Additional Roofing Filter - Kenwood TS-990S In-Depth Manual

RECEPTION 03
Fig. 14 Frequency response of
Fig. 15 Frequency response of
the 500 Hz Bandwidth
the 270 Hz Bandwidth

Additional Roofing Filter

The TS‑990S main band receiver has a slot to mount a roofing filter in addition to the five built‑in roofing filters. (We have
no plan to commercialize additional roofing filters on our own.)
Fig. 16 Additional Roofing Filter Mounting Slot
If an additional roofing filter is mounted, change the default value of "Off" in Advanced Menu 6 "Bandwidth (Additional
Roofing Filter)" to your desired filter bandwidth, and then press and hold the [FIL/SEL] (M) key to open the RX Filter
screen. In the screen, change the configuration for "Roof" to "Add." to enable the additional roofing filter. If "Auto" is set to
"Roof", the additional roofing filter is preferentially selected depending on the IF filter bandwidth.
Concerning the built‑in roofing filters, the PIN diode‑type attenuator at the IF stage corrects the gain, causing no
difference in S meter needle deflection, whether a filter is applied or not. But, if an additional roofing filter is used, it is
necessary to correct the S meter needle deflection by a difference of the insertion loss. To receive a signal with a stable
signal strength, change the attenuation of the additional roofing filter in Advanced Menu 7 "Attenuation (Additional
Roofing Filter)". The "Electrical Specifications" table shows the additional roofing filter electrical specifications. The
"Dimensions (Reference)" diagram shows the additional roofing filter dimensional diagram (reference).
Table 4 Electrical Specifications
Center Frequency 8.248 MHz
Bandwidth (‑6 dB) 300 to 3500 Hz
Terminating Impedance 50 Ω
Insertion loss 8 dB or less
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