The trick to getting the best performance is to start the detector with the frequency control full clockwise, this allows the internal electronics (PLL) oscillator to lock over all of the adjustments using the variable frequency. If you start the detector with the detector frequency control not set to maximum clockwise the detector could go out of locking for the internal oscillator and the detector will either make crazy chirp noises or make bwarp bwarp noises.
If it goes crazy just switch it off and set the frequency to full clockwise and start again.
The frequency control when turned clockwise sets the detector for very tiny gold, the anti clockwise is for larger deeper gold, set the frequency in mind with the coil size that you will be using, do not go using a 25" coil in high frequency as you will lose depth on bigger gold. Rule of thumb..... Small gold = small coil = high frequency. Large coil = larger deeper gold = lower frequencies.. Set the gain to half way (roughly) and ground balance the detector, then move the coil like you are detecting and take notice of the ground noise.. If there is none then increase the gain and set it to the point that ground noise just starts to appear. Always reground balance after adjusting gain of frequency.
A useful tip, lowering the frequency will reduce ground noise as the ground signal has longer to decay, the upside is that by doing this you can use much more gain to compensate and still have a huge advantage in noisey ground.
Pulse induction detectors have great difficulty detecting specimen type gold, try a very small coil with the high frequency to be able to detect quartz veins.. There is also an advantage in using DD coils and upping the gain for a better signal in relation to ground noise response.