August 1997 Short Skip

 

Prez Sez
10 meter Contest
Windjammer Race
Doppler vs Rotating Antenna Direction Finding
Chatter
Vanity Call Signs

Pres Sez

Drat! I had to work last Saturday. That means I missed the monthly club
breakfast that was held at Lyons Restaurant on 41st Avenue. I hear that
everybody had a good time though. Have you been to one of these yet? They’re
another chance to talk about our avocation with like-minded club members.
Eyeball sessions are always fun for hams. One great place for eyeball sessions
is at the Foothill College swap meet (held the second Saturday of the summer
months). We tried to avoid scheduling a club breakfast on that day. This
last Saturday the Club breakfast faced competition
from the Pajaro Valley Century bike race and the Horseman’s Association
Fireworks 50 mile ride and numerous other events (Summer in Vacationland!).
With all our different activity schedules, nobody can make it to every breakfast
but we hope you can make it sometimes. We plan to have them monthly as long
as that’s what suits us. The next one will be at Jeffery’s
Restaurant 2050 Soquel Avenue (cross street: Capitola Road), on Saturday,
September 6, 9AM .

I just found out (from board member Hank KG6EE) that the Stanford Linear
Accelerator Center gives tours to groups if arrangements are made in advance.
Is anybody interested in a club field trip? We’d have to arrange transportation
and get a list of people who will go before we make the arrangements with
SLAC. Sounds very interesting to me. I’ve never seen the accelerator up
close, except while driving over it on Highway 280. Think about it.

The upcoming club meeting on Friday, August 15
(always the third Friday of the month) sounds like a good one. Al
KM6VV will present a project he’s been working on for awhile in his “spare”
time. I understand it’s pretty fancy and could possibly help us with finding
“hidden transmitters.” Al is an accomplished computer programmer
as well as amateur radio operator and this project involves both of those
skills. As I write this, I hear him and Jeff WB6SSY talking over some final
details of Al’s project on 2 meters. I just hope Al finishes the project
in time to demonstrate it to us at our meeting!

Did you know that the NPSARC (Monterey Naval Postgraduate School Amateur
Radio Club) is planning to re-institute their famous Winterfest this winter?
If you’ve never been to one of those, you’re in for a treat.

Hey all you NWS weather spotters, did you know that the NWS Monterey
Forecast Office (MTR) is watching for weather reports on amateur radio full
time now? They now have a computer in their office that runs APRS packet
radio software 24 hours a day to receive weather statistics from hams throughout
Central California who are also running APRS.

Did you know the long-awaited amateur radio satellite, AMSAT’s Phase
3D, may be delayed again (from its currently scheduled September launch
date)? The European Space Agency (ESA) significantly increased its estimate
of vibration levels the Phase 3D payload would be exposed to aboard the
Ariane 502 rocket. The revised estimates mean AMSAT will have to move fast
to make structural changes in the Phase 3D spaceframe in order to withstand
the anticipated rougher ride.

Cap, KE6AFE

K6BDK 1st Place in 10 meter Contest

Frank Carroll, K6BDK, won first place for a single operator on CW, low
power for the Santa Clara Valley Section in the 1996 Ten meter contest.
Frank got a surprize when he received the certificate in the mail from the
ARRL last week. Frank said, “I never expected that” Good going
Frank!

Packet
Operators Needed for Windjammer Race

The Windjammer Race is a sailboat race that begins in San Francisco on
Friday August 29 at about 11:00AM and ends off the Santa Cruz Wharf. ARES
has provided support to the Santa Cruz Yacht Club for the last several years
in the form of the ARES Van and warm bodies trained in the art of packet
radio.

What does packet radio have in common with sailboat racing you ask? Well,
the way we used to send lists of boats that have finished back to the yacht
club, was one by one over the marine VHF, competing with not only Joe &
Fred discussing fishing, but also a very loud fog horn. Using packet radio
all we have to do is enter a list of finishers into the computer and send
it back to another packet station set up at the yacht club. This allows
the yacht club to let family and friends of racers know when they have finished.
It also helps the race committee score the race much faster.

We will need two operators in the van on the wharf, and one operator
at the station at the yacht club per shift. The van should get to the wharf
about 6 P.M. and a second operator around 7 P.M., with someone at the yacht
club at 6 P.M. to set up the station and establish the packet link with
the van. Oh yes, did I mention that boats will be finishing until the wee
hours of the morning? There will be plenty of coffee, and you won’t be overworked.
Maybe there are a few of you out there who (unlike me) actually enjoy getting
up before daylight.

Anyway, everyone has a lot of fun. The crew from the Santa Cruz Yacht
Club park a motor home out on the end of the wharf, there is clam chowder
all night long at the yacht club, and about a hundred boats full of cold,
tired, appreciative sailboat racers who will pack the Santa Cruz Harbor
for the weekend.

If you know your way around a packet station or computer (equipment is
supplied) and can spare a few hours call me Steve Smardan at (408)476-6421
or email “n6tgm@juno.com”.

– Thanks and 73, Steve Smardan

Doppler vs Rotating Antennas
for Direction Finding

The following is my answer to questions about doppler vs rotating antenna
direction finding from rec.radio.amateur.equipment.

Doppler has a bunch of problems. This is NOT intended to discourage anyone
from using doppler, just to recognize its limitations. Credibility check:
I helped design the AN/SRD-22 doppler direction finder for Intech Inc for
use by the US Coast Guard in approximately 1975.

1. A doppler DF can only display the direction of *ONE* transmitter.
If there are any other sources of signal (reflections, other xmitters, adjacent
channel junk, computer noise, synthesizer spurious signals, harmonics of
clock oscillators, ignition noise, images, etc.) the reading will be erroneous.
Reflections is the real killer. A ground bounce mixed with a direct signal
will yield horrible results. (Incidentally, the reason most dopplers have
rather large antenna ground planes is to reduce ground bounce).

2. Switched doppler is susceptible to switching noise which acts as modulation
sidebands. These sidebands (harmonics of the switching frequency) will cause
strong adjacent channel signals to mangle the bearing. The typical “Roanoak”
design is highly susceptible to this. Doppler Systems uses DGMosFet switches
which have a much “softer” (less rise time) switching characteristic.
Intech used a modified sine wave drive to literally modulate the PIN diodes
instead of switching. It totally eliminated the problem, but sensitivity
was reduced. PIN diode matching was also very critical.

3. The typical vertically polarized doppler system does not work well
with horizontally polarized signals. Building a horizontally polarized doppler
is no major challenge, but nobody seems to have done it.

4. Doppler is sensitive to fox frequency. The doppler receiver measures
the phase shift from the antenna to the FM demodulator. Any change in receiver
system phase shift appears as a substantial directional error. The worst
error is caused by the crystal IF filter. The phase shift from IF center
to filter edge goes through radical phase changes. An AFC (automagic frequency
control) is mandatory to keep the signal in one place on the crystal filter
curve.

5. Doppler is sensitive to rotation frequency and FM demodulator distortion.
There two schools of thought here. Doppler Systems uses about 300Hz rotation
frequency. This is good for insuring that the signal will remain in the
IF bandpass (no AFC) but results in harmonics of the 300Hz in the bandpass.
These harmonics cause bearing errors and linearity (approximation of a circle)
errors. The typical commutating audio bandpass filter will not remove harmonics.

Intech elected to use 4.1KHz. Most of the harmonics are outside the IF
bandpass. Combined with the PIN diode modulation technique, this yielded
a very low distortion sine wave at the demodulator and very good linearity.
However, the group delay (phase shift error) of the IF crystal filter was
far worse at the edges (+/-4KHz) than it was near the center (+/-300Hz).
AFC became mandatary.

It turned out that the conventional balanced multiplier FM demodulator
was also slightly sensitive to signal level. Since the AN/SRD-22 was both
an AM (121.5 aircraft) and FM (Marine VHF band) receiver, an ALC (automagic
level control) was used. The error was not large and can be probably be
ignored.

6. Doppler is sensitive to modulation audio. The response time of the
doppler DF is totally dependent upon the Q of the doppler tone bandpass
filter. The wider the bandwidth, the faster the DF. If you make the filter
too narrow, it takes forever to get a bearing. However, too wide and FM
audio modulation and fox tones will leak through the filter and mangle the
bearing. One favorite trick is to use a 300Hz fox tone to mess up the Doppler
Systems DF’ers.

7. Doppler antenna patterns are very sensitive to nearby antennas and
reflections. The AN/SRD-22 had to be mounted at the very top of the mast.
Unfortunately, almost every other piece of electronics equipment wanted
to be in the same place.

On the roof of a car, the AM/FM antenna and other radio antennas create
horrible errors. Nearby antennas from other hunters at the starting point
will mutilate the pattern. This is why the various DF books say (several
times) that the ONLY way to get a decent bearing is while moving. Moving
tends to average out reflection errors. While the error at a given location
may be severe, a few feet away might be perfectly acceptable. The trouble
is you have no idea where there is a reflection free location. Moving while
DFing is the only way.

73 Magazine carried a series of articles in the Homing-In section based
on rotating yagi and quad antenna direction finding. These are basically
AM (signal strength) systems. The advantage is that you can easily see multiple
transmitters, recognize reflections (they tend to blur), do NOT require
an AFC, and have an easily controllable antenna pattern (using boresight
calibration). However, driving down the freeway with a spinning 4 element
quad is a great way to attract the constabulary. Short transmissions are
also difficult to see. Equipment complexity is about the same. Having dealt
with doppler professionally and recognized its limitations, I’m very partial
to rotating antenna DF.

One place where a rotating antenna is far superior to doppler is tracking
a jammer. With a jammer, you have *TWO* signals on a frequency (the person
trying to talk and the jammer). A doppler DF will yield a bogus direction
because of the two signals. A rotating antenna will show both signals.

– Jeff, WB6SSY, ()

Chatter

By Art Lee, WF6P

I have always been interested in the Search For Extra Terrestrial Intelligence
(SETI) program. As many of us know, Aptos resident Dr. Frank Drake, former
UCSC professor of astronomy, has spent most of his life pursuing this subject.
When I asked my son Randy, N6UZI, if his astronomy club or his favorite
magazine, Astronomy, covered this or UFO topics he replied, “Nahhh
…. we are serious star gazers, not speculators.” Lo and behold, the
September issue of Astronomy headlined, “Is Anybody Out there? On the
Trail of UFOs.” OK, so now what? I personally don’t believe we have
been visited by UFOs within the past couple of centuries. But I am convinced
that there has to be intelligence in space and the sheer numbers would be
enough to make the odds pretty great that Dr. Drake is correct. Oh, Dr.
Drake was a buddy of Dr. Carl Sagen who believed the same. Well, I was rewarded
to find the article, “A Field Guide To UFOs,” by my favorite aviation
writer, Phillip J. Klass. Mr. Klass was the Avionics (he coined the term
in the 60’s) editor of Aviation Week for over 45 years.

In his article, Mr. Klass pretty much disproves any of the UFO sightings
(sorry folks). His studies of the UFO phenomenon over the years proved that
much to him. The ending for his article does read, ” So far, I’ve had
no luck (in sighting a UFO) but who knows, perhaps tomorrow and or next
week. He has authored several books on that subject. Read his: UFOs: the
Public Deceived; UFO Abductions: a Dangerous Game, and The Real Roswell
Crashed Saucer Coverup. All published by Prometheus Books, Amherst, NY.

The article, “When E.T. Calls Us,” by Seth Shostak discusses
the attempts by space scientists to copy radio signals from space. If they
succeed in that, think of the QSL card they will receive!

Bad news. A ham, Michael Heindl, of Citrus Heights made the recent centerfold
of a Sacramento neighborhood newspaper, Sunday Neighbors. A big, bold photo
of the ham astride his 65 foot tower was shown. The piece, written by a
local reporter, was highly biased against the ham who had tried, unsuccessfully,
to placate his neighbors effected by TVI. Locals complained about his transmissions
and the FCC, who would not make him stop transmitting. Arguments in favor
of the neighbors who complained about interference with their telephones
were presented by the reporter.

Although I have been out of town for the past two club breakfasts, I
am happy that our club president has rejuvenated this old SCCARC custom.
Good on you, Cap! As the older club members may recall, Norm, N6DAC, and
his XYL Beth, W6RYL, coordinated the breakfasts for the club for many years.

Shucks! My old Navy buddy Stu Keller, K9WNU, and his XYL returned to
their home QTH in Sterling , Illinois. We had lotsa fun doing antenna work
while they were here. We still had some antenna work to do on a defunct
vertical I inherited from Joe Myers, N6AOG, many years ago. While cleaning
up the segments of the tubing, I accidently moved one of the traps. The
book says, “DON’T MOVE THE TRAPS!” Somehow, I missed that important
step. I shipped his wonderful AEA SWR analyzer back to Stu the other day
but I couldn’t keep it forever. Stu has set up a mobile station in his motor
home. Put one of those multi-band Outbacker antennas on his rooftop luggage
rail, had a poor ground, but in a pouring down rain, reported excellent
reports on all sigs sent. “Everything that should have made my signals
bad were there, yet the transceiver and antenna put out a great signal!”

Boy, was I having fun! Was banging away on CW with my pal Marsha, AB7RJ,
in Yacolt, Washington, when my son’s MFJ DeLuxe electronic Keyer went bonkers.

Streams of uncontrolled dits and dahs went out over the airwaves. Nothing
I could do would stop it. I shut down the keyer, restarted it, the same
thing happened. It just went nuts. I tore the cover off the keyer and noted
the date on the battery. “Use before July 1992.” Marsha patiently
awaited my return to the frequency for about 20 mins. It took me 25 minutes
to rob a 9 volt battery out of my 19 month old grandson’s toy car and install
it in the keyer. Too late. Oh well.

Interested in writing articles? Leon Fletcher, AA6ZG, tells you how to
make good endings for them in his latest article in the August issue of
Writer’s Digest, a top-notch guide magazine for writers.

We had an 8 yr old visitor on our July 21st Monday nite net. Mellissa,
KF4KQH, came up on freq to check in. Her QTH was Georgia. “I have a
southern call sign but not a southern accent,” she said. “My father
is in the Army so I guess I’m really from everywhere” Mellissa was
a real rag-chewer. “I used to creep into my dad’s ham shack, turn on
his HF receiver, and tune around the band and listen. That was real fun.”
She was vacationing in Santa Cruz for 8 days.

Vanity Call Signs

The FCC announced on July 3 that Gate 3 for Advanced Class licensees
will open on Aug. 6, 1997. Details on the Vanity Call program can be found
on the ARRL WWW site at www.arrl.org or by calling the FCC National Call
Center at 1-888-CALL-FCC. To file, use Form 610-V available via the FCC
Internet Homepage at <http://www.fcc.gov/wtb/amradsrv.html> or from
ARRL HQ. The fee remains $30 for a 10 year license until Sept. 16, 1997.

The date for opening Gate 4 has not yet been announced. The new fee of
$50 for the 10 year license will take effect Sept. 16, 1997.