Single-Side-Band Techniques at Microwave Bands, Chapter 4
@ OK1AIY
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The 4th Generation 10 Ghz Transverter
In the nineties of the last century, a stormy progress in technology happened
in OK and OM region on frequency bands around 10 Ghz. Some progress was
happening in satellite TV reception, and in terrestrial communication for data
transmission. Individual channels with 18 Mhz bandwidth, also in the amateur
band (Channel No.2) do not make us happy even when the allowed power output is
only 2 mW. As the data-volume demands are growing, new equipment is being
developed and the „old“ ones are discarded. Such discarded devices are
treasured among radio amateurs. The devices are mostly connectorized blocks
which can be used directly or modified for our designs. Mostly such devices
are used in 23.5, 26 and 39 Ghz bands, also at 10 Ghz there are components
available which would be difficult to make at home. Companies which made such
welcome devices are the Czech ALCOMA, in Poland, Norwegian NERA (powers up to
10 W at 3 cm). In 1990¨s a massive update took place in Italy and some
Telettra devices ended up here. The new technology brings newer, more
developed, and sometimes even „charming“ components.
In 1999:
From DB6NT workshop a new „hit“ appeared, the new MK2 transverter, made on a
single small board. Some necessary parts were already available: once I
received the PC board, I coud not resist and started the new 4-th generation
transverter. Following Pavel¨s design, (OK1FRU, an ALCOMA designer), I used a
circulator and waveguide/coaxial transition. The power path from the final
stage to the antenna avoids the antenna relay. Therefore there is no danger of
„frying“ it which often happened with 10 W RF power. The antenna relay is
connected in the receive path, to connect a load resistor to the circulator,
so it converts it to an isolator. A sequencer takes care of a proper TX
timing . A transverter is shown in Figs. 113 through 115, the block diagram is
in Fig.112. In 1990¨s, many designers started developing various versions of
transverters. This huge effort is worth of presenting some designs for the
readers. As the information was coming over time, no historical order was kept,
Figs. 116, 117.
Fig. 112 Block diagram of a 3-cm transverter, 4th generation, OK1AIY
Fig.113: Front panel view
Fig.114: Transverter installed in an enclosure
Fig.115: Rear view on the transverter with a horn antenna attached
Fig.116, 117: Mila¨s transverter, OK1UFL, from 1991. It is built of a R-100
waveguide section. This simple and very well working solution was used by
several other ham and will be described in detail in a chapter devoted to 6-cm
band. This transverter had already used a circulator and was gradually
improved as was possible ( views from the front and top)
More designs on 10 Ghz (3 cm) transverters
Figs. 118 and 119 show nice designs of transverters in a waveguide. Simplicity
is the advantage, no need for then rare Duroid substrate or GaAs transistors.
Transverters were larger and heavier than today but this was not a problem
back then. Other Figures, 120 and 121, show a transverter design from 1991 by
Aleš, OK1FPC. It utilized Duroid substrate, 1.5 mm thick (from the late USSR)
. Standa, OK1WDR used it for many nice QSOs, Fig.122.
After 25 years, new modern components and technologies arrived. Fig. 123 and
124 show a recently built transverter by OK1FPC. Its professional design
quality is top notch without doubt. Figs. 126 and 127 show a transverter built
on a domestic FR4 substrate made by Synthesia Semtín. This was an important
development that allowed to reduce costs and a wider amateur public could
afford it. The design by Jarda, OK1TAY, was already using the most-modern
components, several units were even manufactured at NESKOM company in Benešov.
It was described in PE-AR ELECTUS magazine in 2000.
Fig.118: Transverter by Eda, OK2BPR, in a waveguide
Fig.119: The design by Milan OK1JHM, also in a waveguide
Figs, 119,120: Transverter by OK1PFC on Duroid substrate, 1.5 mm thick, from
USSR, 1991 In later years it was working well for Standa, OK1WDR, Fig.122.
Fig.122 Standa, OK1WDR, 2015, on Křečhoř peak near Velim
Figs. 123, 124: Professional transverter design by Aleš, OK1PFC, top-notch one
Fig.125: Front panel of OK1PFC transverter
OK1KKD in 10 GHZ band
One of regular users of 3-cm band since 1970¨s was OK1KKD of Kladno.
The first photo shows their QTH near Bečov (JO60KC) used originally for
contests. To rise above tree tops, the group had to build a wooden scaffolding
(Fig.128). Since 1988 the trees grew too high, so another peak with lower
trees had to be found. There it was possible to operate with equipment located
on a car roof (Fig.129). The trees, however, continued to grow fast, so a
tower had to be built, Fig. 130.
Mirek, OK1DGI, Fig.131, writes about it:
„This equipment had a measured output of 4 mW and we regularly made QSOs over
up to 350 km.There was no amplifier in transmit or receive path, only a
two-way diode mixer. Later I acquired some GaAs FETs and built an amplifier.
First on an ordinary FR.4 substrate: it worked but the gain was only about 5
dB. As I failed to get a better substrate material, suitable for 10 Ghz, I
attempted to use a Teflon foil on which I deposited a thin silver layer. It
was successful, and my amplifier had then almost 10 dB gain. Now I cannot
locate it to show you. I stll have my original vacuum deposition apparatus I
used (Fig.132). With this apparatus I could deposit aluminum, silver, gold and
mainly chrome-nickel layers to make non-reflective terminations and
attenuators. I made a chrome-nickel layer on glass, with a low reflection loss
and a high stability. I also made a variable attenuator in which the lossy
plate moved by a cam. It was very stable, when it was tested by Zbyněk Škvor
at the Czech Technical University, the loss differed from my tests by less
than 0.1 dB. Back then I deposited silver on Teflon, copper was not
successful. On the silver film one could not solder, I used conductive glue to
attach components. Later I added a gold film on silver, then it could be
soldered. This depositing apparatus I built myself, I know of nobody else who
would try this way. Originally I used an oil-diffusion vacuum pump, also my
own design. The pre-vacuum stage used an oil rotary-vane pump which I found
discarded and recycled it. Later I acquired an industrial diffusion pump which
was more powerful than mine. Of all that vacuum equipment only a torso was
saved till now but you can see what was it and how it looked like. Finally, in
the 1990¨s I built a new 3-cm equipment on Duroid substrate. I installed it
agan into MT-11 enclosure (originally Czech Tesla radio link to transmit a TV
signal over 9.5 Ghz). This equipment still exists even as a new equipment is
used. No tripod is used, it is mounted on a pole, with the transverter box
next to antenna. All is contained in that aluminum pipe behind the dish , a
coaxial cable runs down for 145 Mhz IF and DC power , Fig.130. This is what we
are using now.
Note: we recommend recent designers to read the above more times. Care was
worth of the result, it is now a joy to make QSOs with OK1KKD at 24 an 47 Ghz.
Fig.128a OK1KKD on a scaffold.
Fig.128b OK1KKD equipment for 3 cm in a MT-11 enclosure.
Fig.129 OK1KKD on a roof of a Praga V3S truck
Fig.130 A new version of OK1KKD transverter mounted on a pole.
Fig.131: Mirek, OK1DGI, in the V3S truck, Hořkovec near Rynholec, JO60WD
Fig.132 Deposition apparatus (a torso from the past)
10 Ghz Band (3 cm) On a Tripod or on a Pole
At the beginning, the antennas and equipment for 3 cm band were attached to
tripods. They were needed to accurately adjust pointing by hands of operators.
An example is a setup for 1.3 through 10 Ghz by Milan, OK1JHM (Fig.133). An
advantage is that a precision pointing can be adjusted at lower bands, then
the operator can switch to higher bands if the opposite station is ready.
Combined multi-band radiators are needed in dish focus.
There are more ways how to make a good setup: one is shown in Fig. 134. After
decades of development, technical possibilities improved as well as the design
concepts. 10 GHz became a „consumer“ band allowing the most daring designs.
Due to practical reasons, the complete equipment is located on a pole, with
remote positioning in azimuth and elevation if antenna size is large. Fig.135
shows an example: a dish of 120 cm diameter with a rim requires a really fine
pointing. If it is high above the surrounding terrain and on a strategic
position, excellent resuts are certain. No wonder that Karel OK1JKT follows
this method to achieve his admirable results.
Other figures show a pole with a multi-band set of antennas of Eda, OK1EM,
Fig.136.137. His 3-cm equipment is installed in a weatherproof enclosure shown
in Fig.138. Positioning and controls require cabling ran in „protectors“
underground over tens of meters. Everything should also be protected from
lightning which does not select... On the highest bands, Eda operates also
from a transition QTH, with a tripod. On it he has a flat-plate „professional“
antenna (named „flatka“).
Fig.133 Milan, OK1JHM, with his microwave equipment (meeting on Kozákov, 2015)
Fig.134 A combined feed at dish focus , OK1JHM
Fig.135a A 120.cm dish for 10 Ghz mounted on a pole is a warranty of a
successful work of Karel, OK1JKT
Fig. 135b Antenna on a pole, 10 Ghz, OK1JKT
Fig.136 Eda¨s station, OK1EM
Fig.137 Antennas on a pole, OK1EM (detail of Fig.136)
Fig.138 Transverter by OK1EM in a weatherproof enclosure on a pole
Fig.139 Transverter by OK1EM on a tripod, for an outdoor work
Microwave EME (reflection from the Moon)
In our talk we gradually arrived to a communication using reflection from the
Moon, EME (Earth-Moon-Earth). This is a specific disciplne requiring a great
care, patience and usually a huge investment. Fig.140 shows a 20Watt amplifier
for 10368 Mhz, by Mirek, OK2AQ. For terrestrial communication a substantially
smaller power is adequate as practical results indicate. For a reliable EME
operation, a higher power is needed (also mathematically substantiated).
Generally it holds „power is never enough“. With his knowledge, Mirek has
built an amplifier, now with over 50W output power.
A full book could be written about designing such amplifier. A designer needs
a good theoretical knowledge as well as a well equipped workshop and test
instrumentation. Let us limit us on the fact that given a high cost and
availability the design shown in Fig.141 is a „very expensive adrenaline“.
Also mechanical design must be perfect. For a good heat-sinking, the
transistor should be soldered to the heat sink, here an Indium foil is used
(Fig.142). In Fig.141 we can see the complexity of surrounding elements needed
for a safe operation, e.g. Disconnecting DC voltage if operating temperature
exceeds a preset limit. (For it the transistor has an integrated sensor with
two leads). To avoid a non-necessary heating, also the DC voltage for the
exciter transistor is generated in a DC/DC converter, 24/12 V. (36Watts were
saved this way.)
Fig.143 shows the complete transverter for EME operation at 3 cm, by František,
OK1CA. The transverter can be rotated in the focus of a parabolic dish, 4.2 m
diameter. To change polarization, the body is rotated by 90 degrees by a
motor. Fig.144 shows the gear drive, and under it a potentiometer to indicate
the rotation angle. Another fine equipment is presented by Zdeněk, OK1DFC. His
gear is „portable“ and he travels with in in a modified car. Transverters for
separate bands are easily replaceable. As the old „chicken-wire“ dish is no
more good for 3 cm, he used a „full metal“ dish, 2.5 meter dia. The setup with
a detailed view on the dish feed is shown in Figs. 145 and 146.
Fig.140 A 20 W amplifier for 10 Ghz for EME operation, by Mirek, OK2AQ
Fig.141 A 50 W amplifier from OK2AQ. A massive heat-sink and fans are seen
below
Fig.142 The Indium foil is a thin, soft metal with electric and thermal
conductance comparable to copper
Fig.143 and 144 EME transverter for 3 cm band by OK1CA
Fig. 145 and 146 EME transverter for 10 Ghz at Zdeněk, OK1DFC
3 cm EME operation at OK1KIR
Exceptional results of OK1KIR radio club were described in PE-AR 5/2016, p.40,
and PE-AR 7/2016, p.37. Getting ready at 10 Ghz was demanding a lot of work.
To make things worse, catastrophes came, directly from the sky.
Toník, OK1DAI, writes about it:
The flood of 2002 was a test of what we could survive. At noon of Aug.13th,
the water level rose by some 20 cm over the „worst“ flood of 1981. We hoped
that by moving all equipment over desk level we could save it. But the water
was rising overnight, and our shed was under water completely by morning of
Aug.14th. Only 10 cm of the bottom container were visible. Then Vláďa¨s camera
finished the film. The water level could be seen on another photo taken after
the water receded (Fig.148). As one can see by sediments on the antenna, water
rose by 2.5-3 meters. All the old EME workshop had to be discarded. What was
not put to waste at the moment, followed later as the aggressive water ate
everything. We had to begin from a scratch, fortunately with a new antenna,
4.5 m dia. Fig.149 is taken from the focus of the new 3-cm antenna which we
are using now. The complete antenna expanded to 6 meters is shown in Fig. 150,
by 2012. The container to the right is no more there as in a new flood in 2013
there was 30 cm water in it, so our fellows took it to Sazená for short-wave
operations. At zero elevation angle, the focus is 10 meters above ground. We
had to fit under 15 meters to meet the building code valid back then.
EME stations working at 3 cm are many in our country and surrounding countries,
and each has a history worth of describing. An interesting EME station we
left for a conclusion: it is SP6JLW in Poland, (JO80JK), also SP6OPN and
SQ6OPG operate also at 3 cm (and at other bands, too) with a respectable
output of 600 Watts. They utilize a TWT, available in various versions. They
were used in UHF TV transmitters for 4. and 5. TV band, also used were small
„pencil“ TWTs used in Soviet communication links for 6-cm band, before good
transistors appeared.
The need for a small exciter power is welcome as TWTs have a high gain.
Relatively high voltage needed to operate a TWT is a danger to be respected:
in a wet environment it can be deadly.
Two figures, (Fig.151 and 152) show the final amplifier and feed , before the
cover was attached, and the covered device in dish focus.
Fig.147 OK1KIR station in Všenory near Prague, during the flood of Aug.13th,
2002
Fig.148 Deposit of grass and branches on OK1KIR antenna after the flood
Fig.149 Transverter mounted to rotate in dish focus, OK1KIR, antenna diameter
4.5 meters
Fig.150 A new 10 Ghz EME station at OK1KIR. The ladder allows focus adjustment
in the dish
Fig. 151 , 152 SP6JLW final stage, 600 W. Above without a cover, below under
cover at dish focus. Due to its mass, a small crane is used for handling
This paper was also published in print in Practical Eectronics magazine, with
permissione (PE/AR Magazine – Practical Electronic and Amateur Radio, Czech
amateur magazine, in Czech).
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Česká verze