[AMPS] Grounding Dummy Load ??

[Radiodan W7RF]

Hi Jim,

You are probably experiencing poor isolation on the antenna switch.
To roughly check this, listen to those weak signals while switched to the
DL, then disconnect all the antennas and see if you still hear any signals
while still in the DL position.

73, Dan Magro W7RF, (President WARC 1999, member SCDXC, SCCC)
Manufacturers Rep & Distributor for HENRY RF Power Amplifiers.
www.radiodan.com <http://www.radiodan.com>     RFpower@radiodan.com
<mailto:RFpower@radiodan.com> A trip to our web site is worth the click!




> -----Original Message-----
> From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> Behalf Of Jim Reid
> Sent: Tuesday, September 21, 1999 2:33 PM
> To: amps@contesting.com
> Subject: [AMPS] Grounding Dummy Load ??
>
>
>
> Hi,
>
> Last night while tuning up into the DL to 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?
> 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
> in a container of silicon oil.  The container has fins to
> dissipate any heat,  and the DL is rated to take a
> couple of kW continuous   (Bird 8890 unit).
>
> 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
>
>
>
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>


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