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Single-Side-Band Techniques at Microwave Bands, Chapter 10
@ OK1AIY
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The first experiments in 122 GHz Band
The 122 GHz band is a new one as related to other bands. Vienna IARU conference of 28-29 Feb.2004 had „mixed“ the cards with some substantial changes. The 145 band was terminated and in other bands the frequencies were changed. Two new bands were introduced, 122 and 134 GHz as can be seen in Table 4. The following Table 5 shows the 122 GHz band frequency plan starting at 122.250 GHz where SSB and CW operation is concentrated.

As the frequency shift from the original 145 GHz band was not too significant (23 GHz only), the original transverter was considered for a redesign. (But it was already modified for experiments at 245 GHz as mentioned later in the text). For the first experiments it was not a good idea to develop completely new transverters, so the existing modules were modified. This called for new oscillator crystals, and retuning the „multiplier blocks“ MKU 12LO from DB6NT which seemed to be not too successful. It was finally done with a lower output power. Other components could be used without modifications, even the waveguide (a stainless steel capillary tube, 1.5 mm dia.) was usable. The block diagram is shown in Fig. 387. A practical versions on tripods ready for testing are shown in Fig. 388. A reader might see the above talk as a „fairy tale“, but it had a lot of tough work in it. We lacked any suitable instrumentation, of course, but the experience of 145 GHz band systems was useful as well as that from lower bands. The procedure follows the same pattern : accurate frequencies to be measured, and multiplication works all the time. The most important is a careful adjustment in a workshop, testing the communication between the tables, and then we can try a longer distance outdoors, Fig.389.
The described transverter by DB6NT is the simplest version, with an output power measured in micro-Watts, so no DX can be achieved. One of the obstacles is the water vapor content in air. The better propagation can be expected in a clear dry weather when water vapor has condensed, so the propagation loss is lower. When we did the first test by 2.8.2006, the conditions were not optimal but the SSB QSO over several hundred meters was wonderfully good. A next step was taken over 1.2 km distance but then only CW mode worked.

Table 4 Frequency plan after Vienna IARU conference, 2004

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Table 5 122 GHz Frequency Plan

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Fig. 387 Block diagram of the 122 GHz Transverter, 1st generation

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Fig.388 122 GHz Equipment of 1st generation

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Fig.389 First tests at 122 GHz. As an alkaline battery can be seen, the time was long ago

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Other Transverters for 122 GHz Band
In the mentioned period, also OK1EM and OK1JHM have built their 122 GHz transverters , 1st generation. (Figs. 392 and 393). During 2006-2008, Philipp, DL2AM has worked on a new transverter version. As the „progress cannot be stopped“ and new components became available, he was successful. New diodes for mixers and multipliers could be used, also a professional multiplier, CMA382400AUP for 3 and 4 times, allowing to generate up to 100 mW power around 40 GHz. DL2AM has devoted a large effort in the development, he could use good instrumentation, so his new transverter he described in CQ-DL magazine could generate tens of micro-Watts with SSB, and as a CW beacon for testing, up to 0.5-1.0 mW.

In this time period, also Aleš, OK1FPC entered the new design by a professional approach, Fig. 394. He purchased the necessary diodes (not a simple action), and within a training on West Pond manipulator, he could install them in the circuit boards (I frankly admire someone who could do such a thing on a kitchen table). The resulting circuits worked equally well like those by DB6NT. This offered an opportunity to update older equipment for 47 and 76 GHz. More improvement was given to the beacons, OK0EA, OK0EL and SR6GHC and SR3KHC, so more experimentation became easier. At 122 GHz , new 2nd generation equipment appeared (Figs. 395...398), and thanks to DF9LN oscillators built by OK1UFL, also the frequency stability was good. This time was perceived as the happiest one due to the collective effort leading to good results. Communication was only possible over shorter distances, so the „Contest QSOs“ were only achieved to the „next square“. Our new designs of the 2nd generation had a „beacon“ signal source mounted next to the transceiver on a tripod, with their antennas aligned. This idea by OK1UFL allows a precise pointing of a receive antenna to the stronger beacon signal, then the SSB operation was easier to achieve.
More details are given in the description of 76 GHz designs. We used this nice method with OK1UFL between Benecko and Kozákov, 22 km, by 26.9.2009, Figs. 399, 400.

Fig.392 Eda, OK1EM, during a contest. A nice weather is needed for a succesful operation.

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Fig.393 Transverter by OK1JHM for 122 GHz, 1st generation

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Fig.394 Aleš, OK1FPC, in his workshop, 2007

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Fig.395 Transverter by OK1EM for 122 GHz band

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Fig.396 Transverter by OK1EM, side view This arrangement allows to switch the transverter to a lower band for a precise adjustment

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Fig.397 A view of OK1EM transverter for 122 GHz, from the radiator side

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Fig.398 OK1EM with his equipment for 122 GHz, this time the weather failed to cooperate

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Fig.399 OK1UFL, 26.9.2009 QSO between Kozákov and Benecko on 122 GHz. On the right side, there was a 47 GHz transceiver for a coarse pointing and as a walkie-talkie

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Fig.400 QTH Kozákov, 26.9.2009. The weather was not favorable for 122 GHz, high air humidity

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The 122 GHz band and our Polish neighbors (SP6 exactly)
Also in our Polish neighborhood there was a growing number of 122 GHz equipment. Fig.401 shows three systems tested during our meeting at Three Wells (Tri studny) in 2009. Standa, SP6BTV (Fig.402) took an apprenticeship at OK1UFL in Jilemnice where 122 GHz transverters were gradually put to life, recognized all possible problems, then organized his whole family to develop his equipment. He organized expeditions to locations suitable to communicate with neighboring states: he contacted some local hams for help, and even loaned his equipment if the party lacked one.

One successful expeditions happened in August 2008, one year earlier, then only on 24, 47 and 76 GHz, among Poland, Slovakia and the Czech Republic. From OK the participant was Míla, OK1UFL. The expedition was well documented, so it is worth of mentioning it here. The parties chose a strategic location where three borders joined, and included a meeting with local OMs who had weekend cabins there (Fig.403). Fig.404 shows that several first QSOs were made. The meeting was quite cordial, and they celebrated it joyfully as shown in Fig.405. Standa SP6BTV was a good friend, a perfect organizer and enthusiast. Unfortunately, he passed away abruptly, and the activities ceased.

Fig. 401 Three new systems for 122 GHz at Tri Studny meeting, 2009.

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Fig.402 Standa, SP6BTV, in operation, (SK May 2009).

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Fig.403 A friendly meeting at a cabin of OM6TX

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Fig. 404 The tactical QTH suitable for microwave communication among three countries

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Fig. 405 Standa would not forget anything: He prepared a detailed itinerary and a memorial plaque

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Radio Amateur 122 GHz Band , activities in Moravia
In 2007 the experienced Moravian designers of 47 and 76 GHz entered their activity at 122 GHz. Milan, OK2MH, had attended DL2AM's workshop, and he even loaned him one transverter for experiments. At the same time, Pavel, OK2VJC, and Peter, OK2ULQ, with Eda, OK2BPR, worked on the new transverters (Figs.406, 407). The work was not easy but the team cooperation was good, and after a short time the systems came to life at the workshop and then short-distance was covered outdoors (Fig.408...412). By gradual improvement, the distances grew and the transceivers were qualified for a contest. In October 2008 during the UHF Contest, they made a QSO with OK2KYC over 4.8 km (Fig.413). As Slovakia is not far away, the first international QSO was foreseen.

The first QSO with a new state is always a celebrated event for the actors (at any band), so a suitable path was sought to make it possible. Direct line of sight was essential, and also an accessibility of locations by cars. After some time the locations were found and by 18.8.2009 the first QSO was made between OK2IMH/p and OM/OK2VJC/p over 3 km.

Fig.406 A 122 GHz dish at OK2VJC transverter

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Fig.407 122 GHz, a detailed view of transverter in dish focus, OK2VJC

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Fig.408 Tens of hours of testing at OK2ULQ OK2VJC and OK2IMH

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Fig.409 A testing day at OK2VJC's garden, Peter OK2ULQ stands next to the transverter

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Fig.410 OK2IMH at his workshop

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Fig.411 Left to right, OK2VJC, OK2ULQ

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Fig.412 Eda, OK2BPR (SK2020) pointing the 122 GHz dish

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Fig.413 UHF Contest 2008, Zdeněk, OK2BUC, for OK2KYC communicating with OK2VJC over 4.8 km

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Figs, 414, 415 and 416 present the first OK-OM QSO in the microwave band of 122 GHz, made by 18 August, 2009. OK2IMH described it in detail at:

From our experience we know that such suitable location is often difficult to find. Then the only option can be to make the QSO over the official border check point or close to it. The positive aspect is that the border crossing is on a road, so we can come by a car. Strict DX hams might be annoyed but as the EHF equipment may be not yet finished in development and the power minuscule, such may be the only option.

The first QSO stimulated more improvement of the three functional systems. New components became available for this step. These were MKU LO 8-13 oscillators from DB6NT (Fig.417), installed in a nice box (Fig.418) . And later in 2019 more nice finished products, the „Bodnar“ oscillators controlled by GPS. These oscillators offered the precise and stable operation frequency and made for an easier experimentation. The GPS-controlled BODNAR oscillators can be programmed for output frequency over 400 Hz to 810 Mhz, and output power can be set in three ranges, from 6 to 20 mW. The GPS receiver is included with a magnet to attach to a suitable surface. It usually functions indoors close to a window, to „see“ some satellites in the sky. It is shown in Fig.419, and a view into the „magic box“ is in Fig.420. More detailed information can be found at:

Fig. 414 Pavel, OK2VJC, during the first OK-OM QSO at 122 GHz

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Fig.415 The arrow points to the QTH of OM/OK2VJC/p

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Fig.416 The QTH of Milan, OM2IMH/p

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Fig.417 122 GHz band: Mounting of MKU-LO8-13 PLL oscillator by DB6NT

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Fig.418 Oscillator 8-13 GHz in a box, on the right, a 10 MHZ input connector from GPS

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Fig.419 The BODNAR programmable GPS-controlled oscillator (400 Hz to 840 Mhz)

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Fig.420 A programmable GPS-controlled oscillator by Leo Bodnar (a view on the PCB)

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Two active stations taking part in all contests are a father-and-son team, OK2QI and OK2LL (Fig.421). They use substantial parts in transceivers by OK1FPC, one antenna is from OK1EM, and mounting in suitable enclosures is shown in Figs. 422,423. The beacon as a necessary device is shown in Fig. 424. The distance from the Praděd summit where OK2QI rents his QTH/p, to Jeseník city where he has a permanent QTH, is too far even for 76 GHz band. Therefore their contest QSOs are made over 2 km, OK2LL moves to a parking lot in Ovčárna pod Pradědem. Fig.425 shows Luboš, OK2LL, with one of his transceivers.

The technology advances quite fast, and a next novelty is here: the professional radar modules for motor vehicles to enable them riding without drivers. A kit by VK3CV operates at 122 GHz with CW and FM modes, with about 0.5 mW output power. Inside of a miniature chip there are a phase-lock circuit, a twin antenna systém, and a RX preamplifier. Such components are by now in hands of hundreds of designers around the world, and they discuss design details on the internet. In the Czech Republic we have several functioning systems, after tests some first results, we will present them in next parts of our series. This is a next step forward. More details can be found on OK1EM website.

Fig. 421 Equipment od OK2QI and OK2LL for 122 GHz:

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Fig. 422 Transverter by OK2LL, front view

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Fig.423 A rear view on the transverter by OK2LL

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Fig.424 The beacon is a necessary device for experiments in a workshop

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Fig.425 Luboš Loos, OK2LL, the son of František, OK2QI

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122 GHz band, VK3CV design
The reader may perceive this series a a „historic work“. I do not think of it as too historic when we present designs and events only years or months old. It is true that the progress advances very fast. What happened in the eyes of the community as far away in time, we try to compare it with the really tens of years ago when we had few good components and instruments, and radio amateurs had to create and manufacture most of instruments on a „mass“ scale. The question is what we can use in today's designs with the available low-cost new parts, often ready to use. The answer is yes, it can save time and effort. One good example is the „world-wide“ action, the transceiver design described by VK3CV , with a professional chip made for the auto industry, Figs. 430, 431.

There is a discussion forum running on the internet, where the designers can share their experience:

Also on OK1EM's website there are more informations:

The current action brings a hope in good results which are sure to come by in the collective effort, a hope to achieve longer QSOs in this demanding new band, and move the progress forward. Figures 426...429 present the new transverter for 122 GHz by OK1UFL, 3rd generation, with the TRX 120 radar chip (Figs. 430,431), mentioned above in the earlier part of our series. The development required a suitable workshop instrumentation, good eyes and „sure hand“ skills. (I have not taken part in this collective action myself, I would rather wait for some future versions...)

Fig.426 Equipment for 122 GHz band by OK1UFL made after VK3CV. In the rear, Žalý summit, and on the right on horizon, Černá Hora.

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Fig. 427 Another view on OK1UFL system.

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Fig. 428 Míla, OK1UFL, with his equipment for 122 GHz, made after VK3CV. Front view at JO70SP locator.

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Fig.429 A view on the transverter, also GPS antenna and power supply can be seen.

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Fig.430 TRX12 chip

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Fig.431 TRX 120 block diagram

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For the first testing, not everybody would have access to suitable instrumentation, so the usual method can be used again: listening for the signal by another systém. Then we can hear the „finest nuances“ than cannot be detected by a spectrum analyzer or a SDR receiver at the IF level. We did it this way with Míla, OK1UFL, in 2006 at the very beginning, and later in 2008 when the 2nd generation of the equipment was ready. The original one was used as a „tester“.
Sunday 25 October 2020 was one of last fall days with a good weather, so we arranged a small „testing day“. We started over a short range as seen in Fig. 432. OK1UFL had his equipment adjusted in his workshop,, both signal frequencies agreed accurately, and the signals were strong. Over a longer distance, 600 meters, Fig. 433, we adjusted all elements than cannot be preset in a workshop, like antenna alignment, telescope, etc. Contrary to a contest situation when there is no time for experiments, we had enough time to also test a second equipment, the „tester“. As it was already „aged“, I added the GPS control before the Field Day (Figs. 434,435). From practical reasons the control can be switched (on GPS, off GPS), to tell the difference. A difference was observed even though that the oscillators of DF9LN made by OK1UFL have been fully adequate..
The test by fire the transverter underwent by 26.5.2012 during the first QSO OK-OE, over 26 km, which as was later determined was not along the line of sight. Details can be seen on our pages here as well as on OK2KKW web pages.:




Fig.432 Tests in Horní Štěpánice (JO70SP) over a short distance at 122 GHz

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Fig. 433 A telescope view of the opposite station, OK1UFL equipment

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Figs. 434,435 Two views on OK1AIY equipment for 122 GHz, with BODNAR oscillator, and switchable to the original version, (Field Day 2020).

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Figs.436,437 Microwaves in the U.S.A.. Mike, K6ML and Randy, KI6TWT (www.50mhzandup.org).

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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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