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.

Initial ADC Tests Successful

Today with the help of two heavy lifters (Eric Wachsmann & Bob Tracy) the ADC (Analog to Digital Converter) was tested successfully using CAT commands to read external negative voltage representing the ALC (Automatic Level Control) volts from an amplifier.

This represents a big step in the development cycle as the amplifier ALC voltage is variable from 0 to -12vdc depending on the amp. This voltage has to be inverted and scaled down to a range of 0 to +2.5vdc which is the measuring range of the ADC being used.

Eric created new routines in the bowels of PSDR to implement the functions needed to access the FlexWire interface and Bob created the necessary CAT commands to make the functions usable by us mere mortals. My hat is off to you both.

With this milestone achieved the next step will be to finish coding DDUtil to use the data. This logic will evolve as the usefulness of the data is realized by experimenting with how well I can control the PSDR power level from the amplifier ALC feedback. This is very TBD (to be determined) and if proven to be unusable the ALC portion of the adapter will be scrapped.

One of my fears is that RFI will be a unsolvable problem with a line running directly to the amp. I have attempted to harden the adapter against ESD and RF by shielding and bypassing techniques but how effective it is remains to be seen.

more later...

What is it?

General Info

This adapter is intended to allow users of the Flex-5000/3000/1500 radios the ability to attach BCD controlled devices to the FlexWire port on the back of their radios. This device can be used to control many types of equipment based on the radio frequency or band selected, including but not limited to:

• Band switching of uWave transverters and associated apparatus
  
• Band switching of Coax switches
  
• Linear Amplifier band switching requiring BCD input
  
• Antenna stack management (manual)
  
• Antenna array steering (manual)
  

Features

• Two 8-bit output ports (TTL*) controlled by two DDUtil matrices wired to the VHF+ buttons in the PowerSDR console allows a total of 16 bits of control for each of the VHF+ bands. Data signals may be inverted for use with Phil Theis's Universal Controller Board (UCB) or other device requiring inverted signals.
  
• One 8-bit output port (TTL*) wired to the HF BCD function in DDUtil's device tab. This allows great flexibility in selecting multiple antennas per band based on frequency or controlling other frequency following equipment. Data signals may be inverted.
  
• One 8-bit output port (TTL*) manually controlled by DDUtil's macro function. Uses for this port could be managing an antenna stack or steering an array of verticals or any other need for manual switching not tied to radio band/frequency.
  
• Auto-on port for amps equipped for +12vdc auto-on voltage sensing (Quadra, Prometheus, ?).
  
• ALC input from an amplifier. This port is under development and may or may not be included in the final design depending on the usefulness of the feature.
  
• Power Input is available from the FlexWire connector (13.8vdc) or from a secondary power connector on the card (+7 - 15vdc).
  
• Signal Output is available from two (2) DB25F connectors. DB25 #1 contains the VHF+ signals for ports A & B. DB25 #2 contains signals for the HF BCD port and the Macro BCD port. These plugs plug into the headers on the PCB via ribbon connectors.
  
• Auxiliary Power 12vdc (pass thru), 5vdc (reg) and 3.3vdc (reg) are available in one of the DB25F port connectors if needed. Maximum total current draw from these sources and from the signal lines is 500ma and is fused internally.
  

*TTL voltage level is considered to be 5vdc @ <= 10ma source current or 0vdc @ <= 20ma sink current.

Control

Control of the adapter is provided by DDUtil, a secondary software program written by me and available here. DDUtil interfaces to PowerSDR via CAT commands and allows multiple Radio Control Programs (RCPs) and various equipment to be connected to the radio at one time.
Note: This adapter will not work without an auxiliary software program to control it.
PSDR WILL NOT support this device by itself.

Construction

SMD (surface mount device) components are used primarily for the active and passive components with SOIC and 0805 sizes used.

Current Development Status

• First prototype cards (5) have been received from the board house. Proto #1 has been assembled and initial tests on the BCD ports were successful.
  
• ADC tests are underway using the low-level facility in PowerSDR. Waiting for CAT command creation before additional testing can begin in DDUtil.
  
• Prototype enclosure design is complete and fabrication is in process.