Ham Radio – A contact sport

An update on my Prosistel direction alignment issue. After emails with ArraySolutions and Prosistel, I’m now properly aligned. 

The problem

Just to recap what I was seeing… I had the rotor installed and antennas pointed to 000 (North). After some work (another trip for poor Dave up the tower to reset the stack) everything lined up.

However, if I tried a turn from 000 (N) to 90 degrees (E), the antennas would turn ~170 degrees.

I was certain that I had wired everything properly – so I began to suspect that the rotor itself was not wired properly at the factory. I had found a email thread on the internet from another ham who had a similar problem and traced it to an internal wiring issue.  So, I followed the documentation’s troubleshooting section which described expected resistance values for various combinations of lines (pins). Here is what I saw vs expected:

Pins 1 & 2: 6 ohms (as expected)
Pin 1 and ground: Open (as expected)
Pin 2 and ground: Open (as expected)
Pins 2 & 3: open (expect ~2k)
Pins 3 & 4: 2k (expect ~8k)
Pins 4 & 5: 9.8k (expect 10k)

Ah hah! (I thought).. looked as if some lines are switched somewhere. Before I began switching wires around though, I thought I’d send an email to Prosistel & ArraySolutions to ask what they’d thought.  I was surprised when Gianni (I7PHH), tech guru at Prosistel, wrote to say that those values were all ok.

The Solution – reset the cal factor

Gianni suggested that I recalibrate the control box back to the factory set values – including the “Calibration Factor” which should be printed on the back of my control box. As my box didn’t have that printed on the back, I thought I was doomed to a lengthy calibration procedure. However, he replied:

You don’t need to do the whole recalibrate procedure, just input one of the following numbers and check which one give you the right antenna position.

13914
13981
14049
14118
14187

My Cal Factor was set to a software default value of 8000. Bingo! Entering one of those magic numbers solved the issue – aside from being 180 degrees out of whack. (Which I corrected by switching to North Stop).  I imagine that this value translates to some internal scaling of an A to D counter used to measure the position (looking at the 0 to 5 VDC values across the pot swiper). Anyway, that worked and I’m happy.

Prosistel Alignment – Lessons Learned

Here are my lessons learned from installing and aligning my Prosistel PST-61D (Bigboy):

• The documentation is far from perfect. If in doubt, call or email for support.
• When you get the unit, write down the magic value (Cal Factor) associated with your rotor. If your unit is old enough, this is critical. It should be hand written on the back of the control box.
• Test, test and retest the rotor and control box (Prosistel or any brand) on the ground prior to installation. I tested to make sure it could go CW and CCW and figured it worked ok. Also test to make sure it’s going the right amount (a 90 degree turn on the control box translates to 90 degrees at the rotor).
• Things will go wrong. When they do, it’s good to buy a product from folks who know what they’re talking about and are willing to support it. Although the documentation and support software could be improved, the email/phone support for the Prosistel was very good.