Applications

The C7RFM3 and C7RFM4 are band reject filters that reject the entire FM broadcast band from 88 MHz to 108 MHz. The prime application is to protect
communications equipment from receiver overload. Due to the sharp skirts even aircraft transceivers can be protected from FM stations.
During testing of TV transmitting antennas. A strong FM signal can disturb low power testing. The spectrum analyzer may be overloaded or sensitive equipment damaged. The C7RFM3 filter will attenuate the FM but still pass the desired TV signal.
FM stations can use this filter to suppress the carrier in order to measure harmonic output of the transmitter with a spectrum analyzer. This filter effectively increases the dynamic range by 25 dB.
Aircraft transceivers can be protected from FM by simply inserting a C7RFM3 filter in the antenna lead. A high level FM signal getting into the PA of an aircraft transceiver can create intermodulation products that may disrupt other signals in the 108-135 MHz aircraft band.
Paging transmitters sometimes produce intermodulation products when subjected to a strong FM signal. Attaching the C7RFM3 to the output of the paging transmitter will prevent the strong FM carrier from appearing on the nonlinear, class C PA that is used in the paging transmitter.

Description

The configuration is band reject using a multi-section filter for best performance. The filter passes DC-73 MHz with <0.5 dB of insertion loss and 118 to 1000 MHz with <1.0 dB of insertion loss.

Description-continued

This allows the filter to be used in front-end of HF, VHF, or UHF equipment. Cellular and SMR in the 800-900 MHz bands can also be protected without objectionable insertion loss.
The filter has a power rating of 30 watts continuous(100 watts optional) so that it can be connected in the transmit path of small transmitters without the fear of filter burnout. Thus it is not necessary to modify a transceiver to access the receiver because the filter can not handle the transmit power.
The C7RFM3 is packaged in a nickel plated brass enclosure using stainless steel hardware thus eliminating corrosion due to dissimilar metal action. The heavy duty enclosure provides excellent shielding. Mounting tabs are provided for chassis attachment.
Several different types of connectors are available at nominal extra cost. These include BNC, SMA and N. If a special connector arrangement is desired please contact the factory.
If desired the filters can be supplied in a splash proof version for mounting out-of-doors.

Quality

To insure that high quality is maintained each unit is thoroughly inspected both mechanically and electrically. All units are aged and then retested to insure superior stability over the lifetime of the instruments.

Availability

These filters are normally stock items: 1 week delivery. Special orders or large quantities usually require 2-4 weeks.

Specifications

Please see the next page for detailed specifications, performance graphs and ordering information.

SPECIFICATIONS

Electrical

Impedance:

50 ohm ± 5%

Power Rating:

C7RFM3 30 watts
C7RFM4 100 watts

Voltage Rating:

100V DC+AC

Insertion Loss:

DC-73 <0.5 dB
73-82 <3.0 dB
88-108 > 30 dB
115-123 <3.0 dB
123-500 <0.5 dB
500-1000 <1.0 dB

Environmental

Temperature:

+25 to +50C full specifications
-55 to +125 storage

Humidity:

10-80% RH, non-cond

Shock:

Drop from 1"

Vibration:

100 G any Axis

Waterproof:

No

Mechanical

Case Size:

Weight:

<6.0 Oz

Construction:

Can is of brass .025"; nickel plated. Connectors are stainless steel or brass. All hardware is stainless steel.

Options

Connectors

"BF"

BNC female Standard

"MF"

SMA female

"NF"

N female Standard

"NM"

N male

Test Data:

Test data can be provided on pass band and stop band, return loss, and group delay.

TD

Test Data Plots

COC

Certificate of Conformance

Ordering Information

Select C7RFM3xx or C7RFM4xx depending on power rating and then add correct suffix for desired connector in place of the xx. Call the factory or authorized representative to place the order.

SPECIFICATIONS-cont

Performance Graphs

Click on graph for explanation and enlarged version.

Outline Drawing

Click on drawing for enlarged view