CEDESC CEDESC CP-7-F-V:DESC CEDESC CEDESC by Gudmund Wannberg, EISCAT HQ, March 13, 1992 CEDESC CEDESC CEDESC CEDESC The SP-EI-MODE1-V experiment is written for the VHF system. It uses the CEDESC in a quasi-"mode 1" fashion, i.e. both klystrons must be in operation an CEDESC locked so that a single, phase-coherent wavefront forms in the far field CEDESC the VHF antenna; this produces a beam which in the plane orthogonal to t CEDESC scan plane is only about half as wide as the beam from either antenna ha CEDESC operated alone as a transmitting antenna. The two halves of the antenna CEDESC also be combined through a phasing/power adding network to produce a rec CEDESC beam which is of the same size. However, the switchyard setting must rem CEDESC in MODE 2 all the time !!!!!!!! These changes are expected to increase t CEDESC system sensitivity at least by a factor of two compared to the most effi CEDESC schemes used previously (in theory, if everything works the gain should CEDESC four times !). CEDESC CEDESC Running the two klystrons in parallel requires a major amount of manual CEDESC work on the system and must therefore be coordinated with the site leade CEDESC his staff. Visiting scientists who want to use the system in this config CEDESC are advised to put themselves in touch with the Troms| site leader and t CEDESC Scientific Director well before the experiment should run, and to announ CEDESC their intentions. There are some things in connection with the two klyst CEDESC operation, which must be stressed here, e.g. CEDESC CEDESC - UHF operation is impossible while the system is in VHF mode 1 (paralle CEDESC cap-banks and HV supplies !), CEDESC CEDESC - THE VHF SWITCHYARD SETTING SHOULD BE MODE 2 AT ALL TIMES - this is s CEDESC because the duplexers in the transmitter hall have been removed and al CEDESC signal pickoff for reception is done in the switchyard, CEDESC CEDESC - Turning off either one of the two klystrons should reduce the observed CEDESC S/N ratio at any given altitude by about a factor of four if the recei CEDESC is properly phased and connected - if this is not seen, the system is CEDESC properly set up ! CEDESC CEDESC CEDESC Experimental parameters CEDESC CEDESC This experiment uses the same basic modulation pattern and gating parame CEDESC as the CP-7-E. However, there is of course only one data stream processe CEDESC the correlator, as the whole antenna is operated as a phased unit. CEDESC CEDESC As a consequence of this, CEDESC CEDESC - only receiver channels 4, 6 and 8 are actually used for reception, øÑJ8ÌZ¾Ì[@ CEDESC - the number of ACF range gates in the data is 35 (rather than 22 in CP- CEDESC CEDESC - the first ACF gate is centered on 285.4 km range, as in CP-7-E CEDESC CEDESC - the ACF range increment is 65.25 km, as in CP-7-E, CEDESC CEDESC - but the last gate is now at a range of 2503.9 km. CEDESC CEDESC The increase in range coverage can unfortunately only be bought at the c CEDESC of a sizeable reduction in duty cycle, because of the pulse length limit CEDESC (T < 1 ms) presently imposed on the VHF klystrons. The RF duty cycle whi CEDESC can be achieved with the present set of experimental parameters is only CEDESC However, when the increase in system sensitivity brought about by the us CEDESC the full antenna and the increased peak power are taken into account, th CEDESC S/N at 2500 km should be about the same as the CP-7-D and the CP-7-E can CEDESC achieve at 1700 km. Any further extension of the range coverage would ne CEDESC to be accompanied by an extension of the permissible pulse length in ord CEDESC make good sense. We are currently looking into this...... CEDESC CEDESC CEDESC System configuration CEDESC CEDESC The receiver system should be set up the same as in a CP-7-E experiment. CEDESC simplifies changing between one klystron, CP-7 like operation and the -M CEDESC two klystron mode. CEDESC CEDESC CEDESC Three frequencies (currently F11/10/9), are transmitted. CEDESC CEDESC To save time and avoid losing any more than absolutely necessary of the CEDESC IPP for the noise calibration, only the zero lag of the calibration gate CEDESC is computed. This requires only half as many samples as if the whole ACF CEDESC had been computed and thus the IPP can be shortened by 870 us. The un- CEDESC computed lags in the calibration ACFs are padded out with zeros in the d CEDESC The data can therefore be accessed by unmodified reading and analysis CEDESC routines by specifying the number of calibration gates to be = 2 per CEDESC data block. CEDESC CEDESC The background gates are computed from totally independent samples. CEDESC This should reduce the background contribution to the variance of the CEDESC longest lags in the background-subtracted data by almost a factor of two CEDESC CEDESC The power profile measurement is arranged such that a 45 us pulse is CEDESC transmitted at the end of the transmission period, immediately following CEDESC the long ACF pulse. The receiver is set up so that the three channels ar CEDESC tuned to the three different frequencies used in the experiment. In each CEDESC IPP, one channel is used for receiving the ACF pulse, another channel CEDESC is used for the power profile reception and the third is used for backgr CEDESC and calibration. The roles of the three channels are commutated cyclical CEDESC (modulo 3), which ensures that the power profile and the ACF measurement øÑJ8ÌZ¾Ì[@ CEDESC by the correlator program, i.e. both the ACF background/cal. gates and t CEDESC power profile background/calibration data are computed off the same inpu CEDESC vector. CEDESC CEDESC CEDESC CEDESC EXPERIMENT PARAMETERS: CEDESC CEDESC Antenna pointing.............................VERTICAL CEDESC CEDESC Transmitted pulse length for ACF...............900 us CEDESC CEDESC Transmitted pulse length for PP.................45 us CEDESC CEDESC TX/RX CEDESC CEDESC Frequencies received..........................F11/10/9 CEDESC CEDESC Receiver channels used.........................4/6/8 CEDESC CEDESC Filter (common to ACF and PP)................BU 20 kHz CEDESC CEDESC Filter delay....................................25 us CEDESC CEDESC Sampling interval (common to ACF and PP)........15 us CEDESC CEDESC CEDESC ACF properties: CEDESC CEDESC Number of signal gates....................35 CEDESC CEDESC Number of background gates.................5 CEDESC CEDESC Number of calibration 'gates'..............2 CEDESC CEDESC Number of lags per gate...................30 CEDESC CEDESC MAXLAG....................................29 CEDESC CEDESC VOLUMEINDEX...............................29 CEDESC CEDESC Range of midpoint of first gate........285.4 km CEDESC CEDESC Range increment........................65.25 km/gate CEDESC CEDESC CEDESC PP properties : CEDESC CEDESC Number of signal gates...........................83 CEDESC ¨ÑJ8ÌZ¾Ì[@ CEDESC CEDESC Number of background gates.......................15 CEDESC CEDESC Number of calibration gates.......................2 CEDESC CEDESC Background/calibration gating factor.............29 CEDESC CEDESC Range to midpoint of first gate................75.4 km CEDESC CEDESC Range increment/gate............................4.5 km CEDESC CEDESC CEDESC CEDESC Correlator programme: SP-EI-MODE1-V CEDESC CEDESC CEDESC APB CONTENTS: CEDESC CEDESC APB(15).....VOLUMEINDEX...........................29 CEDESC APB(14).....LPLAGMAX..............................29 CEDESC APB(13).....No. of LP sig gates, TX/RX side ......35 CEDESC APB(11).....No. of PP bg/cal samples to process..493 CEDESC APB(10).....Gating factor used for PP bg/cal......29 CEDESC APB( 9).....No. of PP signal samples to process..166 CEDESC APB( 8).....Gating factor used for PP signal.......2 CEDESC APB( 7).....Process mode switch....................0 CEDESC APB( 6).....CALMODE = (2*)..............58 CEDESC APB( 4).....No. of LP background gates/side........5 CEDESC APB( 0).....APBINCREMENT...........................1 CEDESC CEDESC APM CONTENTS: CEDESC CEDESC APM(15).....Start address of LP sig gates TX/RX side..... CEDESC APM(14).....Start address of LP bg gates TX/RX side..105 CEDESC APM(13).....Start address of LP 'cal' gates TX/RX side..120 CEDESC APM(12).....Start address of PP sig gates TX/RX side..126 CEDESC APM(11).....Start address of PP bg gates TX/RX side..134 CEDESC APM(10).....Start address of PP cal gates TX/RX side..135 CEDESC CEDESC CEDESC APM( 3).....SCANCOUNTADDRESS......1360 CEDESC APM( 0).....APMINCR..................1 CEDESC CEDESC DATAIO..................................1361 CEDESC CEDESC CEDESC CEDESC Kiruna, March 1992, Gudmund Wannberg