— Installer Guide
Bosch CM748B
Antenna
The CM748B ships with a quad band, omni directional, magnetic base antenna rated at 3 dBi, on an integrated lead with an SMA connector. If the module is reporting poorly, the fix is almost always to get that antenna out of the steel cabinet and up above it, on a lead that doesn't eat the gain you just added.
SMA
Connector
3 dBi
Supplied antenna
Band 28
700 MHz supported
Cat 1
LTE, dual SIM
What comes in the box
From the Bosch CM748B datasheet (V1, 18 March 2024):
“Quad Band Omni Directional Magnetic Base Antenna with integrated lead and SMA Connector. 3dbi gain - 50 ohm. Optional high gain outdoor antenna available.”
The box holds the radio module, one antenna, a manual and a plastic standoff pack. The module mounts on the expansion port of the Solution 6000 PCB.
The radio is a Quectel EG800Q-EU, LTE Cat 1. Quectel lists that module on LTE bands 1, 3, 5, 7, 8, 20 and 28, which includes band 28 at 700 MHz, the band that carries best through concrete and steel.
CM748B at a glance
Why the supplied antenna struggles
A magnetic base is designed to sit on metal, and the obvious piece of metal is the panel cabinet. That puts a 3 dBi antenna on the outside skin of the enclosure or, too often, inside it with the door shut. A closed steel cabinet is a very effective shield.
Bosch's datasheet also warns: “if the unit is being installed in a remote location, make sure the carrier you are using has sufficient coverage (signal) for reliable performance.”
In practice the module reports fine at commissioning, then drops out intermittently weeks later, when network load or the weather changes and the margin runs out.
The fix, in order
- 1
Move the supplied antenna outside the cabinet and above it. Free, and often enough in metro areas.
- 2
Fit a higher gain external antenna above the cabinet, on the wall or a short pole, clear of other metalwork.
- 3
Keep the lead low-loss. A thin lead can cancel the gain you paid for. The numbers are below.
Bosch offers its own AN110 outdoor 4G antenna with 15 m of RG58 cable (order number F.01U.401.523). That is a sensible option. The antennas below are for when you need a different gain, a different length, or a different termination.
Which D&G antenna fits
All figures are from the D&G datasheets. The CM748B takes an SMA connector, so order SMA termination. Every antenna is tested before dispatch: what we build in Penrith on our Anritsu Site Master, supply-partner products by the partner to D&G specification.
| Antenna | Gain | Bands | Lead | When |
|---|---|---|---|---|
| DG900MB-HG | 7.0 dBi at 700–1000 MHz, 3.5 dBi at 1710–2600 MHz | 680–960 / 1710–2700 MHz | 2.5, 5 or 10 m ALSR195 low-loss, SMA | Weak or fringe signal, where band 28 matters most |
| DG850LP-MB | 5.0 dBi at 700–960 MHz, 3.5 dBi at 1710–2700 MHz | 700–960 / 1710–2700 MHz | 2.5, 5 or 10 m RG58, 16 mm stud mount | Where a low profile is needed. Ground dependent, so mount it on a metal surface or bracket |
| DG850MB-MINI | 3.5 dBi at 690–960 MHz, 7.5 dBi at 1710–2700 MHz | 690–960 / 1710–2700 MHz | 2.5 or 5 m standard, custom lengths to order | Compact option, strongest on the upper bands |
The lead matters as much as the antenna
On a 10 m run at 900 MHz, a 7 dBi antenna on RG174 nets about −0.05 dB. The thin cable eats more than the antenna gives. The same antenna on 10 m of ALSR195 still nets about +3.35 dB. For runs longer than about 10 m, ask for a heavier cable or a custom assembly.
| Cable | Loss at 900 MHz, per 100 m | Per 10 m | 7 dBi antenna nets |
|---|---|---|---|
| RG174 | 70.5 dB | 7.05 dB | −0.05 dB |
| RG58C/U | 53.2 dB | 5.32 dB | +1.68 dB |
| ALSR195 | 36.5 dB | 3.65 dB | +3.35 dB |
Sources: CoaxRF RG174 guide, McGill Microwave RG58C/U datasheet, Times Microwave LMR-195 datasheet (ALSR195 is the LMR-195 equivalent).
Questions installers ask
What connector does the Bosch CM748B antenna use?
SMA. Bosch's CM748B datasheet describes the supplied antenna as having an "integrated lead and SMA Connector".
What gain is the supplied CM748B antenna?
3 dBi, per the Bosch CM748B datasheet.
Can I put the CM748B antenna inside the metal cabinet?
It will often work at commissioning and fail later. A closed steel enclosure blocks much of the signal. Mount the antenna outside and above the cabinet.
Does the CM748B support 700 MHz (band 28)?
Its radio, the Quectel EG800Q-EU, is listed by Quectel on band 28 along with bands 1, 3, 5, 7, 8 and 20.
What's the difference between the CM746B and the CM748B?
Both are 4G plug-on modules for the Bosch Solution 6000. The CM748B is the LTE Cat 1 module with dual SIM, and its datasheet confirms an SMA antenna connector.
Also relevant: Bosch CM746B antenna · Bosch Solution 6000 guide · How to install an external 4G antenna
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