[CQ-Contest] Enhanced DuneStar 600 Band Pass Curves

Tod -ID tod at k0to.us
Tue Jun 10 18:09:10 EDT 2008

Based upon Pete's email to me I have added return loss curves to the
original attenuation and insertion loss curves. The return loss curve for 80
meters show that at 3860 the VSWR is about 1.9:1 which would account for the
'shut-down' effect that Pete mentions. Pete mentions that he noticed the
effect when operating above 3800 kHz. My measurements suggest that the
increase should not be very noticeable until you operate above 3840 or so.
That may simply be the variability between production units.

If anyone else has used DuneStar 600's and noticed anything they consider
unusual I would be appreciative of hearing from them.


The enhanced curves and commentary are at:

Tod, K0TO

> -----Original Message-----
> From: Pete Smith [mailto:n4zr at contesting.com]
> Sent: Tuesday, June 10, 2008 8:07 AM
> To: Tod -ID
> Subject: RE: [CQ-Contest] DuneStar 600 Band Pass Curves
> What I noticed, basically, was that anywhere above 3800 the input SWR 
> of the filter began to rise quite rapidly, and as a consequence my 
> exciter started folding back.  I probably could have used my tuner, 
> but before I did that (not my usual sequence of events) I realized 
> that it might result in a lot of power being dissipated inside the 
> filter, with destructive results.
> I suppose there are pretty good reasons why a 3-stage filter can't 
> cover
> 3.5-4 MHz, but it would sure be nice to be able to operate up to 3850 
> through it.

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