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FLEX-6000 Signature Series - SmartSDR for Windows Software User’s Guide

Page 99

The FLEX-6300 can be set to 0dB (default) and +20dB

Note: Since the FLEX-6300 always operates in wide band mode, the preamplifier incorporates a

tapered gain with -3db cutoff located at ~14 MHz. This technique is optimized so that preamp gain,

and an improved noise figure is provided above 14 MHz, and the gain is tapered below 14 MHz to

offset the rising noise levels below 14 MHz. At very low frequencies the preamp will function as an

attenuator when enabled.

The FLEX-6500 can be set to -10dB, 0dB (default), +10dB and +20dB.

The FLEX-6400M and FLEX-6600M can be set to -8dB, 0dB (default), +8dB, +16dB, +24dB and +32dB.

The FLEX-6700 can be set to -10dB, 0dB (default), +10dB, +20dB, +30dB and +40dB.

Note: In some cases, the preamp of the FLEX-6700 may overload at the 20dB setting but not at the

30dB setting with the same input signal. This is caused by differences in the hardware

implementation of the two preamp settings. If the 20dB setting is overloading, the 30dB setting

should be tried before changing to the 10dB setting.

25.12 SETTING THE RF GAIN/PREAMPLIFIERS

The RF gain selector is in the ANT menu on the left side of the screen. The gain range is selectable in

10 dB steps from -10 dB to +40 dB on the FLEX-6700, 8 dB steps from -8 dB to +32 dB on the FLEX

6400 and FLEX-6600, -10 dB to +20 dB on the FLEX-6500 and 0dB to +20dB on the FLEX-6300. The

default setting is 0 dB. For typical HF operation below 12M, the 0 dB setting provides the highest

dynamic range and is recommended for most locations. Even in quiet rural locations, gain is not

needed or desired unless a low gain/low noise antenna is utilized.

The best way to determine the amount of gain needed for a given antenna and band condition is to

disconnect the antenna and measure the receiver noise floor with the Slice’s dBm meter. Hover the

mouse pointer over the S meter to enable the pop up dBm meter indicator. Next, connect the

antenna. If the band noise measurement without a signal present in the passband is 8 dB or more

than that with no antenna, additional gain is not needed. If a directional antenna is used, it should

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