See also the GM3VLB Multi-Band Inverted-Vee Dipole
the GM3VLB Mini-Delta
the SCOTIA Bandhopper Multi-Band
the SCOTIA Poor Man's
and the GM3VLB Expedition Equipment List
Most of the author's operating takes place either /M or /P, using homebrew antennas
ranging from his multi-band inverted-vee dipole to a
variety of relatively short verticals. His primary mobile antenna is a Webster
"BandSpanner", acquired second-hand, and free of charge, over forty years ago.
This antenna has adorned many different vehicles and is still in regular use on his
André believes that it is arguably one of the best mobile antennas ever produced and
rues the fact that the company appears to have ceased trading in the late 1960s. He will
happily pit the "BandSpanner" against any other commercial amateur mobile
antenna (some of which cost a small fortune), not only in terms of performance but also in
its ability to sit quite happily, hour after hour, giving no cause for concern, even on
European motorways at speeds sometimes well in excess of the UK legal limit . The author
finds it amazing that no other manufacturer has produced a mobile antenna of similar basic
engineering design, which performs equally well (with no coil-changing needed) on all WARC
bands from 10m to 80m. VK and ZL have often been worked on 80m on this antenna whilst
'early morning mobile' heading north to activate Scottish islands. [The lack of a remotely
comparable mobile antenna has recently prompted Andre and Alex GM0DHZ (winter
2006/7) to design and successfully test an innovative mobile antenna, the proto-type being
called the SCOTIA "Bandhopper".
Like the BandSpanner, it uses continuous tuning, but in a completely new and
ingenious way - details elsewhere].
The BandSpanner screws into a standard 3/8" UNF base, mounted level with
the lower edge of the rear windscreen and is held fairly rigidly in position by a plastic
"arm" to a single rear-mounted roof bar. A small ex-CB meter on the transmission
tunnel permanently monitors SWR A ratio of 1:1 is easily obtained on all bands at
resonance, by adjusting the length of the telescoping high-tensile stainless steel whip
top section (which has band markers etched into the steel). Fine tuning is by means of a
home-brew toroidal base-matching transformer mounted inside the tailgate. This provides
twelve impedance transformations (although, in practice, six would be adequate) in the
range from a few ohms to 50 ohms, selected by a switch whose shaft protrudes unobtrusively
through the black plastic moulding housing the tail-gate lock. André does not believe in
using lossy ATUs if they can at all be avoided. With resonant antennae in a /M situation,
they should be totally unnecessary. At best, they provide under-carpet heating. With the
afore-mentioned method, band changing or tuning takes place in moments. Good earthing is
essential, especially in the above estate-car situation where the tailgate hinges and
locking mechanism normally provide the only earthing. Additional substantial, flexible
copper braid is used for proper bonding (as he had to in the past, when antennae were
often mounted on metal bumpers secured to the vehicle body by rusty bolts / brackets).
There is virtually no noise pick-up and such noise as there is, is easily removed by the
excellent noise blanker on the Kenwood TS-50S.
However, the primary purpose of this article is to show that simple yet efficient and
effective vertical antennas suitable for either /M or /P, can be home-brewed with minimal
cost and effort. When André first became involved in activating Scottish islands, amateur
rallies were a good source of 8' ex-CB fibreglass whips, which were easily converted to
single band, centre-loaded amateur band antennas. All of these easily equalled or
out-performed miscellaneous well-known commercial mobile antennas acquired or tested at
various times, and which, as a result, have all long-since been disposed of.
Anyone contemplating the installation of a mobile antenna would be well advised to read
the articles by Mike Grierson G3TSO, which appeared in Electronics Digest (winter 1987)
and RadCom (February 1988) and in which he challenges some popular myths. These articles
were clearly based on solid research and experiment and GM3VLB considers them to be
definitive articles on mobile antennas. Many, including himself in the past, have put too
much faith in the Mobile Antenna section of the ARRL Handbook - this seems to never have
been updated and has been reproduced word for word, from revised edition to revised
edition, and presented as gospel for half a century or more! Furthermore, the information
is very limited (as indeed is that in the RSGB's Radio-Communication Handbook). It is
worth quoting part of the last sentence in G3TSO's RadCom article: "Commercial
antennas vary from good to bad, and in general will only work as well as a home-made
antenna . . . "
In contrast with the Webster "BandSpanner", the principal disadvantage of
typical centre-, base- or indeed helically-loaded "whips" such as the
"G-whip", "Hustler", "Pro-am"-type antennas, is that they
are generally designed for single-band use. This results in much screwing or unscrewing of
whip sections, loading coils or "resonators". What was needed was a single
vertical antenna that could not only be mounted either on the vehicle or at ground level
on a simple mount, but would be capable of efficient radiation on all WARC bands from 10m
GM3VLB's design of such a relatively short vertical has gradually evolved over the last
10 years or so. It has been thoroughly tested, with considerable success, in locations
that include nearly 160 Scottish islands, half a dozen IOTA islands off British Columbia,
and various locations in the Pacific, the Yukon and the North West Territories. The Mark 1
version was even used by the author's son VP8NJS at Patriot Hills Base in Antarctica over
the millennium, and a more recent version, which telescopes from 4m to 70cm (thus easily
fitting overhead lockers on aircraft - prior to '9-11') was used as the only
antenna on the 2001 round-the-world trip which included OC-121, OC-016 and OC-019.
It was used not so long ago in VE3 by Jack, G0SNV, and was again used by GM3VLB on
OC-121 in 2003 and again as a "back-up" antenna on his 2005 expedition to the
Pacific and VE7 IOTA islands with Alex GM0DHZ and son Niall VP8NJS.
The basic design centres on the use of a 4-section, 4m-long fibreglass fishing rod.
These were originally purchased in French hypermarkets (very cheaply, at around £1 per
metre for the shorter rods), but are now available in the U.K. The SCOTIA team would
recommend Sandpiper Aerial Technology for both quality and value). GM3VLB has also
produced various similar models for more efficient use on the LF bands, again using
fibreglass rods ranging in length from 5m to 11m!
A common feature has been the provision of a
3/8" UNF bolt at the bottom of each "fishing rod". This allows the antenna
to be screwed into either a vehicle mount or a ' ground mount'. The 4m version has also
often been used overseas, roof-mounted on stationary rental vehicles, using a 'mag-mount'
modified to accept 4 radials draped over the vehicle.
All antennas can be mounted on the tailgate
mount of the GM3VLB's Ford Sierra Estate (even the 11m high 160m version, although it has
not yet been used in anger, and certainly not /M!). As the majority of Scottish
islands are inaccessible to vehicles,earlier verticals were mounted on the ground-mount
This consists of a small base plate supporting a CB-type 3/8" UNF socket,
a BNC socket and a brass wing nut to attach the radials. Using whatever ' plumber's
hardware' is to hand, this is supported by, but insulated from, a ground-post about 50cm
long made, in the André's case, from old tank-whip sections (light but strong) with a
pointed end (e.g. a nail) to ease insertion.
More recently, the 5m "Islander" has become the
mainstay of all island activation.A recent development is a clip-on baseplate with
provision for direct connection of the coax feed-line and the radial system. The vertical
can be mounted directly on the ground, either using a "ground-spike" as
above, or held in place by a simple, triple guying system.
Although seldom required, a small, home-brew, base-matching transformer is available,
mounted in a small ABS plastic box (75 x 50 x 25mm) with appropriate BNC plugs and
There can be not the slightest doubt that one of the most useful items of equipment
ever produced for the antenna experimenter is the MFJ-259 type of antenna analyser , one
of which accompanies GM3VLB on ALL expeditions. As this is still a relatively expensive
item for many amateurs, GM3VLB has recently designed an ultra-simple/cheap version
(based on an original design by Jim Tregellas VK5JST) which it is hoped to describe
shortly in RadCom and on this web-site.
GM3VLB also has available a very small,
homebrew, T-match ATU consisting of two 200pF trimmer capacitors (modified to have small
1/4" shafts) and a switched toroidal inductor. This can be used, if necessary, to
match an antenna that may be slightly off resonance. It was used for example in the
N.W. Territories (VE8/GM3VLB) when, with an outside temperature of -20°C or lower, it was
found that the 4m version, already adjusted for resonance on 15m, could also easily be
tuned for use on 10m, 12m, 17m and 20m without having to venture outside!
As stated earlier, longer versions have been
built, but most designs have centred on the 4m fishing rod. The original Mk1 version used
one 'fixed' coil for 20m, and two separate 'plug-in' coils for 40m and 80m, whilst some
later versions use a tapped loading coil that was wound on a length of 32mm diameter
yellow (or blue) plastic water/gas (?) pipe which slides over the fishing rod, to sit on
the first joint.
A wire, bonded to the outer tube (with two-part epoxy resin, fibreglass resin or
similar), connects the 3/8" UNF screw to the base of the coil. This coil (107 turns
of 20 SWG enamelled copper wire) has two taps, one at 72 turns (which, when shorted,
leaves 35 turns for 40m) and the other at 100 turns (which, when shorted, leaves 7 turns
for 20m). The whole coil (107 turns) is used on 80m. (The exact number of coil windings
will obviously depend on the precise diameter of the coil former used).
The radiating element was initially a length of very thin (1mm), 7-strand
Teflon-covered wire hanging from the top of the rod and plugged into the top of the
loading coil. This was used on all three bands. Other shorter wires could also be used,
with no loading coil, to resonate on the 10, 12, 15, and 17m bands, and with the 40m coil,
on the 30m band.
More recently, the coils have been wound directly onto the top of the outer base
The radiating element can also be made to be continuously "adjustable" by
using bare, fairly flexible, thin multi-strand wire wound in place of the steel tape, onto
the reel of a modified tape measure. The modification includes a simple but efficient
sliding contact arrangement. By using bare wire, this eliminates the inductive effect one
would have with a reel, or coil, of insulated wire. With this arrangement, and the
MFJ-259, band changing becomes extremely simple and accurate. A mini-pulley system is used
to carefully pull the wire "back up" the fishing-rod when going down in
The most recent design now uses a 5m fishing rod. The silver-plated paxolin-mounted
coil was salvaged from an ex-MOD 'roller-coaster' unit and modified with plastic
end-plates, with holes cut to allow it slide over the fishing rod and thus sit at the top
of the base section. Some EMC 'finger-stock' (obtained at an Amateur Rally) was bent and
formed into a complete 'ring', which slides up and down the coil, shorting out a selected
number of turns in the process. The 'tape-measure radiator' plugs into the top of the
coil. A green (more UV-proof) soda drinks bottle (also with a Canadian connection !) is
adapted to keep the whole assembly dry.
Yet a later 5m version uses a small home-brew roller-coaster type coil which
allows rapid tuning of all bands from 10m to 40m. An additional fixed coil wound
on the rod's outer casing, provides the additional inductance needed to cover the 80m
band. More recently, and as described elsewhere, the 5m "Islander"
has been introduced. This uses a novel continuously adjustable coil (similar to, but
considerably smaller than the ex-MOD version above), and again covering 10m to 40m but
also the whole 80m band using a plug-in additional coil.
As with his island multi-band inverted 'V', GM3VLB uses an approximately 45' length of
50ohm RG58 coax that, after correction for velocity factor, is a half-wavelength on 40m,
two half-wavelengths on 20m, three on 15m and four on 10m. Previously, 4 radials
were used. The radial system consised of two pairs, each pair connected to a U-shaped
spade terminal clamped by the wing nut on the base-plate. They were made from 5-way
computer ribbon-cable, trimmed back to be a 1/4 wavelength long on each band from 10m to
20m. The same radial system was used on 30m, 40m and 80m and in most situations appeared
to work satisfactorily, although the preferred antenna for these bands remains the GM3VLB's
Multi-Band Inverted-V described on this site and elsewhere (e.g. RadCom, March/April
2005). It does however require a certain amount of space - not always available.
Just as, in GM3VLB's opinion, Mike Grierson G3TSO has made a significant contribution
to our knowledge of mobile antennas, then so has the work on vertical antennas by Ralph
Holland VK1BRH ("Short
Vertical Antennas and Ground Systems", Amateur Radio 1995) and that of Kenny
Silverman, K2KW, and his team. The extensive work of the latter can be seen on his web-site, in particular "Verticals for
Contest Operations" (CQ Contest Magazine, March 1998) and "DXpedition Antennas
for Salt water Locations - A Study on 20m Antennas". Both works are examples of
research at its best.
GM3VLB has studied the findings of these two independent groups and feels that they
reach several similar conclusions that he now tries to summarise:
1. Ground-mounted radials lead to very much reduced efficiency
A significant improvement in efficiency (from almost zero up to of the order of
30%) has been noted for heights above ground as low as 0.005-lambda and up to 0.05-lambda.
In recent years, GM3VLB has increased the length of his original ground-spikes and/or the
position of his base-plates, to allow the radials to be raised to 40cm or more above
ground, representing approximately 0.005-lambda on 3.7MHz and 0.04-lambda on
28MHz).Garden canes with nails embedded at one end, are used to support the ends of the
radials. Whilst no detailed comparative tests have been carried out, we have a very strong
feeling that these "raised radials" have indeed given better
2. Large numbers of radials are unnecessary
K2KW and his team have primarily used only two radials on their CQWW winning
verticals, even on 160m. Here again, the SCOTIA team have not carried out detailed tests,
but have adopted the principle that there is little or no advantage to using any more than
two radials, the same two radials being used on ALL bands. Whenever posible, these are
mounted at 180 degrees to each other.
3. Short verticals, ground-mounted by the sea, can out-perform
full-size mono-band Yagis
For angles of radiation below the so-called pseudo-Brewster angle (~12º), the
sea-reflected waves are in phase with much of the "direct" waves, thus giving
rise to reinforcement. This results in appreciable gain at low angles over the Yagi, which
even if several wavelengths high and multi-element, has a relatively deep null at such low
radiation angles. In practice, an expedition-type multi-band Yagi is unlikely to be
mounted at a height greater than 1/2-lambda, even on 28MHz, resulting in the angle
of radiation of the main lobe being above the pseudo-Brewster angle (in fact, over
certain paths, K2KW reports that on ". . . many occasions . . . a signal was S-9 on
the verticals (on the FT-1000-MP) and S-0, and almost unreadable, on the horizontal
4. Shorter radial lengths may be adequate
The effect of radial length is less clear but one interpretation is that short radials may
be satisfactory for short verticals. Radial lengths in the range 0.1-lambda to
0.15-lambda are suggested, with 0.25-lambda offering little advantage,
except perhaps with 1/4-lambda radiating elements. It had been the intention to
carry out comparative tests, but once again, considerable experience with a single pair of
short radials tends to confirm the "short radial" idea. A 0.2-lambda
radial on 14MHz for example, will be approximately 0.1-lambda on 7MHz. It will be
0.4-lambda on 28MHz. It must be said that as conditions on 10m have been very poor
since we implemented the "short twin radial" concept, we have not been able to
thoroughly test the performance of radials longer than 0.25-lambda.
Indeed, Alex GM0DHZ had some difficulty (during his pre-3V8SS expedition tests) tuning a "Traveller"
using 0.4-lambda radials. Maybe we need to do some further tests before 10m
begins to open up again.
5. Distance from the sea/land boundary affects gain
There is evidence of an increase in gain of about 3dB as the vertical antenna is moved
back to about 0.25-lambda from the sea/land boundary. At 0.5-lambda the gain
drops to -2dB, rising again to +2dB at 0.75-lambda No figures are given for greater
distances, but in terms of choice of site, the interpretation is obvious (even taking the
tide into consideration, operating close to a cliff-edge above deep water, would seem
The proof of the pudding
In 1997, the 6Y4A CQWW CW team, using ONLY verticals, narrowly missed the N. American
record with their claimed score of over 31 million points! The team subsequently operated,
not only with great success as KH5K from Kingman Reef, but also more recently from Jamaica
Although the results obtained with the various versions of the GM3VLB multi-band
vertical have always been extremely gratifying, despite the fact that the radials were
initially always simply laid on the ground, we have now adopted the "raised
radial" technique. Whilss we cannot irrefutably prove the results now
obtained are better, we have a strong feeling they are - they are certainly no worse. With
Andre's back-ground, he appreciates scientific method, but regrets to say that
once on an island, the high QSO-rate takes priority over setting up a proper antenna
test-site! The intention is always there, but basically, if we are being called, the
antenna is working!
We should perhaps admit that there have been one or two occasions when, inexplicably at
the time, it proved virtually impossible to load up the vertical antenna on the 80m band.
One instance was on Isle Martin (CN31). On that occasion, the MFJ-259 analyser was then
not yet available, but it was found that several "temporary turns" added to the
loading coil, allowed some power to be radiated. K2KW reports similar problems. If K2KW is
correct, then raising the radials might have solved the problem. More recently on Uyea
(SI24), serious de-tuning on 80m was eventually put down to unavoidable proximity to a
large corrugated iron shed, as a few hours later on the next island, the same antenna
behaved perfectly normally!
It would seem the advice is simple. When operating /P from islands, forget about
climbing to the highest point. Forget about cumbersome Yagis, rotators, amplifiers etc.
Select a site as close to the sea as possible, ideally surrounded by water (Kingman Reef
would seem ideal!) and use a vertical (0.25-lambda or less) with a couple of
radials, preferably raised and no longer than the radiating portion of the antenna.
Looking back, GM3VLB now realises why certain sites have provided nothing short of
outstanding results. In all cases, they were either the ends of long piers or narrow spits
of land jutting out into the sea. Next time you are /M on Jura, try the end of the pier at
Craighouse, or the one on W. Burra in Shetland, or at Broadford on Skye - or the many
other similar sites available in Scotland. Frequently in the past, André has found that
his multi-band verticals performed better when vehicle-mounted than when
ground-mounted. Could this be because the vehicle body is in effect a raised radial
system, whereas he has was always used to laying his radials directly on the ground?
GM3VLB recently acquired a 'monster' 11m long roach-pole. If a 4-metre rod can be used
effectively on 80m, might an 11m one offer reasonable performance on Top Band? After all,
many "mobileers" obtain quite pleasing results on this band with the ubiquitous
"8-foot loaded-whip". Noting that a recent CQWW CW 160m contest was imminent, a
makeshift support was crafted, allowing the 'monster' to be attached to the fence between
his gable-end and that of his neighbour. For most of its length, the rod was less than 3m
from both gable-ends. A temporary "roller-coaster" type coil was
suspended at the base of the rod that was about 2 metres above ground level. Following
K2KW's suggestions, only two radials were used (each about 10 metres long, the same length
as the vertical section), one running to (and finally down) a 2-metre pole at the pavement
end, the other running along, and in contact with, the gable-end wall. Both were over
tarmac - hardly the ideal DX antenna!
The operation was spread over 3 short sessions, one early on the Saturday morning, and
one on each of the Saturday and Sunday evenings, and totalling about 8 hours. The object
was to contact as many countries as possible on 160m without recourse to the DX-cluster. All
"new ones" were to be found by listening (as we used to do in the old days!!).
The station was a Kenwood TS140-S, a mini-ATU and home-brew keyer. Output power was less
The conditions did not appear very good, the same two-dozen or so "big guns"
being heard each "session". A total of 57 QSOs were made in 26 different DXCC
countries. No doubt some, with their sky-high monster antennas and their kilowatts of ERP,
will think this is pretty pathetic, but André was very satisfied (back in the 60s and
70s, it took him years, even as 5Z4KL, to work 26 countries on 160m and 3 years to make
WAC 160m!). The pleasure was all the more when on the Sunday, Alex GM0DHZ (his regular
island partner) informed him that the "SO6Y" which he had got "first
call" and thought (in his DX ignorance) was Poland, might be Western Sahara! Hearing
that station make frequent, unanswered, lengthy CQ calls on the Sunday evening, GM3VLB
called and worked him again! 7 other countries (including the USA and a UA9) were also
heard but not worked. Next time this antenna is tested, it will be under island
conditions. GM3VLB has high hopes that this very simple, very light, very easily erected
160m vertical will then give an even better account of itself.
In 2003 André activated OC-121 and OC-019 again, prior to teaming up with son Niall
(VP8NJS/GM6GMZ) and friend Alex (GM0DHZ), to activate several VE7- Islands / NA- Groups.
Despite extraordinarily poor propagation, the vertical antennae used on the expedition
worked well. However, there remains plenty scope for further experimenting with these and
other antennas. Please look for us, especially on 160m and on CW, which Alex intends to
give a bigger airing to in the future.
Details of all known intended activity
will be posted on this web-site, or via e-mail via our extensive mailing lists (if you
wish to be added, please e-mail
In the meantime, please feel free to contact him regarding any aspect of
these and other antennas described elsewhere (see the links below), and
also for details of any particular item of associated home-brew
See also the GM3VLB Multi-Band
the GM3VLB Mini-Delta
the SCOTIA Bandhopper Multi-Band
the SCOTIA Poor Man's
and the GM3VLB Expedition Equipment List