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
I would be more inclined to blame the dual-band mobile whip... It is probably designed to provide gain toward the horizon, and likely does not radiate (or receive) well at elevation. While I have had satisfactory results using a 1/4 wave whip for 2-meter up- or downlinks, it did not work well for UHF up or down, and I never had good results on either band using a dual-band Larsen mobile antenna.
73,
George, KA3HSW
On 9/19/2021 3:06 PM, John Geiger wrote:
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
I use that diplexer with an IC9700 and have inadvertently worked SO-50 and RS-44 while connected to a 2m ground plane in the attic. The results are not stellar, as you might imagine. But doable. Perhaps having the gp’s radials as the counterpoise let me get away with it where a whip would not have. 73,RayKN2K
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On Monday, September 20, 2021, 12:17 AM, George Henry ka3hsw@att.net wrote:
I would be more inclined to blame the dual-band mobile whip... It is probably designed to provide gain toward the horizon, and likely does not radiate (or receive) well at elevation. While I have had satisfactory results using a 1/4 wave whip for 2-meter up- or downlinks, it did not work well for UHF up or down, and I never had good results on either band using a dual-band Larsen mobile antenna.
73,
George, KA3HSW
On 9/19/2021 3:06 PM, John Geiger wrote:
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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One of the previous comments was related to antenna pattern being part of the issue. I believe that is probably highly correct depending on where the bird was overhead. Do some research on the Bob Bruniga wb4aprs website. I seem to recall a 1/2 wave two meter vertical over a ground plane has an overhead pattern on both uhf and vhf that is not focused directed at the horizon like most mobile antennas are.
On Monday, September 20, 2021, 10:44:21 AM CDT, crohtun via AMSAT-BB amsat-bb@amsat.org wrote:
I use that diplexer with an IC9700 and have inadvertently worked SO-50 and RS-44 while connected to a 2m ground plane in the attic. The results are not stellar, as you might imagine. But doable. Perhaps having the gp’s radials as the counterpoise let me get away with it where a whip would not have. 73,RayKN2K
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On Monday, September 20, 2021, 12:17 AM, George Henry ka3hsw@att.net wrote:
I would be more inclined to blame the dual-band mobile whip... It is probably designed to provide gain toward the horizon, and likely does not radiate (or receive) well at elevation. While I have had satisfactory results using a 1/4 wave whip for 2-meter up- or downlinks, it did not work well for UHF up or down, and I never had good results on either band using a dual-band Larsen mobile antenna.
73,
George, KA3HSW
On 9/19/2021 3:06 PM, John Geiger wrote:
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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My non-diplexer setup involves using a 5/8 wave 2 meter mag mount for the 2 meter side, and this same dualband mag mount for the 70cm side. Works pretty well on both mode B and mode J satellites. Not sure exactly the electrical length of the 70cm side of things on that antenna. It is a 19 in whip with the little coil in the middle to isolate 70cm.
73 John AF5CC
On Mon, Sep 20, 2021 at 11:18 AM Floyd Rodgers kc5qbc@swbell.net wrote:
One of the previous comments was related to antenna pattern being part of the issue. I believe that is probably highly correct depending on where the bird was overhead. Do some research on the Bob Bruniga wb4aprs website. I seem to recall a 1/2 wave two meter vertical over a ground plane has an overhead pattern on both uhf and vhf that is not focused directed at the horizon like most mobile antennas are.
On Monday, September 20, 2021, 10:44:21 AM CDT, crohtun via AMSAT-BB < amsat-bb@amsat.org> wrote:
I use that diplexer with an IC9700 and have inadvertently worked SO-50 and RS-44 while connected to a 2m ground plane in the attic. The results are not stellar, as you might imagine. But doable. Perhaps having the gp’s radials as the counterpoise let me get away with it where a whip would not have.
73, Ray KN2K
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On Monday, September 20, 2021, 12:17 AM, George Henry ka3hsw@att.net wrote:
I would be more inclined to blame the dual-band mobile whip... It is probably designed to provide gain toward the horizon, and likely does not radiate (or receive) well at elevation. While I have had satisfactory results using a 1/4 wave whip for 2-meter up- or downlinks, it did not work well for UHF up or down, and I never had good results on either band using a dual-band Larsen mobile antenna.
73,
George, KA3HSW
On 9/19/2021 3:06 PM, John Geiger wrote:
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
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
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Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
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participants (4)
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crohtun -
Floyd Rodgers -
George Henry -
John Geiger