[hpsdr] High SWR warning/power reduction with latest PowerSDR code.

[Phil Harman]

Hi Pete,

I ran into the same issue when building my 'idiot proof' 100W PA a number
of years ago.

The solution I implemented was that if the Tune power level setting was
10W or below then the SWR fold back was disabled.

This level was set in Firmware in the PA but could be a user setable
level, plus on/off selection, in the PC software.

73 Phil...VK6APH




> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi all,
> First let me say a grateful thanks to our code magicians for the
> improvements to the mainly DSP part of the original code from Flex, such
> as notch filter, compression and agc improvements. However, may I assume
> that the recent inclusion of an algorithm to calculate SWR, and implement
> this feature in  PowerSDR is still very much work in progress?
> My setup is Metis, Excaliber, Mercury I-Quad, Pennylane, with Pennylane
> driving Pennywhistle/Alex. Software is latest Doug W5WC code running on XP
> machine. Tx drive is manually set so that Pennywhistle gives about 10
> watts out on Tune, which is used to tune a remote auto-ATU, which needs a
> minimum of 3W to tune. From experience, the lowest SWR (best tune) is
> obtained by forcing the ATU to re-tune at each significant frequency
> change, and not rely on memory settings.  A consequence is that the tune
> may take a second or two to complete. With earlier PowerSDR software this
> was not a problem, as there was no feedback of SWR and reduction of power
> while the remote ATU did its stuff. Now it is a different story, as the
> HIGH SWR warning and consequential reduction of output power is activated
> before the tune process is completed - so on most frequencies I cannot
> achieve a good match. Further, even if I do achieve a good match, further
> HIGH SWR warnings can
>  arise in PowerSDR during transmissions using my final amplifier ( an
> Elecreft KPA500), which usually cause the whole station to trip.
> Investigation with other test gear confirmed these readings were mostly
> false. I have also noted that the Forward and Reflected power readings
> displayed often do not compute to the displayed SWR.
> It appears that we need some means of inserting a user selectable time
> delay in the PowerSDR code, accessible on the Setup Form, which allows the
> user to delay the response to SWR readings as necessary, but there may
> well be better ways of dealing with this issue. Any comments/advice? For
> the moment I have disconnected the connector on Pennylane, so I get no
> power or SWR readings on the PowerSDR console, but I can operate as I have
> SWR indication on the PA.
>  
> Pete G3LWT
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