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Everything You Wanted To Know About Microwave Things, But Not So Much You'd Have To Get Too Familiar With James Clerk Maxwell This paper will deal with a variety of microwave information that is not contained on most data sheets. It involves things like cable attenuation, power handling capability, etc. First off, an information tidbit. One of our microwave tools that has not been completely superseded by the electronic calculator is a cardboard sliderule called the HP Reflectometer Calculator, (Lit # 5952-0948). It relates SWR to reflection coefficient to return loss and mismatch loss. It shows you mismatch losses for power measurements when you know the SWR of the source and the SWR of the power sensor. And it is a handy reminder for the numerical vs. the dB ratios of voltage and power. ATTENUATION AND VOLTAGE AND POWER RATINGS OF MICROWAVE THINGS HP sells a variety of accessories that are basically unspecified. These are the connector adapters, cables, etc. A typical customer question might ask for the attenuation of the RG-214/U cable used in the lIP 11500A Cable Assembly. The answer is to look in the Reference Data Book For Radio Engineers. Cable attenuation is plotted for all sorts of coaxial cables from the RG-59/U video cable we use with BNC connectors to large 3 1I8-inch rigid coax, which we don't sell. Incidentally, our lIP 11500A which is 6-feet long would have attenuation of 2.4 dB at 10 GHz (40 dB per 100 feet). The ITT tables on the Army-Navy list of preferred Radio-Frequency cables also shows other useful data. For example, the capacitance of RG-59/U cable is 21.5 pF per foot. This may be useful if you need to know the shunt loading capacitance of some BNC video cable which may connect a microwave detector to the input jack of your oscilloscope, if you want to use it unterminated, and look at the pulsed RF envelope. Those same tables show that the minimum operating voltage of the RG-214/U cable is 5,000 volts rms. In a 50 system, that might imply that you could put one half megawatt on the cable. But there are two things that limit that power. The Type-N connector on each end is only rated at 500 volts and if you look at one, you can see why. It uses air dielectric while the cable itself uses polyethylene dielectric. That connector rating of 500 volts, of course, permits about 5000 watts. But if you consider the attenuation of the cable, that will limit your CW power to much less. Consider the 2.4 dB at X-Band. That means that about 7 feet of the cable would exhibit 3 dB or a loss of half the power. I'd guess that dissipating even 100 watts in 7 feet of cable would be a problem. Think of it as bottling up the heat of a 100 watt light bulb in that length of cable. If you figured that the 7 foot cable could dissipate 50 rI3I HEWLETT JMljd minck.sam 2/94 2 ~PACKA