[Antennas] IMPORTANT ENAIL VIRUS INFO

2002年10月10日 06:45:41 -0700

WARNING, THE FOLLOWING EMAIL CONTAINED A VIRUS=20
NAMED (W32BUGBEAR) Thanks to Norton AntiVirus my computer
was not infected. The sender has been emailed....
=20
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NO, its just that there's no such thing as perfect coax. I had a friend =
six
blocks away and during net time on 10 M I'd flip over to the dummy so he
wouldnt bend my S-meter needle. He still came in S-8. If you look at =
coax
specs you'll find a spec on shielding efficiency. CB coax runs about =
85%.
RG213 runs about 95%. 9913 is best, it has foil and braid. 73
At 01:06 PM 09/21/1999 -1000, you wrote:
>Norm wrote:
>>> Hey all, I always use the dummy position on my tuner to=20
>>feed a DUMMY LOAD....This allows you to tune your=20
>>transmitter but does nothing to tune your antenna.=20
>>Now my question about dummy loads:
>>Last night while tuning up into the Dummy Load(DL) to=20
>work the 3C0 (which I did, hooray), I noticed I could hear
>a faint bit of rcv'd signal in the rig while connected
>to the DL, not the antenna! The antenna tuner unit
>was in the "Bypass" switch position to get to the DL.
>>However, I can also hear a faint active RF signal when
>the wafer switch in the antenna tuner is just set to
>Coax 2, which in my case just goes to an unused
>antenna input 239 socket on the back of the tuner.
>Maybe this is just 60 to 80 dB down or more
>coupling between wafer switch contacts?=20
>Top view down onto my tuner showing layout
>and two wafer antenna/DL switch can be seen at:
>> http://www.palstarinc.com/palmain.htm
>>As I look at it, the DL is a sort of shielded 50 ohm
>resistor connected between shield and center
>conductor of about 8' if coax to the unit sitting outside=20
>in a container of silicon oil. The container has fins to=20
>dissipate any heat, and the DL is rated to take a=20
>couple of kW continuous (Bird 8890 unit, info at
>http://www.rfspec.com/bird/8890.htm ).
>>Should the unit's shielding case be grounded to
>the station common ground point outside? The
>DL is sitting out their just beside the ground
>rod and cold water service pipe to which the
>rod is also strapped with 1" wide braid.
>>Would a 1" wide braid to the DL case be needed,
>wise, or silly??
>>73, Jim, KH7M
>>>>From: 
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