This is all done in a portable configuration no external antennas. I probed the case of the 436 and found an excessive amount of noise coming from the bottom rear of the radio. I am not an engineer so I have no idea what kind of noise it is. I applied some RF shielding tape to the inside of the battery case lid. To my surprise the normal hiss/static/noise what ever you wish to call it diminished drastically. I have tested this for a week and the findings are all positive. There are some UHF RF link transmitters in my area that I could not hear. Now I hear them. If I remove the battery cover the signal goes away. Some weaker signals contain a large amount of hiss on the audio, that is hiss is now gone. If I remove the battery cover while they are transmitting the hiss returns. There are some P25 UHF control channels that I could not hear, but now I do. Over all the radio is not quite as good as the 396 but it is a tremendous improvement over what it was. I do not know how many db of noise reduction my tape provides. I have had it for years. I do know that aluminum foil does not work. This was tested on several 436s and the results were the same on each one. I would be interested in how this works for others.