Field Report: Harris HPX

October 1, 2009

Field Report, Oct. 2009

In June 2009 we took delivery of what has become my favorite transmitter. After 30+ years in broadcasting, most transmitters don't get me excited. You hook them up and then go back to what you were doing before you installed it. The HPX series from Harris right off the truck is just sexy (please don't tell my wife I said this!)

It appears Harris did some serious homework on this transmitter. It really does look good. It came in two cabinets: one for the power supply and the other for the exciter, IPA, PA and controls. I understand there is a kit to separate these boxes; however, my configuration is side-by-side. The combined measurements are 64" wide, 35" deep by 78" high. For a 40kW transmitter, this is a pretty small footprint. I was glad to see a slightly higher box that made for a smaller amount of floor space used up by one transmitter.

Performance at a glance
Integrated RF and control interface
Separate high voltage power supply
VGA GUI for advanced control and diagnostics
1/4-wave grounded cathode design
Analog and/or HD Radio operation
Two cabinets in 64"W × 35"D × 72"H

Installation time on the HPX is very short. In fact, this was the easiest high power FM I have ever installed. This is because all the control connections between the two cabinets are plug-in connectors, and the three phase wires are on a WAGO connector. The high voltage connection between the two cabinets is about 1' long. Remote control connections are also on a WAGO connector behind a front panel. They are easy to get to even with the power on. The entire component layout just makes sense because parts are clearly marked and located in a logical location, as well as easily accessible. Primary power is connected behind a panel on the front … again a convenient location.

The 4CX 20,000C PA tube installation was quick and easy. There was plenty of room to get my hands in the cavity and install the tube. Harris has continued the Flex Patch to allow making quick changes to bypass defective stages should a problem arise.

Get inside

The controller is like nothing I have ever seen before. Software updates are done via a CF flash card. There is no battery backup to remember the last mode but it appears this is written to the CF card. The CF is located behind the control panel door that hinges down. We recently received a software update that just required removing the old CF and installing the new one. Down time was only about 3 seconds.

It took only a few hours to get this box ready to test into a dummy load. When you apply filament voltage, the shorting solenoid energizing will get your attention; however, when the high voltage is applied there is a soft-start sequence that is quiet and easy on the nerves: No loud clang of a relay, no light dimming, just a nice gradual increase in power.

I got a chance to test the VSWR protection circuit. It seems in the process of cleaning a section of 3⅛" rigid line for the inside building, a rag was left in a section of line. The HPX said no thanks, I don't like this load and shut down. After a few tries, we swept the line and found the rag and all was well.


My decision to wait for the release of the HPX was based on the thought that not only is this an efficient transmitter, but this was a transmitter designed for IBOC, not a transmitter modified to pass IBOC. Also, this being the new kid, it is going to get the full support and attention that I wanted for this station. I currently am responsible for more than 10 transmitters made by several excellent companies, but this one is papa's new baby.

I worked with SCMS, the Harris channel partner, when I bought the transmitter, and I would buy this transmitter again. I hope in the near future to see more of these at our facility.

Roberts is the chief engineer of Apex Broadcasting, Charleston, SC.

Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.

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