Class 4 Microwave Antennas

What is a Class 4 Microwave Antenna?

Class 4 Antennas explained:

CableFree Class 4 Microwave Antenna 1Class 4 antennas provide the current best RF performance allowing mobile operators and Wireless Internet Service Providers (WISP) to increase the link capacity of a network by deploying new microwave links where high levels of interference are present. Class 4 antennas will allow customers to offer the highest performance in even the most congested environments. The higher side lobe suppression supports networks in ultra-dense areas and enables earlier reuse of frequencies. The lower interference increases the carrier-to-interference-ratio and allows smaller antennas with better link throughput, reducing tower leasing fees. The lower interference also enables higher modulation schemes, increasing the data capacity per antenna.

Benefits of a Class 4 Antenna

Increase the link capacity of the network
– Improved radiation patterns for ETSI Class 4 providing better performance
– Less interference and higher carrier-to-interference ratio
– Allows radios to operate at higher modulation levels
• Minimize the total cost of ownership
– Improved network efficiency
– Facilitates better re-use of a frequency channel
– Small antennas with better link throughput reduces tower leasing fees

Intended Use for Class 4 Antennas

CableFree Class 4 Microwave Antenna 1Class 4 antennas are intended for “extremely high interference potential” situations, according to ETSI. For a more detailed treatment of antenna classifications and radiation patterns, see the ETSI document “Fixed Radio Systems; Point to Point Antennas.”

Wider channels, larger capacity

For situations where the operator needs to increase capacity from a wireless backhaul site, the easiest way remains widening the channel size. But at sites that experience extremely high interference, the operator may not be able to coordinate radio frequency pairs in wide channels with Class 3 antennas. However, moving up to Class 4 antennas would allow the operator to optimize the signal-to-noise ratio and let higher modulations come into play, so wide channels could be coordinated with correspondingly higher data rates

Smaller is Better

In cases of high interference, larger antennas can be used to reduce it. For a subset, smaller Class 4 antennas can be used instead of their oversize Class 3 counterparts. Thus, operators who deploy Class 4 antennas gain the added benefit of dropping down a parabolic dish antenna size as compared to a Class 3 antenna in the same application. In general, smaller dishes advantage the operator due to their lighter weight and lower opex tower charges, albeit with an initially bigger upfront capex. Because Class 4 antennas represent an elevated level of precision tooling and more detailed manufacturing versus lower class antennas, capex of these passive, higher-performance infrastructure pieces always weighs in the balance.


According to Andy Sutton,  Principal Network Architect at EE:

Using Comsearch’s iQ.linkXG microwave planning software, CommScope analyzed the technical and commercial benefits of using Class 4 Sentinel antennas in the network. The results were most impressive. For the two frequency bands of the microwave backhaul network studied, which is comprised of over 6,200 links in total, the core findings were:

  • Potential savings of $5 million in total cost of ownership (TCO) over five years by enabling a greater link density and therefore reducing the need for third party Ethernet Leased Lines
  • Greater utilization of owned block allocated spectrum reduced the need for link by link licensing (from the national regulator) and therefore could save $44,000 in license fees over five years
  • $4.5 million could be saved per year based on optimizing capacity by freeing congested channels while still ensuring new links met the strict quality of service criteria
  • 96 percent and 31 percent of links which couldn’t be planned due to frequency congestion in 40 and 10 GHz could be assigned a channel, respectively
    • A strong opportunity to trade some of the above by reducing antenna size and thus reducing TCO on tower lease costs

(content from EE above reproduced with acknowledgement from Commscope. Other content including photos from RFS).

For Further Information

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Microwave Antenna Alignment

Alignment of Microwave Antennas for Digital Microwave Transmission Systems

This article contains generic instructions for alignment of Microwave antennas.  Specific products may have different features, in which case please refer to the documentation provided for those products:

CableFree Microwave Antenna Alignment
CableFree Microwave Antenna Alignment

Antenna Alignment for Microwave Links

This guide explains how to achieve the optimal antenna alignment of microwave antennas when used with modern digital microwave products.  Before attempting to do the alignment it is highly recommended that you read this guide in detail.  For specific commands please consult the manual of the product being installed

Step 1:  Preparation:

Mount the antenna on the tower according to the antenna installation instructions:  Ensure that the adjustment bolts move smoothly and the range of motion is sufficient for the expected angle of up and down (elevation) tilt. Ensure that the mount itself is attached securely and all safety precautions have been taken.

CableFree Microwave Antenna Alignment using DVM
CableFree Microwave Antenna Alignment using DVM

Step 2: Coarse Alignment:

Visually align the antenna with the far end.  The most common ways to do this are :

1)      If the visibility is good and the sun is in the correct position, have someone at the far end location reflect the sun with a mirror so the location is obvious.

2)      If visibility is poor, use GPS coordinates and a GPS compass to aim the antenna coarsely.

CableFree Microwave Antenna Alignment avoiding Sidelobes
CableFree Microwave Antenna Alignment avoiding Sidelobes

Step 3: Fine Alignment.

Before conducting fine alignment, the ODUs at both ends of the link must be attached properly to the antenna via the direct mount or remote mount (using Waveguide) and the far end ODU must be powered on and transmitting.  The ODU lightning surge suppressors and grounding provisions should be put in place as well before alignment. The local ODU must be powered on, but need not be transmitting.

Ensure that:

1)      Frequency of the far end transmitter matches the frequency of the local receiver.

2)      The TX output power is not set above the level of the license.

3)      ATPC is turned OFF on the far end.

4)      Alignment mode is ON for SP ODUs – Display on ODU and IDU will update at 5 times per second.


1)      Adjust the azimuth over a 30 degree sweep by turning the adjustment bolt in increments of 1/10th turn to avoid missing the main lobe. When the highest signal has been found for azimuth, repeat for the elevation adjustment.

2)      Turn the local transmitter on to allow alignment at the far end.

3)      Move to the far end of the link and repeat step 1.

4)      Lock down the antenna so no further movement can occur.

5)      Install the antenna side struts supplied with the antenna.

6)      Verify the RSSI remains the same and is within 2-4 dB of the expected levels.

7)      Check the ODU connector seals.

8)      Turn alignment mode OFF

9)      The alignment is complete.