[TowerTalk] TowerTalk Digest, Vol 275, Issue 21

[Drew Vonada-Smith]

The poster's point was that you cannot do that as there would be no isolation between antennas and the RX would be toast.  The duplexer adds isolation, maybe enough without filters, maybe not, but quite a bit.

73, Drew K3PA

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Subject: TowerTalk Digest, Vol 275, Issue 21

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Today's Topics:

   1. Re: Looking for a HP 80/40 Duplexer (john at kk9a.com)


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Message: 1
Date: Tue, 18 Nov 2025 11:47:21 -0500
From: <john at kk9a.com>
To: <towertalk at contesting.com>
Subject: Re: [TowerTalk] Looking for a HP 80/40 Duplexer
Message-ID: <003a01dc58ab$029f79d0$07de6d70$@kk9a.com>
Content-Type: text/plain;	charset="utf-8"

W8FN?s QRZ pages listed his 40m/80m antenna as a fan dipole, not a trap dipole.  I am sure most people on this towertalk list can figure out how to separate a fan dipole into two antennas with two feedlines.  If a diplexer is a better option than go for it, I was just suggesting another option.  

 

John KK9A

 

From: Jack Brindle <jackbrindle at me.com>
Sent: Tuesday, November 18, 2025 9:42 AM
To: john at kk9a.com
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Looking for a HP 80/40 Duplexer

 

Two feed lines on one antenna is definitely not a solution. The only isolation would be whatever loss is in the feed lines. Basically you would be putting high power directly into the *other* receiver. I doubt that is survivable.

 

Pavel has a page that specifically discusses his 80/40 diplexer. It is definitely worth a look. That is at: https://va6am.com/2017/01/01/4080-band-diplexer/

 

73,

Jack, W6FB

 





On Nov 17, 2025, at 10:04?PM, john at kk9a.com <mailto:john at kk9a.com>  wrote:

 

As others have stated I am sure that VA6AM can make a 80/40 duplexer for you however the easiest approach would be to just run another feedline to your fan dipole.

John KK9A


Randy Farmer w8fn wrote:

I'm investigating upgrading my station from its present 500W capability to 1500W. I've located sources for most of the up-rated bandpass filters and other hardware required for the project, but can't seem to find a source for a duplexer to split a 80-40 dipole for SO2R use. I'm presently using one of the Low Band Systems 500W 80/40/20 triplexers for this function. LBS apparently makes a 1500W 80/40 duplexer, but it appears the LBS stuff is no longer available in the USA. Does anyone have or know of a suitable 1500W unit? I do NOT need it to be rated for 100% duty cycle since I'm only interested in CW and occasional SSB use, but it needs to hold up under contest conditions with a full power amplifier.

4O3A makes a nice 20/15/10 triplexer, but they don't have any high power
80/40 units. Antennas-Amplifiers (distributed by DX Engineering) makes nice HP bandpass filters, but not a triplexer or duplexer. VA6AM (also distributed by DX Engineering) doesn't have any high power devices.

73...
Randy, W8FN


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End of TowerTalk Digest, Vol 275, Issue 21
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