```Mal, ``````The only accurate way to measure loop inductance for an installation is to use an inductance meter. Calculations do not take into account the loop environment like trees and other objects in the vicinity. ``````100s of hours of measurements on my part indicate that trees have next to no effect on TX loop performance, including inductance values. All my loops amount to a conductor placed over the top of, and resting on at least 6 trees. The ground has some effect on the inductance, but less than 10%. ``````The same applies to natural resonant frequency, the loop or any other ``````antenna ``````needs to be measured in situ, calculations for real situations can be totally different from theoritical values. ``````I find the resonant frequency also comes out very close to the theoretical value once the inductance is calculated and/or measured. ``````This is where a lot are going wrong on LF. ``````I believe what is going wrong is that many guys fail to start out with good reference material and not 'going through the numbers' on paper. Secondly they don't reach a basic understanding or 'feel' of how a loop performs by getting the Rac down to an acceptable value consistent with the loop dimensions and conductor type. They will be putting 99%+ of the power into that Rac and it is all wasted in heat - so it better be as low as possible! A low power level must be used for this experimentation because only a tiny breakdown of a component will totally mess up results/conclusions/opinions. Then comes the problem of selecting a capacitor that can handle the voltage and current in the loop. At 1w my loops run up to 1.5A at 150v RMS... no problem for plain old 500v micas. At 100w the current and voltage is 15A and 1500v RMS. Getting tough? Darn right! - but doable. At 1000w you are at 47A and 4700v. For those that are this crazy, the loop conductor will have to use #6 or multiple runs of smaller size wire and the capacitor will have to be...... well, something exotic! My gestimation is that at 1000w you will be ```exceeding 1w ERP, anyway, so this likely a theoretical design. Bill A ```********************************************************************* This footnote confirms that this e-mail message has been scanned for ```the presence of known computer viruses by the MessageLabs Virus Control Centre. However, it is still recommended that you use ```local virus scanning software to monitor for the presence of viruses. ********************************************************************* ```