Wednesday, November 3, 2010

Microwave antenna alignment (Cont..)

Simplifying the Process:

We have laid the groundwork for establishing the Path Align-R™ test set as a viable and effective solution for the path alignment process. We will now describe how this process of aligning the microwave link is greatly simplified.

1. Review the Engineering Profile to determine the expected RSL (received signal level, or path loss)for the link under test (this should include the free space path loss and the gain of the antennas). Note that the loss exhibited by the installed cable or waveguide transmission lines are not included in this value because the Path Align-R™ test sets are connected directly to the antennas with a short coax cable with minimal insertion loss to impact the test.

2. Both tower climbers (technicians) should go over their check lists, prior to climbing the tower, to assure that, included with the Path Align-R™, they have:

• A charged battery installed (possibly a spare if you are planning to be up for over 4–5 hours);
• The proper waveguide-to-coax adapter for the antenna;
• A coax cable (SMA to coax connector on the coax-to-waveguide adapter);
• The supplied headset; and,
• A cabinetry and a nylon runner, strap, or lanyard of appropriate length to attach the back-pack's'D' ring to the tower.

3. Set one Path Align-R™ unit to ‘Master’ and the other Path Align-R™ unit to ‘Slave’ (it doesn’t matter which is which, as long as they’re different).

4. Using the front panel thumb-wheel switches, select the proper link frequency (Note: both units must be set to the same frequency, e.g. 6.2 GHz).

5. After reaching the antenna, check that the antenna polarization is properly setup.

6. Locate each Align-R™ unit near the back of the antenna, with its weather-resistant instrument backpack’s‘D’ ring attached to the tower structure using a carabiner and a nylon runner, strap, or lanyard.

7. Attach the coax-to-waveguide adapter at the back of the antenna’s waveguide flange.

8. Connect the coax cable from the appropriate output connector on the Path Align-R™ to the adapter.

9. Connect the headset to the Path Align-R™.

10. Turn the Power Switch ON. An LED will indicate which output connector is active (make sure the cable is connected to that connector) and begin talking. Typically, the antennas can be off alignment by as much as several beam widths and the voice channel will still operate.

11. While one technician simply observes the reading of the path loss meter at his/her site, the other site commences Azimuth (horizontal) adjustment. As the voice channel is full duplex (FM), each technician can communicate with the other during the alignment process. Check for both side lobes as well as the main lobe response to ensure that the antenna is being aligned to the main lobe and no tone of the side lobes. The Path Align-R™ test sets have enough sensitivity (-100 dB) and update speed(300 ms) to quickly check for side lobe and main lobe response.

12. Once Azimuth has been optimized, the Elevation adjustment is performed.

13. When steps 11 & 12 have been completed at the first site, the technicians switch roles and steps 11 &12 are repeated by the other technician at the second site.

14. Once step 13 is completed, for both Azimuth and Elevation, the link is aligned. As a record, note the final path loss value displayed on the meter.


The difficulties of scheduling an antenna alignment test with the radios can cause significant delays, as described earlier. Furthermore, traditional test methods can produce significant costs in mobilization,deployment and testing of the antenna system. If the transmission lines (waveguides, etc.) connecting the antenna to the radio were to have a problem, the test is in jeopardy until they are corrected. If the path under test is questionable (due to site choice, obstructions, etc.), the Path Align-R™ can step right in with minimal effort to verify if there are any problems. Using the Path Align-R™ test set, the overhead associated with offering path alignment services (cost of equipment, level of expertise required, and training time) has been greatly reduced. Offering path alignment services with the Path Align-R™ translates to providing more revenue opportunities for your company.