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Mars2010
- 2. Mars Equipment Conversion Dr. Roger B. Hughes, AFA9HR / AFE9TS USAF SW Area MARS Technical Support AE6MI / AFF9TD 2
- 3. Types of Equipment • Transceivers • Need to enable general transmit • Antennas • Many military frequencies, best antennas to cover this? • Linear Amplifers • Valve and solid state 3
- 4. Why Modify? • Frequencies are outside amateur bands • All ham equipment is restricted to transmit only within amateur bands • Need to modify in order to enable transmission on military frequencies used by M.A.R.S. • What frequencies are used? 4
Editor's Notes
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- We’ll cover each of these equipment types in order during this talk.\n
- In general, let’s look at the frequencies that are used for MARS\n
- If we look at the radio spectrum, the MARS frequencies go all the way from MF through all of HF, that is, 2MHz to 30MHz. Let’s look at just the HF spectrum from this chart,which is highlighted in the third row here.\n
- If we focus on the HF spectrum, we see that the frequencies as shown here, we note that the MARS frequencies, which are fixed singled frequencies inside the Red areas are always outside the amateur frequencies, which are shown in green. Sometimes these are a long way outside, but often they are close enough to let amateur equipment such as linear amplifiers to be used with little or no modification.\n
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- What this slide shows is how an antenna needs very little trimming for a height of 0.5 wavelengths but as the height is reduced, the antenna length needs to be trimmed progressively more in order to maintain resonance.\n
- Note how the directly overhead radiation is very low when at 0.5 wavelengths. There is little difference in direct overhead radiation when height is lowered from 0.25 to 0.125 wavelengths. For NVIS, 45 deg and above, this can give 500 miles radius.\n
- Note how that as the antenna is lowered, the pattern becomes more straight-up, it becomes a “cloud-burner” which is ideal for NVIS. Note how pattern depends less on orientation of the dipole as it is lowered, that is it becomes more “ball” like in shape with an omnidirectional pattern that is independent of antenna orientation.\n
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