Flex 6500, question on panadapter/waterfall BAD SIGNALS??

  • 2
  • Question
  • Updated 5 years ago
  • Answered

I have the 6500.

I have noticed quite a few signals show on the panadpter a wide spreading out signal...meaning if I let's say have 2.9 as my rcv bandwidth I see a very large spreading of the signal at the bottom (maybe 2 KC or more than the bandwidth image.

Also on the waterfall I see horizontal spikes going out each side of the signal. Reducing Pre-Amp or using ATTN does not change the display (Anytime??).

Is this a problem with the Flex design?? OR are these signals really that bad?

It seems only with very strong signals...but I have seen many +10-20 signals look OK.

Is the front end of this radio getting overloaded or are there that many bad TX's out there??



Photo of Lee


  • 84 Posts
  • 19 Reply Likes

Posted 5 years ago

  • 2
Photo of Andrew Russell

Andrew Russell

  • 278 Posts
  • 44 Reply Likes
Official Response

G'day Lee,

The 6000 series sees all the warts on other signals. Phase noise and IMD.

The strong signal is actually not bad.

Running at 13.8V really does make a clean signal at 100W difficult. I suspect that many PSU and cable combinations just sag on low voice frequency peaks. 

The guys running 50V PAs look great.

I have seen many where a slight reduction in drive makes the emission a lot cleaner.

The Flex SDRs can also cut the level of low frequencies that can be dominant in male voices.

These add little to intelligibility and are likely outside the RX pass band as well as stressing the PSU and PA.

There is a boat anchor net in South Eastern VK, its fascinating to see the range of signals on the old gear. From almost perfect to horrible.


Photo of Jay / NO5J

Jay / NO5J

  • 1674 Posts
  • 262 Reply Likes
Official Response
Yep it is not your Flex, Those wide signals are really wide. You just were unaware, you cant hear outside the pass-band, but now you can see what your not able to hear. Report violators to the band police, No, don't do that because then a different sort of pollution will move inside the pass-band, and you will hear that. I'd just fall back on reporting back that they are 599 no matter how they sound as is the custom. Your not broken, they are, unless you have your mic gain adjusted beyond a 0dB level. in which case your signal probably looks about the same. -0.1dB is ok, > 0.0 is always bad. Now that we can hear and see, lets call it good before someone develops a DSP method of displaying how a signal smells, It's bad enough that my boat anchor equipment has the delightful scent of ashtray/spitoon when ever I turn them on. I don't want my Flex smelling like most of the signals look.