{Collins} Re: Swamping Attenuator information



I like to stack paralell resistor 2 watt units between two pieces of circuit board material leaving one resistor diameter spacing between resistors. Makes a neat compact unit with low inductance leads and relatively easy to get any resistance power rating required.
My 2 cents worth
K0UYA
----- Original Message ----- From: "k7fm" <k7fm@xxxxxxxxxxxx>
To: <collins@xxxxxxxxxxxxx>
Sent: Saturday, December 01, 2007 8:36 PM
Subject: {Collins} Re: Swamping Attenuator information


Either a Pi-network or T-network will work fine. The Johnson example is a good choice if you want 6 db of attenuation.

I calculated the power needed for a 3 db pi attenuator and came up with 300 ohms at 20 watts at the input (standardized values), 20 ohms as a series resistor at 25 watts and the end resistor at 300 ohms and 10 watts. Any combination of series and parallel that will reach the appropriate resistance and power should work fine.

If you use carbon composition resistors, remember that they will fail if used near the rated value. As they warm up, the resistance changes - and keeps changing. The newer resistors are much more stable when run at rated power, although you should be sure you are using non-inductive resistors. No wire wounds.

73,  Colin  K7FM
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.
SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
     http://www.collinsradio.org/membership/    -paypal accepted-
.
NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
 SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
      1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)





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