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The ARRL Letter

Published by the American Radio Relay League
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July 1, 2010

Editor: S. Khrystyne Keane, K1SFA

ARRL Home Page http://www.arrl.org/ARRL Letter Archive
http://www.arrl.org/arrlletter/Audio News
http://www.arrl.org/arrlletter/audio/ IN THIS ISSUE

- + Public Service: WX4NHC, VoIP Weather Net and Hurricane Watch Net
Activated for Hurricane Alex
- + Amateur Radio in the Classroom: ARRL Teachers Institutes Wrap Up in
New Mexico, South Carolina and California
- + ARRL Field Day: It's a Wrap!
- ARRL in Action : What Have We Been Up to Lately?
- + The Doctor Is IN: D-STAR, Antennas and Amplifiers
- + Solar Update
- + ARRL to Close in Observance of Fourth of July
- This Week on the Radio

+ Available on ARRL Audio News http://www.arrl.org/arrl-audio-news

== + PUBLIC SERVICE: WX4NHC, VOIP WEATHER NET AND HURRICANE WATCH NET
ACTIVATED FOR HURRICANE ALEX

As Tropical Storm Alex turned into Category 1 Hurricane Alex, three
Amateur Radio mainstays during the Atlantic hurricane season -- WX4NHC,
VoIP Hurricane Net and Hurricane Watch Net -- activated at 8 AM EDT on
Wednesday, June 30; WX4NHC is the Amateur Radio station at the National
Hurricane Center in Miami, Florida. Alex made landfall at Soto la
Marina, Mexico late Wednesday, but weakened Thursday as it moved across
Mexico and was downgraded to a tropical storm, dumping heavy rain over
Mexico and south Texas; the storm's center made landfall with 96 MPH
winds in San Fernando in the Mexican state of Tamaulipas, 75 miles
south of the Texas border. According to the NHC at 11 AM EDT Thursday,
Alex was centered about 165 miles west-southwest of La Pesca, Mexico,
and about 150 miles east of Zacatecas and was moving west at 12 MPH; it
is expected to stay on that trajectory for the next day or so. Read
more here
http://www.arrl.org/news/wx4nhc-voip...-watch-net-act
ivated-for-hurricane-alex.

== + AMATEUR RADIO IN THE CLASSROOM: ARRL TEACHERS INSTITUTES WRAP UP
IN NEW MEXICO, SOUTH CAROLINA AND CALIFORNIA

After the first ARRL Teachers Institute on Wireless Technology (TI)
of 2010 concluded this past February in Tucson, Arizona, three more TIs
happened in quick succession -- New Mexico, South Carolina and
California -- in May and June. The Teachers Institute on Wireless
Technology is a four-day, expenses paid in-residence learning
opportunity designed for motivated teachers and other school staff who
want to learn more about wireless technology and bring that knowledge
to their students. A variety of topics are covered during the TI,
including basic wireless technology literacy, electronics, the science
of radio, radio astronomy, how to bring space into the classroom ham
radio operation, introduction to microcontrollers and basic robotics.
Participants do not need to have an Amateur Radio license to attend a
TI session. The Teachers Institute program is one component of the
grant offerings within the ARRL's Education and Technology Program
portfolio of resources made available to schools and school teachers to
advance the integration of wireless technology literacy and ham radio
into school curricula. Read more here
http://www.arrl.org/news/arrl-teache...ew-mexico-sout
h-carolina-and-california.

== + ARRL FIELD DAY: IT'S A WRAP!

With more than 500 Field Day logs already received -- and more
coming in every day -- it's safe to say that this year's ARRL Field Day
was a smashing success! Conditions, at least on the East Coast, were
quite good. Operators at W1AW, the Hiram Percy Maxim Memorial Station,
worked almost 3000 stations during Field Day, including a few
California stations on 6 and 10 meters, as well as North Dakota on 10
meters on Saturday. Don't forget to send in your Field Day logs. Logs
for 2010 ARRL Field Day must be postmarked, e-mailed to the ARRL
, posted to the Field Day Web Submission Applet site
http://www.b4h.net/cabforms/ or submitted by 2059 UTC Tuesday, July
27, 2010. Late entries cannot be accepted. You can also post your Field
Day stories and photos on the Field Day Soapbox
http://www.arrl.org/contests/soapbox. The 2011 ARRL Field Day will be
June 25-26.

== ARRL IN ACTION : WHAT HAVE WE BEEN UP TO LATELY?

This feature -- including convenient Web links to useful information
-- is a concise monthly update of some of the things ARRL is doing on
behalf of its members, including advocating for Amateur Radio operators
at the national and international level, instructing classroom teachers
on wireless technology, activating W1AW for ARRL Field Day and more.
This installment covers the month of June. Read more here
http://www.arrl.org/news/arrl-in-action-what-have-we-been-up-to-lately-23.

== + THE DOCTOR IS IN: D-STAR, ANTENNAS AND AMPLIFIERS

Tom Copley, K4YAZ, finds that he needs to use more power to
consistently reach my local D-STAR repeaters in the Tampa Bay area. I
live in a condo and my VHF/UHF antenna is on a second floor porch.
Moving it higher or into the clear is out of the question, due to my
condo association. I am using a dual band transceiver with 50 W output
on high power. This is not enough to consistently reach the local
repeaters.

Since I am mainly using the 70 cm band, I have purchased an amplifier
that has an output of 100 W with 30 W drive on 70 cm. The amplifier
also has a useful receive preamp. To obtain the full 100 W output from
the linear, one must input 30 W. My 50 W radio would be over the input
rating of my linear, and the approximately 15 W output from the radio
on medium power will not drive the linear to the full 100 W output. Is
there an easy solution to this issue, or do I have to get a different
amplifier?

Here's what the Doctor had to say:

If you are right on the edge of the coverage area, the 3 dB increase in
power may make the difference. Also consider any other losses, such as
in the coax run to your antenna -- at 70 cm, coax loss can be a big
factor, and if the length is more than a few feet, better coax may
reduce loss by almost as much as the amplifier gain -- get every
decibel you can.

Your amplifier drive problem turns out to have an incredibly simple
solution. If you have 2.2 dB loss between the radio and the amplifier,
your 50 W radio output will be just 30 W at the amplifier. This only
makes sense because of the preamp in the amplifier; otherwise, the loss
would also reduce receiver sensitivity. With a preamp that has a
reasonable gain, the noise figure and thus signal to noise ratio is
determined largely by the noise figure of the preamp. On HF, making a
reasonably accurate attenuator using power resistors can be easy. At
UHF, component, lead and wiring inductance can make it a very difficult
job -- but all is not lost!

Now for the really simple part. You need coax cable between the radio
and amplifier anyway (see Figure 1). If you use coax with a loss of 2.2
dB, you're done. On 440 MHz, it takes just 16 feet of Belden 8259 RG-58
coax to get the loss -- hopefully emphasizing my earlier point! If you
select a different cable, make sure you have the cable attenuation
specs available. The extra coax can be neatly coiled out of the way, or
better yet, move the amplifier closer to the antenna to reduce the coax
length and attenuation between the amplifier ad antenna. Note that this
all assumes that the amplifier input is a good match to 50 ohms; if
not, the coax loss will be higher. If you have a wattmeter, it will be
a good idea to confirm all the power levels when you're done -- and
life being what it is -- plan to do a little trimming.

Thanks Doctor! Do you have a question or a problem? Send your questions
via e-mail
http://groups.yahoo.com/group/Allegh...=zpPOqQ_tDRUgz
8PtrOLu7ReN8SebO3NBKYSpUQMK52ADP9llBYDxeNcBsVrABCP PnXowtP8cnIt4
or to "The Doctor," ARRL, 225 Main St, Newington, CT 06111 (no phone
calls, please). Look for "The Doctor Is IN" every month in QST
http://www.arrl.org/qst , the official journal of the ARRL.

== + INTERNATIONAL SPOTLIGHT: ARRL REPRESENTED AT EUROPE'S LARGEST
AMATEUR RADIO CONVENTION

Billed as Europe's biggest Amateur Radio exhibition, HAM RADIO 2010
was held in Friedrichshafen, Germany, June 25-27, 2010. The event is
held annually in the Lake Constance region. Each year, a contingent
from the ARRL has attended HAM RADIO in Friedrichshafen, greeting our
non-US members and networking with other national radio societies. ARRL
also supports DXCC card checking at its booth -- a very popular
activity among the international community who travels to this large
show. The ARRL, as International Secretariat for the International
Amateur Radio Union, also hosted a meeting area for IARU officials and
friends at the convention. Last year's HAM RADIO had 17,400 visitors
and nearly 200 exhibitors from 30 nations. Pictures from this year's
event have been posted to ARRL's Facebook page. Read more here
http://www.arrl.org/news/arrl-repres...amateur-radio-
convention.

== AMATEUR RADIO IN SPACE: IARU INTERNATIONAL AMATEUR RADIO SATELLITE
FORUM SCHEDULED IN CONJUNCTION WITH AMSAT-UK MEETING

The IARU International Amateur Radio Satellite Forum will be held in
conjunction with the AMSAT-UK Colloquium
http://www.uk.amsat.org/content/view/32/42/ in Guildford, England on
the weekend of July 31-August 1. The forum -- chaired by IARU Amateur
Satellite Advisor Hans van de Groenendaal, ZS6AKV -- will take place on
Sunday morning, August 1. A report back on the activities of the IARU
Satellite Adviser and his Advisory Panel will be one of many items on
the meeting's agenda. There will also be a brief presentation covering
the ITU notification requirements for satellites operating in the
Amateur Service and the requirement to disable transmissions should the
signals interfere with other users of the radio spectrum. The forum is
open to all delegates at the Colloquium. For more information,
including hotel and registration information, please see the AMSAT-UK
Web site http://www.uk.amsat.org/content/view/32/42/.

== + SOLAR UPDATE

Tad "Like a vast river, stretching in the Sun
http://www.bartleby.com/145/ww290.html" Cook, K7RA, reports: The
conditions were not great for ARRL Field Day last weekend, but some
nice sporadic-E openings on 6 and 10 meters livened things up.
Geomagnetic conditions were quite active over the past week, which
increased absorption, with the higher latitudes more affected than
mid-latitudes. The average daily sunspot numbers over the past three
weeks were 26.9, 16.1 and 11.7, so quiet conditions continue with very
little solar activity. Look for more information on the ARRL Web site
on Friday, July 2. For more information concerning radio propagation,
visit the ARRL Technical Information Service Propagation page
http://www.arrl.org/propagation-of-rf-signals. This week's "Tad
Cookism" brought to you by William Wordsworth's Growth of a Poet's
Mind: Book Fourth, Summer Vacation
http://www.bartleby.com/145/ww290.html.

== + ARRL TO CLOSE IN OBSERVANCE OF FOURTH OF JULY

ARRL Headquarters will be closed in observance of Independence Day on
Monday, July 5. There will be no W1AW bulletin or code practice
transmissions that day. League Headquarters will reopen Tuesday, July 6
at 8 AM Eastern Daylight Time. We wish everyone a safe and festive
holiday weekend.

== THIS WEEK ON THE RADIO

This week, there is another running of the NCCC Sprint Ladder on
July 2. The DL-DX RTTY Contest and the Venezuelan Independence Day
Contest are July 3-4. The Michigan QRP July 4th CW Sprint is July 4-5.
Next week, the FISTS Summer Sprint is July 10 and the IARU HF World
Championship is July 10-11. All dates, unless otherwise stated, are
UTC. See the ARRL Contest Branch page http://www.arrl.org/contests,
the ARRL Contest Update http://www.arrl.org/The-ARRL-Contest-Update
and the WA7BNM Contest Calendar
http://www.hornucopia.com/contestcal/index.html for more info.
Looking for a Special Event station? Be sure to check out the ARRL
Special Event Station Web page http://www.arrl.org/special-events.

== ARRL CONTINUING EDUCATION COURSE REGISTRATION

Registration remains open through Sunday, July 25, 2010, for this
online course session http://www.arrl.org/online-course-registration
beginning on Friday, August 6, 2010: Amateur Radio Emergency
Communications Level 1. To learn more, visit the CEP Course Listing
page http://www.arrl.org/online-courses or contact the Continuing
Education Program Coordinator .

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