[Elecraft] K3 Filter Plots

[Mike Downs]

AD6XY wrote:

> This is very interesting and useful. It looks a little bit like a Borland 
> app
> but I expect it is not.

It is a VB6 application. I used the older VB technology to keep the program 
small and to avoid users having to download .Net updates which consume a lot 
of resources and can take 30 minutes or more to download even on a fast 
Internet connection.

> The first time I tried the linearity check I had the volume up - loud
> mistake!

I hadn't thought about having the program turn the AF gain down for users. I 
can add that capability if it would be desirable.

> It takes a very long time to sweep a filter this way, it may be better to
> implement some form of variable sweep based say on the difference between
> the last value. One tends to want detail in the passband but not so much 
> in
> the stopband.

I will look into this change. May want to make it optional for users to 
implement. Or I suppose the user could just set the frequency range narrower 
to focus on the passband portion of the response.

> One thing we are missing is phase response (AM/PM), I would be interested 
> to
> know if there is any way to measure this with a sound card.

Maybe Jack Smith can respond to this question. I have no idea.

> There are a few rough edges, it is easy to crash if you enter nothing into 
> a
> checkbox that is not explicitly checked.

Could you point me to the unchecked checkbox that caused the program to 
crash?

> The stop button does not always get
> enough attention paid to it. (Application->ProcessMessages ?)

The scans/procedures operate under control of a Do Loop and as a result the 
program is slow to respond while the scan is in progress. Usually, if the 
user clicks Stop Test/Stop Sweep the procedure will end within several 
seconds. Sometimes you have to click the button a second time. The 
procedures are purposely slow because each time the RF Gain or Frequency are 
incremented it is necessary to wait a couple of seconds for the dBV reading 
to settle. The program uses Application.DoEvents to track events while the 
loop is running and allow the user to stop a scan.

Thank you for your observations and suggestions.

Mike, KS7D