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[OT] Duplexer/Diplexer

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GeorgeP1111

[OT] Duplexer/Diplexer

2 Radios, 2 Antennas, 1 Coax.

That pretty much says it all. I currently have a KX3 and a 2-meter rig (but I’ll probably be outfitting the KX3 with 2m’s in the future) and I use a HamSticks for HF or a 1/4 wave GP for 2 meters. Running another coax here is not a option (apartment) so I have been swapping radios/antennas. Now I’m thinking of using two HF/VHF Duplexers (or Diplexer as they are also called) to join/split the RF. For example using two of the MFJ-4916S, one port is 1.6-56mHz and the other is 140-540mHz. Hf power output is limited to the KX3 (12w?) and VHF is currently the IC-2300H at 65w. I understand that there will be insertion loss/isolation issues. I have never pursued using splitters on a coax feed before and tho two simple A/B switches (manual or remote) would work better, I’d just like to keep things simple.

From what I have been reading, the Diplexer route looks like it should work fine given the above?

tnx
de George
WD0AKZ
dit – dit

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k6dgw

Re: [OT] Duplexer/Diplexer

Used triplexers for years, HF, 2, 70 cm, one run to tower, worked great. I think mine were Comet. Just watch the SEE with higher power.

Fred K6DGW

George Pasek <[hidden email]> wrote:

>2 Radios, 2 Antennas, 1 Coax.
>
>That pretty much says it all. I currently have a KX3 and a 2-meter rig (but I’ll probably be outfitting the KX3 with 2m’s in the future) and I use a HamSticks for HF or a 1/4 wave GP for 2 meters. Running another coax here is not a option (apartment) so I have been swapping radios/antennas. Now I’m thinking of using two HF/VHF Duplexers (or Diplexer as they are also called) to join/split the RF. For example using two of the MFJ-4916S, one port is 1.6-56mHz and the other is 140-540mHz. Hf power output is limited to the KX3 (12w?) and VHF is currently the IC-2300H at 65w. I understand that there will be insertion loss/isolation issues. I have never pursued using splitters on a coax feed before and tho two simple A/B switches (manual or remote) would work better, I’d just like to keep things simple.
>
>From what I have been reading, the Diplexer route looks like it should work fine given the above?
>
>tnx
>de George
>WD0AKZ
>dit – dit
>
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Bob McGraw - K4TAX

Re: [OT] Duplexer/Diplexer

In reply to this post by GeorgeP1111

You will need a duplexer on each ends of the coax. Preferably these
should be identical.    One at the bottom end to combine the HF and VHF
signals to one coax and then on the top end to split the HF and VHF
signals to feed each respective antenna.   Do be mindful that these
units are a bit fussy regarding operating in applications where the SWR
may be high.   Thus they really prefer installations where the impedance
if near 50 ohms otherwise where the SWR is low, usually less than 1.5: 1
or so.    Also, physical separation of the two antennas is also desirable.

Good luck with the project. I do understand as I lived and operated
from a condo in S. FL for several years.

73
Bob, K4TAX

On 12/27/2017 10:10 AM, George Pasek wrote:

> 2 Radios, 2 Antennas, 1 Coax.
>
> That pretty much says it all. I currently have a KX3 and a 2-meter rig (but I’ll probably be outfitting the KX3 with 2m’s in the future) and I use a HamSticks for HF or a 1/4 wave GP for 2 meters. Running another coax here is not a option (apartment) so I have been swapping radios/antennas. Now I’m thinking of using two HF/VHF Duplexers (or Diplexer as they are also called) to join/split the RF. For example using two of the MFJ-4916S, one port is 1.6-56mHz and the other is 140-540mHz. Hf power output is limited to the KX3 (12w?) and VHF is currently the IC-2300H at 65w. I understand that there will be insertion loss/isolation issues. I have never pursued using splitters on a coax feed before and tho two simple A/B switches (manual or remote) would work better, I’d just like to keep things simple.
>
> From what I have been reading, the Diplexer route looks like it should work fine given the above?
>
> tnx
> de George
> WD0AKZ
> dit – dit
>
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Jim Brown-10

Re: [OT] Duplexer/Diplexer

Exactly right! And MUCH more than "a bit fussy" -- these are passive
networks, and ALL passive networks depend on both source and load
impedances being right. Don't expect something like this to work right
(or handle power) with non-resonant antennas.

73, Jim K9YC

On 12/27/2017 9:18 AM, Bob McGraw K4TAX wrote:
> Do be mindful that these units are a bit fussy regarding operating in
> applications where the SWR may be high. Thus they really prefer
> installations where the impedance if near 50 ohms otherwise where the
> SWR is low, usually less than 1.5: 1 or so.

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Phil Kane-2

Re: [OT] Duplexer/Diplexer

In reply to this post by GeorgeP1111

On 12/27/2017 8:10 AM, George Pasek wrote:

> Now I’m thinking of using two HF/VHF Duplexers (or Diplexer as they are also called)

Not the same. A duplexer is used to permit simultaneous transmit and
receive functions in an application such as a repeater. A diplexer is
used to combine the simultaneous output of two transmitters, such as the
visual and audio sections of an analog TV transmitter.

And as others have said - they are very fussy to set up and keep in
alignment.
----

73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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