The
Pres Says…..
Saturday 2nd September saw a few members doing some major
work around The Club Shack. Next time you are there,
if you are one of those who take note of what antennas
the Club actually has in the air, you will notice that
another mast has grown with a dedicated 70cm and a 6m
vertical mounted on top. That was one job done on the
day. Others included repairing the metal outer skin on
the external door of the Club Rooms, relocating the 70cm
repeater to its new location near the antenna patch panel
and replacing the tower tilt over winch with a brake
winch. Workers on the day enjoyed a BBQ lunch supplied
as a thank you by The Club. Those people were Noel King,
Ron Robertson, Bruno Tonizzo, Reg Goddard, Jan Oncken,
Ivan Blezard, Mike Ide and myself. Many thanks to those
people for putting in a whole day for The Club.
You will
notice this month’s edition has a copy of
the Club Membership list. (if all goes to plan) . Please
advise if any changes are applicable as a few discrepancies
have already been noticed. Unless you tell us of your changes,
we cannot keep it updated. This especially applies to email
addresses. In the near future the Cub will be running its
first Foundation Licence training and examination session.
Tentative dates are 28th and 29th of October.
With the warmer weather on its way, we can turn our attention
to spending a bit more time outdoors. Two items on the list
are up for discussion again. They are a trip to the Moorabbin
Airport Aircraft Museum and a Fox Hunt. Hopefully we can
pull both of these off during the better months to come.
For a
bit of fun, the Committee came up with the idea of a new
bumper sticker
for Amateur Radio promotion. We will
be looking for suggestions that will get a laugh. Try Mike’s “Amateurs
do it with Higher Frequency” as an example. Or “Amateurs
do it on Air”. Have a think about it. Maybe Andrew
will give a prize for the best one and we may get it printed.
See you at the meeting.
73s Albert VK3BQO
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Editor’s Musings
Well I sit here on Monday evening all ready to put the
magazine together and realise I have nothing (or next to
nothing)
to put in it. I am not a technical guru as you have all guessed
by now, I can’t write technical articles. I can waffle
a bit but that wont fill the mag. I can find little bits
off the internet that might fill a page or two but it’s
not about the club so don’t know if it’s worth
it. I don't , at the moment, have time to chase people for
articles so either you just decide to do it or nothing will
happen. End of whinge, don’t complain to me about the
lack of stuff in here I am only the Editor!
As I said earlier this year I am happy to do the mag for
another 12 months (expires at the Annual General). It will
be somebody else's turn then.
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Signs and Notices:
" Because of the impropriety of entertaining guests of the opposite sex
in the bedroom, it is suggested that the lobby be used for this purpose." --
A sign in a Swiss hotel.
" Ladies, leave your clothes here and spend the afternoon having a good
time." -- A sign in a laundry in Rome.
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If you were travelling at the speed of sound and
you turned on your radio would you be able to hear it?
" You can listen to thunder after lightning and tell how close
you came to getting hit. If you don't hear it, you got hit,
so never mind."
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Upcoming Events
|
| Friday
Sept 15th |
General
Meeting Night |
Guide
Hall |
| October 6th |
Prac Night |
Club Shack |
| October |
JOTA |
Guide Hall/Club Shack |
| November
4th, 5th, 6th, and 7th |
Melbourne
Cup Weekend |
TRIP
TO MARYBOROUGH |
| November |
Moorabbin Airport |
TBA |
| Australia Day |
Fox Hunt |
TBA |
| Link
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|
|
A Folded Dipole
( borrowed from www.elmerhamlet.com)
A variation of the dipole is an antenna called a folded
dipole. It radiates like a dipole but sort of looks
like a squashed quad.
Having a folded dipole does not mean that you have an antenna
that is folded in half and so you obtain an antenna that
now takes up half the space of a regular dipole. No, the
antenna is still approximately the same length as a regular
dipole. It is however, an antenna that has a wire folded
back over itself, hence its name.
The starting formula for the folded dipole calculation is
the same as a dipole, 468 / Frequency (in MHz). Let's try
an example: Design a folded dipole for the 40 meter band.
The frequency that is chosen might be 7.15 MHz. Plugging
this in to the formula (468 / 7.15) gives a folded dipole
with a length of 65.45 feet. When I modeled a dipole on the
computer at 30 feet, I came up with a length of 65.47 feet.
When I added a second wire to make the folded dipole shown
above, I designed the antenna with 1 inch spacing between
the two wires. Note that this adds 1 more inch to each of
the two antenna wires over that of a single wire dipole.
This plus the fact that we are actually turning up the ends
of the antenna, means that the horizontal length actually
need to be a little shorter to be once again at resonance.
The total length came to 64.38 feet, 1.09 feet shorter than
the straight dipole. If you use a greater spacing, say 1
foot between the wires the length is 63.1 feet, 2.37 feet
shorter. So be sure to shorten the antenna a bit or you'll
find yourself operating lower down the band than you expected.
The feed point impedance is also modified by the second
wire. Let's say the original dipole was 72 ohms. The step-up
for a two wire folded dipole is 4 times which means 4 * 72
= ~288 ohms. (The computer shows 281 ohms on my example,
but remember, we reduced the length slightly also.) This
step up continues if you add more and more wires. A three
wire antenna would provide a step-up of 9, and a four wire
antenna provides a step-up of 16.
We can see why this step-up occurs by looking at the power
formula P=(I*I) * R, this can be rewritten as R = P / (I*I).
If the power to a regular dipole antenna was 100 watts and
the current was 1.2 amps, we'd solve for R as R = 100 / (1.2*1.2),
which is the same as R = 100 / 1.44, which is 69.44 ohms.
In the folded dipole the wires are in parallel, the current
must be divided between the two wires. The current in each
is half and the total power has not changed, so now the formula
is R = 100 / (.6*.6), which is the same as R = 100 / .36,
which of course is 277.77 ohms, 4 times the normal dipole
antenna.
So now you ask, why would anyone want an antenna with a
feed point impedance of 277 ohms, my coax cable is 50 ohms!?
Well let's say you wanted to feed the antenna, not with 50
ohm cable but with 300 ohm twin lead? Ah ha, now we have
a decent match and a feed line that can also handle a higher
SWR with low loss. You'd probably use a tuner (ATU) in the
shack to match the 50 ohm radio to the 300 ohm feed line.
You could also use the antenna on other bands with the tuner
and have an efficient antenna system.
What are the drawbacks to the antenna? Well for one, the
currents on each wire will begin to cancel each other out
on even multiples of the cut frequency, so a 40 meter folded
dipole should not be used on 14 MHz. On other bands even
though the signal may cancel broad side to the antenna, you'll
find that there is actually gain! This occurs about 45 degrees
off broad side to the antenna. And this might make for interesting
contacts.
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Confessions of New Chum
Well nobody else wrote anything so I will babble on a bit.
Have just started taking an interest in Community Radio.
I have always wanted to be a radio dj so now I get my chance
apparently.
103.1
3BBR FM is the local Community Radio Station down at Drouin.
Hey
I have lived down this way for 12 years and
I never knew about it so don’t feel bad!
So what
is Community Radio? Well to put it simply it is a bunch
of volunteers
getting together to present programs
that are meant to add to the lifestyle of the people they
are aimed at. Now that’s pretty broad and is meant
to be I think. 3BBR provides lots of local content (e.g.
it broadcasts the local footy finals). Community Radio is
also an outlet for music that would not get played on mainstream
radio. So you are a member of the Ham Radio Punk Band and
want your music played you could probably find a station
that would you give you an airing (not 3BBR I hasten to add!)
3BBR aim is to present family friendly programmes so you
wont hear too much rap music (sorry to all you rap fans)
but there is a wide variety of music on the station from
jazz to techno, gospel to country and just about everything
in between. During the day they play middle of the road stuff
(Music for West Gippsland) but from 6pm there is quite an
interesting array of programmes run from Trad Jazz to Classics
to Rock to Sports Programmes. I am hoping to be on Wednesday
nights from 8pm playing music to move too (healthy lifestyle
promotion etc) and ending with some relaxation music from
10 to 11pm.
To get there I have to do some training sessions. I have
already got a handle on the mixing desk in the Production
Studio. A variety of delivery methods are used, including
CD, cassette, MD (mini disk - I had not seen these before
- quite interesting!), and of course the old turntable to
play those big black CD things. The next step is into the
live studio, I have already sat in with a couple of the other
presenters and have been made to feel very welcome. There
is also some theory sessions to do but I think they are keen
to fill the empty spot so I might be on air earlier than
I think!
Like
I said it is all voluntary, maybe you could help out at
a local station –does
not have to be ON AIR. The only problem I have is NOT saying
VK3BBR!
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Intrepid Travellers
(Sorry I Forgot Last Month)
Dorothy and myself will be away on holiday from the 19.08.2006
- 18.09.2006.
Our trip will be to Alice Springs, Halls Creek, Wyndham,
Kakadu, Mataranka and back to Alice Springs. From there home.
We will be on the Travellers Net daily between 12.00 - 13.00
hours every day. If anyone wants to contact us, the Traveller
Net is on 14,116 Mhz.
We will be on 80 metres as well. Time will be about 21.00
hours every Friday, Sunday and Wednesday. Frequency is 3,640
Mhz +/- QRM. We may hear you there.
Best 73 de Helmut VK3DHI and Dorothy
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This
Months Challenge
Don’t have one, last month was Russ VK3MWR, apparently
nobody guessed!
No the one on the left is not our trainee pom after a few
beers!
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Happy Birthday to you……..
Some birthdays on the club database this month :
Judy Robertson, David Rosenfield VK3ADM, James Shilton VK3ZRG
Not listed?
We don’t know then, please tell us!!!
Let the Treasurer know…...
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Remembrance Day Contest
Remembrance Day Contest 2006
On the weekend of 12th and 13th of August, the club’s
station VK3BJA was once again activated for this time honoured
event. At 6.00pm local time on Saturday, Albert VK3BQO, Bruno
VK3BFT, Graeme VK3YCG and Mike VK3KTO were all manning VHF,
UHF and HF rigs, and ready for the action that came thick
and fast.
They
were later joined by David VK3XMF and Paul VK3TGX. As operators
gradually
headed off to their warm beds, the
station was kept alive by VK3KTO during the small hours.
At around 7.00am VK3KTO was joined by VK3YCG and a hearty
breakfast of bacon and eggs was partaken of. A little later
in the morning the “Jackson Three” in the form
of Diane VK3JDI, Ian VK3BUF and Ross VK3ZAP arrived, closely
followed by David VK3BJV; so allowing VK3KTO to depart for
some badly needed horizontal polarization. It was pleasing
to note that all rigs performed without fault during the
event and the club’s new 6 metre antenna worked well,
even at only 20 feet, although the SWR is a little high down
the bottom end as to be expected, since it is really designed
for the FM portion of the band. The logging program of John
Drew VK5DJ is certainly a beauty and John is to be greatly
commended for making it available to all participants.
In comparison to last year the level of participation by
club members was rather disappointing, but those who took
part had a great time and managed to make an almost identical
number of contacts on 80 and 40 metres to last year and even
10 more on 160. A breakdown of the logs is as follows.160
metres:44 contacts for 88 pts
80 metres: 51 contacts for 67 pts, 40 metres: 86 contacts
for 86 pts, 10 metres: 4 contacts for 4 pts. 6 metres: FM
15 contacts for 18 pts, SSB 4 contacts for 5 pts. 2 metres:
FM 101 contacts for 144 pts. 70 cm FM 62 contacts for 68
pts. SSB 8 contacts for 9 pts. No activity took place on
20 or 15 but four locals were worked on 10 metre SSB and
FM.
The activity on VHF and UHF seemed well down on last years,
perhaps due to the 2005 results fiasco. Please remember that
the Remembrance Day Contest is held on the weekend closest
to the 15th of August every year and let us try to make a
big effort for next year. Mike Ide VK3KTO.
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CTCSS FOR IRLP IS NOW 123Hz
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If I raise the volume on my radio, does it use more electricity?
If the professor on Gilligan's Island can make a radio out
of coconut, why can't he fix a hole in a boat?
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Van Allen Belt discoverer dies
James Van Allen, the US physicist who discovered the radiation
belts surrounding the Earth, has died. He was 91. In a career
that stretched over more than half a century, Van Allen designed
scientific instruments for dozens of research flights, first
with small rockets and balloons, and eventually with space
probes that travelled to distant planets and beyond. Van
Allen gained global attention in the late-1950s when instruments
he designed for the first US satellite, Explorer I, discovered
the bands of intense radiation that surround the Earth. These
bands are now known as the Van Allen Belts. (from WIA Website)
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Why not
listen to the WIA news each week on the
VK3RML repeater. It is on Sunday nights at 8pm and Wednesday
11am
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Hard at Work on the Working Bee day.
Meeting Minutes
General Meeting Minutes
Date: 18th August 2006
Start time: 08:00 PM.
Location: Guide Hall Cranbourne.
Chairperson: Albert Hubbard VK3BQO
Minute Taker: David Campbell VK3XMF
Present: As per attendance sheet.
Visitors and Guests:
Apologies: Dorothy & Helmut Inhoven VK3DHI, Geoff Williams
VK3ZGW, Ian Benson VK3KSZ, Phil Pavey VK3YB, Grahame Coleman
VK3YCG
Correspondence Received:
Pat letter (?), VK3DWH regarding hamfest, EMDRC July & August
magazine, SES Letter
Correspondence Sent: Nil tabled.
Treasurer’s
Report: as tabled
Read by: Mike Ide, VK3KTO Moved by: VK3KTO Seconded by:
Russ VK3MWR Carried: Yes
New Call signs – Phil VK3YB has now also been allocated
Peter’s call VK3VB
Previous Minutes: As printed in the August GATEWAY magazine.
Business Arising from Previous Minutes:
Hamfest – Albert thanked Bruno. Report as tabled
Village Green Pub Night – good night had by all
RD Contest. Those who attended had fun, but more members
attending would have helped things along. 46 contacts on
160m, about 400 contacts over weekend.
Working bee on 2nd of September. All members asked to assist
with antenna work etc
KITS – CTCSS decoders in hand with Paul VK3TGX. Albert
asked for interest in handsfree mic kit
30th Anniversary – ACMA will now only issue VI calls
for 25, 50, 75 year celebrations.
Maryborough Trip – Dianne has booked observatory for
the Sunday
Shack Gear. Mike reported on donation of test equipment.
Miscellaneous Gear – mic’s & speakers for
sale as supplied by Richard
WIA Grant – GGREC has missed out on funding from the
WIA “Clubs Grant” for 2006. This was to be used
for reverse cycle heating/cooling in shack
New Business:
Helmut & Dorothy away. Scheds are 1200-1300 on 14.116,
80m at 2100 Fri, Sun, Wed on 3.640 + QRM
Foundation Licence Course. First course will be 28/29th October.
$40 per person for course and pro-rata membership + book
Mystery photo in last magazine was Russ
Club Rules – please review and send amendments to Albert
Club membership list. Please advise committee of any changes.
Photos from Graeme VK3XTA have been circulated by Paul
Meeting Closed at around 09:10 PM.
Next Committee Meeting: Monday 25th October 2006, at the
Club Rooms starting at 8:00pm.
Next Prac Night: Friday 6th October 2006.
Next General Meeting 20th October 2006
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