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P-725/m (1)

Direction finding system P-725/m (1), Telefunken Telegon IV / PST638-U/20-180; manufactured by AEG Telefunken AG, Ulm & Berlin.

The direction finding system Telegon IV was improved with an adaptor to cover the military VHF frequency ranges. The direction finder SiG 638 with the VHF adaptor UK-838-80, was acquired in a number of 6 systems in the year 1971.

P-725/m (1)

Technical data

Power supply

Dimensions

Accessories

  • Direction finding antennas: H-Adcock DF antennas A 638/80 and A 638/180
  • Range selector BU 638 (switch 20-80 / 60-180 MHz)
  • Panorama display PaG 148

P-725 in the Unimog S

Plant material

P-725/m (1) The VHF direction finder Telegon IV from AEG - Telefunken, Ulm, is based on the SiG 638/4 direction finder with adapters for the two VHF ranges and a changeover switch.

The core component is the receiver and DF indicator with a round cathode ray tube, the SiG 638/4 is solid state and equipped with a DP 10/14 cathode ray tube. A round bearing dial is manually aligned with the maximum deflection on the DF display and the bearing is read off the dial. The frequency of 10.7 MHz is permanently tuned in on the direction finding receiver to be used as the intermediate frequency of the adapter, the frequency is tuned in on the VHF adaptors UK 638/80/1 and UK 638/180/1, the reception principle is therefore double superheterodyne.
P-725/m (1) The FA 990/100 frequency indicator is used for the frequency display, the reception frequency is displayed with Nixie tubes in the range 20 kHz - 180 MHz, the frequency reading accuracy on the analogue scales of the two adapters is 55 and 160 kHz / mm respectively.

Using a 10.7 +/- 1 MHz wideband output, the IF signal can be fed to a panoramic display, in this case, the PaG 148 is used to display radio activities in the VHF bands.

H-Adcock antennas with eight dipoles each are used as DF antenna, the length of a dipole is 1.4 m for the A 638/80 antenna and 0.84 m for the A 638/180. The antenna crosshead is connected to the direction finding system with an 60 Ohm coaxial cables.

Technical principle

Tube assembly

Development

Deployment

P-725 on vehicle Unimog S In Switzerland, four systems were installed in a „Unimog S“ and two transportable systems were procured in six payloads for field use. Two Clark SCAM 12.5 m pneumatic telescopic masts were procured as antenna masts for each station.

The six systems were acquired in 1971 and were assigned to EKF Kp IV/46. They remained in service until liquidation in 1986.
The VHF direction finder stations P-725 were then upgraded to the Plath SFP 218.43.

In the DF trucks, a SE-208 or later a SE-227 was installed to exchange DF commands and results, but usually wired telephone connections were used for this purpose.

Technical documentation

Further information

en/p-725_1.txt · Zuletzt geändert: 2024/01/06 19:31 von mb