This page is
intended to show that you do not need large amounts of RF power or massive
antenna arrays to work stations far away.
Here in the UK the maximum RF
power permitted without a special exemption for 'Full' licence holders is
400 Watts, that is nearly equivalent to a single
bar of an electric fire! In some Countries they permit an even higher maximum of
The maximum power I have ever
used for SSB speech on HF is 100 Watts, although
for many years now I use nothing more than 50 Watts as that
significantly reduced for me cases of RFI breakthrough, TVI etc. This
50 Watts is
the maximum permitted power level for 'NOVICE' licence holders and is plenty
enough for all of my needs too.
I have in recent years used the
PSK31 data mode on HF in preference to Speech and
use an even less 5 or 25
QRP Low Power is defined
usually as using 5 Watts or less and this is what I
am going to talk about on this page and provide you with some of my experiences.
If you cannot see the full
index shown on the left edge of your screen, please go to my main page athttp://www.qsl.net/g0isw
Firstly, on VHF and using the
(2 metres) band you will find that your height above ground level (AGL)
and a clear unobstructed line of sight (LOS) path can permit QRP level
transmissions to travel significant distances. I live on the edge of the
Lake District National park and often carry a handheld transceiver with
me. I have managed to easily work stations on the Isle of Man (GM) and
as far away as North Wales (GW), just using the handheld and its own
Your antenna height above sea level will affect how far
your signal can travel, try the
Line of sight calculator by G4VWL
to see for yourself how far your signals can travel from home via conventional
line of sight propagation. Don't be
concerned that you do not live at a great height above sea level! This
will only affect your ability to work greater line of sight distances
to a maximum of 100km, even more important is your ability to have an
unobstructed view of the horizon. Believe me it is better to be located
in Norfolk than amongst the valleys of the Lake District, from a VHF DXer's perspective.
Different propagation modes enable VHF/UHF signals to travel further than
because they are reflecting your signals from different heights, above sea
level, in the Earth's atmosphere.
takes place below
height (Mt. Everest is by comparison
high), whereas the majority of
Meteor Scatter takes place at
90km altitude and
Sporadic Escan be up to
110km height, allowing much greater distances to be achieved.
height asl, where the signals are trapped between layers of hot and cold air (temperature
inversion) and if over a good calm sea path may extend for huge
distances. Contacts between Scotland and the Canary Islands on
have been achieved this way.
Auroral signals shown to typically achieve a lesser distance than
Meteor Scatter even though the reflection takes place at a greater height
in the Atmosphere? They do actually travel further reflected off the Auroral
curtain near the Arctic and back again, but the receiving station may be a lot
closer to you in Europe.
The International space Station and the
Space Shuttle are both over
the mode by which most of your local 144/432 MHz
simplex conversations will be made, either direct to stations or via
antenna height above sea/ground level and visible radio horizon distance. Line
of sight (LOS) distance can be increased with height or decreased by
obstructions such as mountains, buildings etc.
of sight is the direct free-space path that exists between two points. Using
binoculars on a clear day, it is easy to determine if visual line of sight
exists between two points that are miles apart. To have a clear line of
sight there must be no obstructions between the two locations. Often this
means that the observation points must be high enough to allow the viewer to
see over any ground-based obstructions.
obstructions might obscure a visual link:
features, such as mountains
The curvature of
other man-made objects
any of these obstructions rise high enough to block the view from end to
end, there is no visual line of sight.
that can interfere with visual line of sight can also interfere with radio
line of sight.
But one must also consider the Fresnel effect. If a hard object, such
as a mountain ridge or building, is too close to the signal path, it can
damage the radio signal or reduce its strength. This happens even though the
obstacle does not obscure the direct, visual line of sight. The Fresnel zone
for a radio beam is an elliptical area immediately surrounding the visual
path. It varies in thickness depending on the length of the signal path and
the frequency of the signal.
shown in the picture above, when a hard object protrudes into the signal
path within the Fresnel zone, knife-edge diffraction can deflect part of the
signal and cause it to reach the receiving antenna slightly later than the
direct signal. Since these deflected signals are out of phase with the
direct signal, they can reduce its power or cancel it out altogether. If
trees or other 'soft' objects protrude into the Fresnel zone, they can
attenuate (reduced the strength of) a passing signal. In short, the fact
that you can see a location does not mean that you can establish a quality
radio link to that location.
There are several
options to establish or improve the line of sight:
antenna mounting point on the existing structure
new structure, i.e. radio tower.
the height of an existing tower
different mounting point, i.e. building or tower, for the antenna
Your LOS signal, which can be blocked by
high terrain can sometimes be diffracted or bent over the top of the
obstruction, particularly in mountainous areas if the top of the obstruction
is 'sharp', hence the term 'Knife-edge diffraction'.
I live in a mountainous area and have
experienced a few instances where contacts have been made with stations that
should have been totally obstructed by high mountains in between.
more serious VHF DX though, you will need a multimode transceiver capable of
Single Sideband (SSB) transmissions and you will also need a horizontally
polarised beam antenna, which has significant gain compared to a dipole.
Probably the best and most commonly used is a Tonna 9 element beam. Ideally you
will also need a rotator so that you can point your aerial at the station or
Country you are trying to work/hear.
your multimode radio in Upper Side Band (USB) and calling initially on
MHz it is possible
daily to have speech contacts in the region of
propagation, depending on where you are in the UK you may be able to have
regular QSO's with amateurs in Europe.
the months of
August you may be very
lucky to experience a rare form of propagation called 'Sporadic
E', which can appear from nowhere and allow you to work vast distances.
Distances achievable are in the region of
have managed to work North Africa,
on 144 MHz
USB with only
and a small Log Periodic aerial (equivalent to a 4 element yagi) via this mode. A distance of
Whilst I used more than
I am convinced I would have managed the contact using QRP, it was just calling
at just the right time that resulted in me being successful, the power was not
so important and the signal levels for Es propagation are typically
59+ in each
direction, unlike all other modes.
Many Radio Amateurs have reported success
working both the International Space Station and
Low Earth OrbitingFM satellites using only handheld QRP
on 145 MHz
uplink and 435 MHz FM downlinks using a portable Arrow
II antenna. Click on the images below for some YouTube video clips
demonstrating this antenna. K7AGE,
in particular, seems to have a wealth of experience and videos on this
AGW packet engine software to give me the ability to transmit and receive
packet without a TNC and only using my computer soundcard. The
UISS software works in tandem with AGW and is a very useful tool for working
the ISS or digipeating through it.
See the image below, showing my QTH and
those of other successful Hams,
displayed in real-time, as heard by the ISS. The ISS position is shown and
where it will be in 5 minutes later (ISS-5).
I have had great success with my
Yaesu FT-817 HF multimode radio from beaches in
France using 5 Watts of RF on SSB speech and a
Miracle Whip antenna, working around Europe easily. I've also managed to work
the USA and South America too.
From home with slightly
larger aerials I have had even more success with QRP.
you already use your computer soundcard for data modes such as
you can use
WSPR (Distant Whispers) software
by K1JT, with
your existing hardware. The software transforms your station into an automated beacon and weak
signal reception hub.
You will be amazed how far your low power signals
can be heard and can see maps in real time. Great for antenna
experimentation and comparison too. There is even a searchable
WSPR spots database.
Below is an
computer screen grab using
WSPR software and taken from the
showing my 5 Watts QRP signals on
on Friday 3rd September 2010. Comparing this with my HF vertical aerial I can
see immediately better results for working the nearby Continent, which is what
I would expect.
'spot database query'
research tool, I can enter search parameters for callsign, band, number of
spots, and select the order they are displayed in such as timestamp, distance, SNR, km per Watt etc.
example below, dated from late 2010, I have selected 5 spots for my signals on the
band and placed them in longest distance order. I can see that my best
distance was to W3HH
and I can also see that all 5 spots were using my Sandpiper MV6+3 HF vertical,
as I only put up my
Racal Military tactical adjustable wire dipole on 1st September 2010.
Using spot archive (no
automatic refresh). 5 spots:
Query time: 0.004 sec
on 14 MHz
it is a different story, as I can see from the results shown below that my
two best distances were both on dates after 1st September 2010, when I was
Racal Military tactical adjustable wire dipole. Obviously you have to take
into account the variations in propagation, but this software does allow
you to compare antenna system performance if tests are carried close in
April 2011, I have returned to using
my Sandpiper MV6+3 HF vertical
as my primary aerial, as it will tune up on 50 MHz
for the Sporadic-E season in April-July, whereas my dipole won't.
Below is a map showing my QRP 5W 10 MHz WSPR
signals reaching the USA using a
Sandpiper MV6+3 HF vertical on
the morning of 6th April 2011.
Below is a map showing my 5W 10 MHz WSPR
signals reaching VK1UN
in Australia using my 2m tall
Sandpiper MV6+3 HF vertical on
8th April 2011.
Solar Flux for
this day is shown as 112. I have since been informed that due to an OTHR
system that the 10 MHz band now suffers from
severe QRM in Australia, so I will be trying 14 MHz
The WSPRnet database shows my 10.140195 MHz signal to
VK1UN in Australia had a
SNR of -28 dB and
the distance was until recently my best ever at 16947 km.
The WSPRnet database shows my best ever DX signals
have all occurred so far on the 10 MHz band and I can
tell by the dates that all were achieved using my
Sandpiper MV6+3 HF vertical,
rather than my dipole. I would expect this due to the low angle of radiation
from the vertical aerial which is better suited for long distance (DX)
Here below is my 10 MHz
signal being received on 16th April 2011 by the man himself
Taylor, the author of WSPR and WSJT software. I owe a great debt of
gratitude to Joe as his software has transformed the experimental side of
the hobby for me, making Meteor Scatter immense fun and QRP HF too!
After my Summer
holidays I have experimented again with WSPR, this time looking at the
14 MHz band and QRP level 5 Watts of RF. Shown
below is a screen grab for the morning of 12th September 2012, using my
TS-2000 transceiver and Sandpiper MQ6+3 HF vertical antenna, showing where my weak signals
have been heard.
Here are the corresponding signal
levels, VK3GMZ heard my 5
Watts signal at -25 dB and at a new
record distance for me of 16,981 km. In reality
due to the height of my 3rd floor house radio station and the distance to
the garden ground level where my antenna is situated, with only a long run
of lossy and thin RG-58 coaxial cable, I
wouldn't expect much more than 3 Watts being
In October 2011 I started to look at other HF data modes and tried
just to see what band conditions were like. Wow!
Shown below is a screenshot using
of stations heard by me on
mode, on Tuesday 18th October 2011.Amazing conditions considering we are
only a little way out of sunspot minimum and already DX is visible on 4
Continents all at the same time.
below is the accompanying
JT65-HF software screen grab showing
in South Africa,
and several US stations.