10GHz is probably,
in the UK at least, the most popular of the amateur microwave bands.
It has seen some sixty years of development since the first
experimental contacts made by W2RJM and W2JN in the USA
during 1946. These two "pioneers" could not have known what was
to follow their 2 mile (3km+) contact! A year later, in 1947 the
world 3cm record was extended to 7.65 miles after a contact
between W6IFE/3 and W4HPJ/3. W6IFE is now the callsign of
the San Bernardino Microwave
Society, the oldest amateur microwave group in the world
and one with a fascinating
history of its own.
Even before that epic QSO,
the Radio Society of Great Britain had published a series of articles
in its journal, "The RGSB Bulletin" (or the "Bull" as it was known
to UK amateurs) during 1943, a period when amateurs were not allowed
to transmit signals as we had a thing going on with a man called
Adolf at the time! These articles, entitled "Communication on centimetre
waves" were followed up in 1947 with a booklet about microwaves,
"Microwave Technique". Its 54 pages cost readers 11 pence in present
day UK terms.
By that time there were
a few UK amateurs taking an interest in microwaves. Two of them,
Des Clift, G3BAK and G3LZ, began experimenting in 1949 and,
in January 1950, were rewarded with the first UK two-way contact
on the 10GHz band. Des (pictured below) eventually migrated to Australia
where he carried on his microwave activities, mainly on the 5.6GHz
band, until his death in early 2005. He was VK2AHC in New
South Wales at first but then relocated to South Australia as VK5ZO.
His 10GHz equipment for
that 1950 contact with G3LZ consisted of a mains powered klystron
transmitter/receiver and the path was just a "few miles" (actually
about 1.75 miles) across the Manchester Ship Canal in North West
England.Of just as
much interest was his use of 70cm for talkback. At that time
even the 432MHz band was for radio pioneers!
Another 3cm pioneer was
Jim Spragg, G3APY. Sadly Jim became a Silent Key in 1997
but his contribution to amateur microwave radio will be remembered
for a long time to come. On September 23rd, 1950, he made
contact with G8UZ over a new world record distance
of 12 miles. (Details of this contact can be found in the
RSGB Bulletin for October 1950, page 138)
The R.S.G.B Bulletin for
January, 1951, records Jim's next world 10GHz record contact,
this time with G3ENS/P over a distance of 27 miles.
This took place on 22 October 1950, just a month after his contact
with G8UZ. Jim's gear was a dual band affair, 23cm plus 3cm
and was mounted on the top of his saloon car. Separate, 5 element
yagi antennas were employed on the 23cm transmitter/receiver system
while an 18 inch diameter dish with dipole/reflector feed (waveguide
fed) radiated the 3cm RF. On 23cm, CV90 oscillators were used
with a klystron on 3cm for wideband FM . A common IF/AF unit
was employed on both bands. Simple crystal diode receive mixers
were employed on both 23 and 3cm. Most interestly for this writer,
Jim used the Alport Height location at IO93FB, near the town of
Matlock in Derbyshire for much of his UHF and microwave work. A
photograph of that location as it is today, 1035 feet above sea
level, with G3PHO/P in evidence, can be seen in the Photo
By the way, another page
in the same issue of the RSGB Bulletin mentioned above details the
70cm activity tests held in 1950. Reading the reports is very much
like reading those for the 10GHz activity days of the 1970s and
'80s, such was the state of the art on UHF in those days. G3APY
was in the forefront of this as well as experimenting on 10GHz.
The UK record on 70cm was only 161 miles at that time...dead easy
now of course, but a milestone in 1950!
In the UK, the 10GHz band
was exploited by a small group of dedicated enthusiasts who built
simple klystron transceivers, using wideband FM modulation.
The most popular klystron during the 1960's and 70's was the 723A/B.
( This was identical in appearance to the
3GHz klystron type 726A, shown below).
These were really designed to work best at around 9.5GHz but amateurs
found ways of "bending" them up to the lower 100MHz of the 10GHz band
(the UK had 10.0 to 10.5GHz available at that time). Power
outputs were in the region of a few milliwatts. The klystron was used
as an oscillator on both transmit and receive, the wideband FM modulation
being applied to its repeller. Unfortunately, fairly high voltages
(by modern standards) were needed, up to 300 volts or so, and
portable power supplies were usually of the 12v dc input/300v dc output
inverter variety. As a result, they often produced a distinctive whine
on the modulation! Many amateurs used directional couplers in their
equipment so that the klystron oscillator could be used as a receiver
local oscillator as well as a transmitter. Waveguide switches and
other items of waveguide 16 "plumbing" made these rigs bulky
and off-putting to non-microwavers! Frequently, a duplex arrangement
was used with a common IF of 30MHz or 100MHz (with bandwidths around
200kHz). One station in a contact would transmit, say, a signal on
10.100GHz and the station at the other end would set his local oscillator
on 10.070GHz (10.130GHz)to hear the signal in a 30MHz receiver. The
first station, also equipped with a 30MHz receive IF would hear the
second station at the same time. For initial signal finding, each
station would modulate the transmitter with a 1kHz tone. When the
two stations found each other the two tones would beat with each other
in an unmistakable manner! The 10GHz receive front end was, in most
cases, a simple diode (for example a 1N23E or similar).
In 1959, Bob
G3GNR and Don G3JHM, had their very first 10GHz QSO,over a 4km
path(later extended to 30km) between Worthing and Newhaven, in Sussex
They were using the "evergreen" modified 723A/B
on 10050 MHz at about 10mW o/p and their PSUs were two small rotary
converters running from 12V batteries. The receivers were single-ended
mixers with LOs fed by a 10dB directional coupler and NF measured
at 11dB! Both these operators were still very active
on 10GHz up to the late 1990s and are probably two of the longest
serving 10GHz ops, at least in the UK.
It was equipment of this
type that enabled the 150km "barrier" to be broken for the first
time in the UK, when G3RPE and G3ZGO made contact between
Dartmoor (SW England) and the Prescelly Mountains (SW Wales). This
distance became the yardstick by which the rest of us measured our
10GHz performance. The RSGB Microwave Distance Awards still recognise
that level of achievement .... easy now with modern narrowband gear
but quite difficult for simple wideband equipment of those days.
Dain Evans, G3RPE, who
wrote the first microwave column in the RSGB's RadCom magazine,
became chairman of the RSGB Microwave Committee and then RSGB
Microwave Spectrum Manager. Until his untimely death, he worked
unstintingly for the good of UK microwavers. He is remembered to
us all in the UK by the G3RPE Trophy, awarded to the leading
station in the annual 10GHz Cumulative
Contests, formerly run by RSGB and now by the UK MIcrowave
Americans put on the pressure..
In 1960, W7JIP/7
and W7LHL/7 achieved a two-way contact on 3cm of 427km. This
was a remarkable contact for that time and it stood as the
10GHz world record until 1976.The QST newsclip to the right
shows W7LHL/7 in action on Green Mountain, Washington. I'm
indebted to Jimmy Oldaker, W7CQ, who read this page
and forwarded the following interest email:
"I ran across
this in QST November 1960 and thought you might be interested
in it for your 10Ghz history page. Ernie W7LHL, is still active
on 10Ghz and I talk to him almost every morning on 75 meters
in a gathering of UHF enthusiasts. Ernie is presently building
equipment for 24GHz.I have a 10GHz beacon ...see my web pageat
and Ernie regularly
copies the beacon's 240mW signal over a 349km path from his
home, with mountain ranges between our two homes. This is
definitely not a line of site path."
Many thanks indeed
Jimmy for the most interesting piece of 10GHz history!
Diodes and new records...
During the mid 1970's the
Gunn diode appeared on the amateur market and revolutionised
the wideband scene. Power supplies shrank, the Gunns requiring a low
current supply of around 7 volts or so. Since the diodes were also
very small (a few millimetres long), 10GHz equipment became highly
portable and the UK saw what many Old Timers still regard as
the "Golden Age" of 3cm! Almost all active 10GHz amateurs in the UK
would operate from portable locations. The summer cumulative contests,
organised by the RSGB Microwave Committee became very popular and
the hilltops of North Wales, the Pennines, the North and South Downs,
as well as many other areas, "grew" tripods, dishes and 2 metre talkback
stations on a regular basis.
Here at G3PHO I
developed a compact 3cm transceiver based on a Gunn diode oscillator,
a 1N23E RX mixer diode and a small solid state 30MHz IF (with a
1.5dB NF post-mixer amplifier). This,
together with an 18 inch dish and short portable mast, an IC202S
2 metre ssb handheld with a quarter wave whip antenna and a small
12 volt "dryfit" battery, was frequently backpacked up some of
the country's highest mountains in the search of longer and longer
line of sight paths. Some of the photographs in the
Microwave Photo Album show this gear in use at that
Duplex operation was still
very much the norm, as in klystron days, but 10.7MHz IFs replaced
the 30MHz ones in many cases.
The limitations of the
line-of-sight path became a challenge to 10GHz operators...
studies open up the potential for real 10GHz DX...
Some excellent DX was worked
with simple Gunn equipment of this type. Operators such as GM3OXX/P,
GW3PPF/P, GW4BRS/P, G3RPE, GM8BKE (now G8BKE) and many others
made long distance contacts, during the 1970s, that would still
give pleasure to some narrowband operators today. The longest line-of-sight
path worked at that time was that between the summit of Mt. Snowdon
(North Wales) and the Cairnsmore of Carsphairn (South West Scotland).
At 245km it represented the best you could do in the UK without
enhanced propagation. (Your scribe repeated the
path in 1987) . Longer paths than this were worked, however, due
to the inquisitiveness of amateurs such as GW3PPF, who saw
the potential of the moist air ducts that often form over the sea.
He, and others, spent a considerable amount of time and money travelling
around the UK to establish the existence of these "super
refraction" paths, often hundreds of kilometres in length. In fact,
the longest path covered by this propagation mode during the 1970's
was a new world DX record (on the 14th August 1976) between Pendeen
Sands, Cornwall and Portpatrick in South West Scotland, a distance
521km, thus exceeding the W7's record of the 1960 period by
a handsome margin of almost 100km. For this remarkable contact G4BRS/P
(The Barry Radio Society) and GM3OXX/P used simple 10
milliwatt Gunn transceivers to small dishes (60 to 75cm diameter).
The signals were exchanged directly on 10GHz, without recourse to
prior talkback on 144MHz. The signals peaked 45dB above noise.......very
loud ones! A super-refractive sea duct was the means by which the
two stations were able to work well beyond line-of-sight with such
low power and wide bandwidth receivers. They had made eight previous,
separate attempts for this world record by the way!
World 10GHz records made
since, either on wideband (by Italians) or narrowband (by Australians)
have made use of this "super-refraction" propagation mode to exceed
even 1000km! (Present world record is now
The 1970's produced many "firsts"
for UK 10GHz operators.
The first GW to GM contact
took place in 1972 when GW3CKT/P worked GM8AZU/P (now
G4NNS). The QSO was a world record at the time, only to be exceeded
a few months later by GM3OXX/P. A photograph of the GM team of operators,
carrying the gear (including an 80cm dish) up the Cairnsmore of
Fleet, appeared on the front cover of Short Wave Magazine
a few months later and is worth seeing if only for a look at G8DKK's
The first G to PA contact
was made on the 3rd August 1975 by G8APP/P and PA0KKZ.
The former used a 20mW klystron while the latter ran just 3 milliwatts
to cover the 240km path. Both stations were again located at or
very near sea-level. This contact had immediately followed a one
way attempt by G4ALN, who used 10 mW to a DUST BIN LID
as an antenna!! G8APP/P was located at Walton-on-the Naze, a
site that has become famous in the annals of 10GHz in the UK and
one that is still used by the UHF/Microwave contest group
G0VHF. It is arguably the finest /P location in the UK for
working into the European Continent.
By the November of 1976
some 12 countries had been worked by G stations. The first GI
to GM contact was made in August 1976. Germany, Denmark, Norway
and Sweden were still awaiting contact.
Throughout the wideband period
described above, there existed a small group of British amateurs who
were developing crystal-controlled, narrowband systems for 10GHz.
Such systems usually consisted of a vhf crystal oscillator, with watts
of output in some cases, driving a chain of varactor diode multipliers.
The multiplier chains provided both narrowband transmitter RF (cw
and nbFM) as well as local oscillator drive for simple diode mixer
receivers. At this time there were no transistor devices available
that would work as amplifiers or mixers at 10GHz.
Perhaps the most well-known
team of operators at that time was the G3BNL - G3EEZ partnership.
Les and Alan both built remarkable (for that period) narrowband
systems that were used to establish UK records on all microwave
bands at the time.
Unfortunately G3BNL is
now a Silent Key and he is greatly missed by the UK microwave fraternity.
His name lives on in the form of the G3BNL Trophy, awarded
annually to a microwave amateur for expertise and innovation in
Another narrowband pioneer
in the UK was Mike Walters, G3JVL. During the period when
Gunn diode wideband equipment was very popular, Mike was experimenting
with image recovery, narrowband filter systems leading to the development
of what has become known as the "JVL RIG". This consisted
of a step-recovery diode multiplier (mounted in waveguide 16) driven
by a lower frequency crystal oscillator source.....typically 384MHz
at around 500mW. The multiplier produced a low power ( c. 5 to 10mW)
at 10224MHz which passed through a narrow bandwidth, waveguide filter.
This filter was the secret of the JVL rig's success, for its three
cavities were iris coupled and reduced the image signal to negligible
proportions. The filtered 10224MHz then drove a waveguide in-line
diode mixer to which a few milliwatts of 144MHz was applied and
the desired 10368MHz ssb/cw signal was then passed through another
three-stage, iris-coupled filter to produce around 1 mW at
the antenna port. The JVL RIG was therefore a complete transceiver.
As a receiver, it could certainly hold its own ,since, as a result
of the excellent image rejection, noise figures of 6 to 7dB
were possible with the "bare" diode mixer ............... and this
without a GaAsFET preamp in sight!
The following photograph
shows a complete JVL rig, built by Lyle, VK2ALU.
The 384MHz local oscillator
is lower left and drives a small amplifier at 384MHz into a multiplier
to 1152MHz (top of photograph). In this example 1152MHz drives the
JVL waveguide multiplier to 10GHz, The long waveguide section of
the JVL system is clearly visible in the centre of the picture.
Other circuitry show includes receive post mixer amplifier (at 144MHz
and send/receive changeover system).
This little rig enabled
many a UK amateur to taste 10GHz narrowband for the first time,
but unless you had a TWT amplifier, the 500 microwatt to one milliwatt
of RF output did not get out much better than the wideband rigs
of the day, although the writer did work several obstructed
paths with his JVL, paths that the Gunn equipment would not work.
Something was obviously
needed to raise the output into the dozens of milliwatts region.....the
G4DDK and G3WDG.....
During the mid to late 1980's,
a number of German designs for solid-state, GaAsFET-based systems
appeared in the UK. A commercial transceiver made by SSB Products
retailed at over £400 sterling and many amateurs thought the
dreaded "black box" had finally arrived on microwaves! However the
microwave bands do not attract amateurs with little or no interest
in home construction. The reverse is true, for the microwave
regions are a "magnet" for amateurs who have grown tired of the commercial
equipment approach to our hobby. A few SSB Product systems were sold
but the home constructor was spared the headache of making up his
or her mind whether or not to purchase one. Sam Jewell, G4DDK
was, at this time, developing a series of compact local oscillator
printed circuit designs for the 1 GHz region. In March 1987, the RSGB
Microwave Newsletter published the DDK001 design....."A local Oscillator
Source for 1152MHz". This was closely followed by a companion1 watt
amplifier, the DDK002. These two pcbs, once built up into working
modules, offered a reliable narrowband route through to the
23cm band and provided the basis of transverters for the higher microwave
It wasn't long before Sam,
G4DDK, introduced the DDK004 board giving 10 to 12 milliwatts out
at around 2.5GHz. This little gem was to have a profound effect
on the way 10GHz narrowband was to go in the UK for, at the same
time as Sam was doing his development work, Charlie
Suckling, G3WDG, was working on a 10GHz transverter system
that was to bring ssb/cw to all UK 10GHz operators. In fact he virtually
"killed off" wideband FM as the preferred mode of operation! Charlie's
designs use the G4DDK driver modules to feed a transmit multiplier/amplifier
module and a receiver, each using cheap and readily
available GaAsFET devices . They included RF amplifiers to provide
what was, in 1990, HIGH power (50 to 100 milliwatts) and low noise
receivers (around 2 to 3dB NF). The WDG 10GHz kits soon became the
most popular and widespread 3cm equipment in the UK. As if by fate,
a large quantity of cheap (approx. £2 sterling each!)
10GHz GaAsFETs became available on the surplus market, just as Charlie
was developing his system. The supplier, J.Birkett of Lincoln, and
the devices' code names "Red Spot" and "Black Spot" became by-words
in the UK microwaver's vocabulary!
These photos illustrate
some of the G4DDK and G3WDG microwave modules:
The G4DDK 004 source
for 2.4 -2.6GHz
A partially completed G3WDG001 unit (10GHz x4 multiplier/amplifier)
This unit is built on teflon
pcb and mounted in a tinplate box 11cm x 3.5cm x 3cm.
A basic WDG transverter
for 10GHz uses a WDG001 x4 multiplier/amp, a WDG002 receive converter
and a WDG003 transmit downconverter. The DKK004 source at 2.5GHz
drives both local oscillators. All that is needed for full transceiver
operation is a low power 144MHz transceiver such as the IC202 or
FT290, microwave coaxial relay and a +12 volt DC power supply. The
modules are constructed in small tinplate boxes and are fully connectorised
in SMA. The use of tinplate boxes allows very efficient shielding
and pcb mounting.
Charlie later added several
other modules to the WDG system, including a 1 watt PA and a sub
2dB HEMT receive preamp.
These kits and many others
(including designs for the 23cm and 13cm bands) are available from
the Microwave Components
Service, operated by Petra Suckling, G4KGC, the wife of
Charlie proved how good
his equipment was by making the very first UK to Australia EME
(Earth-Moon-Earth)contact when in 1995 he worked VK2ALU, Lyle Patison
of Wollongong, New Sout Wales, Australia. This historic contact
saw WDG equipment in use at both ends of the contact.
the early 1990's ...
A number of surplus M/A-COMM
10.5GHz data link transceivers arrived on the UK surplus market.
Nicknamed the "White Box", it sold for around £100
sterling, quite cheap for a 200mW transceiver! Dozens have been
modified by UK amateurs and they often form the heart of a home
or portable station and microwave beacons. Modification details
were already available from the USA, where the "White Boxes" appeared
in their hundreds, particular on the West Coast. Modifications were
also developed in the UK. G3WDG's WDG 005 receive preamp fits nicely
into the Box for example, and improved the "barefoot" ring mixer's
11dB NF to around 2 to 3dB. The WDG HEMT preamp can be added to
get down towards 1dB NF.
The "White Box" was the
basis of the writer's 10GHz system in
those days and is still occasionally used for both home and portable
late 1990's to early 21st century ...
The G3WDG/G4DDK systems
led to more and more HOME STATION operating in the UK. A
number of cheap (sometimes free!) 4 to 5 watt Travelling Wave Tube
amplifiers (TWTs) became available during the '90s. These were easily
driven by a couple of milliwatts. Higher powers were also around
with quite a few UK amateurs running power outputs in excess of
10 watts and one or two around 60 watts.
In the latter half of the
1990s, a series of excellent amateur microwave kitsets, including
complete transverters, oscillator/multipliers and power amplifiers,
came ontothe European market. These are produced in Germany by three
main companies: Eisch Electronics, Kuhne
Electronic (DB6NT) and Philip Prinz (DL2AM). They are all
stillgoing strong in 2005.
There's no doubt, however,
that Michael, DB6NT and Kuhne Electronics has changed the
face of amateur microwaves, certainly in Europe, if not the world,
as he now supplies both kits and ready made equipment available
from 1.2GHz right up into the submillimetre bands and all at an
affordable price and of excellent quality. Nowadays there must be
few active microwavers in Europe who have not at least one item
from the DB6NT "stable" in their shack! Indeed, The
writer's own equipment is based largely around DB6NT transverter
In the USA, the Down
East Microwave company has grown into that continent's major
supplier of amateur microwave equipment with many original US designs.
Today, in 2020,
in addition to the excellent German, UK and USA kitsets, there is
a wide variety of SOLID STATE power amplifier (SSPAs) easily
obtainable and indeed produced for the amateur microwave market.
Power levels of over 50 watts are available (at a price!)
on 10GHz while bands lower than 10GHz have seen the widespread availability
of surplus SSPAs from commercial radio links and abandoned defence
contracts.These power levels and home station operating have seen
the exploitation of unusual propagation modes such as rainscatter
and aircraft reflection, as well as troposcatter and ducting, being
used to work some very long paths
in the UK and over the sea to Europe.
10GHz narrowband power levels of 1 watt are now "de riguer".
In the UK at least, the 60 to 90cm, offset fed dish antenna(often
ex- satellite TV)is now the most popular 10GHz antenna and contacts
up to 400km are the norm. Some home stations work daily skeds over
this sort of distance and have 800 to m1000km+ contacts when tropo
conditions are good. During the monthly contest weekends, when activity
is at its highest,portable stations often work long distances on
10GHz narrowband, sometimes beyond 600km under apparently flat band
conditions! This is usually due to the exploitation of aircraft
In spite of the growth
of home stations, portable operation is still popular, as any Cumulative
Contest weekend will show.
propagation is now quite common on 10GHz and there are now a number
of UK operators equipped to make overseas contacts via the Moon.
The contacts have been a little "easier"(!)by the introduction
of computer software that not only keeps the large dish on target
but also sends the contact exchange details by datamode, often at
a level at the limit of, or even below, the human ear.
Today, the 24GHz band
is now going through a similar sort of "revolution" that 10GHz had
a decade ago. Narrowband and "high" power (3 watts)has
arrived at 24GHz......kits and surplus "boxes" are changing that
that's another story ....
10GHz may have
become "old hat" for some people but there is still plenty to do
there and room for more converts to microwaves......
WHY DON'T YOU TRY 1OGHz?
The writer wishes to thank the following for their help and information
in getting this article together:
Naylor, G4KLX, Bill Capstick, G3JYP, Des Clift,
VK5ZO, Lyle Patison, VK2ALU, Bryan Harber, G8DKK,
Jimmy Oldaker, W7CQ
1 January 2006)