PATHLOSS 4.0

MICROWAVE REPEATERS

1. PASSIVE REPEATER

Microwave repeaters can be classified as:

a Passive Repeaters

b. RF Repeaters

WHY USE THEM ?

Ø When a microwave hop is required in a place which has some unavoidable physical obstacles.

Ø Where a mountain peak has to be surmounted which may be so inaccessible that power cannot be provided for a usual active repeater.

There are two main types of Passive Repeaters:

1 Passive or plane reflectors

2 Back-to-back antenna passives

Passive repeaters have the following advantages over active sites:

Ø No power is required;

Ø No regular road access is required;

Ø No equipment housing is needed;

Ø They are environmentally friendly;

Ø Little or no maintenance is required.

Ø Use of back-to-back antennas are practical when the reflection angle is

Ø large. The gain of a repeater with back-to-back antennas is given by:

2. CREATEING PASSIVE REPEATER USING PATHLOSS 4.0

The Aloum to Lolodorf CRTV link has been used as an example in this document

Step 1:

The first step is to generate and save two path profiles and link budgets:

Profile 1 - Site 1(Aloum) to Passive (Lolodorf Passive)

Profile 2 - Passive (Lolodorf Passive) to Site 2 (Lolodorf CRTV)

The passive repeater site has to have the same co-ordinates and elevation in both profiles.

When entering the frequency for the second path profile use the same frequency and Hi/Lo configuration as the first profile but change the polarisation.

It is not necessary to enter the microwave terminal equipment for the passive repeater site as they are not used in the final link budget. It is advisable to enter the antenna information for the passive repeater site as this will provide a link budget starting point when optimising the link performance.

Step 2:

Open Profile 1 (Aloum-Lolodorf Passive) in the Worksheet section of PL4.

Step 3:

1. Click on the Operations tab and select Create Passive Repeater.

2. Next select the type of passive repeater to be created Back-to-Back Antennas

3. Select Profile 2 (Lolodorf Passive-Lolodorf CRTV.pl4) from the list of profiles

4. The second profile will be joined to the first and the passive repeater site indicated. Save the new profile under a name indicting that it is a passive repeater profile (Aloum-Lolodorf Passive-Lolodorf CRTV.pl4).

Step 4:

The connection between the two passive antennas has to be made. Click on the P symbol to open the Passive Repeater information and enter the cable information

Step 5:

Adjust the antenna sizes, TX power outputs etc. to ensure that the link budget meets the performance requirements for the link.

Once satisfied with the results save the profile.

Reports:

Two reports need to be generated for the passive repeater link:

1. The Full Report – this provides the configuration and performance information of the complete link, but excludes the passive repeater site.

2. The passive repeater report – this provides configuration information on the passive repeater site.

Full report:

Select Reports – Full Report from the menu at the top of the page

The full link report will be generated:

Passive repeater report:

Select Reports – Passive from the menu at the top of the page