best antenna

[abcd567]

......With regards cable runs would reducing length from 30ft to 15ft make any noticeable difference to coverage with a whipped Coco that uses an amp?

Mike

Mike, at 1090 MHz, the attenuation (loss of signal) in normal RG6 coaxial cable used in homes is about 6.5 to 6.8 dB per 100 feet (depending on quality/manufacturer). Taking worst case of 6.8 dB/100feet, the attenuation for extra 15 feet will be 6.8x15/100 = 1 dB, which your 20dB amplifier will cover, and you should not notice any difference in coverage.


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[1090 MHz]

MERRY CHRISTMAS & HAPPY NEW YEAR

Same to you and your family... I see Santa bringing you some UHF radios on a very slow sleigh from China !

[abcd567]

Same to you and your family... I see Santa bringing you some UHF radios on a very slow sleigh from China !

Hahaha...Santa was scheduled to deliver between 16 & 23 Dec, but it seems I will not get it on Chistmas, maybe new year's gift.

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[1090 MHz]

Hahaha...Santa was scheduled to deliver between 16 & 23 Dec, but it seems I will not get it on Chistmas, maybe new year's gift.

Did they give you any tracking number?

[abcd567]

Did they give you any tracking number?

Yes, but it is not full tracking. It tracks only up to dispatch. Anyway since their declared delivery date expired only today, and since I have lost my 'impulsive' interest in these radios, I am not anxious to receive then quickly.

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[abcd567]

Same to you abcd567

I made a half wave dipole today and was impressed with the results. Max distance was 320km this without any amp. It does have a very short cable run but still impressive........

Mike

Half wave dipole has the beauty that its impedance (73 ohm) matches with coaxial cable's impedance (75 ohm) and DVB-T receiver's impedance (also 75 ohms). Another advantage is that there is no velocity factor involved in calculating length, hence no assumptions, and it can be cut to accurately 13.8 cm total height, tip-to-tip. That is why one can get a gain almost equal to it's theoretical gain of 2.15dBi. On the other hand, although 4-element CoCo has a theretical gain of 5 dBi, the CoCo cut to wrong dimensions (due to assumption of velocity factor), may actually have much less than 5 dBi, even less than 2 dBi of 1/2 wave dipole.


Franklin half-over-half diploe has theoretical gain of 5 dBi and can be cut to precise dimensions like half wave dipole, but has a very high impedance (4000 ohms) and if proper matching method is not used, gives a low gain & poor coverage. I have covered loss of gain in Franklin by using 2 amplifiers, and got a very good coverage. But without amplifier and without impedance matching, Franklin gives poor performance.With Franklin, you must have at least one: either impedance matching or amplifier.


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[VE6CPP]

For 'abcd567 and Rooster'.. Interesting article from 'AUSTRALIAN ANTARCTIC MAGAZINE"..

Moon bounce from Antarctica
Amateur radio operator Craig Hayhow has used the moon to bounce
a radio signal 742 000 km, from Mawson station in Antarctica to
Cornwall in England.
Proving the feat was no accident, two nights
later he performed another ‘moon bounce’ to
communicate with radio operators in Sweden
and New Zealand.
‘The “Holy Grail” for many serious amateur radio
operators is bouncing a radio signal off the
moon and reflecting it back to Earth to have a
conversation with another station on the other
side of the world,’ Craig says.
‘The technical challenges are immense, but
with modern high speed computers and
sophisticated software, it has become a lot
easier in recent years.’
Craig, who is wintering at Mawson station as a
Senior Communications Technical Officer, says
his first moon bounce on May 4 this year, was
the first time it had been achieved from an
Australian Antarctic station and only the third
time from the Antarctic continent.
Until recently, the technique was only possible
using the largest, most powerful and expensive
amateur radio stations. This is because of the
distance the signal has to travel, the amount of
power needed to send a strong signal and the
loss of signal as it travels through space.
‘The moon has to be lined up perfectly between
the two stations to achieve an adequate
reflection, so we use computer programs
to find the optimum time to communicate,’
Craig explains.
‘However, most of the transmitted signal is lost
into free space and only about seven per cent of
the signal that strikes the moon is reflected; the
rest is absorbed.
‘The Earth’s atmosphere distorts and attenuates
the signal even further so that by the time
the signal reaches the receiving station
it is very weak.’
As Craig is operating from a small, ‘home-made’
station, he can only communicate with receiving
stations that use multiple, ‘high gain’ antennas
and vast amounts of power.
Craig built his own radio station using an
off-the-shelf antenna that is small enough
not to get blown away in a blizzard, but large
enough to generate a signal that can reach the
moon. He also built an amplifier to boost his
transmitting signal from 4 watts to 500 watts.
To bounce a signal off the moon he uses
customised software to target it. Objects other
than the moon can also be used and Craig has
targeted commercial aircraft and meteor trails.
‘The software is tailored for each
application,’ he says.
‘It takes around 2.7 seconds for a signal to
be bounced off the moon, while it is virtually
instantaneous from an aircraft. If a signal comes
back, you can be sure it’s reflected off the object
you are targeting.’
Moon bounce from Antarctica
Amateur radio operator Craig Hayhow has used the moon to bounce
a radio signal 742 000 km, from Mawson station in Antarctica to
Cornwall in England.
Craig passed the exams to become an amateur
radio operator when he was 17 and some
30 years later he still enjoys the surprise of
chatting to people from around the world,
sometimes in remote or unusual places.
As Antarctica is also considered ‘remote’ and
‘unusual’, Craig says he is often bombarded by
operators clamouring to add his unique call sign
to their log books.
Craig’s moon bounce achievement comes
100 years after the first radio communication
between Antarctica and Australia, via Macquarie
Island, was established by the Australasian
Antarctic Expedition (AAE, 1911–1914), led by
Douglas Mawson. The AAE was the first Antarctic
expedition to use radio communications,
using ground waves (Very Low Frequency or
VLF). Sadly, Mawson’s first use of the radio,
on 24 February 1913, was to relay news of
the deaths of his companions, Xavier Mertz
and Belgrave Ninnis, during the Far Eastern
sledging journey.
Fortunately, Craig’s experiences are happier.
‘Usually the talk is of a technical nature, but
we also talk about work, family and the places
we live,’ he says.
‘However, amateur radio is mostly about
furthering the science of radio by testing,
research and development, and sharing ideas
within the radio community.’
WENDY PYPER
Australian Antarctic Division 1

F-CYQL1

[abcd567]

For 'abcd567 and Rooster'.. Interesting article from 'AUSTRALIAN ANTARCTIC MAGAZINE"..

Moon bounce from Antarctica
Amateur radio operator Craig Hayhow has used the moon to bounce
a radio signal 742 000 km, from Mawson station in Antarctica to
Cornwall in England. .............
F-CYQL1

Thank you Jerry for sharing such a useful info. 73

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[mickopla]

Half wave dipole has the beauty that its impedance (73 ohm) matches with coaxial cable's impedance (75 ohm) and DVB-T receiver's impedance (also 75 ohms). Another advantage is that there is no velocity factor involved in calculating length, hence no assumptions, and it can be cut to accurately 13.8 cm total height, tip-to-tip. That is why one can get a gain almost equal to it's theoretical gain of 2.15dBi. On the other hand, although 4-element CoCo has a theretical gain of 5 dBi, the CoCo cut to wrong dimensions (due to assumption of velocity factor), may actually have much less than 5 dBi, even less than 2 dBi of 1/2 wave dipole.


Franklin half-over-half diploe has theoretical gain of 5 dBi and can be cut to precise dimensions like half wave dipole, but has a very high impedance (4000 ohms) and if proper matching method is not used, gives a low gain & poor coverage. I have covered loss of gain in Franklin by using 2 amplifiers, and got a very good coverage. But without amplifier and without impedance matching, Franklin gives poor performance.With Franklin, you must have at least one: either impedance matching or amplifier.


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Thanks abcd567 for the explanation. A very informative post.

Mike

[abcd567]

Impedance-Matched Franklin Dipole
With 1/4 wavelength Impedance matching Stub & adjustable sliding tap

400 km Range Without Amplifier!!!

franklin+impedance-matching-stub-2.jpg
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DSC02985R.jpg
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DSC02989R.jpg
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DSC02990R.jpg
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DSC03002.jpg

Best position of sliding tap is found by trial & error. In case of antenna shown in the pictures above, the best tap position was found at 18mm from shorted end of stub (i.e about 25% of stub's total length of 69mm), but this may vary from antenna to antenna. The position of sliding tap for each individual antenna is to be adjusted by trial & error method.

[peterhr]

Impressive!

[mickopla]

Great work. I'm lucky to get 340km with an amp and CoCo.
I finally got all the pieces together to test a shorted 3 part Coco but only have a spare 12v adapter. Would 12v be enough to run the power inserter and onto the amp?

[peterhr]

Great work. I'm lucky to get 340km with an amp and CoCo.
I finally got all the pieces together to test a shorted 3 part Coco but only have a spare 12v adapter. Would 12v be enough to run the power inserter and onto the amp?

12v worked for me - I'm not sure going to 15v made much difference (could be dependent on the amp)

[abcd567]

Great work. I'm lucky to get 340km with an amp and CoCo.........

Impressive!

You can built a mechanically stronger version of Franklin, suitable for outdoor installation, as shown here:

http://www.lesaunier.com/htm/franklin1_eng.htm

Note: It will be easier to carry out the adjustment of tap with Antenna at location easily accessible without need of a ladder or climbing to roof (unless you want to burn some of your fat ). Ranges can be compared for various settings, and once the best one is found, the antenna can be moved to & installed at roof top.

I have tried half-a-dozen different settings of cable tap between 10mm and 40mm (from shorted end of stub).
For each of these 6 settings, I have run the antenna on adsbScope for 24 hrs

.

[peterhr]

Would a capacitor work where the two halves are soldered, so an amp could be used?

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