Shame you can only get up to 50 ft. D-Star is exciting mode and the
telewave 4 can duplexer is good. I would consider something other than
the LMR400 for with their dis-similar double shields it can cause noise.
I would seriously consider 1/2" heliax and 80 ft will not be big
investment.
I am not familar with the Anitron-150, but since similar to the 220 it
will play well. One problem with fiberglass antennas is that they are
made of coaxial lines that are often soldered together. Lightning tends
to melt the solder when hit and being top mounted can be a concern.
I think all ICOM D-Star gear is lower power than the 120+ Watts. Wonder
what PA you are using.
As so many Ham repeaters start they begin at a low site. Then they get
going and others find them and someone comes up with a better site often
a broadcast engineer with an inside tie or commercial guy that has
access to a higher site. You just need to be ready to jump on it when
it comes, and if you hang in there it will come...not a question of if,
but just when.
Good luck with your system. You've gone this far so might seriously
consider replacing the feedline. I am sure there are others that agree.
73, ron, n9ee/r
Ron Wright, N9EE
727-376-6575
MICRO COMPUTER CONCEPTS
Owner 146.64 repeater Tampa Bay, FL
No tone, all are welcome.
On Sat, May 31, 2008 at 6:49 PM, atms169 wrote:
It's the KE5KAF Dstar system in Laredo.
2 Meters
120 watts after duplexers
Telawave 4 cans 600 Split
Coax LMR-400 80feet
Antenna I want to put up is a Commercial Anitron-150 Similar to a DB220
--- In Repeater-Builder@ yahoogroups. com
<mailto:[email protected]> , Nate Duehr <[EMAIL PROTECTED]> wrote:
atms169 wrote:
Hey guys, I'm trying to find radiation patterns or a calculator to
see what would be the best possible coverage for our repeater.
There's a number of calculators on the web, and some good links in the
RB website for Excel spreadsheets where you can see the math if you
like.
We are in the very flat lands of Texas and our repeater is only up 50
feet (total of 530 above sea level). With 120 watt output.
120 watts after the duplexer loss, or before? What kind of duplexer,
feedline, etc.
Assuming 50' for the transmitter and 8' (I'm being generous) for a
mobile rig, the radio horizon between those two is approximately 14
miles, according to the popular calculators.
Anything else isn't line of sight propagation.
Which do you think would work better? A dual folded dipole antenna
with low angle of radiation or a fiberglass vertical at 6db?
Let's assume power doesn't matter for a moment, and just break it down
into comparison of the antennas.
Remember, altitude trumps all, antenna gain and feedline losses next,
and the PA is *last* place you want to make up for a weak antenna
system. The antenna is gain both directions, transmit and receive.
The
PA only helps people hear the repeater... it doesn't help them get
into it.
So... the important info is missing in your question...
What band? Can't answer the antenna question without knowing what
band you're looking at to compare different sized antennas. Makes a
big difference. I will assume VHF for these answers for the moment.
You say 6dB. Is that 6 dBd or 6 dBi? That also makes a big
difference,
since we're going from your numbers for the one antenna, and don't
know which other antenna you're comparing to.
What specific antennas are you looking at? Spec sheet on the web
somewhere to reference? For both... the dipole array and the stick.
Most dual-dipole- array antennas claim about 6 dBd gain when set up
in an
elliptical pattern. That assumes a 1/2 wave spaced (from the mast)
dipole array, like this Sinclair:
http://www.sinclair technologies. com/catalog/ product.aspx? id=1680
<http://www.sinclairtechnologies.com/catalog/product.aspx?id=1680>
There are different configurations for 1/4 wave spaced (from the mast)
dipole arrays, the lowest gain being the purely omni-directional
setup. The "offset" setup where you pick a direction to "push" your
RF one way more than the others, gives you a little more gain that
direction at
the expense of the other side.
http://www.sinclair technologies. com/catalog/ product.aspx? id=326
<http://www.sinclairtechnologies.com/catalog/product.aspx?id=326>
Generically, there's no free lunch. The same sized antennas exhibit
much the same gain, but you can do tricks with the dipoles a stick
can't
do... like offset the pattern a bit.
You could always go for an enormous VHF corner-reflector!
(Yep, they make 'em...)
http://www.sinclair technologies. com/catalog/ product.aspx? id=1403
<http://www.sinclairtechnologies.com/catalog/product.aspx?id=1403>
It's ONLY 10' wide... hahaha...
More info needed... the devil is in the details.
Nate WY0X
<http://www.sinclairtechnologies.com/catalog/product.aspx?id=1403>
