+++++++++++++++++++ Date: Mon, 17 Dec 2001 20:29:39 -0600 From: "George, W5YR" Subject: Re: [Elecraft] Milliwatt Mod for the K1 Set the power output as low as it will go and insert a resistive pad in the line to the external tuner or antenna. The Handbook describes how to select resistor values for pads of various configurations and attenuation and power levels. 72/73, George W5YR - the Yellow Rose of Texas QRP-L 1373 NETXQRP 6 Fairview, TX 30 mi NE of Dallas in Collin county EM13qe SOC 262 Amateur Radio W5YR, in the 56th year and it just keeps getting better! Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437 All incoming and outgoing email virus-checked by Norton Anti-Virus 2002 Tom Mihelich wrote: > > Has anyone or does anyone know of a way to bring the K1 power level > down > lower than 100mW? I would like to try working with this great rig in > the 1-25mW range. > If the rig can not be tweaked then maybe something in-line between the > rig and the watt meter? +++++++++++++++++++ Date: Mon, 17 Dec 2001 23:43:29 -0800 From: "Ron D' Eau Claire" Subject: RE: [Elecraft] Milliwatt Mod for the K1 Tom asked: > Has anyone or does anyone know of a way to bring the K1 power level > down > lower than 100mW? I would like to try working with this great rig in > the 1-25mW range. > If the rig can not be tweaked then maybe something in-line between the > rig and the watt meter? A simple attenuator will do the trick, Tom. One very common configuration is the "Pi" configuration, that looks like the greek letter "pi". At the input there is a resistor to ground and a resistor going to the output. At the output there is also another resistor to ground. So the schematic of the attenuator looks like the greek letter "pi". For 10 dB attenuation in a 50 ohm line you want 91 ohms for the resistors to ground at the input and output and 68 ohms for the resistor across the "top" of the pi between the input and output. For 20 dB attenuation the resistors to ground are 62 ohms and the resistor between the input and output is 240 ohms. Of course 10 dB of attenuation will drop your power by a factor of 10, so 100 milliwatts becomes 10 milliwatts. 20 dB will give you 1 milliwatt out for 100 milliwatts in. Use non-inductive resistors to avoid adding reactance to the circuit. I understand that metal film units are good in that regard. The old 'carbon composite' are good too. Be aware that the power 'lost' in the attenuator is dissipated as heat by the resistors. They have to have sufficient wattage to handle the power. Ron AC7AC K2 # 1289 ++++++++++++++++++++++