Juma PA-100D v2.00a Build 5

Software developed by Adrian

Juma PA-100D v2.00a Build 5

Postby 5B4AIY » 23 Sep 2015 13:27

This version of the firmware, v2.00a Build 5, alters the way the SWR alarm is processed. I had originally written the firmware so that a high SWR alarm would be asserted in both the STANDBY and the OPERATE states. The intention was that this would provide an additional protection for transceivers that might not have an internal SWR alarm feature. In fact, this is unnecessary, and more of a nuisance than a help. In this version of the firmware, the high SWR alarm can only be triggered in the OPERATE state.

The second change is related to the way that the high SWR is determined. The original firmware used two successive cycles of the main software loop to assert a high SWR alarm, and I had continued this feature. However, after much testing I can find no reason to continue this practice. The amplifier is mainly susceptible to spurious high SWR alarms when using CW and output powers at or near the maximum rating. Despite this, even with the power averaging set to a single sample, I could not provoke a high SWR alarm in the CW mode even with repeated attempts keying the driving transceiver.

This version of the firmware therefore now uses a single sample per software loop, and in this setting the Power Averaging menu page in the Calibration & Setup mode will show 'Off'. If you wish to operate in the same way as the previous firmware, then set this to '2'. Each additional sample will add about 5mSec to the delay to registering a high SWR.

The averaging feature was originally added at the request of a US amateur who was using the PA-100D as the driver for an even higher power linear, and in the CW mode this configuration could provoke a transient high SWR alarm when initially keying the transceiver for the first element. This was caused by the somewhat slow operating time of the transmit-receive relay switching, where the PA-100D would find itself operating very briefly into an open-circuit as the final amplifier switched from receiver to transmit.

If you find that you have to use more than 8 - 10 samples to eliminate this transient then you should give serious consideration to using an external sequencer. At high power, and with an excessive delay there is the distinct possibility of triggering the 24A over-current alarm, so use caution, and use this feature at your own risk. The default setting is Off.

As there are no EEPROM changes, this version can be safely loaded over the previous version 2.00a, Builds 1 through 4. If you are updating from an earlier version of my firmware, then as the EEPROM checksum calculation now uses a completely different algorithm, there will be a checksum error on initial load, which will cause the defaults to be loaded. Please make a note of your existing calibration and configuration settings prior to loading this firmware. There are pages at the rear of the User Manual specifically intended for this data.

If you are updating from an original version of the firmware, then you will have to re-calibrate as the measurement system is completely different. Fortunately the PA bias setting is determined in hardware, and thus only the software calibration factors will need setting.

73, Adrian, 5B4AIY
Attachments
PA-100D v2.00a Build 5 (C-Source+HEX Load File+User Manual).zip
Minor modifications to the High SWR alarm.
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5B4AIY
 
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