Test Findings

I have made some very interesting observations while running the ALC tests. As I stated in the last post, I set up an indicator that would blink Red when the ALC exceeded the stored setting in DDUtil.

SURPRISE, the indicator never turns Red. Thinking there had to be a mistake I tracked the actual ALC voltage readings and sure enough the ALC voltage never exceeded the stored setting. Well, isn't this interesting. This just goes to show that once you set the Flex drive that it never exceeds that level. I even tried yelling into the mike and every other trick I could think of to make it over drive and it wouldn't.

Conclusion:

• Given the fact that there is no longer any compelling reason to monitor the ALC and
  
• Such monitoring is very expensive in CPU usage and
  
• Even if ALC excursions exceeded the setting, it takes a 1/2 second or more to react to such actions which is a little late to be of any practical benefit and
• There is a lot of software overhead required in DDUtil to support this feature.
  

I have decided not to pursue the ALC experiment any further. I have always been dubious of this being a practical solution to ALC control. I think the Auto Drive feature in DDUtil is the answer for controlling amplifier power output and no other device/cost is required. For those interested in the Auto Drive feature see DDUtil version 1.7.2

However, not to say a different type of connected device wouldn't be of practical use. I can see a Micro Processor Unit to monitor the ALC voltage and other functions. The ALC monitoring would be mainly for catastrophic events like the antenna being open or shorted. Adding a MCU would greatly increase the complexity and cost of a project like this to the point of being pointless. I do plan to play around with an ARM 9 MCU as a connected device (TCP/IP) some time later this year.

What's Next
As far as the FlexWire Adapter, the BCD ports has proven to be a real success and so far reliable. However, without the ALC feature I'm unsure there would be enough interest to make it feasible to continue with the project. This will have to be determined later after I poll the group.

There probably won't be much more activity on this blog unless something creates a need.

Thanks for the interest.

Operational Testing

The initial testing is proceeding well at this point. A few words about the setup and software.

Hardware Setup

• Flex-5000A driving a Prometheus amplifier.
• The FlexWire adapter is band switching the amplifier.
• Amplifier output is running into a dummy load.

DDUtil Setup
I have made modifications to DDUtil to allow the ALC to be read and displayed in a text box. Also, I have added a new function that works with the Auto Drive feature that compares the current ALC reading with a previously stored ALC setting. The purpose of this is to have a basis of reference to compare against.

The Auto Drive function works like this:
DDutil has a button on the Amps tab that saves the Drive level and the current ALC level from the amp into permenent memory. This button is pressed after setting the drive to produce the desired amplifier output power and the amplifier is keyed. DDutil also reads the ALC voltage from the amplifier and stores it as well. This must be done for each band. When the Auto Drive feature is enabled DDUtil will retrieve the settings from memory and apply them when PSDR changes bands thus giving the correct drive & ALC reference setting for each band.

Back to the new feature. If the current ALC is > the stored ALC then DDUtil turns a new indicator Red to show the ALC is higher than it should be otherwise the indicator is Green. This is only a means to test the ALC read function at this point.

Results

• So far the band switching has worked reliably without fail. But, this is the easy part as the band switching is always done when the amplifier is not keyed.
  
• The ALC Read function is also working reliably, so far. Amplifier power has been run upto 1500 watts and all is stable.

Next Steps
On the air tests are next. The adapter will be exposed to more RF when an actual antenna is connected to the amplifier rather than a schelded dummy load.

Stay tuned,
Steve

The Enclosure

Well, the prototype enclosure is finished and the FlexWire Adapter has a new home (see the photos below).

The front panel only has one lonely LED to show when power is applied, but the rear of the box is where all the action is. Each DB25 connector contains connections for two (2) 8-bit BCD ports.

• The top connector is wired to the VHF+ buttons in PSDR and the External Control matrices in DDUtil.
• The bottom connector is wired to the HF BCD file in DDUtil and is controlled by PSDR frequency and/or band status. Additionally, the port that is connected to the DDUtil macro function is on this connector.
  

Also, either one of these DB25 connectors can carry auxiliary power of +12, +5, +3.3vdc and ground for powering other devices if needed. The adapter is internally fused at 500ma so as to protect the Flex's internal fuse. I'll post the plug connections in a few days.

The +12v connector on the back can be used to power the adapter if the fuse is blown in the radio, but shouldn't be used otherwise.

The Amp+ connector is for amplifiers that have a auto power on feature requiring +12v such as the Quadra, Prometheus and others.

The ALC connector is intended to connect to the amplifiers ALC output. Much testing left to do on this yet.

Serious testing under full amplifier power will now begin.

More to follow.