[TowerTalk] Looking for a HP 80/40 Duplexer

[john at kk9a.com]

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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