SSDR: 1.5 New Features Q1: RTTY Q2: FDX

  • 1
  • Question
  • Updated 3 years ago
A two fer....

1.5 is looking pretty good.

A question off the deep end.
Setting mode to RTTY and trying to decode the NavTex broadcasts, FlDigi won't lock (AFC ON) to the signal.  Switching tje 6500 mode to DIGU, it locks right up and prints.  Tried to copy Pt. Reyes station at 8.415Mc but can't with RTTY mode.  The 170cy shift looks okay but suspect the M/S frequencies are swapped.

Q2:  With FDX can one monitor their own Xmit signal (being careful to attenuate properly) and do 2-tone tests for example?

_..--
k3Tim
Photo of k3Tim

k3Tim

  • 849 Posts
  • 166 Reply Likes

Posted 3 years ago

  • 1
Photo of K6OZY

K6OZY, Elmer

  • 532 Posts
  • 198 Reply Likes
Q1:  RTTY is LSB.  If you are using FLdigi with RTTY Flex mode and RTTY mode in FLdigi, you must click the "Rv" button in FLdigi (it's in the bottom right corner).   FLdigi expects USB.

Q2:  Unsure, but there is a good worksheet on determining proper isolation.  http://www.flexradio.com/downloads/flex-6000-fdx-power-calcualtion-worksheet-pdf/
(Edited)
Photo of Walt

Walt

  • 236 Posts
  • 74 Reply Likes
Was using the RTTY mode with MMTTY in its standard default tone mode to copy some 30 meter RTTY stations - worked great.  I have never used FLDigi for RTTY so I cannot speak to that program.

Will find out how well the RTTY mode is for sure this weekend with CQ WW RTTY.

Cheers
Photo of Chris DL5NAM

Chris DL5NAM

  • 597 Posts
  • 130 Reply Likes
... from FLDIGI user manual:

You must operate your transceiver in the USB mode for the fldigi RTTY signal to be the correct polarity. If your transceiver is set to LSB then use the fldigi "Rev" button to reverse the sense of the mark and space signals. 
Photo of K6OZY

K6OZY, Elmer

  • 532 Posts
  • 198 Reply Likes
Thats what I already said!
Photo of k3Tim

k3Tim

  • 849 Posts
  • 166 Reply Likes
I think his point was to quote the manual in case further reference was required.
Photo of k3Tim

k3Tim

  • 849 Posts
  • 166 Reply Likes
RTTY:
Thanks guys for the help about FlDigi and RTTY mode.  I believe that solves the Navtex mystery.  The Pt. Reyes station was sending only syncs this morning, but it looks like the signal was locked properly.  The Rv button did the trick.

FDX:
It took a bit to find the FDX button (lower left hand side or main menu).  The manual just says enable the mode but doesn't show where it is located.  Now that I know....

I tried 1 W RF output and separate antennas with the Rcv A antenna disconnected.  Hence isolation should have been good.  One could hear the tones FlDigi was sending and observe the signal in the waterfall on the FDX slice.

It looks very promising to test the transmitter by dumping the RF into a dummy load and use a 2-tone IMD test via the 2nd (FDX) slice.  The I/Q channel of the receiving slice should be usable for this and have sufficient resolution.  Pure conjecture but so far can't see any show stoppers.

The above notwithstanding, the Xmit slice displays the transmit signal very well.  I'd turned off "waterfall in Xmt" but switched it back on for this test.  This seems to be improved in the new code drop.  Will now leave this feature enabled.

Next step is to find a 2T software audio generator and shove some audio from the PC to the 6500. 


Thanks for the help with these two questions!

_..--
k3Tim
Photo of k3Tim

k3Tim

  • 849 Posts
  • 166 Reply Likes
Many thanks for the link Chris as my google searches were somewhat unproductive.

Best Regards,

Tim
Photo of Winston VK7WH

Winston VK7WH

  • 248 Posts
  • 42 Reply Likes
Please let me know if you find one Tim, as I as also looking for a software two tone generator .

Wins ton VK7WH
Photo of Winston VK7WH

Winston VK7WH

  • 248 Posts
  • 42 Reply Likes
Oh, I now see the post above. Thanks Chris
Photo of k3Tim

k3Tim

  • 849 Posts
  • 166 Reply Likes
The more direct link is:
http://dl6iak.etonlein.de/projects/projects.htm

Again, thanks Chris of the link.

It looks like one can use the 2nd receiver to check the transmitter output via the 2T.  Don't make the mistake I did and forget to turn off compression / processor or the results are "messy".  Check it out:



The lower is the Xmtr, upper the FDX receiver.

One could capture the I/Q output of the slice and save for later analysis / record keeping.
Lot's of fun.  
With FDX capability one has to wonder how far predistortion can be. :-)

_..--
k3Tim
Photo of Bob Wright, N7ZO

Bob Wright, N7ZO

  • 268 Posts
  • 66 Reply Likes
Hi Tim,

-34 dB from the individual tones or -40 dB from PEP.  Not bad.  What, exactly was your signal loop?

73, Bob, N7ZO
(Edited)