[VHFcontesting] diplexer vs coax switch

Sun Jul 10 14:20:02 EDT 2016

> John
> KM4KMU wrote:  No single cable had a VSWR over 1.10 with most being 1.05 
> or less. With the CF-4160 inserted the VSWR to the 440 antenna >jumped to 
> 2.4  to 2.9 and the 144 was at 1.6 to 1.8 across the simplex frequencies.

    That sounds like a failed component in the diplexer. I have run 
back-to-back Comet  tri-plexers on my 3 band omni stack for 6m-2m-70cm for 
over 10 years with no standing wave issues with either 10W beacon or 50~100W 
transceiver power levels. I did take the time to carefully waterproof the 
triplexers.

 Although a diplexer or triplex may have .4 to .7 dB insertion loss, it 
would seem you could easily make that up with a single higher grade cable 
(LMR600, etc.).  Another advantage is the diplexer or triplexer provides 
additional filtering. A triplexer is a low pass, band pass, high pass filter 
arrangement and you get the additional filtering benefits on both receive 
and transmit for each triplexer port.  When you use a triplexer or diplexer 
on each end of a single cable, the filtering performance is approximately 
"dB additive"  See below...

https://www.dropbox.com/s/8owsumh7yxa2zzs/2tripxr.jpg?dl=0

Reference: 2016 ARRL Handbook, Supplemental CDROM, CH13, VHF and UHF Beacons 
WA3TTS

73, Mike wa3tts

----- Original Message ----- 
From: <vhfcontesting-request at contesting.com>
To: <vhfcontesting at contesting.com>
Sent: Sunday, July 10, 2016 12:00 PM
Subject: VHFcontesting Digest, Vol 163, Issue 8

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> Today's Topics:
>
>   1. Coax Switch vs. Duplexer (Jarred Jackson)
>   2. Re: Coax Switch vs. Duplexer (Mark Spencer)
>   3. Re: Coax Switch vs. Duplexer (Floyd Rodgers)
>   4. Re: Coax Switch vs. Duplexer (nosigma at aol.com)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 9 Jul 2016 22:59:51 +0000
> From: Jarred Jackson <Jarred.Jackson at hotmail.com>
> To: "vhfcontesting at contesting.com" <vhfcontesting at contesting.com>
> Subject: [VHFcontesting] Coax Switch vs. Duplexer
> Message-ID:
> <BLUPR11MB0081791683A194BA35A463719A3D0 at BLUPR11MB0081.namprd11.prod.outlook.com>
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I have an IC-7000 with a common VHF/UHF output and switch between 2m and 
> 70cm amplifiers/antennas using a Diamond CX-210A  coax switch. I am 
> thinking of replacing the switch with a Comet CF-4160 duplexer that I have 
> had laying around unused. I would like one less thing to do when switching 
> between bands. It looks like there is 10dB less isolation (60 vs. 70 dB) 
> and about 0.1 dB additional loss by using the duplexer. The radio sends 
> the amplifiers 5W on 2m and around 28W on 70cm.
>
>
> Any concerns / thoughts on making this change? It seems straightforward, 
> but I have had the same thought on other changes that haven't turned out 
> so well.
>
>
> Thanks,
>
>
> Jarred - KF2MR
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 9 Jul 2016 16:14:35 -0700
> From: Mark Spencer <mark at alignedsolutions.com>
> To: Jarred Jackson <Jarred.Jackson at hotmail.com>
> Cc: "vhfcontesting at contesting.com" <vhfcontesting at contesting.com>
> Subject: Re: [VHFcontesting] Coax Switch vs. Duplexer
> Message-ID:
> <8F05ADE0-ABBA-457C-B322-D9FE4C39B28B at alignedsolutions.com>
> Content-Type: text/plain; charset=us-ascii
>
> I've used a Comet CF 4160 for a similar purpose with an Icom 706 MkiiG. 
> I didn't experience any issues.
>
> (The only caveat I'll mention is that I almost exclusively use double 
> shielded patch cords in my roving set up.)
>
> 73 Mark S
> VE7AFZ
>
> Sent from my iPhone
>
>> On Jul 9, 2016, at 3:59 PM, Jarred Jackson <Jarred.Jackson at hotmail.com> 
>> wrote:
>>
>> I have an IC-7000 with a common VHF/UHF output and switch between 2m and 
>> 70cm amplifiers/antennas using a Diamond CX-210A  coax switch. I am 
>> thinking of replacing the switch with a Comet CF-4160 duplexer that I 
>> have had laying around unused. I would like one less thing to do when 
>> switching between bands. It looks like there is 10dB less isolation (60 
>> vs. 70 dB) and about 0.1 dB additional loss by using the duplexer. The 
>> radio sends the amplifiers 5W on 2m and around 28W on 70cm.
>>
>>
>> Any concerns / thoughts on making this change? It seems straightforward, 
>> but I have had the same thought on other changes that haven't turned out 
>> so well.
>>
>>
>> Thanks,
>>
>>
>> Jarred - KF2MR
>> _______________________________________________
>> VHFcontesting mailing list
>> VHFcontesting at contesting.com
>> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 9 Jul 2016 18:52:02 -0500
> From: Floyd Rodgers <kc5qbc at swbell.net>
> To: Jarred Jackson <Jarred.Jackson at hotmail.com>,
> "vhfcontesting at contesting.com" <vhfcontesting at contesting.com>
> Subject: Re: [VHFcontesting] Coax Switch vs. Duplexer
> Message-ID: <b0cfec0c-fb6a-f20e-270d-9a390a380ef5 at swbell.net>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> For field day I run an ft857 using a diamond mx72 duplexer to split
> vhf/uhf to single band amps and recombine the signal with another mx72
> which goes to a dual band beam. At home similar ft847 to single band
> amps combined into 7/8 hardline feeding separate beams. I've never had
> an issue running up to 150w. The pair of duplexers in this configuration
> yields 120db of isolation
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 9 Jul 2016 22:28:40 -0400
> From: nosigma at aol.com
> To: Jarred.Jackson at hotmail.com, vhfcontesting at contesting.com
> Subject: Re: [VHFcontesting] Coax Switch vs. Duplexer
> Message-ID: <155d2a29eb9-7885-1f819 at webprd-m61.mail.aol.com>
> Content-Type: text/plain; charset=utf-8
>
>
> The below relates to FM Simplex frequencies.
> If this is just for casual conversation use the diplexer it makes life 
> very easy.  If this is a weak signal contest set up go with the switch. 
> After the January VHF/UHF contest I put a lot of effort into minimizing 
> losses and getting VSWR, losses and reflected power as low as possible on 
> my set up. I was running Yagi's on 144 and 440 with an FT8800 (dual band 
> radio) single output.  I was using the Comet CF-4160 to let me run a 
> single cable up the mast from the radio to the two Yagi's.  No single 
> cable had a VSWR over 1.10 with most being 1.05 or less. With the CF-4160 
> inserted the VSWR to the 440 antenna jumped to 2.4  to 2.9 and the 144 was 
> at 1.6 to 1.8 across the simplex frequencies.  Not a big deal at 144, a 
> horrible outcome for 70cm.  I installed a coax switch (Alpha Delta) and 
> saw the VSWR at 440 drop to below 1.4 at 144 and below 1.6 at 440.
>
>
> When I add start adding TE amplifiers,with integral pre amps, this summer 
> I may use a triplexer between the radio's and and the amps but the added 
> reflected power and insertion losses will be have no effect on output 
> power and minimal effect on received signal since they are between the 
> radio and the amps.  I will never use a triplexer or diplexer between the 
> antenna and TX output or first stage RX amp again.
>
>
>
> 73
> John
> KM4KMU
>
>
>
> -----Original Message-----
> From: Jarred Jackson <Jarred.Jackson at hotmail.com>
> To: vhfcontesting <vhfcontesting at contesting.com>
> Sent: Sat, Jul 9, 2016 7:01 pm
> Subject: [VHFcontesting] Coax Switch vs. Duplexer
>
> I have an IC-7000 with a common VHF/UHF output and switch between 2m and 
> 70cm amplifiers/antennas using a Diamond CX-210A  coax switch. I am 
> thinking of replacing the switch with a Comet CF-4160 duplexer that I have 
> had laying around unused. I would like one less thing to do when switching 
> between bands. It looks like there is 10dB less isolation (60 vs. 70 dB) 
> and about 0.1 dB additional loss by using the duplexer. The radio sends 
> the amplifiers 5W on 2m and around 28W on 70cm.
>
>
> Any concerns / thoughts on making this change? It seems straightforward, 
> but I have had the same thought on other changes that haven't turned out 
> so well.
>
>
> Thanks,
>
>
> Jarred - KF2MR
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> End of VHFcontesting Digest, Vol 163, Issue 8
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