TV Antenna Equipment
Rejection Filters
CDMA band-stop filter (462.5-467 MHz, 30dB)
Code: R49603
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This filter eliminates interferences coming from CDMA base stations that influence TV reception. Despite CDMA service uses different channel, it may cause deterioration of TV signals. The reason is in overdriving transistors in antenna amplifiers by strong CDMA signals.
CDMA interferes with terrestrial TV because:
- Preamplifiers/amplifiers used in antennas/antenna installations usually amplify the whole TV band (broadband amplifiers)
- Typical broadband antennas have half-power beam about 45 degrees, receiving also unwanted CDMA signals
- CDMA base stations are often at the same direction as TV transmitters, which does not allow to eliminate the interferences using directional antennas
- In all the three cases the interferences are increased by typical preamplifiers/amplifiers used in home TV installations. Even amplifiers with independent VHF and UHF gain adjustment do not solve the problem due to immediate proximity of CDMA band and the lowest UHF channel.
In the case of such problems we advise to:
- use low-gain preamplifier e.g. B4007
- change the broadband antenna to a directional one e.g. A2670
- use the dedicated steep CDMA filter R49603 before the first amplification stage
The filter has DC pass for powering an optional preamplifier (not recommended - the filter should precede the first amplification stage).
Specifications
| Name | CDMA filter | |
| Code | R49603 | |
| Pass band | MHz | 0-862* |
| Pass-band attenuation | dB | <1** |
| Stop band | MHz | 462.5 - 467 |
| Stop-band attenuation | dB | >30 |
* without stop band
** channel 21: 4dB
** channel 21: 4dB
Frequency characteristics
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