TX bandwidth audio for packet 9600 and VARA

Luis del MOlino · May 2020

Problem with my Flex.6500 and SmartSDR v.2.6.0

I have been trying to use DFM mode for a new FM digital wider mode, VARA FM WIDE, that needs a very similar TX audio bandwidth as the one needed for packet 9600.

I think that the TX filter bandwith on the TX Phone display only applies to Phone modes, and you have forgotten to apply it to DFM mode,.

When I try to use a 6 kHz TX audio bandwidth for VARA Wide Mode that needs almost 6 kHz audio width, there is a roll-off at 4 kHz on TX audio that does not change increasing the transmitter TX audio fllter bandwiidth to 6 kHz in the DFM mode.

Please see the spectral audio image herewith enclosed that shows the Roll-off in the audio spectrum transmited by my Flex 6500 as seen in a RSPduo SDr receiver..

Luis EA3OG

W0DHB · May 2020

Luis

On the RX side I have been able to get a Flat response 0 to 7 kHZ by adjusting the equalizer and various other parameters which are only accessible through the SmartSDR API.

On the TX side I am close to getting a flat response from 0 to 7 kHz making similar adjustments.

I have filed a ticket with Flex and it has been issued #4888.

Here the settings I have had some success with:

RX equalizer settings

level_32Hz= -2
level_63Hz= -2
level_125Hz= -2
level_250Hz= -3
level_500Hz= -1
level_1000Hz= 1
level_2000Hz= 5
level_4000Hz= 5
level_8000Hz= 2

RX Slice Settings

FMDeviation= 5000
FilterHigh= 10000
FilterLow= -10000
PostDemodHigh= 8500
PostDemodLow= 0
DFMPreDeEmphasis= False

TX Equalizer settings

level_32Hz= -4
level_63Hz= -4
level_125Hz= 8
level_250Hz= 5
level_500Hz= 2
level_1000Hz= -5
level_2000Hz= -10
level_4000Hz= -5
level_8000Hz= 10

TX slice settings

FMDeviation= 5000
FilterLow= -10000
FilterHigh= 10000
PostDemodHigh= 8500
PostDemodLow= 0
DFMPreDeEmphasis= True

Radio settings

TXFilterHigh= 8500
TXFilterLow= 0

Dave W0DHB

Jeremy_W2JG · September 2020

I was just able to send VARA FM WIDE Mode with a 6700 and no special settings, but I used FM mode (standard 16KHz filter), versus DFM. My equalizer was turned off, but both my Tx and Rx DAX Gain settings were set to 50, the half way point. In VARA, I was set to -10dB.

I am running SmartSDR V3.1.12

Jeremy

W2JG

Mark K0JM · December 2020

I am attempting to use my 6700 with a DownEast Microwave transverter and LDPA to operate at 9600 bps on the FalconSat-3 satellite. I am using DFM at 20 kHz bandwidth and have good copy on the downlink signals on 435.1 MHz. However, I cannot make the satellite hear my uplink. I've tried a wide variety of settings, but no luck. This shouldn't be so hard.

glider73 · January 2022

Can you let me know which modem and SSDR settings you were using to copy the 9600bps signal from FalconSat-3? I have a good strong signal from the satellite using an Oscar array with az&el tracking but no luck on the copy so far thanks for the help.

W0DHB · March 2022

Mark, K0JM, is using FlexSATPC software in conjunction with SATPC32 to copy FS-3 9.6K Packet. FlexSATPC applies the settings specified in my post dated May 2020 to allow FS-3 Downlink (9.6K packet in general)

This works with AGW PacketEngine (Pro), MixW and UZ7HO hs_soundmodem software.

The issue of uplink not working has been reported to Flex along with detailed information as to why it's not working.

Note that a couple of the settings must be done via Flex API based software, they are not user settings in SmartSDR .

You can email me (good in QRZ.com) if you are interested in FlexSATPC software.

Dave W0DHB

TX bandwidth audio for packet 9600 and VARA

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