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For about the last two or three years I have been working with OVRO to be able to use their 130foot dish for EME. The San Bernardino Microwave Society has been the main support. Thanks to a group effort and that of Chuck WA6EXV, we have made a transverter and used it with the dish a number of times. This link takes you to our main page. http://www.ham-radio.com/sbms/ovro/

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The Microwave Rigs

10Ghz Transverter

This is my old favorite 10Ghz rig “Lord of the Dishes” (One dish to hear them all) It is about 6 years old in one form or the other. Did I mention that I like Quickset Sampson tripods? Output si 2 watts and the NF is about 1db. I can aim at the palm tree across the street, peak up on the noise and hit all the locals. Great path finder. Some more subtile things are the 3A switching power supply on the side, The FT 51R with external antenna and speaker mic. We have found that for liaison work, radios without wide range receivers are much better in high intermod areas. Kenwood THF6a is one. An LCD clock on the face of the dish, An external speaker and around the neck earphones. Noting sticks out on any of the radios that can be broken off in getting it in and out of the car. One last accessory not shown is a Petzl red LED forehead light to use at night. They work forever and always point where you are looking hands free. Best DX with this rig was Huntington Beach to Fresno. Not too long but over a considerable range of mountains. Otherwise it would have to be Figueroa Peak near Santa Barbara to Mexico: 900 or so Km.

24 Ghz Radio

I run most of my transverters off of AC inverters and switching PS to keep the Oblique view. Celeretek modules and OCXO/Qualcomm synthesizer.

voltage stable. It does wonders. Current penalty is minimal. I could make it smaller, but I wanted to keep the dish and mounting intact.

The wild red color on the feed is to keep from bending it again.

47 Ghz Progress

Not quite finished but all tested. A 6” dish, Philco module and CTI DRO locked to a 20Mhz TCXO and doubler. The 47.088Mhz operating frequency makes for some interesting LO problems. The Internal tripler in the Philco necessitates a 10ghz IF, which actually works out nicely. With my standby DB6NT 10Ghz transverter used as in IF, all the DC and switching is already done. It is a very simple system that runs on 12v. Again all the rigs run off switching supplies through an AC cord to an inverter on the batteries. All kinds of stability and output problems are minimized. Since the TCXO is not multiplied in the strict sense, this source may work ok. I have a very good OCXO that can be substituted- also 12v. The Philco unit also has a small supply to peak the mixer diode sensitivity. Out of the box these units perform well up through 100Ghz as transverter mixers and spectrum analyzer front ends.

78Ghz Transverter Project

All of it works on 12v except the relay Front view-1foot Cassegrain dish and Celestron spotting scope.

The rig is composed of a 1’ Cassegrain dish from N1WR. It has an excellent pattern and gain. The mixer is a DB6NT that has been modified by Will, W0EOM with a waveguide input from the LO tripler. The DRO has an interesting Ref. It has a 100Mhz OCXO fed into a divide by 4 prescaler to lock the DRO with a reference of 25mhz at 13.375Ghz. That gives me an operating frequency of 79.8Ghz with 450Mhz high side injection. I hate high side, but this is the way the pieces fell together. I have a WR15 waveguide relay in the projects pile and as soon as I get a waveguide amplifier, I will improve both the noise figure and output. At this point, it is operational and that was the first step. Once I have the bugs ironed out, I will move it up.

78Ghz Notes- Here are some notes of what I used and what I did along the way.

Here are some choices a person needs to consider: If you transmit CW through a regular mixer you loose power from the LO and IF through the mixer -6db and because of the DSB signal it produces -3db. There are other losses that put you above 10db loss. By having a separate LO for transmit, you can just multiply up to the frequency and get at least a 10db better signal.

However, with a switchable amplifier, you get an improvement in noise figure and gain as well as transmit output, so two serious problems are solved for the added expense of a baseball switch and amplifier. The latter seems to be the way most SBMS stations are looking at it.

Another gain in performance can be had by using a fundamental mixer instead of a sub harmonic mixer like the DB6NT. On both RX and TX you could lower losses by as much as 15db by using a fundamental mixer, That would also mean that you would have to put a doubler on the end of the tripler to feed 79ghz straight into the mixer. An amplifier after that setup could make a first rate rig.

Others have found impatt amplifiers and are using them on transmit.

Who is active locally?

As far as I know, there are three groups of stations getting ready for 78 in the area

The 50mhz and up group. About four operators. Most have their rigs on standby as they have all talked to each other, but are willing to get them out and talk with us on any frequency.

SBMS- two to 4 stations in the process. One done.

San Diego Group- Two or more stations in process but proceeding slowly. I am sure that they will quicken their pace as others get closer to being on the air.

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Test Equipment for Microwave work

Probably the most bang-for-the-buck investment I have made has been the Tektronix 494ap spectrum analyzer. It keeps you from guessing! It has a reference input for 10mhz- like your lab GPS source. It reads frequency to the hertz at 78ghz. You can find out where your real signal is quickly. It accurately measures power. Once you have calibrated the loss of your mixer, you can infer the level of any signal in the same range. It memorizes setups. Turn it on and press two buttons and take up where you left off. It also saves screen shots. It also does a million other things. I have used analyzers as far back as the Polarad SA 84w and HP 8551 and most things in between. There are other analyzers like the HP 8566B and HP 8569B that do pretty much the same thing. The point is that an analyzer like this takes out the guesswork and hours of tweaking on the wrong frequency. If you are concerned about the cost of mixers, there are many modules that do a very creditable job, and do so way beyond their designed frequencies. The Phillips boxes were available for under $50.

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EME Projects

432Mhz

432Mhz Continues to be a challenge due to a poor location and monstrous local interference. I am running 4x25el K1FO antennas, a Henry 2004 amp at about 1.3kw output, and a .3db NF preamp. I have used an FT 847 for quite a while and like it. A Timewave DSP 599zx also helps a lot.

Here’s a link to the 432 and Up Newsletter

Two meter 1kw amp on top, Henry on the bottom. They share a HV power supply.

1296Mhz

I now have a 300watt output GS15b amplifier running and ready. I am transitioning from a 7’ dish to a 10’. I hope to have it on this year.

GS15b Amp. Water cooled and about 300watts output at 2kv and 10watts drive.

Me in the garage with the rig. The 7foot dish is just outside and hand steered. The black box on the far right is the control cable interface. That and two coax cables go to the dish. Easy to use and operate. The Hi Spec has been replaced by the More Power GS15amp.

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