6500 Running Multiple Bands

  • 1
  • Question
  • Updated 4 years ago
  • Answered
I did a presentation on my Flex 6500 to my local ham club and a question came up.  Since the Flex selects the initial bandpass filter prior to the ADC, if two panadapters are open on different bands would the selected bandpass filter be 'mismatched', allowing too much noise on the second band?  Is this a disadvantage compared to a radio like the Elecraft which can autoselect a roofing filter for each of the two receivers installed?

I presume that the Flex 6700 could have a bandpass filter auto selected for each of the two receivers.

Thanks, Ron
Photo of Ron


  • 71 Posts
  • 4 Reply Likes

Posted 4 years ago

  • 1
Photo of Lawrence Gray

Lawrence Gray

  • 182 Posts
  • 87 Reply Likes
You can select whatever bandpass you wish on each slice?
Photo of K6OZY

K6OZY, Elmer

  • 542 Posts
  • 212 Reply Likes
If you are on a 6500 and widen your Pan or open two pans that are out of a single ham band, the PreSelector disables and you see "WIDE".  On a 6700, you can feed each SCU with an antenna and keep their corresponding preselectors enabled if you are within a reasonable border range of a single ham band.

Honestly, in my operating environment, I have never needed a Preselector, which is why it is wise that the 6300 has it omitted as a cost savings.   I use a Carolina Windom which is multi-banded and never isolate myself to a single band on my 6700.
Photo of George Molnar, KF2T

George Molnar, KF2T, Elmer

  • 1680 Posts
  • 616 Reply Likes
Since there's only one SCU in the 6500, when two bands are selected, or if a very wide pan adapter is created, the bandpass filters normally engaged for single-band use are not in-line. This is shown by the "WIDE" indication on the panadapter.

In some situations, this could lead to higher noise levels, depending on your environment, and the characteristics of your antenna system. With a lot of installations, the bandwidth of the antenna tuner in line is a limiting factor. 

I don't notice a meaningful performance hit. It's great fun looking at 14 MHz of spectrum and placing slices wherever something interesting appears.
Photo of Robert -- N5IKD

Robert -- N5IKD, Elmer

  • 488 Posts
  • 152 Reply Likes
Tim described the operation of the band pass filters in this post "SCU bandpass override
Photo of Al K0VM

Al K0VM, Elmer

  • 615 Posts
  • 103 Reply Likes
   The 6500 has one  selectable, ham band width filter per band between the antenna and the ADC unless the 6500 is on two or more different bands ( WIDE)  then there is no band filter ahead of the ADC.  ALL other filtering is provided in the digital domain and filters for each slice are totally independent.
    In this technology there is on such thing as a 'roofing' filter in the sense of analog radios.
   With the 6700,  each ADC (2) has its own set of selectable band filters  .

Photo of Ron


  • 71 Posts
  • 4 Reply Likes
Thanks for the quick and knowledgable replies.  I guess I will spend some time with the pre-selector on and off and get a personal impression of the impact.