====== P-728 ======
**UHF direction finder P-728**, **Rohde & Schwarz PA003/CH**; manufactured by [[Rohde & Schwarz|Rohde & Schwarz, Munich]].

The PA003 UHF direction finding system from [[Rohde & Schwarz]] was purchased around 1980 for the EKF of the Swiss Air Force / Air Defence and remained in service until 2010. The [[ESM2]] VHF/UHF receiver is used as the systems main receiver, which was also used separately as a surveillance receiver and carried the Army designation [[E-652]] (Rohde & Schwarz [[ET001]]).

===== Technical data =====
{{ :images:p-728-e-652-et001.jpg?direct&400|P-728}}
  * [[Principle]]: UHF direction finder [[Rohde & Schwarz]] **PA003**
    * [[Receiver]] [[Rohde & Schwarz]] ESM2: [[Double conversion]], [[IF]] 199.3 or 339.3 MHz, 10.7 MHz
  * [[Operation modes]]: [[A3|AM (A3)]], [[F3|F3 (FM)]], 
  * [[Frequency range]]: 25 - 1000 MHz; analogue display
  * [[Sensitivity]]: 1 - 2 μV, [[Selectivity]] - 3 dB: 15, 30, 250 kHz, 1 MHz

==== Power supply ====
  * [[Mains operation]]: 220 V

==== Dimensions ====

==== Accessories ====
  * **Frequency controller EZK**, digital display, 100 Hz
  * **Panoramic display EZP**
  * Direction finder adaptor **PV003**
  * Rotating antenna **AP 815A1**
  * **Antenna rotation control RD003A1**

===== System material =====
The system consists of the **VHF-UHF receiving system ET001** with the components VHF/UHF receiver [[ESM2]], the frequency controller [[EZK]] with the digital frequency display and the panorama display unit [[EZP]], plus the direction finder PV003, the rotating direction finding antenna AP 815A1 and the antenna rotation control RD003A1 used specifically for the direction finding system.

The receiving system with the [[Rohde & Schwarz]] designation [[ET001]] was also used in the Swiss army for interception with the designation [[E-652]].

{{:images:e-652-rohde-schwarz-esm2-front.jpg?direct&400 |P-728: Receiver ESM2}}The **VHF-UHF receiver [[ESM2]]** covers 25 - 1000 MHz in nine band ranges, it has an analogue dial with a conventional tuning knob, AM, FM and PULS can be selected as [[operation modes]]. The IF bandwidths are 15, 30, 250 kHz and 1 MHz, and the receiver has various AGC and MGC options.

The frequency can also be set on the **frequency controller [[EZK]]** with an up/down switch at different speeds, the digital frequency display with a resolution of 100 Hz is part of the frequency controller. Alternatively, the receiver can be controlled via TTL signals with BCD code or in master-slave mode from another receiver.

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{{:images:e-652-rohde-schwarz-ezp-front.jpg?direct&400 |P-728: Panoramic display EZP}} In the **EZP** panoramic display unit, a frequency spectrum or the signal itself can be displayed at the level of the second IF of 10.7 MHz.

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{{:images:p-728-rohde-pv003-front.jpg?direct&400 |P-728: Direction finder PV003}}
The bearing is read off on the automatic **Peilsichtgerät PV003**.\\ 
The direction finding equipment includes the **AP815A1** rotating direction finding antenna and the antenna rotation control.

===== Technical principle =====

==== Tube assembly ====

==== Development ====

==== Use ====
In 1980, seven units of the PA003 UHF direction finder system developed around 1975 were procured for the EKF Flieger Flab Trp and remained in service until 2010.

In the so-called [[SZUS]] (Search, Allocation and Monitoring System) of the Flieger/Flab troops, the frequency spectrum in the [[VHF]]/[[UHF]] range is monitored. The signals can be analysed and also their bearing can be taken (the [[SZUS]] used the same receiving system as the [[P-728]] direction finder).

{{gallery>:images?p-728*.jpg&0&80x80&lightbox&showtitle&titlesort}}

===== Technical documentation =====

==== Further information ====
  * [[http://armyradio.ch/radio-d/p-728.htm|P-728 at www.armyradio.ch]]
  * [[http://www.radiomuseum.org/r/rohde_vhf_uhf_empfaenger_esm_2e.html|Receiver ESM 2 on the website of www.radiomuseum.org]]