Four basic rules govern the tuning scheme for the coupler RF sensors and servo systems.

1. For the phase detector, a capacitive load produces a negative output.
2. A negative error signal increases capacity.
3. For loading, an antenna less than 50 ohms produces a positive output.
4. A positive error increases inductance.

An RF attenuator using (7) 75 ohm 100 watt carbon resistors is ahead of the tuning network to limit impedance variations seen by the amplifier during tuning. If the attenuator is not used, the VSWR trip circuit would activate under some load conditions and terminate the tune cycle. The attenuator switching is capable of providing three states:

1. 6 dB attenuator
2. 50 ohm test load
3. Bypass (normal operation)

The attenuator is arranged as a "Pi" section with two of the 75 ohm resistors in series at the input and output and two in parallel as the series leg. For the 50 ohm load the output leg is parallel connected and the load removed.

She weighs in at 77 pounds and is 28" x 23" x 11" high. The enclosure is described as "splash proof" with rubber gasket and all. Ambient operating temperature for 1000w continuous operation is -30C to +65C. One degradating factor concerning modified operation over 1000w would be dissipation of internal heat to outside enclosure, and then to air. Ventilation of enclosure NOT INSTALLED outdoors in the weather may improve this discourse.

The tuning motors are 24 vdc and have rotational safety limits to prevent end stop damage to components. Most circuitry seems to be 24 vdc but technically the coupler is operated from it's companion amplifier. You can figure it out.

Two large insulated feedthrus are used for the tuner output. One is for an approximate 75' long wire and the other is for either 35' whip or 150' wire. The RF input is a UHF female, SO-239. The electrical connector is a 12 pin circular style that can be provided as an option. Full GCU-1935 and and GSL-1900A manuals are included with purchase of tuner to facilitate circuit tracing and synthesis of a control circuit for your application. Order this part number (EQP) SUN-GCU1935 to receive the new, unused tuner. No factory warranty is expressed or implied even though units are factory fresh. Weighs 85 lbs.

Order this part number to receive mating 12 pin circular connector.