4-meter Band Pass Filter Designed for 100 W Transmitters with a frequency range of 70 – 70.5 MHz

This filter is designed to withstand 100 W transmitters but is also ideal for receiving. Its low losses of only 0.12 dB will not be noticed in the system. Filter has a 50% power margin. So even power spikes or more power won’t be a problem.

70 MHz bandpass filter has input return loss better than -35 dB and more on the whole 4-meter band!

External appearance for 70 – 70.5 Mhz 100 W Low Loss Bandpass filter:

 

 

Achieved results on a built Bandpass filter:
1.8 MHz < -96 dB
3.8 MHz < -96 dB
7.1 MHz < -87 dB
14.15 MHz = -68 dB
21.2 MHz = -56 dB
28.4 MHz = – 47 dB
50 MHz = -20 dB
70 MHz = -0.12 dB, Input RL better than -35dB
70.5 MHz = -0.12 dB, Input RL better than -35dB
100 MHz= -15 dB
144 MHz = -38 dB
146 MHz = -39 dB
148 MHz = -39 dB
432.1 MHz = -63 dB
460 MHz = -57 dB

These excellent results were achieved by careful selection of the components and design of the filter.
The measured data on the assembled filter with HP8753ES full 2-port calibrated are presented below. The following images show the S parameters of the most important points.
Characteristics of 70 – 70.5 MHz Band-pass filter:

Insertion loss 0.119 dB, return better than 35 dB.

 

 

Characteristics of the filter outside the receiving range:

1. Measured HF attenuation:

 

2. Measured HF – 50 MHz – FM attenuation:

 

 

3. Measured attenuation for 2-meter and 70-cm bands:

 

 

Feel free to send e-mail if you need something more specific.

All band-pass filters are here: HF, VHF, and UHF Band-Pass Filters

Direct link to all 4-meter filters. We have 50 W, 100 W, 200 W, 300 W, 1500 W and 4000 W versions: 4 Meter Band-Pass Filters