GETTING STARTED WITH FM ANTENNAS
The importance of an
Without using a high
gain, rotatable external antenna, any given "DX-capable" tuner, with
adaptive or conventional narrow filters may not perform optimally. The
antenna (pictured) is the most critical part of my DX system. One
exception may be when you are lucky enough to live in
an elevated location.
In December 2003, Electronics For You
published a comprehensive article about FM antennas in their magazine.
The PDF article explains
how enthusiasts can improve their FM reception in the home. The author
which antenna is good for long distance FM reception (FM DX). The
author also discusses the characteristics of car FM antennas.
For those starting out
in FM DX, with about $200 to spend... one recommended option is to
engage a professional installer to erect an eight element antenna on
your property. To maximize the performance of this investment, mount
the antenna in isolation, on its own mast, above roof level and ensure
it can be manually rotated from the ground.
Several antennas covering similar frequencies may 'interact'. For the
best performance, locate one FM or wideband antenna as far as possible
away from another. Put the FM antenna atop a mast with a height of
roughly 1.7 metres above roof level. Motorized rotation is an
available at an additional expense of $200-$300.
While installing the highest gain dedicated FM antenna is desirable, it
is a luxury in the city and may not be suitable for everyone. Brian Beezley tests a wide range of antennas on
his site including smaller unobtrusive models. Antenna Specialties
Adelaide offers a selection of inexpensive FM DX antennas and motorized
rotators to suit. Of all the commercially manufactured,
yagi style antennas available in
Australia, those models offering three FM elements (pictured) are
probably the most unobtrusive.
Can't install another antenna? Good results may be achieved simply by
temporary installation in
the backyard. Alternatively, a single, high quality, wideband antenna
can be used for both TV and FM. I share my experiences in detail here. Listed are
which can be used
to help you determine the elevation of your property.
Easy-to-understand photos contributed by others or myself are also
included on that page.
Many have suffered fatal injuries falling from rooftops, in an effort
to save a few dollars. Please, delegate the responsibility to antenna
On this page, we will
typical installation. At my residence, two antennas are mounted on the
roof of the single storey house, at opposite ends of the house. The
recommended option, an eight element FM antenna (pictured) is
positioned above the garage and a
non-rotatable VHF/UHF TV antenna on the pitch of the roof. Please visit
this detailed page which
contains the specifications of all the recent model antennas used. It
contains data about the models used permanently at home and temporarily
during field trips or on vacation.
Connections, amps &
The external antennas
are cabled to separate F-type wall plates. No splitters, combiners
or wideband preamplifiers are used the majority of the time. An inline
F-type splitter is used on those
rare occasions when it is essential to use two tuners at the same time
on the same antenna.
successfully used for long distance TV reception only. It is
unsuccessful for FM reception. Why doesn't it work? I simply live too
close to the major FM broadcast site. Using a preamplifier causes
images or "ghost signals" of excessively strong local FM stations all
over the dial, swamping the receiver.
is an oversimplification. Unfortunately, the experience with preamps
may vary markedly from location to location. You may find that by
rotating the antenna to a particular azimuth (antenna position), tuner
overloading is not a problem. Should that be the case, then it is
likely a preamplifier may be successful for improving weak FM
reception. You may need to reduce the gain of a preamp to reduce
overload by using an F-type attenuator at the output, for example.
Please be aware that this will cause the specified noise figure of the
preamp to worsen, as
Brian Beezley explains here. I
don't consider reducing the supplied voltage to a preamp the ideal way
to reduce the gain, but that's another option I suppose!
Unfortunately, the use of preamps to potentially aid FM reception is
complicated. This subject is beyond the scope of a website
designed to be
non-technical and elementary level. Detailed information is available here.
The author of this historical paper looks
at the pros and cons. Both papers are written from an amateur radio
RG6 Quad Shield Coaxial
Cable is used to connect all antennas to the wall plates. It
would appear that some sources of RG6 Quad Shield Coaxial Cable are not
as durable as others, so you might like to try different brands of
cable until you find one you prefer. A better quality cable, RG11, is designed for
underground, professional cable TV
available at specialist retailers by the metre. However, considering
specialist tools are required to crimp the connectors and with the
additional expense over RG6Q, its use seems overkill. RG6 Quad Shield
Cable is perfectly fine for the lowly black art of long distance FM
F-type connectors are
used to standardize connections between the receiving equipment and the
wall plate. For dwellings that come with PAL-type wall plates, this
requires the use of an F-type to PAL adapter. F-type splitters,
adapters cost only a few dollars.
a major broadcast site is in close proximity, a 3
decibel F-type attenuator is used in-line. It is used in circumstances
where I am using a
non-rotatable antenna that is fixed in the direction of the site. Judicious
use (for example, 6 decibels maximum) of
attenuation may improve sensitivity on certain tuners
which overload from excessively strong local TV audio and FM signals. Weak signal reception noticeably improves, under
those circumstances, on
adaptive IF receivers, including the Sony XDR-S10HDiP docking radio and JVC
UX-SG5B micro system, particularly the latter.
Inside the home, car
receivers can be connected to an external directional antenna by simply
inserting the stripped end of a RG6 Quad Shield Coaxial Cable firmly
into the Motorola antenna socket on the receiver and the other end of
the cable into the wall socket. Belden ultra low loss
RG59 is unsuitable for use as car receiver "fly leads" as it is too
thin to snugly fit into the Motorola antenna socket.
Siting your antenna to
Ethernet Over Powerline
home networks, Wired Home Alarm
systems, Plasma televisions and Air Conditioning units can generate
Electromagnetic Interference (EMI) that may be picked up by your
external FM antenna. These devices have prevented the reception of
permanent fringe FM signals entirely at certain times.
ADSL Routers may trigger EMI if the telephone line connecting the
device is excessively long, as the line may act as an antenna.
According to LD Blake, certain Wireless Routers may cause
round-the-clock interference on frequencies up to 160 MHz. Ethernet
Over Powerline adapters can radiate interference for hundreds of metres
round-the-clock according to Dave Sergeant. Ethernet Over Powerline
adapters are in a league of their own! Several correspondents on the
Australian Whirlpool forum have reported significant interference to
analogue television reception whilst operating these networks. Nigel
Coleman tested one model which is readily available in Australia. The
most significant interference was found in the spectrum that covers FM
and DAB reception. Reception was entirely destroyed. The device
pollutes frequencies between 0.1 MHz and 370 MHz.
Ed Hare tested
some other common household devices (pictured). He found that the most
devices included old televisions, old Cathode Ray Tube (CRT) monitors,
old computers which are not housed in metal cases, hairdryers, vacuum
cleaners and drills.
20 metres or more may be affected whilst the offending devices
are operational. In extreme cases, EMI may even penetrate the outer
shield of RG6 coaxial cable lying inside the walls and ceiling of your
dwelling. It is a genuine problem in congested urban areas.
Unfortunately, it seems to be increasing in severity every year, such
is our hunger for new technology to meet our desires.
Whilst listeners have
considerable control over what interference their own household
produces, the neighbours' household produces interference that cannot
be eliminated. Before erecting an antenna, try the antenna out in the
backyard, close to where the proposed antenna erection site is. Lie the
antenna fully extended, as elevated as possible, to maximize the
Point the antenna North
and tune through all the clear frequencies. Clear frequencies are the
frequencies where an FM broadcast is not normally heard. If possible,
use a tuner featuring a detailed signal meter and listen with
headphones. Ensure pure white noise (or weak troposcatter signals) are
heard on all clear frequencies. Repeat this procedure with the antenna
pointed Northeast, East and Southeast. This entire band "survey" should
minutes or less.
After this field test
is complete, you may identify one neighbour that is spewing
interference across the FM band, into virtually all of the empty
frequencies whilst the antenna is pointed in the direction of that
property. In all likelihood, the interference will also affect
reception in the lower bands, including analogue VHF TV channels 0-2.
Reception of AM radio broadcasts may be significantly impaired.
Ensure you locate the
antenna as far away from the offending property as possible. Remember,
your neighbour is probably oblivious that this is occurring, and has a
legitimate right to operate their household devices in peace. The onus
is on you - the listener - to locate the antenna in a proper "quiet"
location. The centre of your property probably provides the most
protection, but in the real world, this is often not possible.
Trying to hear a weak
FM broadcast through stubborn interference is a frustrating experience.
There is rarely a remedy to interference once it occurs. DSP Noise
Reduction devices, such as those manufactured by BHI (pictured) may
situations where interference poses a moderate problem.
Prevention is always
best! Find out your interference sources before you engage a
professional to erect the antenna. Once the antenna is up, moving it
because it is too close to a source of neighbourhood interference is
both costly and inconvenient. Sadly, I speak from experience.
Find out why your
FM reception is being ruined by modern electronics here.
information concerning sources of interference is available here
from an amateur radio perspective. Jim Brown has authored an excellent paper
provides solutions for interference into VHF and FM bands. Jim is a
qualified Electrical Engineer, Audio Engineer and amateur licensee.
Solutions include ferrite suppressors and in-line filters (both
Using a tuner that
permits fine-tuning in 0.01 MHz (10 kHz) steps such as the Yamaha
TX-9xx and T-8x series is very useful in situations where
interference is problematic. Tuning off by 10-20 kHz on
the Yamaha TX-930 will allow reception of stations otherwise masked by
overwhelming noise when tuned in on the proper centre frequency. For
example, tuning off to 92.28 MHz to receive interference-free ABC Local
Radio Coffs Harbor FM 92.30.
The ultimate FM antenna
If you have the space,
please consider importing a high performance FM antenna designed by
Körner (marketed by VHF Teknik of Sweden). Prices including air freight
are very reasonable compared to lesser
performing domestic offerings.
Peter's 15 element antenna is only 3.73 metres in length and 2.08
height. A typical eight element antenna is about 2.3 metres in length.
The photographs above show the antenna installation in July 2010. Full
assembly is required. Engage a professional to perform the assembly or
if you are really keen, set aside a full weekend and assemble it