Whats going on here then - Part II

Well,

Following my musings about the really pants audio bandwidth from the Yaesu SCU-17 back here:

http://g0mgx.blogspot.co.uk/2015/05/whats-going-on-here-then.html

I've found an old external USB soundblaster soundcard thingamabob and hooked it up to my PC with the audio in and out directly to the PKT jack on the FT-DX5000 (the same connector the SCU-17 uses for audio to and from the radio).

Here's the comparison between the two:

So the old battered USB soundcard has a completely flat audio response, the SCU-17 is totally pants. I am rather horrified at the frequency response from this expensive Yaesu unit - I don't think it's even fit for purpose!

What  load of Dingos Kidneys.

Local conditions.

What's going on here then?

Well,

You may remember I've been dabbling with the WSJT modes using meteor scatter and you also might remember that I have a FT-DX5000 with a SCU-17 rig interface.

I tried using the 5000 for 6M MS the other day and found widely swinging power out during transmit. I've done some simple tests today on the set up and with the radio in TX and using a PC based signal generator I see this power output vs. audio frequency:

Now, I would expect this to be reasonably fat across the audio spectrum - this is far from my expectations! This clearly explains why, on TX in JT6M, the power out of the radio varies so much as the tones change.

It's not much better on RX when receiving noise on the band:

Again, I would expect this to be flat.

So, is there something strange going on in the radio itself in the audio circuits or is this the symptom of a spectacularly pants sound card in the SCU-17?

I wonder.....

More on this will follow.

** UPDATE **

I've drawn some conclusions here:

http://g0mgx.blogspot.co.uk/2015/05/whats-going-on-here-then-part-ii.html

Odd, egh?

Left a jumper on the desk today:

Local conditions....

The Yaesu SCU-17

Well,

I've been to see my chums at LAM Communications today and I brought home one of these:

It's a Yaesu SCU-17 radio interface unit. I've owned a lot of radios in my time, the most "modern" perhaps being the Kenwood TS-990 and the Yeasu FT-3000. Both these radios have USB ports on the rear and built in sound cards. You connect the USB port to a PC and low and indeed behold, you have an audio device to send Audio to and receive Audio from the Radio, you also have a "Virtual" COM port that you can use for CAT control. The other really neat feature of the FT-DX3000 that I believe is unique to that radio, is that you also get a second "virtual" COM port that you can use to control PTT, FSK & CW switching from PC applications. The 990 doesn't have this second virtual port and hence you still need a simple interface between the radio and the PC if you want to hard control the PTT line, run FSK RTTY or use an external CW keyboard.

This interface from Yaesu kind of gives you a half way house. I have two "virtual" COM ports, one for CAT control and the second for PTT & FSK - but unfortunately no CW keying so I've had to construct another simple interface to do that on the new FT-DX5000 I have:

It seems a real shame to me that I need to build an external one transistor switch to use a CW keyboard with a very expensive radio! If anyone knows different to me then please let me know. The 990 I have has two of those circuits (actually opto isolated equivalents) for CW and FSK keying.

Th Yaesu SCU-17 also connects to the Packet and RTTY rear connectors on the 5000 and takes care of AFSK audio interfacing as well as the FSK switching and CAT control.

I had some difficulty getting the COM ports to be recognised by the Logger32 software that I use here; I ended up swapping some ports about and assigning the SCU-17 ports a number under 10. Once I had done that all seemed to be well.

Good, egh?