Hamilton Rangemaster AM Transmitter

Probably the best known of all the certified Part 15 AM transmitters on the market today, the Hamilton Rangemaster AM1000 has many installations and satisfied customers under their belt. It would be a disservice if we didn't give the in-house testing staff the chance to run it through its paces.

While we've had several of their transmitters available to us for almost a year, a variety of circumstances prevented us from performing the installation and testing on it. We once again called on Joe from PelhamBroadcasting.com. Joe is an experienced RF and broadcast engineer who has installed numerous Rangemasters in the tri-state area, so it seemed fitting to have him supervise the testing.

Opening The Box:

It's been awhile since we received the units, but I believe they had been delivered via UPS. The units were well packed and came with all the items that were ordered. Besides the standard outdoor transmitter, we ordered the companion mounting brackets with hardware as well as the frequency agile tuning module instead of crystals. The only module we didn't order for our installation was the AM1000T tuning module. The AM1000PR audio interface adapter, a ferrite bead for the audio wire as well as a plastic tuning tool is included the transmitter package. The required Citizen's Band whip antenna is readily available from Radio Shack or any decent amateur radio dealership. While Hamilton can gladly supply you with the antenna its size is cause for a premium shipping rate.

The Inside Story:

The transmitter is housed in a watertight one-quarter inch thick fiberglass enclosure measuring 4.65 inches by 3.64 inches by 8.65 inches. Four long captive screws attach the cover to the transmitter. The cover has an integrated gasket to prevent rain and other outdoor elements from affecting the unit.

AM1000 Interior View

Inside the box is a single high quality printed circuit board. All the integrated circuits are socketed which can allow for in-field replacement should the need arise. Power on/off, wire screw terminals, audio and power output controls; coil jumpers and output tuning capacitor are easy to locate and access. Two collared access holes that allow for weather tight connections as well as a ground terminal are located on the bottom part of the transmitter enclosure. Besides screw terminals for power and audio input there are connections that allow the operator to synchronize multiple transmitters to increase range. High frequency stability is achieved with under crystal frequency control, which is recommended for synchronized operation. The optional frequency agile module provides good frequency stability while offering selectable transmit frequency. The frequency agile tuning module is a daughterboard that installs in place of one of the integrated circuits and is secured with plastic standoffs.

Exceptional operation is due to the many high quality components used in the AM1000. Specialty components such as a internally sealed trimmer capacitor and custom tapped output output coil assures peak efficiency with any operating frequency, especially when compared to inexpensive "real estate" type transmitters. While quality components come at a cost the user is rewarded with great performance.

Fire It Up:

To be totally on equal ground with previous tests performed by the CBN/HBN labs, the Rangemaster was mounted in the same location and utilized grounding used for previous transmitter reviews, which we refer to as the "City Dweller" test setup.

As the experienced Rangemaster installer, Joe performed the installation for the review. Tuning the Rangemaster requires the use of a Volt Ohm Meter (VOM) if you don't have the AM1000T tuning module or a newer version of the AM1000 with the tuning module on-board. Since our transmitter has the frequency agile module installed, we programmed a transmit frequency by selecting the correct dip switch settings according to the instructions provided. Those who ordered a crystal-controlled unit would only have to install the crystal if it hasn't already been installed. Once the transmitter is mounted and the whip antenna and wiring have been connected, the system is energized and is ready for tuning. After following the manual's pre-flight settings for both the power control and tuning capacitor you need to experiment with finding the optimum output by moving the coil tune jumper block. This is performed while monitoring the voltage of the transmitter's power amplifier with your VOM connected to the appropriate test points. After this, you adjust the tuning capacitor for a maximum peak reading on the meter. Lastly, you set the power control for 100-milliwatt power input power to the final amplifier. Using the conversion chart in with the manual, you measure the two test points and adjust the power control adjustment. While not as accurate as using a VOM, the onboard computer may used in a pinch.