User Manual

VCom Inc.

AP5857 Manual; ml_ap5857_08 (Oct 2005)

Approved: R.B.

3.0 CONNECTORS & CONFIGURATION

3.1 AP5857 Connection

The only required connection to the AP5857 is made through the F-connector. Connect the coaxial cable

from the powered tap to the F connector of the AP5857.

Note the power and voltage requirements as mentioned in the Power Requirements section.

3.2 AP5857 Configuration

The AP5857 status and configuration may be monitored and modified either remotely through an Ethernet

connection via the cable, or locally via the local interface. For local control of the radio, use the 9-pin RS232

local interface located on the baseplate of the unit, with settings as described in the Direct Connection section

of this manual.

Since the AP5857 is capable of providing a wide range of upstream gains and downstream transmit levels,

the setting of these levels is very important to maintain optimum performance.

 The downstream frequency of the radio is automatically configured by the radio to match the

internal cable modem downstream frequency. Note that the downstream frequency cannot be set directly by

the user. The user may either let the internal cable modem lock on to a channel by itself, or the configuration

file for the modem used by the CMTS may be written to direct the cable modem to a specific downstream

channel.

3.2.1 Downstream Transmit EIRP

The downstream transmit EIRP is normally set to the maximum value of 28 dBm EIRP. For very short

distances, the transmit power should be reduced to prevent overdriving of the CM at the customer site.

When operating normally, the status will show the downstream output as “Unmuted”. The AP5857

automatically mutes if there is a problem such as the internal cable modem unable to register on the system,

no valid signal for the downstream demodulator, or a hardware problem indicated by a hardware alarm. It

will indicate “Muted (Alarm)” under these conditions. If it shows “Muted (Manual)”, this indicates that the

output has been manually muted by the user. It can be unmuted in the downstream menu.

The downstream power may also be adjusted to optimize subscriber CM receive SNR if desired. On all but

the longest links, reducing the transmit EIRP by a few dB may improve downstream receive SNR by

improving transmit linearity.