Some additional information to supplement my presentation called “Building and Contesting on 10 GHz.”
This is not a complete listing of “microwave amateur radio knowledge” but it is a one-page resource to help you get started.
The first thing I would recommend is to find and join your local VHF and above ham radio club. There are clubs that focus on microwave technology and operating all over the world – find yours to meet new people, learn new things, get a rig going and join the fun!
Microwave Update (MUD)
One of the best places to meet active microwave band hams and learn more about the SHF ham bands is the Microwave Update (MUD). The event is sponsored by various clubs around the USA.
The printed papers (Proceedings) are available from the Lulu print-on-demand service.
The IF Radio
All-mode transceivers become the IF on the uWave bands
All-mode transceivers become the intermediate frequency (IF) stage in a microwave transverter system. I like to call the IF rigs the human to “transceiver interface” because this is the unit we use to tune the operating frequency, hear through the speaker and transmit audio via the microphone. Usually the IF radio also initiates the receive to transmit change-over as well.
It is important to know that IF radio performance does not affect overall performance on the microwave frequency.
In other words, fancy filtering, special ovenized oscillators and even CW or SSB filtering are not mandatory. While all those features and functions can enhance enjoyment, it’s the transverter at the microwave frequency that determines performance for the microwave station. In fact, I have two Yaesu FT-817s. One is equipped with CW filters, one is not. Sometimes, because stations often drift, the IF radio with the filter may not be able to hear the other station because the stations have drifted beyond the receiver passband. I normally bypass the filter on my IF radios.
But this is also a good thing, since it means inexpensive and even used VHF, all-mode rigs can be used.
Also remember, for transverter use, the transmit power from the IF rig is on the order of a few mW or less. So, if you are able to find, for example, an all-mode 2m rig being sold “for parts or repair” – that may be a viable candidate for an IF radio.
On most of my IF radios, I added a “convenience box” interface. This box converts all the interface connectors to ordinary RCA jacks. This is very handy in case my IF radio breaks: I can quickly swap any IF radio and swap it almost instantly, regardless of the IF radio model. My IF radios include a Kenwood TR-751, Yaesu FT-817, Radio Shack HTX-10, and some others.
Here is a picture of the convenience box on my FT-817 . . .
KH6WZ IF Rig with RCA Jacks
IF Radio Convenience Box – Control
The white box front panel, from left to right: Multi-pin interface jack for DC power and control. Center left: Above, blue LED for “PTT Closed” indicator. The locking toggle switch is used to lock the IF rig into transmit (PTT Lock) mode to make it ready to send a carrier/beacon tone. Center right: Above, the yellow LED indicates “Key Condition.” The locking toggle switch is closed and locked to key the transmitter after the PTT is locked into transmit. The red push button is used to send CW in case I forget to pack my key or the key breaks in the field.
Essential for Success: Accurate Reference Frequency
To help ensure successful two-way operation on the microwave bands, a stable and accurate 10 MHz Reference oscillator is essential.
This can take the form of Ovenized Crystal Oscillators (OCXO), GPS-Disciplined Oscillators or Rubidium Oscillators. All of my transverters have OCXO units that I calibrate at a friend’s lab. Once set, I can depend on being very close to the displayed frequency. One secret: I keep the reference oscillator continuously powered throughout the contest weekend.
Although some club members have rigs using a rubidium or GPS standard, my OXCO-equipped rigs are able to match those other, more sophisticated radios without any problems.
Improvement Paths
Receive
Low Noise Amplifier (LNA) for 10 GHz
Low Noise Amplifiers (LNAs) can be found as Low Noise Block converters (LNBs) for Ku-band (12 GHz to 18 GHz) satellite TV receivers. Noise figures at or better than 1dB and 20dB-plus gain can be achieved. The modifications are easy and can be done without test equipment. Chip, N6CA published an example on his webpage.
Antennas
2-ft Dish vs 6-ft Dish
I call the picture above “Dish Envy.” On the left is Dick, WB6DNX with his 2-foot prime-focus dish. On the right is Robin, WA6CDR with his 6-ft dish.
Most beginning 10 GHz ops start with discarded and usually free satellite TV offset-fed dish antennas. But 24-in. diameter prime focus dish antennas or 24- to 30-in. offset feed antennas work better. Paul Wade, W1GHZ is an excellent online “microwave antenna handbook” – a great resource for hams.
Amplifiers – SSPA, TWTA
10 GHz SSPAs
It is amazing what one can find on eBay and other online auction sites.
High power amplifiers – Solid State Amplifiers (SSPA) and Traveling Wave Tube Amplifiers (TWTA) as well as other materiel for the microwave bands such as waveguide, SMA, Type-N and other connectors and assemblies are becoming available to just about anyone.
As mentioned briefly in the presentation, you must be careful when bidding or buying an amplifier for the 10 GHz ham bands, since some non-ham band amps may not be easy or may be impossible to convert to the 10 GHz ham allocation.
However, there are also many 10 GHz amplifiers that can be re-tuned (“snowflake tuning”) or used as-is. The term snow flaking is used when describing the tuning of microwave amplifiers or other surplus items. A step-by-step article about snow-flaking a surplus amplifier for 10 GHz is posted on the San Bernardino Microwave Society (SBMS) website. See “10 GHz Qualcomm Modification Notes” and “Modifying the Qualcomm 1W Ku-Band PA for use on 3.4, 5.7 or 10.3 GHz.”
When snow-flaking, a small wooden stick with a tiny speck of copper foil is touched and moved around the traces of an RF section while monitoring RF power. Watching for peaks, the small probe is removed, and a piece of copper foil is soldered in that location.
It is tedious but can be fun and rewarding when the job is completed and you have more power on the X-band.
An excellent example of a small amplifier often found on eBay can be used without modification is the Harris-Farinon Model SD-108175 / 076-108687-001 solid state power amplifier (SSPA). I have several of these in use, and the power varies from about one watt to three watts on 10368 MHz.
See “Harris-Farinon 10 GHz Amplifier for Amateur Radio Use” in the References section below.
The good news is that many microwave ham bands over-lap the commercial or other non-ham service allocations (such as Wi-Fi, Bluetooth and Industrial, Scientific, Medical [ISM]), and amplifiers intended for these services can often be used as-is without modifications to the RF section. No tuning necessary.
In any case, all amplifiers will require a power supply (various voltages), power supply sequencing and high power transmit/receive changeover to integrate into a “beginner system.”
Sequencers: Protect Your Investment
Sequencer Demo at Maker Faire
When moving to higher than “driver power” (milliwatts), it is important to protect the receiver and amplifier circuits by delaying the time between receive and transmit. The delay needed is only a few milliseconds, enough time to allow the relay contacts to close and settle before the change from receive to transmit happens.
A sequencer automates switching various stages in this specific order:
- Antenna relay
- Transverter enable
- Power amplifier enable
- Transmit enable
The order is reversed when going from TX to RX.
In my Maker Faire display, pictured above, the W6PQL 4-Event Sequencer is used to drive a large Type-N relay (for T/R) and three high current power relays used to turn on the transverter support functions. It is available as a kit from the W6PQL website.
I have also built and use several sequencers based on Chip N6CA’s “Time Delay Generator” circuit, presented in many years of the ARRL Handbook (1997 and others).
I hope my presentation inspires more hams to try something different. There are many developments and new technologies to explore in ham radio, let’s continue the century-old Ham Radio Tradition in the 21st century style and remind people ham radio is still relevant today!
References and Resources
I am an SBMS member. Join us!
The San Bernardino Microwave Society (SBMS)
The World Above 1000MHz – Peter Day, G3PHO
USA Amateur Radio Frequency Allocations – The tiny bottom right corner of the chart
Microwave Update: The best technical conference to meet other active VHF-plus ops and learn more!
10 GHz Qualcomm Modification Notes, by Dale Clement, AF1T – SBMS
Modifying the Qualcomm 1W Ku-Band PA for use on 3.4, 5.7 or 10.3 GHz by Kerry Banke N6IZW
DUBUS – the serious magazine for VHF and up amateur radio
A List of VHF and Up Contest Locations in Southern California
Down East Microwave – Transverters and other kits and parts
Kuhne Electronic – Transverters and other kits and parts
Microwave Ham Radio Tom Williams WA1MBA
Jim Klitzing W6PQL – Sequencers, accessories, amplifiers and general information
Mike King KM0T – Great website with lots of pictures and construction notes
Read my LinkedIn profile article about ham radio and my career
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Advice when soldering de KH6WZ
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