TX Waterfall Gain

W9WLX_Chuck

I was curious if anyone else has seen the TX waterfall display gain vary from band to band?  I'm using the same antenna for RX and TX and the TX waterfall display intensity seems consistent on 40-6 meters.  On 80 meters, the display gain appears to be less.  Audio levels are identical as well as display settings.  Receive display gain is consistent across the entire spectrum, in the ham bands as well as outside. Am I missing a setting somewhere that is persisting?  I'm running V2 on a 6500, but I noticed the same prior to V2.  Using Gain 30, Black 1 & Auto on, Rate 80.

-Chuck, W9WLX

Jim Gilliam

Does your noise floor appear to be the same on all bands? Less noise will make the background look darker.

Jim, K6QE

Paul - K6HR

Curious if the zoom level of each band observed is the same?

W9WLX_Chuck

The noise floor does creep up on the lower bands, with 80m about 5-15 dBm higher than 15m.  The darker display is on the higher noise floor band.  The zoom is pretty consistent.  When in QSO mode, I like to see signals at my preferred width, so the zoom is comparable from band to band.

Tim - W4TME

First off, the waterfall data is a representation of the sampled RF and has nothing to do with audio levels or AGC-T.  It is a representation of the actual signal.

The black level since it is set to auto takes into account the noise floor within the spectral bandwidth of the dispaly and this is effected by zoom level.  The amount of black level also affects the gain level of signals.  Since there are two variables involved, one is constant (gain) but adjustable and the other is dynamic (black level) so that changes in the digitized spectrum data stays fairly constant over a broad range of conditions.

The noise floor does vary from band to band.  What you are seeing in the panadapter is highly averaged data so that you can visually see signals at or near the noise floor.  I suspect this averaging is giving you the appearance that the actual noise floor is constant from band to band, but it is not, even if it is a small difference of a few dBms.

Also, display settings are remembered by band, so you might want to check the settings for 80m vs 40m for any differences.

W9WLX_Chuck

Yes, the display settings are the same.  I don't understand your comment about the audio level not affecting the display intensity since I'm looking at my signal in the waterfall while transmitting.  On SSB, if I am undermodulated or no audio, it should be less intense or absent.  The signals I see in the waterfall while receiving are all ok and consistent across the bands and the entire spectrum.

Tim - W4TME

Sri, I didn't pick up you are using the waterfall on TX. Most of the time, that setting is turned off.  I would not use the waterfall to validate over or under modulation.  Use the TX level meter as it is described in the SmartSDR Software Users Guide.

W9WLX_Chuck

Thanks Tim.  No, I wasn't using it to set or verify mic levels, but when I saw the difference between bands, that's the first thing I checked.  The question was just one out of curiosity.  There's no impact to usability--no worries!

-73, Chuck  

BH4AAD

I've noticed the same thing, but no one ever seems to mention it.  I wonder why this is so？

KD0RC

I think that most people set the option to stop the waterfall during transmit - I certainly do. With this setting, you would not see this effect.