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Tuning 70cm duplexers, what -dBm
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Topic: Tuning 70cm duplexers, what -dBm (Read 2406 times)
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hostile
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Tuning 70cm duplexers, what -dBm
«
on:
May 01, 2021, 03:03:58 pm »
What is a decent dBm attenuation to shoot for on the filtered and passed signal ?
Right now I am at -90dBm and -0.8dBm
repeater would be on same antenna and operate 100-200' with 100W. Not sure receiver sensitivity yet.
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Last Edit: May 01, 2021, 03:48:43 pm by hostile
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thinkfat
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This is just a hobby I spend too much time on.
Re: Tuning 70cm duplexers, what -dBm
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Reply #1 on:
May 01, 2021, 03:31:05 pm »
That depends on the output power and the noise floor of the receiver, how well it suppresses close-by signals and the maximum no-damage input power. But typically, you'd want more than 100dB between the TX and RX path.
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hostile
N0NB
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Amateur radio op; electronics dabbler
Re: Tuning 70cm duplexers, what -dBm
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Reply #2 on:
November 20, 2021, 01:59:49 pm »
Here I have a TX RX Systems 28-70-02 that is spec'ed at 100 dB isolation per channel and 0.6 dB if insertion loss. I measured 0.6 dB on one side and 0.7 dB on the other and approximately 90 dB notch depth. The receiver has a measured SINAD of -118 dBm and the transmitter is set for 25 Watts with the antenna at about 190 feet, Height Above Average Terrain of 156 feet. The repeater is a Kenwood TKR-850 V1.
Range is about 30 miles and after a year I have not noticed any desense and is rather well balanced.
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