Friday, September 26, 2014

It All Makes a Difference

Tonight I was listening and watching the ZD9XF Tristan Da Cunha & Gough Is pileup on 40M

He had them spread out over about 9 khz and was working the entire 9 khz.

The band was fairly noisy.  With 25 hz filters he was virtually un-copyable 

The noise floor was -99 dBm at 25hz.  I decided to give min bandwidth a try

At 10hz I had a -110 dBm reading for a noise floor

You can see his peak signal strength was -104 dBm at 10hz, 5 dB under the noise at the 25 hz bandwidth.  At this level he became readable BUT at this level tuning has to be exact 

3 hz makes a difference.  Tonight I added a FlexControl to my DDUTIL setup giving me the ability to tune easily in 1 hz steps 

The FlexControl marry's with DDUTIL and gives a wide variety of control options to the radio.  Its other feature is it is persistent and does not loose control with change in focus

I was involved in the design of this device and it is quite powerful and plastic to its functionality. 

I use a second FlexControl on my 6300.  I guess there is still a debate raging over knob v. no knob in SDR but for me this device is perfect and I highly recommend it.  

I already had ZD9XF in the log on a few bands including 40M so I didn't turn on the transmitter to add to the QRM.

Speaking of the 6300 I switched the 40M vert over to that radio to see how it compared.  ZD9XS was about equally copyable but the 6300 only goes to 50hz bandwidth.  I used APF and adjusted the AGC-T to compensate.

The signal strength was virtually identical at -102 dBm average, but the noise floor was about -104 dBm with the wider filter so the signal to noise was a bit worse on the 6300.  This is one of those cases where pulling out all the stoppers did make a difference, but I could have made the contact on either radio.

Here is a shot of the pileup in all of its raging glory.

Good times!  I notice 80M is starting to pick up a bit as well as 160M  

73  W9OY