SE-415 2-30MHz Antenna Systems (Zellweger, Switzerland)
Original Zellweger Antenna and AGD/AGV Brochure May 1974
The AGD/AGV System is described here as a "commercial" product and was used e.g. in embassy radio installations. The Swiss military SE-415 just had the AGD (called SD-415) and the portable control KG-415 not pictured but shown elsewhere on this page. However data for the inverted-V antenna is given which has for many years now provided excellent NVIS service on 40, 80 and 160m at my portable location in the mountains.
The AGD-415 symmetrical 1kW ATU
The ATU is contained in a box protecting it from the weather allowing it to be installed at the foot of the antenna mast feeding the ladder line to the dipole (described in the brochure above). It is connected to the transceiver via a control unit which also provides power over the coaxial cable.
The data here is also relevant for users of the later 1980ies SE-430 transceiver as the proven antenna concept was reused there, only the dipole length was increased to 2x30m to cover 1.6MHz.
Modified KG-415: use the AGD-415 with modern transceivers
The AGD is an analog machine despite its digital control circuits. It requires constant RF power (approx. 20W) while presenting wild SWR excursions to the source. Modern transceivers - except units with a "Tuner" output - will cut back power at high SWRs. As the AGD measures reflected power from the antenna it might think to have reached a match - wrong of course. An attenuator of 4-5dB in the transmit path will suffice to allow correct operation by keeping the SWR below about 1:1,5. With the setup described apply about 50W CW or FM and switch to tune - and it will work!
KG-415: ATU Remote Control, as modified for modern transceivers
The KG provides all 24VAC power to the AGD through a bias-tee and measures and indicates SWR. The "Tune" switch starts the tuning process - the AGD always starts from scratch, there is no memory. Once the "Tune" light goes out, the switch can be returned to its normal position and the power supply now just feeds the fan in the AGD - 1kW RTTY may heat up things inside.
