>RG6 will handle several hundred watts at 2m, more at 6, less at 70cm. If
> >you are using it to feed a single frequency antenna, you can make a
> >transformer to go from 75 down to 50 ohms at each end. Since directTV uses
>block downconverters built in to the feeds and these are in the 1 GHz
> >range, most of the RG6 that is used is pretty good stuff and fairly low
>loss. >If you are going to use it for 2m and 70cm, the same transformer
>should >work since it would be one quarterwave on 2 and three quarter wave
>on >70cm.
One might observe that feeding a 36 ohm ground plane antenna with a 75
ohm feedline, the quarter wave matching section would be in the 50 ohm
range. F to PL259 adapters are readily available. A good RG6 foam cable
should not be that far off from LMR400 or CNT400 cable if the RG6 specs are
found to be accurate/applicable for the previous RG6 installation. If you
make/acquire a single 1.5:1 unun you should be able to test the cable loss
with a MFJ-259B or similar antenna analyzer. Two ununs, a 50 ohm watt meter
and 50 ohm dummy load would yield similar performance information. Remember
to make a test with the two ununs back-to-back (no test cable) so you can
subtract the measured transformer losses from the measured cable loss.
Depending on the antenna type, it may be possible to directly adjust the
driven element/feed point for a 75 ohm match. Mike wa3ts
PS: Be gentle to the dish when removing it, the LNB support arm is easily
bent is tossed to the ground from the roof level. A dremel tool with a
cylindrical rasp bit does a much cleaner job on the inside of the 3/4 inch
guide section. As for the polarizer plate in the guide section, the pot
metal is soft enough to cut with a small manual razor saw. Seal up the small
coupling port notch in the base of the guide section with metal tape or
other conductive material. I have used both both the SMA monopole and the
WR90 waveguide mod versions and both work great............
http://www.youtube.com/watch?v=40SIcR7tin4
73, Mike wa3tts
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