Check the listing for details. Heathkit 70 dB Attenuator Mod. Listed at 15.00 USD. Data Professionals Main Page Heathkit 70 dB Attenuator Mod We designed a very nice external attenuator for the original IG-57. This attenuator was then passed on to the IG-57A and the IG-5257 in later kits. You probably own one, or have seen these at various Ham swaps or auctions. This external box allows attenuation from 1 to 70 dB in 1 dB steps. The only issue is that it was originally designed for a 75 Ohm input and output impedance. It is possible to re-build the attenuator with different value resistors so it will operate with 50 Ohm equipment, but it seems that doing the calculations, finding the required passive parts, ordering them, and testing the final product is a lot of trouble to go through. For that reason, if you have one of these nice little attenuators, like us, it has probably just sat on the bench. Maybe you have even used it, but the switches were not accurate because of the difference in impedances. It had been suggested by a few of our customers to create a simple kit of resistors to make it more convenient to do the modifications from 75 Ohms to 50 Ohms. This makes all of the values of attenuation printed on the face accurate. In the process of doing this, we decided to upgrade all of the resistors to 1 Watt. Newer 1 Watt resistors are about the same size as the original ½ Watt resistors. This allows you to work with up to a 1 Watt signal source continuously, or we have had good luck going as high as 5 Watts intermittently. This kit of parts gives you all of the resistors required to re-build your Attenuator for a 50 Ohm system. This will give you more options of using it and the printed attenuation levels printed on the face can now be used to determine sensitvity and s/n measurements. The 4-page manual includes a pictorial,step-by-step instructions, picture of the final project, and a schematic of finished attenuator. Attenuator pictured below is not included in the Mod kit. This is an example of how the finished unit will look.