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Re: Feed line help



One thing I'd add:
The cable companiues have used for a long time (at least around here) a "quad
shield" version of this stuff.  It has several braids, and a solid sheet, along
with a continuiously running shield conductor.  They use this to minimize
radiation from their cables, which can get them in big trouble.  I've found it
extremely useful as Ron indicated, with the additional advantage of very low
pick up of the IF.  That's really important is your 2ghz downconverter is
mounted at the antenna, and you're feeding 2m down to the shack.  If it's quad
shield, .15 a foot is probably reasonable, in my humble opinion.

Bottom line:  I really like this stuff for piping IF up to and down from
mast-mounted transverters.

Good luck & 73,
Jim
wb4gcs@amsat.org

Ron Sparks - KC5ODM wrote:

> Your question has several parts.  Here is what I know about the feedline:
>
> 1. The term "flooded" has to do with how the foam dielectric is made.  For a
> cable to be rated as direct burial it needs to be both flooded and
> polyethylene jacketed.  If it is flooded with a PVC jacket, it is suitable
> for weather resistant service.  A non-flooded cable tends to wick up water
> when outside.
> 2. RG-6 is a 75 ohm cable.  Most of your amateur equipment and connectors
> are 50 ohm.  This impedance mismatch can be either trivial or very serious
> depending on what you are trying to do.  I forget the exact SWR that
> results, but I think it was in the 1.2 or 1.5 range.  If you are using the
> cable for receive only, it is fine.  Transmitting is more problematic.
> 3. 15 cents is about right for a good wholesale price if it is dual.  For
> single it is a bit high.  I think I paid about 16 cents for the last spool
> of dual I bought and something like 6.9 cents for the single (inclusive of
> shipping to the Houston area - wholesale only).
> 4. It works superbly for VHF and UHF receive cable from the Antenna to the
> shack/house.  Far better than the standard RG-59 that you get at RS (or
> equiv.).  It has much less "tilt" - a condition where the channels on the
> upper UHF get to the receiver with much more loss than the low VHF (for
> example channel 2 vs. channel 67).  Also in that range other receive uses
> are scanner antennas, EMWIN weather data, NOAA weather data, "low band" ATV,
> Aircraft, public service, etc.
> 5. It works very well for low microwave systems (1 GHz to 2 GHz) where you
> have a preamp at the antenna.  For example, remote GPS antenna's (watch out
> for timing errors though),  GEOS receivers, ATV, and DSS, C, & Ku band
> receivers.
> 6. It is overkill, but cheap for receive feedline from SWL dipoles, slopers,
> etc.  and it is nice in that the PE jacket flooded conductor stuff can be
> direct buried and then mowed over easily so your antenna farm doesn't have
> to be hand edged.
> 7. Another source of, usually free, 75 ohm low loss cable is your friendly
> cable installer.  They often have roll ends of aluminum jacket 0.5 inch
> hardline that they will give you.  All of the above applies to it as well.
> If you need to know how to solder to the aluminum or to adapt an N connector
> to it, just let me know.
>
> Basically I use it for just about any general receive only use.  I try to
> transmit through good "high dollar" 50 ohm cable though.  Good cable is
> almost always cheaper than buying more watts.  Hope this helps point you in
> the right direction.
>
> Ron
>
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