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Re: attenuator construction questions



If I understand the question correctly, you probably need to fix the noisy 
component rather than use an attenuator.  The attenuator will attenuate the 
good with the bad.  You can reduce the noise floor by 15dB, but you will 
also reduce the target signal by the sams 15dB.

I do not have the formulars handy, however the RSGB handbook has a table of 
values for attenuators. They have both T and pi pads with impedances og 
both 50 and 75 Ohms.
Tell me what attenuations you want and I will send you the values.

73
Glenn
WB4UIV


  At 11:10 AM 9/8/01 -0400, Mark L. Hammond wrote:
>Hello all,
>
>To receive AO-40, I'm using a DEM preamp into a modified Transystem 3733 
>downconverter and BBQ style dish.  I'm getting about an S9+5 or S9+10 
>"background" signal.  I'm interested in constructing an in-line attenuator 
>to put between the downconverter and my TS-790A help bring this down to a 
>reasonable level.  (yes, the 144 ATT in the rig helps, but I want more.)
>
>I'm guess I'm showing my ignorance here, but how do I do the calculations 
>to determine the circuit needed for various levels of 
>attenuation?  Meaning, suppose I want an attenuator that achieves 15 dB of 
>attenuation?  What about 12 dB, or 20 dB?  I've perused/searched my ARRL 
>Handbook CD, but can't find what I need.
>
>Instinct tells me it will probably only be resistors--I just don't know 
>what values or how many, etc.
>
>Any help is much appreciated.
>
>73,
>
>Mark L. Hammond  [N8MH]
>
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>

---------------------------------------------------------------------------
Glenn Little                         glittle@awod.com   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv@amsat.org   AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)                      ARRL  TAPR
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