PI7CIS VHF beacon
The PI7CIS beacon is located in a remote site at the sea-shore of Scheveningen, approx. 100 m away from the beach. The locator is JO22dc. The frequency of operation is 144.416 Mc. The call is keyed using FSK with 1 Kc downward shift. The transmitter is a modified PYE T4002, providing 45 Watt to the antenna, a Kathrein dipole at 40 m ASL beaming 90/270 degrees.
The transmitter is a gift of Gordon, GI6ATZ. (thanks again Gordon!!)
This is a picture of the beacon location. It is a remote watchtower on top of a dune, a bit north from the city of The Hague.
In the mast you see from top to bottom :
- weather station equipment
- 23 cm receive antenna (for remote control tests only)
- PI7CIS Kathrein dipole
The location is a favorite place for youth to hang out in summertime. The various "paintings" were left by them.
The beacon operates on 432 Mc as well. It uses a home made exciter and an Ericsson PA, providing approx. 75 Watt output. The antenna is a Kathrein dipole at 42 m ASL, bearing 90/270. The frequency is 432.416 Mc.
The location is quite hostile to electronic equipment. The little building in which the transmitter is located is leaking, has no heating system and wind and salty air from the nearby sea have free access. The temperature inside the building ranges from -15 C up to 40 C, depending on weather conditions. Relative humidity reaches sometimes almost upto100%, given the leakage of the roof.
The equipment is mounted in a 19" rack.
The following equipment is installed (from top to bottom) :
- 70 cm 75W PA for 90/270 direction
- 70 cm 75W PA for 0/180 direction (not yet operational)
- message generator
- PYE T4002 45W beacon transmitter, with GI6ATZ FSK print
The 70cm exciter is missing in this picture.
The PI7CIS beacon has been on the air since 1988. Its initial frequency of operation was 144.935 Mc. At first the beacon used an old paging transmitter, providing approx. 30 Watt rf output. This transmitter was not very stable at first and suddenly started to generate harmonics.
In 1989 it got a major overhaul, including a new frequency generator chain. Power output was increased to 50 Watt. Its design has been unchanged until the new station became operational.
The old beacon was capable of transmitting 4 different CW messages, a standard one with call sign and locator and three messages warning for aurora, e-skip or tropo conditions. The beacon was remotely controlled via the national paging system with publicly known telephone numbers to activate the various messages. Nowadays dx-clusters are widely used, making this feature obsolete. The transmitter could be keyed on/off remotely as well, using a dedicated (and this time secret) paging number. In August 1997 the frequency was changed to 144.416 Mc, according to the new band plan.
The 19"rack on the right contained the beacon transmitter (yellow cabinet), 24V power supply (at the bottom) and message generator (aluminum rack in the middle).
A quarter wave filter connected the transmitter to the antenna. The two pagers for remote control can be seen on each side of the filter.
The rack on the left contained a weather station.
Both racks (including equipment) have been removed when the new set-up became operational.
The 144 MHz beacon has been on air almost without interruption. During a major storm huge parts of the dunes were washed into the sea, taking the 220V AC power cable which was buried in the dunes as well. The beacon was QRT for about 4 weeks, the time necessary to dig up and repair the AC cable.
In 2001 it became clear that the beacon was almost end-of-life. The tone of the transmission sounded harsh while the cabinet and PC boards had taken their toll given the continuous attack of salt and moisture. At the same time plans were made to improve the situation of the building.
A new roof was necessary so the mast had to be taken down. In January 2002 the beacon went temporary QRT for renewal and roof repair. (which was cancelled due to the bad weather and was done in August).
March 11th 2002 the beacon became active again, using the new 144Mc transmitter.
After the new mast had been put in place also a 70 cm antenna was installed. A Kathrein dipole at 42 m ASL beaming 90/270 degrees. The 70 cm beacon became active on 432.816 Mc on October 2003, but has been of the air quite a lot, the reason being the instability of the oscillator. After a change of bandplan the frequency was changed to 432.416 MHz.
The 70 cm beacon utilizes only one of the amplifiers at the moment, providing 75W rf to the 90/270 degree dipole antenna.
During the Christmas holidays of 2003 the 70cm beacon was changed and became operational again in January 2004.
December 27th 2003 the 144Mc beacon went suddenly QRT. The whole location has lost 230V mains. The building is not 100% watertight and some water had leaked into the main 230V AC switch box, effectively shorting the wiring and ruining the mains switch.
After an emergency repair (partly new cable run and temporary switch box) the location had 230V AC and beacon became active again on December 29th.
In June 2009 the 70 cm beacon was reported sending all kind of spurious signals. It was taken from the site for a major maintenance overhaul. Transmissions were resumed in November 2009.
Despite all kind of measures like a temperature controlled oven the 70 cm beacon is still suffering a slow frequency drift due to the harsh environmental conditions.
The frequency stability is still one of the major issues, due to environmental influences. (notably the 70 cm beacon). It is the intention to build GPS locked exciters for both beacons in order to improve the frequency accuracy and eliminate the drifting.
As a second step a modified transmission pattern will be provided, enhancing the coverage to the South.