Single-Side-Band Techniques at Microwave Bands, Chapter 8
@ OK1AIY
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Mixers and amplifiers for 47 GHz band, second generation
Almost at the same time as the described amplifier, MASCOM company
manufactured diodes similar to those used in the first-generation HP
multipliers, but with better parameters. The first equipment was built by
Philipp Prinz, DL2AM, who also offered these diodes for purchase. For simple
harmonic mixers , MA4E1307 was suitable (one diode on a chip), MA4E1318 was
suitable for sub-harmonic mixers (two anti-parallel diodes on a chip), it
generated over 1.5 mW, and noise figure was 6-7 dB. Another suitable diode was
MA46H146. With 120 mW input at a half-frequency, the output is around 20 mW,
just suitable to create a test device for an easy antenna pointing, usually
named a „beacon“. In Figs. 261 through 263 below one can see a practical
version of some such beacons: surplus components from Siemens and Ericsson
links can be used. At 15.6 GHz, the amplifier delivers 0.6 W output, and the x
3 multiplier delivers the mentioned 100 mW output. If we used a 25-cm diameter
dish with the transverter, it required a precise pointing, within +/- 0.5
degree. Using a horn antenna instead for the beacon, pointing is less critical
and offers a better chance to detect the signal by the opposite station : this
makes a half of the full communication sure.
Beacons have a stable and known frequency. They operate in CW mode, so with a
weak signal the QSO can be made by CW at a contest. OK1UFL perfected the
assembly by locating the beacon on a tripod next to the transverter, and
precisely aligned both antennas.
Fig.258 Transverter for 47 GHz band in an enclosure, by OK1DGI
Fig.259 Transverter for 47 GHz, 2nd generation, with an amplifier and filter,
by OK1EM, 2005
Fig.260 Transverter for 47 GHz, 3rd generation, OK1AIY
Fig. 261 47 GHz beacon, OK1EM
Fig.262 47 GHz beacon by OK0EL, front view
Fig. 263 OK0EL beacon, rear view, horn antenna
76 GHz band (3.9 mm wave length)
At DB6NT, there was a „microwave technology explosion“ in the start of 1990s.
One design was followed by another, and each DUBUS magazine issue brought
something new. Designs for the higher bands were similar as well as the
components used. Only LO frequencies and mixer PCBs were different. The 76 GHz
band (Fig.264) was a quite high frequency , and wave length of 3.9 mm was
highly respected. We had some experience with 47 GHz band, so we could not
resist the temptation to try the new band. With OK1UFL we started developing
new transverters.
Several months later the basic design was ready to install the diodes. It
happened at Michael, DB6NT, on 1st May 1997, and during the return trip we
made our first SSB QSO at the border check-point. The other day we extended
the distance, and with OK1UFL we tested our equipment and achieved more than
10 km point-by-point communication (Figs. 265,266, 267). For the start we were
satisfied, and later we tested our capabilities in the contests where in the
result tables we were the only two stations at 76 GHz. The frequency table for
76 GHz amateur band can be seen in Fig.264, and the first QSO between OK and
DL is shown by the QSL in Fig. 268.
This was only the beginning, an improvement period followed like earlier in 47
GHz band. But it took a long time. New diodes with more power, and
descriptions of better designs by Philipp, DL2AM, brought the 2nd generation.
During that time, Aleš OK1FPC used his professional approach. The first diodes
were installed in new mixers at ERA company in Pardubice, others at ALCOMA in
Prague. More interested hams came (Fig.269), and one transverter after another
was coming to life.
Fig.264 76 GHz frequency plan
Fig.265 First tests at 76 GHz band, and the first public
Fig.266 76 GHz transverter by OK1UFL, 1st generation
Fig.267 Transverter 1st generation by OK1AIY, with a pointing scope
Fig. 268 QSL DB6NT for a QSO at 76 GHz
Fig.269 The first 76 GHz transverter by Milan, OK1JHM
76 GHz band in Walachia
In Walachia there is a lot of activity at 76 GHz as well as in lower bands.
The first equipment was built by OK2BPR, OK2VJC and OK2UYU (similar design as
shown in Fig. 270). Eda, OK2BPR and Josef, OK2STK, then built a new.generation
equipment with better parameters, mainly a higher power, Fig. 271 and 272. As
accentuated in earlier descriptions, the most demanding part in the design was
(and still is) the installation of a mixer diode due to its minute size. So
far a two-component conductive glue was used but in Walachia they succeeded in
using a low-temperature soldering which is barely believable.
The process is described by Tonda, OK2VMC:
I soldered the diode, MA4EA3A8, by a low-temperature solder, by „reflow“, Fig.
273. I connected an ohmmeter to the PCB, without any choke, to indicate the
moment when the diode „sat“ in place. The temperature was 187 deg.C but it was
on the Al block, not on the diode. Then I removed the block from the hot-plate
and started cooling it. The diode sat a bit slant as the capillary forces
moved it toward the 90-degree pad of the microstrip line but I left it there.
I would attach a masking tape next time to force the diode in place. The whole
action started when Eda OK2BPR built our rig for 76 GHz but we had to pull it
up on a 9-meter pole to avoid the trees. We switched between the bands (24,47
and 76 GHz) so that all three TRVs are permanently under power, only PTT and
IF are switched. The installation, however, was not working well. What can go
well in the workshop, can fail outdoors in a bad weather (Fig.274). The systém
worked in Eda's workshop, or what can work on a tripod when the owners change
TRV's in their dish focus but is not left Sun-heated. On a high pole it
failed. I had to add a cooling plate for the tripler and a fan which through
holes in the bottom cover to cool it but protected it from a horizontal rain,
sometimes occurring on Radhošť. With the cooler everything works just fine
even under a summer Sun. For me this is comfortable, I can sit in my car and
can switch the bands by only one knob.(Fig.275). I can erect the pole by
myself (no other people at hand). Now I am finishing the „central switch“ by
DB6NT, I will feed all TRV's by 12 GHz from the switch, with the frequency
locked to GPS, but again it will have to be weatherproof and located on pole
top. I am concerned about switching and cabling at 12 GHz into each TRV.
Fig.271 Testing equipment for 76 GHz at Toník, OK2VMC
Fig.272 The 76 GHz band can be heard and seen in OK2VMC laboratory: a nice
view can be seen in a detail from Fig.271
Fig.273 Soldering the mixer diode in 76 GHz mixer on an old Tesla hot plate
Fig.274 24, 47 and 76 GHz bands on a 9-meter pole to avoid trees (Radhošť,
frost during the 2014 sub-regional contest).
Fig. 275 Toník, OK2VMC, controls the equipment for 24, 47 and 76 GHz (OL9W,
Radhošť. 2nd sub-regional contest, 2015)
Fig. 276 QTH OL9W at Radhošť, 2nd sub-regional contest, 2015
Fig. 277 OL9W party on Radhošť, Field Day 2007
More design updates for 76 GHz band
In a practical use there is a significant difference between 47 and 76 GHz
bands: more propagation loss at almost twice higher frequency, lower power and
poorer receiver. More technology challenges as well as operator skills. The
beacon use described under 47 GHz , designed by OK1UFL, is very helpful for
adjustments, so it was incorporated directly into the transverter.
Figs. 278 and 279 shows the arrangement of the beacon: the transverter port
with an output lower than 0.5 or 1 mW, holds a 25-cm diameter dish. The
waveguide port on the left wall (beacon) is not used but it can hold a smaller
antenna like a horn with a wider radiation pattern. The opposite station can
receive the beacon signal even without a precise pointing. After both
operators finish a precise pointing, one can switch to „receive“, he can
switch the beacon OFF and find the opposite signal at the same frequency .
In a team effort, one more equipment was installed into a standard Tesla
Jihlava enclosure (Figs. 208 thru 282), and both designs were presented during
a VHF meeting in Zieleniec, Poland, in 2008. Philipp Prinz, DL2AM, the famous
designer and „ethereal father“ of these designs was quite surprised by seeing
his followers and their equipment (Fig. 283). His designs presented in CQ-DL
magazine were for us an example to follow, Fig. 284. He had later redesigned
his equipment, and waited for the best moment for a QSO, in cooperation with a
meteo station. After several postponements, by 8-3-2011 he has utilized good
conditions, and on the Feldberg-Zugspitze path the air moisture dropped under
20%. His QSO with DJ5AP/p over 224 km was then a world record. In our
conditions we possibly cannot hope in a similar situation. If an inversion
happens between two statios not located at an adequate altitude, it would not
support a good propagation condition. Even with our knowledge, the propagation
mechanism is so complex that any DX QSO is rather a random event. Our beacons,
however, are a welcome aid at these high bands.
Fig.278 Transverter by OK1UFL, 76 GHz, 2nd generation. On the left the
waveguide port for a suitable low-gain antenna like a horn
Fig.279 Transverter by OK1UFL for 76 GHz, 2nd generation, top view
Fig.280 A 76 GHz transverter made by a team (for a prominent customer) in a
Tesla Jihlava standard enclosure
Fig.281 Transverter from Fig. 280, front view. The flat bar at center holds a
pointer scope. Horn antennas were purchased as kitchen „decorators“, they seem
to be small but their gain is similar to horns for 23 cm band, 2.76 m long
Fig. 282 A rear view of the transverter from the previous figure
Fig. 283 DL2AM was always a bit forward in technology and design: at BBT 1979
he powered his rig by a solar battery
Fig.284 Philipp, DL2AM, is known by a precise workmanship. Here he points his
demanding sight at our transverters for 76 GHz. He worked many years as an
educator, as a „master of manufacturing training“.
More devices for a successful work at 76 GHz band
Following several QSOs with OK1FPC at contests when we observed the signal
levels were adequate, we were seeking for suitable QTHs and tried to extend
the distance as far as possible. A QSO between Žalý and Vyklantice by
Stražiště was successful in a summer weather, so after several months we tried
another attempt. We needed a permission to enter the 1st protected zone in the
Protected district of Krkonoše National Park, to use Zlaté Návrší mountain
(1400 m over sea level). OK1FPC traveled to Větrný Jeníkov from where he had a
line of sight to Zlaté Návrší, Fig. 285). That day (15-10-2017) we had a nice
fall weather with an inversion but unfortunately at the same height as our
stations. Signals were weak and fading. The distance was 141 km so far the
longest but we hope that was not the last trial (Figs.286,287).
Successful results on these high bands require a lot of work and good
instrumentation. A spectrum analyzer is not common for everyone at these
frequencies , and more experiments are needed. One of possible approaches is
to use a converter with a Gunn oscillator from old professional links. Then an
available spectrum analyzer for 1.5 GHz can be used...to be described in some
following texts. A really necessary part is a reliable signal source with a
known frequency, for use in a workshop (Figs. 288, 289), later one with a
higher power to be used as a beacon on a hill. Gradually we have developed
slot antennas with a circular radiation pattern, also for 76 GHz. (Figs. 290,
291). We plan to utilize them in new beacons here and in Europe- so far only
small horns are used, pointed into selected directions. We can see these horns
on OK0EA beacon (Figs. 292, 293). To govern a particular band requires a long
time of development. After simple designs, better ones follow with better
parameters, and the „old“ ones are saved for testing. Most designers have
usable devices in both versions.
Fig. 285 Terrain profile for the 76 GHz QSO between OK1FPC at Větrný Jeníkov-
Zbinohy, and OK1AIY at Zlaté Návrší, 15-10-2017
Fig. 286 Equipment by OK1FPC at Zbinohy, Větrný Jeníkov
Fig. 287 Aleš, OK1FPC at his equipment for 47 and 76 GHz, 15-10-2017
Fig. 288 OK0EL beacon at 76 GHz, with a slot antenna (front view)
Fig. 289 OK0EL beacon at 76 GHz, rear view
Fig. 290 Slot antennas for 47 and 76 GHz beacons
Fig. 291 Slot antennas for 24 and 76 GHz beacons, result of a good workmanship
of metal workers in Podkrkonoší
Fig. 292 OK0EA beacon for 47 and 76 GHz, rear view
Fig. 293 OK0EA beacon- detail of a horn antenna for 76 GHz and a section of
slot antenna for 47 GHz (all mounted behind a laminate window on Černá Hora)
Technology and operations at 76 GHz in Moravia
Pavel, OK2VJC, Eda, OK2BPR, and Petr, OK2ULQ, have been building equipment for
47 and 76 GHz already in 1990s when there were no digital cameras to document
their effort. Also their modesty of the best designers contributed. The first
QSO at 76 GHz was made by OK2VJC and OK2ULQ in March 2007 in a workshop, then
in April they extended it outdoors to 26 km. Following figures illustrate
their achievements.
Team work always brings good results. Someone is the „driving engine“, invents
a new technology and others go on to learn it and improve on it. The process
includes a lot of hard work and it then brings the „team joy“. Over 2013 to
2019, in all contests at 76 GHz, the following stations took part: OK2BPR,
OK2ULQ, OK2VJC, OK2QI and OK2LL, also the teams of OK2C, OK2KWS and OL9W.
Fig. 294 Eda, OK2BPR, at one of his rigs. His designs were the first and most
admired
Fig.295 Pavel, OK2VJC, expresses his joy of the first QSO at 76 GHz
Fig. 296 Petr, OK2ULQ, starts climbing a tower at Kubánkov hill. All this must
go to the top
Fig. 297 Petr, OK2ULQ, during the first QSO at 76 GHz over 26 km to OK2VJC.
Here he adjusts an optimum antenna pointing
Fig. 298 Petr, OK2ULQ, during a QSO (assisted and photographed by Milan,
OK2IMH)
Fig. 299 Milan, OK2IMH, with the transverter for one of the highest bands: All
was documented on his web page
Fig. 300 47 and 76 GHz equipment being built at OK2BPR's workshop
More important devices for a successful work on microwave bands
For a successful QSO at a high band , antenna precision pointing is essential.
Large parabolic dishes are nice to achieve a high gain but they also bring
more problems to resolve. The more perfect the parabola is as a mechanical
structure, the sharper it is in operation. Any minor deviation in any plane
would prevent a QSO from happening. (Many blame the problem to poor
propagation conditions which often do contribute). An important device for
antenna pointing is the pointing scope (a telescope or a gun aiming scope)
used on hunting rifles. We do not need a nightscope but a simple one like that
shown in Fig. 301. A good alignment is essential, best using a cross on the
opposite antenna, or on a known tested object. At night, under a fog or rain
this does not help, and the following solution is suitable:
The mechanical union of the higher-band transverter with another for a lower
band where the pointing is easier (Figs. 301 and 302). One can combine for
instance two bands like 10 and 24 GHz where a combined feeder in a common
antenna, but where the transverters use individual antennas , the combined
mount is needed, and should be easily dismantled as necessary. Transverters
can be located above and below each other, important is that the mount is
rigid and stable. For a fine alignment one can use a beacon, best if from one
location all bands are served. (Fig.303). Careful adjustment in both planes,
horizontal and vertical, is needed as an error of less than one-half of a
degree is too much at the frequencies involved. A water level is also needed.
Fig.304 shows three transverters mounted above each other. Electrically sound
but mechanically unstable on a plastic tripod with the high mass point. The
pointing and alignment procedure should be trained in advance. Precise
pointing of the dish is difficult, so OK2UFL invented another way:
Along with the correctly pointed antenna, viewed 90 degrees from side, he
extends a straight line like holding a ruler on it, pointed to a chosen point
in the surrounding terrain (like a tree). To the same point he aims the
straight line from the dish which should lay on the first one. With some skill
this method works well in the field, Figs. 305, 306.
Fig. 301 Transverters for 47 and 76 GHz on one tripod with a pointing scope
Fig.302 47 and 76 GHz transverters on one tripod
Fig.303 OK0EA beacon for 5.7 and 10 GHz, and for 24, 47 and 76 GHz, 2017
Fig.304 76, 47 and 24 GHz transverters on one tripod . The thick pipe belongs
to the professional dish in the rear
Fig.305 OK1UFL at Benecko. Outdoor operation on more bands is demanding, 2nd
sub-regional 2016
Fig.306 76 GHz and other bands were difficult to manage even then, 1999
The 145 GHz band, nonexistent today
The 145 GHz band was (around 2000) one of the microwave bands assigned to
radio-amateur experimenters. The band started at 145.152 GHz, and the wave
length of 2.06 mm was fearful. Making a simple equipment and trying to make a
QSO was really a bare experiment but DB6NT had already described his design in
DUBUS magazine, so we started with Míla, OK1UFL. We had some experience from
76 GHz band and knew what to expect including poor results.
We had to build all new devices, we only purchased the multiplier block, MKU
12. The block diagram is shown in Fig.307. The multiplier and mixer in a
two-section aluminum block were demanding. On the output the antenna feeder
flange was mounted (Fig.308). System used quartz oscillators (by DF9LN) at
125.875 Mhz with crystals from Tesla Hradec Králové. A high multiplication was
needed, (96x, 2x and 6x), in total 1152x, posed a high demand on oscillator
stability as well as the DC voltage. One Hz step at the oscillator frequency
results in 1.15 kHz on the output which was not acceptable. Therefore the DC
voltage , 12-13.5 V,had to be well stabilized by a good regulator like
MC33269 . (Another voltage regulator for 5 V is inside oscillator block).
After several months, both transverters were completed electrically and
mechanically. The next step was to attach mixer diodes, possibly like we did
at 76 GHz. To do this we again visited Michael DB6NT, he glued the diodes in
the mixer circuit and hardened it in a dryer. The devices were functional,
they even exhibited equal values on a spectrum analyzer. The following day at
home we measured the exact frequency at the SMA interconnect or where our
frequency meter still worked.. To finalize, we aligned the antennas, etc. As
usual, we tested our first QSO in the workshop between two tables, another
trial was from the window to the garden (Fig.309). At the beginning of May the
weather was acceptable as shown in Fig.310, so by 1-5-2002 we made our first
SSB QSO over close to 0.7 km (Figs.310,311).
Fig.307 Block diagram of the transverter 1st generation, for 145 GHz band.
Fig.309 145 GHz transverter, 1st generation, OK1UFL adjusts the antenna. The
opposite station is outdoors at garden's end
Fig.310 May Day 2002, experiments with OK1UFL in Horní Štěpanice
Fig.311 MayDay 2002, the first SSB QSO at 145 GHz, over 0.7 km distance , with
1st generation transverters
Description of individual parts
In the above figures the first is the block diagram of the transverter.
Following the thermo-stabilized oscillator is a 96x multiplier with an output
power of 30-40 mW. This section is used in all transverters starting from 24
GHz, with minor frequency differences. Fig.312 shows the design by Aleš,
OK1FPC. The following multiplier and mixer (Fig.308 above) offers a side view
in Fig. 313. Between the PC boards there is a band-pass filter composed of
R220 waveguide sections, to reject lower frequencies. (see table 4,3 on page
151, „Wave length cut-off“ in the book by Šír, P.: Radio Amateur Designs for
Microwave Bands, 2nd edition, 2001).
Another demanding part was the primary radiator for the parabolic dish. The
round waveguide with 1.4 mm diameter guides the low output power from the
mixer to the sub-reflector which irradiates the dish. Its inner surface must
be smooth and flashing: as DL2AM insisted, one should not blow the air by
mouth to prevent oxidation. We of course had no such material, we used a
stainless steel capillary tube with similar size. Steel has a flashing surface
but a poorer conductivity (including skin-effect), so one should expect a
higher loss than a copper tube, silver-plated. We must consider that the
feeder length 10 cm comprises 50 wave lengths at 145 GHz. It can be compared
to a 100-meter cable to antenna at 144 Mhz. The problem caused many designers
to simply mount the transverters in dish focus. The feeder is shown in Figs.
314 thru 316. The capillary tube is protected by a larger copper tube, 5 mm in
diameter. In the following time we made several trials over longer distances
but the signal was weak and we had to use CW mode. We never tested our design
in a contest as the distances between stations were much larger.
After some time I had a revelation and remembered that even that first QSOs
were not records, they were significant for a SSB communication at over 100
GHz in the Czech Republic. Although I am not a fan of big celebrations, we
organized a small team symposium in a cozy hotel at Benecko, Fig.317. We also
had a special guest, Ing. Vladimír Kratochvíl, our friend and a fan of our
experiments. He knew the VHF problems since 1940s when he worked at Elektra
Hloubětín, later TESLA Praha-Hloubětín. He remembered the war manufacture of
German vacuum tubes, and the special VHF receiver „RAS“ by Rohde/Schwarz, for
75-480 Mhz. These receivers were used in submarines and ships to detect Allied
radar and communication signals. He told us that there was a „glitch“ in the
receiver mixer: the local-oscillator injecting probe was located close to
antenna input, so when the receiver was ON, the airplane detectors could
locate it, even under water. TNX INFO OK1VAM
(Translator note: Why would anyone run an UHF receiver under water? From other
sources I knew that the local-oscillator leakage was intentionally planted by
an UK captured radio operator to Germans in 1943, and due to that German
monitoring receivers were redesigned in 1944)
Ing.Kratochvíl expressed his joy of each of our successes. Fig.318 presents a
photo of him leaving our meeting. We had no idea this was his last one.
At the IARU conference in Vienna, 28-29 February, 2004, the 145 band was
canceled and replaced by two new bands, 122 and 134 GHz.
Fig.312 The 96x multiplier from the workshop of Aleš, OK1FPC
Fig.313 The 12x multiplier and mixer for 145 GHz used also in other high bands
Fig.314 Assembly of dish radiator by OK1UFL for 145 GHz (241 GHz)
Fig.315 Detail of radiator assembly
Fig.316 Location of a passive reflector (parabolic antenna suitable for
microwaves)
Fig.317 A small symposium at Benecko, From the left: OK1AIY, OK1KHK, OK1UFL,
OK1THK, ad the guest, Ing. Vladimír Kratochvíl
Fig.318 A group photo of our tean before the advertisement plaque, at the left,
the honorary guest, Ing.Vladimír Kratochvíl (Summer 2002)
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).
Related links:
Česká verze