[Diabolical Artificer]

You'll find you only really need a range of about 1p to 1n so you could build your own in 100p steps but a decade box is really useful, mine was £20. When do the 1khz/10khz square wave test you might find a 560p is good at 1khz but when you jump to 10khz it needs lowering or whatever. It's just a case of mucking about till it's good compromise for both.

Andy.