[amsat-bb] Station advice: coax

Tue Nov 20 02:56:21 UTC 2018

Mark, you suggested that you would ". . . avoid the diplexer like the plague."     Why exactly?

I use a Comet CFX 4310C at each end of 60' of cable.

 .3dB not 3 dB of insertion loss.

CFX-4310C 
2M/440/1200MHz Triplexer

Band Pass        Loss      Max Power
1.3-150MHz        .25dB      1000W PEP
 350-500MHz     .25dB        500W PEP
 840-1400MHz  0.3dB        200W PEP

Isolation: 50dB

One run of cable and one surge protector with three antennas. In operation for 25 years with no problems.

73,

Ron VA7VW

-----Original Message-----
From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Mark D. Johns
Sent: Saturday, November 17, 2018 12:06 PM
To: wd9get at amsat.org
Cc: AMSAT <amsat-bb at amsat.org>
Subject: Re: [amsat-bb] Station advice: coax

With that kind of coax run, you'll definitely want the lowest loss feedline you can afford, and you'll probably want the pre-amps sooner than later. If hard line is out of the picture, LMR 600 is a good alternative. Several outlets will sell custom lengths with connectors attached. You can get by with LMR 400 or Belden 9913 on the 2 meter side, but loss at 435 MHz will be greater. I would avoid the diplexer like the plague.

As GEO mentioned, you really only need the flexy stuff at the point where things are rotating. I run LMR 600 to the pre-amp, just below the rotor, and ultra-flex from the pre-amp to the antenna. A good, moderate-cost alternative for pre-amps are the "Mini" pre-amps from SHF Elektronik in Germany http://www.shf-elektronik.de/en/
--
Mark D. Johns
KØJM / MØGZO / ex-9H3DJ / ex-KØMDJ
Brooklyn Park, MN USA   EN35hd
-----------------------------------------------
"Heaven goes by favor; if it went by merit,
   you would stay out and your dog would go in."
    ---Mark Twain

On Sat, Nov 17, 2018 at 1:12 PM GEO Badger via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> Keith,
> You want the lowest loss coax you can afford for your run. ½" hard 
> line would be a good choice, though not inexpensive and neither are 
> the connectors. Plus it is rather rigid and can be difficult to handle.
> Terminate it at the rotator and use a flexible jumper from there to 
> the antennas.
> To use a diplexer you'll need one at both ends, assuming 2 antennas.
> Recall that a diplexer will have insertion loss of >3 dB. And that I 
> don't believe they will pass DC. Though I haven't ever checked that. 
> ---  Ciao baby, catch you on the flip side.
>  GEO
>
>  http://www.w3ab.org
>
> Time flies like an arrow, fruit flies like a banana.
>
>       From: "Keith E. Brandt, WD9GET" <wd9get at amsat.org>
>  To: amsat-bb at amsat.org
>  Sent: Saturday, November 17, 2018 10:11 AM
>  Subject: [amsat-bb] Station advice: coax
>
> There's been a lot of good station advice on the reflector recently 
> that I've really appreciated. I'm slowly but surely building up my sat 
> ground station. I've got my Yaesu G5400B connected and running and 
> I've got an antenna plan. The next issue is running coax.
>
> What's the recommendation on coax runs? It looks like I'll have 
> between
> 75 and 100 ft from the shack to the mount. I can envision running a 
> separate line for 2m and 440, but is it also effective to use a 
> diplexer at the antenna? Does that limit my ability to later add a 
> mast-mounted preamp with power-over-coax? (I'll probably add preamp(s) 
> at a later date)
>
> Is the ultraflex coax really necessary for hooking up around the 
> rotator? I'm sure it's better, but is it really worth the extra cost? 
> I certainly don't want to pay the high price for ultraflex for the 
> full run, especially if I'm using two lines.
>
> Thoughts appreciated.
>
> 73,
> Keith
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Keith E. Brandt, MD, MPH
> /wd9get at amsat.org/
>
> /Christianity and science are opposed… but only in the same sense as 
> my thumb and forefinger are opposed- and between them I can grasp 
> everything.
> /—Sir William Bragg (Nobel Prize for Physics- 1915)
>
> *This message transmitted with 100% recycled electrons 
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