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Author Topic: Diplexer advice  (Read 239 times)

AF5CC

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Diplexer advice
« on: September 19, 2021, 01:08:16 PM »

Over Labor Day weekend I went out of town and took the FT847 with me hoping to hand out Em15 on a few satellite passes.  Instead of taking 2 mobile whips with me, as I have in the past, I decided to try and simply things by running 1 dual band mobile whip and a diplexer for the radio.  I bought a Comet CF-416 Diplexer which is supposed to have 60DB of isolation between ports.  Results were less than expected, though.  I really couldn't hear myself on the satellite downlink at all, where I usually have no problem with separate antennas.  Have others used a diplexer with 1 antenna with good results?  What might I be doing wrong?  Any advice on how to make this setup work?

73 John AF5CC
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N4UFO

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Re: Diplexer advice
« Reply #1 on: September 20, 2021, 12:12:44 AM »

I have an MFJ-916 I use with my two 817's without a problem. And I even still use the internal diplexer in the Arrow when not using the Elk. Doubling filtering and one one cable to wrangle.

That said... I noticed when I had an FT-847 that sometimes I would get third harmonic problems INTERNAL to the radio. Could it be you are on a different bird than the last time you used two whips? Also could be it doesn't like the duplexer for some reason. I would say do an A/B test and/or try a different duplexer.

GL, Kevin N4UFO
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KD7RDZI2

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Re: Diplexer advice
« Reply #2 on: November 07, 2021, 07:30:48 AM »

I have been using a diplexer for satellites and a single antenna with no issue. Uplink on 70cm and downlink on 2m to a downconcoverter . Isolation of my diplexer is not better than yours.
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