Suggestions for a 2MLDPA TX RX duplexer/combiner?

  • 1
  • Question
  • Updated 4 weeks ago
Looking for suggestions for a duplexer/combiner to join my normally split feed line configuration into a single common feed line from the back of my 2MLDPA. Thank you!
Photo of John - WA7UAR

John - WA7UAR

  • 125 Posts
  • 30 Reply Likes

Posted 2 months ago

  • 1
Photo of WX7Y

WX7Y

  • 665 Posts
  • 124 Reply Likes
Easy enough to build one but I seen one on MFJ Web site  a MFJ-1708SDR TX/RX switch that should do what you want, looking at the Schematic and reading the description.

Hope this is what you where asking about.
73's
Bret
WX7Y

(Edited)
Photo of John - WA7UAR

John - WA7UAR

  • 125 Posts
  • 30 Reply Likes
Thanks for responding Bret but I don’t think the 1708SDR is what I’m looking for. The amplifier in the picture can push out 70 watts on 2 meters. I think I’m looking for a duplexer that can merge the two separate N-type antenna connections into a single feed line connection. Maybe one of these from Comet or another manufacturer? But maybe my terminology is wrong? Maybe a diplexer/splitter/combiner?

http://www.cometantenna.com/amateur-r...
(Edited)
Photo of David-N5PSM

David-N5PSM

  • 104 Posts
  • 23 Reply Likes
Why not change the internals to combine the connections?  I think DEM will help you with documentation?   Mine was ordered with both connections combined.
Photo of Mack McCormick

Mack McCormick, Elmer

  • 389 Posts
  • 135 Reply Likes
I agree with David. DEMI provides instructions to rewire the RF and IF connections as combined or separate. It usually takes me less than 20 minutes to make the changes if you have moderate soldering skills. Or if not, send the unit back to DEMI to make the changes. 

73,

Mack
W4AX
Photo of David-N5PSM

David-N5PSM

  • 104 Posts
  • 23 Reply Likes
John,   Did you problem get resolved?

Photo of John - WA7UAR

John - WA7UAR

  • 125 Posts
  • 30 Reply Likes
Thanks David. Sandra at Down East Microwave Inc. responded to my query with the following:

“Now if you are using a external amplifier then the proper T/R relay needed will depend on the amount of power you will be running. As a example you could use a CX520D. This particular relay will only be good to 300W at 144MHz. If you are running more power then you will want to look for a different model that will be good for the amount of power you will be running. And pay attention to select one that has >60dB of isolation.”

I’d prefer an external device approach to combine feeds in the short run so I have a quick and flexible way to reverse things if ever needed. But if I can’t find something then I can fall back on rewiring the internal connections.

Any other suggestions for an external solution that is in a nice case and ready to “plug in and go”?
Photo of John - WA7UAR

John - WA7UAR

  • 125 Posts
  • 30 Reply Likes
I finally decided to go with this unit from MFJ after reading more about it in the March QST magazine.

https://www.mfjenterprises.com/Produc...

Thanks everyone.