MASSASOIT AMATEUR RADIO ASSOCIATION
                              Bridgewater, Ma.

                       Monthly Electronic Newsletter
                              
                    Massasoit Amateur Radio Association
                          Founded January 6, 1962
                                 PO Box 428
                           Bridgewater, MA  02324
                                 July  1995

MAYOR SALUTES AMATEURS

Mayor Win Farwell of Brockton formally declared the week of June 19-25
as Amateur Radio Week!  In the official proclamation, the mayor cited
that ‘The City of Brockton and surrounding communities have more than
100 FCC-licensed Amateur Radio operators’, who ‘donate their services
free of charge to the City, in the interest of the citizens and the
surrounding communities’.  The proclamation was mounted on a wood
plaque and presented by the mayors staff to Carl Aveni, N1FYZ, and Joe
Deree, N1SGU, on Thursday June 22, just before Field Day.  The plaque
will be at the next meeting for everyone to see.

The mayor extended his regrets that he would not be able to attend
Field Day with MARA.  Perhaps he had heard of the now-famous goulash!

FIELD DAY WRAP-UP

Field Day has come and gone - chock up another one for MARA.
Attendance was a bit down from last year, but scores were still up.
MARA is claiming 988 points overall, and an additional 720 points in
bonuses for a total of 1808 points,

Saturday was a great day, with a light breeze to keep the bugs down.
Setup went well, and the 22 who attended were well fed all day.  MARA
used PC’s at all the stations for logging, which made the post-contest
cleanup go very easily.  The club had a total of 150  CW/-packet
QSO’s, and 194 Phone QSO’s, which included 2 Meters & 440 for the VHF
& UHF scores.  Bob Johnson, WA1OFR, brought his 440 gear up Saturday
night for some points, and also assisted on packet

Carl, N1FYZ, ran 20 Phone on Saturday then switched to 80 Phone on
Sunday.  Mark & Sheryl Greenlaw worked 2M and some HF.  Lenny Amabile,
N1MII brought along a complete packet station and 2M transceiver & amp
to help N1FYZ’s SSB/CW rig score points on VHF.  Joe Deree worked 20
and 40 Phone for some of his first contesting.

Wayne, N1MAG, worked some 40 CW logging to get his CW speed up.  Ron
Smith, N1PXX, sat in his car (with the AC on) and worked 10 Phone down
in to the deep south to add to the QSO’s.  His friend Priscilla (who
has passed her 5 WPM and is working on her Theory) worked 40 phone on
Sunday AM.  Don Benecchi, K1DC, stopped by on Saturday to help set up
and then warmed up 80 CW for about 50 QSO’s before he had to leave.
Don’s wife made up a MARA club flag that Don had hung near the
entrance.  Really looked sharp.

Thanks to everyone who stopped by to help set up for Field Day.  And
thanks to Dave Bourque, WB1FLD, in NH, for fixing a 2M 150W amp that
we used on SSB and FM.  It helped to punch through the ether and make
points for the contest.

VHF was more fickle this year than ever before.  Before FD started,
the repeater was blowing signals in from NH, CT, and ENY.  Field Day
started, and the bottom fell out of 2M propagation.  Then, after we
tore down from Field Day (just before some impending storms), as cars
were leaving the picnic grove with all their gear packed, you could
hear 2M open again on the repeater.  Arrrggghhhh!!!

Special thanks goes to Joe, N1SGU, who not only pitched in to help
with some of the preliminary setup on Friday, but worked all day
Saturday with setup, cooking, and contesting.  Then Joe stayed till
4PM to help with the final tear down and cleanup.  Thanks again for
your help Joe.
For those who stayed overnight, Sheryl Greenlaw, N1QXY, crashed around
midnight, but got up about 2AM for some more operating.  Joe Deree,
N1SGU, kept it up till 4AM.  Mark Greenlaw, N1NLR, and Carl Aveni,
N1FYZ, both pulled all-nighters.

After a breakfast of eggs, sausage, coffee, and juice, folks went back
for more operating..... until the rumble of thunder and black skies
invaded.  Knowing that lightning and antennas don’t mix too well, it
was decided to pull up stakes and head for the hills, and some sleep.

NEW MEMBERS AT MARA

At Field Day, MARA was fortunate to have two new members join the
ranks.  We would like to say ‘Welcome’ to Evelyn Foley, AA1NJ, and
Charley Pear, N2HGU.  Evelyn is also a member of the Whitman club and
has been licensed for only one year.  She just earned her Extra,
became a VE, and has already worked one VE session.   Charley hails
from Long Island and works at Radio Shack at the Taunton Galleria.
Make sure you say ‘Hello’ when you hear them on the repeater.

ARRL NEW ENGLAND DIVISION CONVENTION
Manchester, New Hampshire, Friday, 28 July to Sunday, 30 July 1995

New England's largest convention will be once again be held in
TAX-FREE NH!  New England is beautiful in the summer, so combine your
vacation with a trip to Manchester in late July, 1995.  We guarantee
you won't be disappointed.

Commercial Vendor Display Area;  Giant Indoor (Air Conditioned) Flea
Market;  Walk-In License Exams;  Free Indoor Parking;  Forums;
Banquet;  Wouff Hong;  DXCC & WAS Field QSL Check and much more!

Tickets:                        $7 in advance, $8 at the door
Flea Market:            $15 per table
Talk-In (W1NH): 146.85 (wide area), 145.17 (local)

Information/Tickets/Flea Market/Vendors:
North East Convention Associates, Inc, P.O. Box 475, Goffstown, NH
03045.  (603)487-3333

DIRECTIONS: Take Rt 93N into Manchester, NH.  Take Rt 293N to Exit
5/Granite Street.  Granite St. runs into Elm Street.  Convention hall
on corner.  Or, if you miss Exit 5, take Exit 6 to Elm street. Turn
right on Elm.  CNH Convention Center will be down the street on your
right.

4-sale

There are still some items available from the K1ZLI sale, at good
prices.  Items still for sale include;
·       2 Halicrafters HT-32B's.  One has a spare power transformer
included, and needs only minor work (cleaning audio pots, etc.) for
$125.  The second unit needs a little work in the meter circuit
(though it still transmits OK) and doesn't have the spare power
transformer included.  It is selling for $100.  Both units are very
clean.
·       HA-2 Halicrafters 2-Meter transverter with P-26 power supply
(needs tubes) that is made to plug in to the HT-32B.  $50.
·       6-Meter 5-element yagi; $25
··      Boxes of assorted books.  $5 each.  Some have 3-ring binders
which can be 'recycled' in the shack.
·       Electric motor with right-angle speed-reduction drive.  Could
be modified into an antenna rotor; $10
        8-Conductor rotor cable, heavy duty.  5/8" OD, black neoprene
jacket.  One 50-ft and one 100-ft length (give or take).  100-ft piece
is $25.  50-ft piece is $12.  Both for $35.  Please measure them to be
sure of the length.  Cable would run at least $.50/ft when brand new.

Items are at 454 High Street, Bridgewater.  Ask for Lorraine Gunnison.
508-697-6552 or contact Don Benecchi, K1DC, in West Bridgewater;
508-587-7045

SECRETARY’S REPORT

The June meeting was called to order at 8PM with 22 members and guests
present.  The Club had a special guest speaker, Phil Temples, ARRL
Section Manager for Eastern MA.

The club treasury was at $1031 but encountered an unexpected bill for
over $500 for modifications that needed to be made to the new Motorola
repeater.  The bill was more than expected - a bill of $300 was
anticipated.  The club voted to pay the bill. [NB: A few days after
the meeting, it was discovered that the Eastern Edison payment will be
coming in - and should be in the Treasury by now, to bolster our bank
account back to a more comfortable figure.]

Carl Aveni, N1FYZ, mentioned that even after the payment by Eastern
Edison, MARA still has two drills to participate in before the end of
the year that will help the Treasury.

Ron Smith, N1PXX, noted that the Marshfield Fair approached the
Whitman ARC about putting on a Ham Radio exhibit at this years fair.
Antennas will be put up and left up for the duration.  If you would
like to work the fair, coordinate with Bill Hayden N1FRE (617
447-1655).  You would be required to bring your own equipment (except
for antennas).  You will receive a free family pass and free parking
for the day.  Dates are for the fair to start on the weekends of
August 18-20, and 25-27

Jay Zappulla, N1FDX, reported on the repeater.  The one estimate he
was able to get called for $1500 to connect up the wire service to
code.  The club voted to get a work party together to do as much of
the physical labor as possible to save money.  [NB: since that
meeting, Carl; N1FYZ, may be able to obtain the services of a
volunteer licensed electrician (who is also a ham) who will pull the
appropriate permits and do the work for just the cost of materials.

As reported above, Phil Temples, K9HI, visited the club and reported
on a variety of ARRL topics.  Phil spoke for about 30 minutes,
answering questions and taking comments to report back to the League,
then spent another hour or so talking with members on a more personal
basis to get more info.  Phil’s talk was very informative.  One area
covered was how the Massachusetts Legislature is trying, once again,
to get language put in to State law, similar to PRB-1 to prevent
antenna zoning restrictions for amateurs.  He said the bill has passed
the House but is bogged down in committee in the Senate, where is has
died more than once before.  Contact your state Senator to make sure
this bill gets passed!  Phil can be contacted on packet as K9HI @
WA1PHY, or on Internet - k9hi@net.com.

Free Antenna Handbook

Write at The CBC (Canadian Broadcasting Corporation), They will send
you a free Antenna Handbook. It's an 18 page, 14 chapters. Describes
many antennas and how to construct them. Discuses Whip antennas,
Vertical, Marconi Inverted "L" antennas, Windom, Half-wave dipole,
folded dipole, triple dipole, vertical dipole, fan vertical antenna,
long wire, "V" beam, rhombic antenna and antenna accessories. Very
complete book. Write:

Radio Canada International
C.P. 6000
Montreal, Canada
H3C 3A8
Available free in English and French versions.
Transmitted:  95-05-04 21:27:19 EDT

Grounding Tips
Downloaded from America on Line (SWL Area)

With grounds the most common experience is "the more the merrier".  As
you add more, however, you usually reach a diminishing returns (no pun
intended) situation where there is no *observable* improvement: That's
usually a good place to stop.  There are also exceptional
circumstances where grounding increases noise problems, but these, in
my experience, are much rarer than the pundits who preach against
"ground loops" seem to think.  Even a semi-quantitative theoretical
treatment of grounding in oversimplified situations requires heavy
math at RF.  Experimentation is thus required even if one has done
elaborate calculations.  It's often easier to use the theory as a
guide to what to try, and then experiment.

What is Ground?
If I connect the shield of my coax (which is grounded outside) to the
antenna input of my receiver, I hear lots of junk, indicating that
there is an RF voltage difference between the coax shield and the
receiver chassis. Last night this measured about S5.5, which is about
-93 dBm (preamp off, 6KHz bandwidth).  That's a lot of noise: it was
18 dB above my antenna's "noise floor", and 26 dB above the receiver's
noise floor.

This sort of disagreement about ground potential is characteristic of
electrically noisy environments.  The receiver will, of course,
respond to any voltage input that differs from its chassis ground.
The antenna, on the other hand, is in a very different environment,
and will have its own idea of what ground potential is.  If you want
to avoid noise pickup, you need to deliver a signal, referenced at the
antenna to whatever its ground potential is, in such a way that when
it arrives at the receiver, the reference potential is now the
receiver's chassis potential.  Coaxial cable represents one way to do
this. Coax has two key properties:
1. The voltage between the inner conductor and the shield depends only
on the state of the electromagnetic field within the shield.

2. The shield prevents the external electromagnetic field from
influencing the internal electromagnetic field (but watch out at the
ends of the cable!).

So, it's easy, right?  Run coax from the antenna to the receiver.
Ground at the antenna end will be whatever the antenna thinks it is,
while ground at the receiver end will be whatever the receiver thinks
it is.  The antenna will produce the appropriate voltage difference at
the input side, and the receiver will see that voltage difference
uncontaminated by external fields, according to the properties given
above.

Unfortunately, it doesn't quite work that way. It's all true as far as
it goes, but it neglects the fact that the coax can also guide noise
from your house to your antenna, where it can couple back into the
cable and into your receiver.  To see how this works, let me first
describe how this noise gets around.

The noise I'm talking about here is more properly called "broadband
electromagnetic interference" (EMI). It's made by computers, lamp
dimmers, televisions, motors and other modern gadgets.  I have all
these things. In many cases, I can't get them turned off, because it
would provoke intrafamily rebellion. However, even when I turn them
off, the noise in the house doesn't go down very much, because my
neighbors all have them too.  In any case, one of the worst offenders
is my computer, which is such a handy radio companionI'm not about to
turn *it* off.
Some of this noise is radiated, but the more troublesome component of
this is conducted noise that follows utility wires.  Any sort of cable
supports a "common mode" of electromagnetic energy transport in which
all of the conductors in the cable are at the some potential, but that
potential differs from the potential of other nearby conductors
("ground").  The noise sources of concern generate common mode waves
on power, telephone, and CATV cables which then distribute these waves
around your neighborhood. They also generate "differential" mode
waves, but simple filters can block these so they aren't normally a
problem.

So, let's say you have a longwire antenna attached to a coaxial cable
through an MLB ("Magnetic Longwire Balun" [sic]).  Suppose your next
door neighbor turns on a dimmer switch.  The resulting RF interference
travels out his power lines, in through yours, through your receiver's
power cord to its chassis, and out your coaxial cable to your MLB. Now
on coax, a common mode wave is associated with a current on the shield
only, while the mode we want the signal to be in, the "differential"
mode, has equal but opposite currents flowing on shield and inner
conductor.  The MLB works by coupling energy from a current flowing
between the antenna wire and the coax shield into the differential
mode.  But wait a second: the current from the antenna flows on the
coax shield just like the common mode current does.  Does this mean
that the antenna mode is contaminated with the noise from your
neighbor's dimmer?

The answer is a resounding (and unpleasant) yes!  The way wire
receiving antennas work is by first moving energy from free space into
a common mode moving along the antenna wire, and then picking some of
that off and coupling it into a mode on the feedline.  In this case,
the common mode current moving along the antenna wire flows into the
common mode of the coax, and vice versa.  The coax is not just
feedline, it's an intimate part of the antenna!  Furthermore, as we've
seen, it's connected back through your electrical wiring to your
neighbor's dimmer switch.  You have a circuitous but electrically
direct connection to this infernal noise source. No wonder it's such a
nuisance!

The solution is to somehow isolate the antenna from the common mode
currents on the feedline.  One common way to do this is with a
balanced "dipole" antenna.  Instead of connecting the feedline to the
wire at the end, connect it to the middle.  Now the antenna current
can flow from one side of the antenna to the other, without having to
involve the coax shield.  Unfortunately, removing the necessity of
having the coax be part of the antenna doesn't automatically isolate
it:  A coax-fed dipole is often only slightly quieter than an end-fed
longwire.  A "balun", a device which blocks common mode currents from
the feedline, is often employed.  This can improve the situation
considerably.  Note that this is not the same device as the miscalled
"Magnetic Longwire Balun".

Another way is to ground the coaxial shield, "short circuiting" the
common mode.  Antenna currents flow into such a ground freely, in
principle not interacting with noise currents.  The best ground for
such a purpose will be a earth ground near the antenna and far from
utility lines.  Still another way is to block common mode waves by
burying the cable.  Soil is a very effective absorber of RF energy at
close range.

Unfortunately, none of these methods is generally adequate by itself
in the toughest cases.  Baluns are not perfectly effective at blocking
common mode currents.  Even the best balun can be partially defeated
if there's any other unsymmetrical coupling between the antenna and
feedline.  Such coupling can occur if the feedline doesn't come away
from the antenna at a right angle.  Grounds are not perfect either.
Cable burial generally lets some energy leak through.  A combination
of methods is usually required, both encouraging the common mode
currents to take harmless paths (grounding) and blocking them from the
harmful paths (baluns and/or burial).

The required isolation to reach the true reception potential of the
site can be large.  According to the measurements I quoted above, for
my site the antenna noise floor is 18 dB below the conducted noise
level at 10 MHz. 18 dB of isolation would thus make the levels equal,
but we want to do better than that:  We want the pickup of common mode
EMI to be insignificant, at least 5 dB down from the antenna's floor.
In my location the situation gets worse at higher frequencies as the
natural noise level drops and therefore I become more sensitive: even
30 dB of isolation isn't enough to completely silence the common mode
noise (but 36 dB *is* enough, except at my computer's CPU clock
frequency of 25 MHz).

Getting rid of the conducted noise can make a huge difference in the
number and kinds of stations you can pick up.  The method I use is to
ground the cable shield at two ground stakes and bury the cable in
between. The scheme of alternating blocking methods with grounds will
generally be the most effective.  The ground stake near the house
provides a place for the common mode noise current to go, far from the
antenna where it cannot couple significantly. The ground stake at the
base of my inverted-L antenna provides a place for the antenna current
to flow, at a true ground potential relative to the antenna potential.
The buried coax between these two points blocks noise currents.

Question: There has been some discussion of grounding problems before.
I believe it  has been mentioned that electrical codes require  that
all grounds be tied together with heavy gauge wire.

I'm no expert on electrical codes, and codes differ in different
countries. However, I believe that any such requirement must refer
only to grounds used for safety in an electric power distribution
system: I do not believe this applies to RF grounds.  Remember that
proper grounding practice for electrical wiring has very little to do
with RF grounding.  The purpose of an electrical ground is to be at a
safe potential (a few volts) relative to non-electrical grounded
objects like plumbing.  At an operating frequency of 50/60 Hz, it
needs to have a low enough impedance (a fraction of an ohm) that in
case of a short circuit a fuse or breaker will blow immediately.

At RF such low impedances are essentially impossible: even a few
centimeters of thick wire is likely to exhibit an inductive impedance
in the ohm range at 10 MHz (depends sensitively on the locations and
connections of nearby conductors).  Actual ground connections to real
soil may exhibit resistive impedances in the tens of ohms. Despite
this, a quiet RF ground needs to be within a fraction of a microvolt
of the potential of the surrounding soil. This is difficult, and
that's why a single ground is often not enough.

Question:  A little experimentation with my radio showed that the
chassis was  directly connected to the third (grounding) prong of the
wall plug.  I  am concerned that by connecting my receiver to an
outside ground I am  creating a ground loop that involves my house
wiring.  Can you comment  on this?

Yes, you have a "ground loop". It's harmless.  In case of a nearby
lightning strike it may actually save your receiver. My receiver isn't
grounded like that, so I had to take steps to prevent the coax ground
potential from getting wildly out of kilter with the line potential
and arcing through the power supply.  I'm using a surge suppresser
designed to protect video equipment.  It has both AC outlets and
feedthroughs with varistor or gas tube clamps to keep the various
relative voltages in check.  Of course the best lightning protection
is to disconnect the receiver, but I'm a bit absent minded so I need a
backup.

Question:  This may seem like a trivial point but I recently
discovered that the main ground from the electrical service panel in
my house was attached  to a water pipe which had been painted over.  I
stripped the paint from  the pipe and re-attached the grounding clamp
and I noticed a reduction  in noise from my receiver.
Not trivial.  Not only did you improve reception, but your wiring is
safer for having a good ground.  I suspect part of the reason I see so
much noise from neighbors' appliances on my electric lines may be that
my house's main ground wire is quite long.  The electrical service
comes in at the south corner of the house (which is where the breaker
box is), while the water (to which the ground wire is, enters from the
east corner. If it was shorter, presumably more of the noise current
would want to go that way, and stay away from my receiver.

Much antenna lore comes from folks with transmitters who, armed  with
the "reciprocity" principle, assume that reception is the same
problem.  The reciprocity principle says that an antenna's
transmission and reception properties are closely related: it's good
physics, but it ignores the fact that the virtues required of a
transmitting and receiving antenna are somewhat different.
Inefficiency in a transmitting antenna has a direct, proportional
effect on the  received signal to noise ratio.  On the other hand,
moderate inefficiency in an HF receiving antenna usually has a
negligible  effect on the final result.  A few picowatts of excess
noise on a  transmitting antenna has no effect on its function, but is
a big deal if you're receiving (of course, one might not want to have
transmitter power going out via unintended paths like utility lines:
This is indeed the "reciprocal" of the conducted noise problem,  and
has similar solutions).

John Doty  "You can't confuse me, that's my job."
jpd@space.mit.edu Transmitted:  95-04-23 12:56:48 EDT

NEWS FLASH!!
The Museum of Antiquated Technology will be open on Sunday July 22,
from 10AM to 3PM.  The museum is located at 303 High St. in Hansen.
Talk in will be on the Bridgewater repeater.

OWWWW!!
Bruce KA1HTN had an unpleasant encounter with a runaway German
Shepherd last Monday, July 2 on his way home from the Whitman club
meeting.  We were having coffee at the Honeydews when he went out to
the car to check something.  Bruce came back in all chewed up.  The
police and animal control responded
Honeydew Donut Shop when Bruce stepped out to his car to retrieve some
information for yours truly!  He came back in shortly sans left pants
leg.  He was also missing some flesh.  The police and animal officers
responded and at last report had corralled the crafty canine.  Bruce
went to the emergency room at South  Shore Hospital where he was
treated and released.  We hope you’re doing well, Bruce.

PAN MASS CHALLENGE

The “Pan Mass Challenge anual bike ride (Sturbridge to Provencetown )
will be passing through our area on August 5th.  PMC, headed by Ed
Parish WA2SCA, needs volunterers to operate the event’s commercial
radios.  Lunch is included as is a cookout at the Mass Maritime
Academy is schedualed for the evening of the Aug 5th.  This benifits
the Jimmy Fund and is a worthwile event.  Contact officials at (617)
254-5820 or (508) 664-1771 or email Ed Parish at Eparish@netcom.com

New Packet Switch

Gil Follett WA1GDJ has set up a  packet switch on 145.67.  Connect and
follow the prompts.  You can send and receive messages and lots more..

Coming Next Month

Sunspots..The sunspot cycles, and how they affect our radio
transmissions and reception.

Saldering..The how and whys..
De -Soldering..When you mess up the “hows and whys”.

NEWSLETTER EDITORS:
N1EDM-BOB
N1MII-LENNY