160M bandpass filter

Greg

On 160M this morning I noticed the bandpass filter turns off even though I am still in the 160 ham band. I am on 1.875 and if I pan the display to the right the filter changes to WIDE as soon as 1.790 appears on the left side and effects the frequency I am tuned to and the noise floor drops by about 6-8 dB. Only have one slice open. Shouldn't the bandpass filter stay on unless the slice is tuned outside the band? Thanks Greg AB7R

Al K0VM

Greg, The switch from band filter to wide filter is also dependent on the width (span edges) of the panadapter that the slice is in.. For the band filters to be effective, all of the the RX slices and the pandatpers using the same SCU must be 'in band'. For a narrrow, low frequency band such as 160m, the switch points are near the band edges. I am not sure what the switch points represent in terms of actual filter width ( 1 db point , 3 db point ? + design margin ) . The software does take into account the the filter loses and thus the calibrated loss for the 160m filter is more than the WIDE loss.. The shift in noise floor is likely only noticable if you have no antenna connected or have an in-efficent receive antenna. AL, K0VM

Greg

The noise floor shift was noticeable on both the inverted L and a Hi-Z 4el array. I really don't like the idea of the filters switching on the panadapter edges. It should be base on the slice receivers only. If I am tuned anywhere in the 160M band the filter should be on, regardless of where the panadapter is. The way it is, if I am almost anywhere on 160 if the display is pretty broad the filter is not on. 73 Greg

Greg

That's a good point. But as it is, I agree to have the band edges...they're obviously necessary but should be based on the slice frequency and not what part of the panadapter is in view.

Tim - W4TME

The preselectors are on the SCUs. The SCU is providing the digitized data for the panadapter FFT and the defined slices, so there is an underlying dependency in play with the panadapter. The radio is configured to provide the best out of band rejection (performance) automatically by selecting the proper preselector and other filtering based on the radio's configuration

Greg

Thanks Tim. But it doesn't select the best configuration all the time. If I am working say 160 CW but panadapter happens to have moved so that 1.790 MHz is showing the filters turn off....even though the station I am working is above 1.8 MHz. If I move or open a slice below 1.8 then yes, the bandpass filter should turn off....but not when I am still tune to the ham band. Greg