Furuno 620 high v's low frequency - advice pls

[jack_attacks]

Help please - my 620 works fantastically on high frequency in everything from around .6m to 60 metres (deepest I have had it in), however I really struggle to use the low frequency. I generally leave it on the auto range/auto gain mode, however when I switch it to low, the display seems to be full of static and cannot recieve a strong bottom signal, even on the auto mode.

Does anyone have any tips on how to alter the settings to get the best out of the low frequency? Also, in general, when should the low frequency be used versus the high frequncy?

Playtime

[Deiter]

Playtime, I have never used your particular sounder, but i can tell you a few thigs about low vs high frequency in general.

Firstly, your high frequency mode give you your best detail. It works fine till you start getting into deeper water, where it suffers more losses and will eventually be useless. This depth will alter with different sounders and different power output capacities. No idea on yours, but this would be over 100m at a guess..

Low frequency penetrates the substrate (in this case water) much better, (same as HF radio working over greater distances than VHF) and so is handy for picking up bottom once over the shelf. If you never go that deep, you will probably never have to use the low frequency setting.

If in shallow water using LF, you may find that because the signal travels further easier, it picks up a lot more 'false' echos (signal rebounding from bottom to water surface, to bottom to surface and so on), with your transducer-receiver picking up a bit of the echo each time it rebounds.

i am sure someone on here will be able to provide a better explanation, but i hop this helps you understand the difference (LF vs HF) a bit more.

If all else fails, consult the manual

Damo

[Grand_Marlin]

Easy fix ... slow down.

For 50khz to work properly, it is best travelling at 4 - 6 knots ... at speed, forget it.

Cheers

Pete

[jack_attacks]

Thanks guys - I will try both pieces of advice...now just need the wind to stop blowing!