, is ground independent. It does not
need a ground connection to work, and will in fact work in free space
with no ground connection present at all. Many verticals, longwires,
and some other asymmetric designs need to work against a ground reference.
That ground reference, however, doesn't necessarily need to be a
connection to Earth. A counterpoise, radials, or the like can serve
just as well, or better, than an Earth connection. And that connection
needs to be under the antenna, and not back at the shack.
2. Elimination of stray RF in the shack.
This is often a reason given for a RF ground connection to Earth.
However, this is like taking aspirn for a brain tumor. It may
suppress the symptoms to some extent, but it doesn't address the
real underlying problem. The real underlying problem is a station
design or layout fault. If the equipment has poor Faraday shielding,
or if the feeder currents aren't well balanced, or if station
interconnections create daisy chains or ground loops, then there
will be stray RF in the shack. Grounding one or more cabinets may
actually create more circulating currents which can *increase*
the problems of stray RF. In some cases, attachment to a good RF
ground will reduce stray RF problems at some frequency, but may
increase problems at another frequency. This is not the proper
approach to dealing with stray RF. The preferred approach is to
eliminate the *cause* of the stray RF.
3. Electrical safety.
This is the *real* reason for an effective grounding system for
the shack. There are two different hazards that an effective
grounding system will solve. One is ordinary electrical shock
hazards. In the US, the National Electrical Code is the standard
that addresses this. One of the cardinal rules of the NEC is that
*all ground connections must be bonded together*. If you fail to
do this, you can have a shock hazard between cabinets connected
to different ground references. So the myth that you need to
keep utility and RF grounds separate is not only false, it can
be a safety hazard. (There are a couple of *very* specialized
circumstances where the Code permits isolated grounds, but as
a general rule, failing to bond all grounds together is a major
Code violation.)
The second reason for an effective grounding system is for lightning
mitigation. This can be a difficult problem and must be approached
with care. A single mistake can be very costly. Lightning is RF,
and like any other RF, downlead inductance is a primary concern in
setting up a grounding system. Lightning surges also represent peak
currents on the order of 8,000 amperes (with ocasional so called
"super bolts" going up to 200,000 amperes). These discharges only
last for microseconds, so the average power is low, but the peak
power is intense. It only takes a slight amount of inductance in
a downlead to generate a potential difference of tens of thousands
of volts between one end and the other. If these potentials are
allowed to express themselves between equipment cabinets, devastating
damage can occur to sensitive electronic components.
There are two concepts you must apply to your station ground system
as your first lines of defense against these potentials occurring
across your equipment. The first concept is that of a single point
ground, and the second is called ground window technique.
Single point grounding is simple in concept, but often subtle in
execution. Basically, all connections to Earth must be interconnected
at a single common point, and all connections from equipment that
needs a ground termination must run to that single point and to
*no other connection with Earth*. Daisy chained connections are
strictly prohibited. Every connection to the single point must
be straight and direct from the equipment requiring the ground
connection. Ground "busses" are a serious no-no despite their
being touted in amateur literature. They form instant ground
loops for the equipment, and at the high currents present in
a lightning discharge, they can cause thousands of volts to
express themselves across the various cabinets connected to the
"ground" buss. Don't do this.
The idea here is that because everything is forced to a single
potential, that of the single point, *whatever it is*, no current
can flow through the equipment. Zero potential difference results
in zero current flow. It's those damaging currents you are
trying to control. You don't want the path *to* ground to be
*through* any of your equipment. Rather, you want the path to
ground to be through the single point, and only through the
single point. Note well that "ground" is *not* zero volts,
and will not *be* zero volts in any sense except a *relative*
one during equipment operation or during a lightning strike.
This doesn't matter if your layout topology is correct. All
"ground" is supposed to be is a *common* potential for everything
in the system to reference against. Use of a single point
connection *enforces* this single common potential, whatever it
may be at any given instant.
When you start thinking about the many "ground" potential
interconnections in your station, achieving a true single
point ground system seems a daunting task. This is where
the related idea of a ground window can help. The purpose
of the ground window is to *short out* any possible ground
loops in your system at the station entry point.
A ground window is simple in concept, and simple in execution.
Basically, it is a physically small conductive plate through
which *every* cable that enters or leaves your station must
pass. Every cable that is supposed to be at "ground" potential
is bonded directly to this plate as it passes through. Every
conductor that is not supposed to be at "ground" potential
is bonded to the plate via an appropriate suppressor device.
(A book could be written on that subject alone.) Then the
plate is connected to your single point ground by a heavy
low inductance strap conductor. Now any large potential
difference that tries to express itself across cables
connected to various cabinets in your shack will find itself
shorted out at the ground window.
Note carefully that *every* cable must pass through the ground
window plate on its way in or out of your shack. That includes
*power*, telco, CATV (if present), and any network wiring as
well as the usual antenna feeders, rotator control leads, etc.
If only *one* wire bypasses the ground window, the protection
it offers is lost. Don't run extension cords to power outlets
that don't pass through the ground window. It can cost you
everything you own in a strike, including your life.
Now since you've taken great pains to do this protective grounding
system right, you'll find that it makes an excellent general purpose
RF grounding system as well. This is not to say that you'll generally
*need* a general purpose RF ground for the shack if you've done your
homework on antenna feeds, Faraday shielding, and the like, but you'll
have one anyway. And if you've done the job right (which requires
attention to a level of detail I haven't fully addressed here), your
station will be able to work even during the worst thunderstorms,
and even during direct strikes, without damage or interruption.
Proper grounding is a specialized, but well understood, part of the
protective process that radio and television stations, commercial
and military two way, and *amateur* radio stations should understand
and apply.
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | emory!kd4nc!ke4zv!gary
534 Shannon Way | Guaranteed! | gary@ke4zv.atl.ga.us
Lawrenceville, GA 30244 | |
End huge quote
I'm nothing but a good audience (I hope) and practical student of such
things, so address questions to Gary if you like - I probably won't have a clue!
73,
Pete N4ZR (n4zr@ix.netcom.com)
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