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Re: One Coax Feedline.



A very good friend of mine has a loooooong run from the shack to the tower.  He duplexes, on one piece of 75 ohm 7/8 hardlins, 2m, 70cm, and 10m.  The vhf antennas have preamps at the antenna, the power amps are at the base of the tower.  Duplexer loss (including
hf/vhf) is minimal, and by careful placement of preamps and amplifiers, it's all transparten to his station performance.

It can be done.  It can make sense.

All the best of luck with it.

73,
Jim
wb4gcs@amsat.org


K5OE@aol.com wrote:

> Pat,
> I agree with Jon's comments, but really suggest you think this through.  Even 2 inexpensive duplexers, like the MFJ units, are $30 each.  For $60 you can buy 100 feet of 9913F and avoid all the problems noted below.
> 73,
> Jerry, K5OE
> ps:  the duplexers do provide a significant amount of filtering.  I use one of the MFJ units ahead of my 70 cm preamp (just use the 70 cm side) and it completely eliminates the 2 m de-sense problem; a pretty good tradeoff for a slight amount of S/N degredation.
>
> << on 8/23/00 6:19 PM, Pat McGrath at pat_mcgrath@yahoo.com wrote:
>
> > I would like to use one length of coax to connect a 2m and a 70cm antenna to
> > a ICOM 821 transceiver.
>
> Curious why you want to do this.
>
> >
> > Do I use two duplexer? One at the antennas and the other at the
> > transeceiver?
>
> That's sure one way to do it.
>
> >
> > Would I need a 2m and a 70cm DCI filter at the transceiver?
>
> Well, duplexers are filters.  So you'd probably get enough filtering action
> from that.  They do have loss though and sometimes significant depending on
> whose you use.
>
> >
> > Are DC passthrough  DCI filters and duplexers available to power the mast
> > mounted preamps?
>
> Oh boy....probably not.  Most (but not all) filters are DC shorts.  I don't
> remember what the DCIs look like.  Why not run separate DC feeds.  You'll
> need to run control lines anyway to turn the preamps on and off unless you
> have auto sensing units.
>
> 73,
>
> Jon
> NA9D
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Member:  ARRL, AMSAT, DXCC, NRA
>
> http://www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
>
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>  >>
>
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