Icom IC-751 Инструкция по эксплуатации онлайн [25/37] 68913
Макгруп McGrp.ru
Задайте вопрос
Зарегистрироваться

Icom IC-751 Инструкция по эксплуатации онлайн [25/37] 68913

Icom IC-751 Инструкция по эксплуатации онлайн [25/37] 68913

Содержание

Похожие устройства

Slowly turn the AF GAIN control clockwise to a comfor table level Rotate the tuning knob until a signal is received The meter needle will move according to the signal strength so tune for the highest possible meter reading and the clearest audio If you cannot get a clear signal you may be receiving in the opposite sideband If so change the mode to the proper sideband position when receiving weak signals In the PRE position an RF preamplifier is inserted into the receiving antenna circuit increasing sensitivity and giving easy reception Place the PREAMP ATT switch to the ATT position when strong nearby signals disturb signal reception or make S reading difficult In the ATT position the RF amplifier is removed from the circuit and a 20dB attenuator is inserted into the receiving antenna circuit reducing interfering signals and giving more stable reception In normal opera tion the PREAMP ATT switch is left in the OFF position Adjust the RF GAIN control and TONE control for com fortable reception If squelch operation is required to cut out noise when no signal is received turn the SQUELCH control clockwise until the noise from the speaker stops and leave it just below this threshold 5 5 5 P B PASS BAND TUNING Pass Band Tuning is a system to narrow the bandwidth selectivity of the frequencies that will pass through the crystal filter electronically from either the upper or lower side continuously by up to 800Hz This is very effective in reducing interference from nearby signals For tuning memory channel operation and scanning opera tion please refer to 5 1 HOW TO TUNE on page 12 5 2 MEMORY CHANNEL OPERATION on page 17 and 5 4 SCANNING OPERATION on page 20 The PBT control has a click stop at the center 12 o clock position This is the widest pass band position and use the set at this position usually 5 2 2 NB NOISE BLANKER When there is pulse type noise such as ignition noise from automobile motors turn the NB LEVEL control clockwise further click ON so that noise will be suppressed and even weak signals will be received comfortably While receiving in the LSB mode if you get interference from a lower frequency interfering signals are high pitched tones narrow the band width by turning the P B tuning control counterclockwise When the interfering signals are low pitched tones they are from a higher frequency and you should narrow the bandwidth by turning the P B tuning control clockwise When the NB switch is set in the WIDE locked in position the noise blanker will effectively work for woodpecker s noise however if the receiving signal is too strong the noise blanker may work with the receiving signal itself and some distortion may cause in the receiving audio or keying form At this time set the N B Switch in the out position or turn the NB LEVEL control completely counterclock wise OFF position When receiving in the USB mode the bandwidth is nar rowed in the opposite manner Interference from a higher frequency will be high pitched tones and the P B tuning control should be turned clockwise Interference from a lower frequency will be low pitched tones and the P B tuning control is turned counterclockwise 5 5 3 AGC AUTOMATIC GAIN CONTROL The IC 751 has a fast attack slow release AGC system which holds the peak voltage of rectified IF signals from the IF amp circuit for a certain period Therefore during the pauses in normal speech of the received signal uncomforta ble noise will not be heard The meter indicates the peak value fo a certain period facilitating reading of the meter S function This control can also be used for audio tone adjustment so it may be set for the most comfortable reception Receiving LSB signal For normal SSB reception turn the AGC control clockwise to the SLOW position Turn the AGC control counter clockwise to the FAST position when tuning or receiving signals with short interval fading When in the FAST position the time constant is shortened Interfering signal Receiving LSB signal When this control is set at the OFF position the AGC circuit is turned OFF and the S meter does not work even if a signal is received However the RF GAIN control is still active and the needle of the meter moves depending on the control position 5 5 4 PREAMP ATT SWITCH Place the PREAMP ATT Switch on the TOP to the PRE 22 When P B TUNE control is turned counterclockwise goes out of the pass band When P B TUNE control is turned clockwise

Скачать