De Magnetic Loop als zendantenne voor de FM band
Een bijzondere FM antenne voor als je echt geen ruimte hebt voor een full size Yagi
Englisch translation on the page bottem However i'l didt found the time to moderate the translation , so its not gramatical correct
Magnetic Loop Antenne is al veel geschreven , soms
verguisd soms de hemel in geprezen . De waarheid ligt
ergens in het midden.
Ook in de zendamateur
wereld wordt dit type wordt de loop wel gebruikt op 2 mtr
en 70 cm band . waarbij de loop vaak niet groter is dan
10 - 15 cm
About the Magnetic Loop Antenna Much has been
written, sometimes reviled sometimes praised. The truth lies
somewhere in the middle.
About one thing we all agree "Miracle Antennas" do not exist, but the Magnetic Loop comes very close.
The MagLoop is usually used in the frequency range from 4 to 30 M / c below 4 M / c the thing starts getting a little bit
huge, over 30 M / c start "normal" antennas have to be quite tractable. Yet also for Loop antennas
higher and lower frequencies used
Elsewhere on this website I have an excellent Magnetic Loop Antenna
which also describes the medium is useful as a transmitting antenna
But at higher frequnties loop antenna is very useful.
Many modern "onboard antennas are of the type of course
Also in the 70 commonly used pagers and pagers using a
Magnetic loop as a receiving antenna, where the measurements sometimes very
small were made ??eg 1.2 x 4 cm in the 169 known M / c pagers.
However, loop antennas already pretty long time. in Vietnam
they were widely used by the American army, but even in the
Over 50 years has been applied to the right is a picture
Police motorcycle show from the early 50's with a back
Loop antenna can be seen on the mobile phone. In the vastness of
California met these loops at 33 M / c better than normal
the rod antenna for 33 M / c was very long and vulnerable
This course did very well in long distance traffic between
engine and dispatcher and was also virtually indestructible
the previously used rod antennas would sometimes break
at higher speeds something these "Solid Rock"construction design
not get in the loop shown here is a type of the DDRR
In the amateur world, this type is being used on over 2 meters and 70 cm band. often the barrel does not exceed 10 to 15 cm
Elsewhere on the web there was a loop antenna at a 51 M / c, I simply divided by two sizes and antenna tried to
fm band through the antenna to my spectrum analyzer. With the use of 5 pf trimmer at the top, the antenna tuning
of 70 M / c to above 150 Mc. Compared to a 1 / 4 wave rod directly to the analyzer were afstempunt the average signal strengths
4 to 6 dB stronger with the loop antenna, like all this gave me a hopeful feeling.
Now here I had a small stereo 100 milliwatt transmitter on the bench stand with a 75 cm long whip antenna. After this the loop to have
connected and have adjusted the signal was on the spectrum analyzer over 15 dB! faster than with the 75 cm rod antenna
However, the very narrow-band antenna and the correct matching is really a loosing, the antenna has many hanfeffect and you have to adjust some
ingenuity, and something about turning around the point to you is just too low, your hand away when you see the field grow strongly.
With a little practice you'll quickly master this and the adjustment is a peanut.
For a good return, the antenna thickness, we often use for SW 22 mm copper pipe for a good VHF antenna you have to
at least 6 millimeters, I'm here for the test setup VD 2.5 mm wire, not optimal but it worked better than expected
And here the schedule this May as I walk him to the
have mounted transmitter
The transmitter has a 199 BF in the final stage with a
DC input power of approximately 100 milliwatts
Even with this small power station is to a large
miles on the car radio can be received well.
Before adjusting I use a similar course with
and a 100 uA meter at about 1 meter distance, this is the
transmitter and loop easy adjustment of radiation amximale
My second experiment of this evening was a
A Symmetrical Magnetic Loop where the tuning at the bottom to earth's
i.p.v. floating in the air at the top of the loop.
I also have over a
made smaller with a diameter of 12 cm
The radiation appeared to be about equal to my first performance
Advantage of this construction is the easier way to adjust
Because the trimmer with a side that shows the earth is now
smoothly with a normal screwdriver adjust without load
to have the hand effect which occurs when the floating trimmer
symetische the first execution. Photos follow.
It is also the intention is again a symmetric
where the control history d.m.v. a balanced pair of transistors to
In this way a greater output to bring up as much as the
small mono channel with the circuit board etched loop antenna that
elsewhere on this site is.
This type of antenna and a control of 300 to 500 milliwatts
be be sure
to get a range of 3 to 5 Km by the station
fairly freely on a
top floor of a united home is located
Below are two pictures of the little over 12 inches, including
clearly the two trimmers on the side Vande channel are visible