[Moon] Cabling a dish

[Edward R Cole]

I concur with Steve's observations:

I put up over 50 TV dishes in late 1980's and had some blow out a 
panel with customer not even realizing it.  Of course sat-TV is not 
weak-signal so there is a bit of margin.  Losing a panel would more 
likely affect ground noise pickup (might see it more on Sun Y-factor 
observations).

But as regards signal blockage the cable is minimal.  The feedhorn 
blockage is much larger area and even it is hard to measure on a 
large dish.  My guess is smaller than 2.4m on 23cm band a offset feed 
dish wins for sure.

73, Ed

At 12:47 PM 12/25/2015, Steve Gross wrote:
>John it takes a whole lot of junk in the way to have any effect on your
>dish. You could lose 20% of the reflective surface and never notice it.
>I run a bundle of cables the size of your forearm down one strut & it makes
>no difference.
>I've had whole panels on a tower mounted 6 foot dish blow away & I noticed
>it only by looking at it. Figure out how many square feet your dish is and
>compare it to some tiny blockage. Nothing. My dish is over 200 square feet.
>It takes a hell of a lot of junk in the way to have any effect.
>73
>Steve N4PZ
>
>-----Original Message-----
>From: Moon [mailto:moon-bounces at moonbounce.info] On Behalf Of g4bao
>Sent: Friday, December 25, 2015 2:38 PM
>To: Sam Jewell
>Cc: moon
>Subject: Re: [Moon] Cabling a dish
>
>I've got a small hole in my dish and bring the feed back down the axis of
>the dish. It is self-supporting and I assumed the blockage would be minimal
>as it's the diameter of the coax bundle. Certainly saw no improvement or
>degradation on the original way where I took the feed down a tripod leg
>
>John
>
>On 25 December 2015 at 20:00, Sam Jewell <jewell at btinternet.com> wrote:
>
> > Hi everyone,
> > Please excuse this question, but as I sit here, digesting my Christmas
> > dinner, I started to wonder about the effects of coaxial cables in
> > front of a dish.
> > Many of us run dish feeds with the power amplifier behind the dish
> > rather than at the feedpoint (23cm and 13cm typical). I suspect most
> > of us then run the transmit feeder ( and receive feeder) down one of
> > the support tripods to the rim of the dish and then either back to the
> > centre of the dish rear or maybe away at an angle to wherever the PA
>connection is.
> > Clearly the route back to the rear centre of the dish is more than two
> > times the dish radius and even in the case of my 2.3m dish is a fairly
> > long run of what might not be the very lowest loss coax size because
> > of weight constraints.
> > My question is:
> > Is it better to bring the transmit feeder back from the feed to the
> > centre
> > (hub) of the dish or to keep it off to one side where the effects of
> > blockage and illumination level are lower, but longer coax than to the
> > centre?
> > I'd be interested to know what others do before I cut any
> > (inadvisable) holes in my 2.3m dish mesh?
> >
> > Ohh, and Merry Christmas, if it isn't too late!
> >
> > 73 de Sam, G4DDK
> >
> >
> > Sent from my DDKpad
> >
> > g4ddk.com
> > g4ddk.blogspot.com
> >
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> >
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73, Ed - KL7UW
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