I own and operate IsoHorns and Cyber Antennas, RF Elements competitors.
Uplink refers to the access point’s (AP’s) ability to receive a signal from the client station.
Downlink refers to the client station’s ability to receive a signal from the AP.
DS11 represents two spatial streams using MCS 11 (1024-QAM).
SS11 represents one spatial stream using MCS 11 (1024-QAM).
To achieve reliable DS-11 802.11ax MIMO 2×2 performance, sufficient isolation between the two spatial streams is required. In a dual-polarity system, these spatial streams correspond to the vertical and horizontal polarizations. RF Elements does not publish port-to-port isolation figures on their datasheets. Independent measurements of TwistPort adapters show only about 12-19 dB of isolation across the 5 GHz band—which is by far the worst in the WISP industry.
RF Elements UltraHorn antennas use TwistPort adapters that do not have threading on the RP-SMA connectors. This lack of threading can result in loose or inconsistent connections, leading to high VSWR (Voltage Standing Wave Ratio), where the transmitted signal power is reflected back at the radio.
High VSWR can damage the sensitive receive components of the radio—particularly the low-noise amplifiers (LNAs)—which are responsible for amplifying very faint incoming signals, leading to loss of chains and elevating the noise. Excessive VSWR can also occur when operating the radio outside the antenna’s specified frequency range.
Although RF Elements UltraHorn antennas and TwistPort adapters are marketed as supporting the 5 GHz band, most of their antennas do not actually cover the full range from 5.15 GHz to 5.85 GHz. Instead, many models only support down to 5.18 GHz. Operating below 5.18 GHz can cause excessively high VSWR, which may damage the radio, especially over time.
Other common causes of high VSWR include manufacturing defects, user error (e.g., improper assembly), or environmental issues such as water ingress.
Professional antenna manufacturers specify the maximum VSWR on their datasheets and test every unit to ensure it meets or exceeds that specification. RF Elements does not publish VSWR values on the UH-TP-5-24 datasheet (or most other datasheets).
If you want to max out the capabilities of your Cambium radios, you need good antennas. I assume your link distances must be short if you are getting DS/SS11 with RF Elements 24 dBi horns. If you are on a budget, I recommend IsoHorns 0.6m CPE dish. If you want top performance or you are colocated with many other radios, I recommend Cyber Antennas 0.6m high performance dish. Both are amazing values and offer the best price-performance in the industry.
If you don’t have the budget for new antennas, just swap out the UltraHorns with any 5 GHz antennas and see what happens.
Will keep you posted…