Inline................
Ralph wrote:
If EVERYONE is misled, then EVERYONE needs a lesson in radio- especially you
Jonny-O. My "BS" as you call it comes from over 30 years in 2 way and data
radio and over 10 years in RF Engineering. But before you tell folks to
leave radios on the ground, you'd better check your sources again.
I'd love some of your $1.50 per foot 7/8" Heliax.
7/8" Heliax was $3.00 per foot 25 YEARS AGO!
Back then, 1/2" Heliax was about $1.80 per ft.
There is a ton of this on the market. We are presently buying 7/8" x
1000' rolls from many other cell site construction companies at about $1
foot. I presently have a source for 6K feet and I am sure I could find
a poop load more in 48 hours.
I'm surprised that the price hasn't changed that much since then, but I'll
bet there's not as much copper in it. I know the center conductor is copper
clad aluminum now.
Maybe your $1.50 7/8" Heliax was the piece that got water in it and was
discarded by the radio shop.
See above..
For 900 MHz, 1/2" would possibly *adequate* but I would not recommend it at
all. For 2.4 GHz, you might consider 7/8", but for 5.8, better forget
anything less then 1 5/8", but most real users use waveguide.
Please research your statement. You cannot use 1 5/8 Heliax for 5Ghz
anything.....
Heck- even XM Radio uses elliptical waveguide at their frequency of about
2.3 GHz for their terrestrial transmitters- and they have 100 watt power
levels! I can send you a picture right now!
Putting the radios at the antennas saves vast amounts of costs in feed line.
Your tower owners are happier, and your rent might be cheaper. I know that
we charge the other WISPs we rent space to much less because they use CAT5.
The best use of $ for RF is to use antenna gain. You have nearly wasted
that if you long feed lines of improper sizing.
As far as justifying my statements- I don't really need to. Anyone can do
the calculations, taking feed line and connector loss and subtracting it
from antenna gain and radio power. The procedures and the numbers are there
and speak for themselves.
Andrew makes a spiffy calculator for this purpose and it is available, free,
at http://www.andrew.com/downloads/ilcalc/default.aspx
All of the following figures include a pair of Andrew N type male
connectors.
A 100 foot long piece of Andrew LDF4-50A (1/2") at 2450 MHz has a loss of
3.64 dB. That's over half of your power wasted. List price (cable only) is
$1.56 per foot. The connectors are $20.00 - 45.00 each depending on
material.
A 100 foot long piece of Andrew LDF5-50A (7/8") at 2450 MHz has a loss of
2.1 List price (cable only) is $3.58 per foot. The connectors are $34.82
each
A 100 foot long piece of Andrew LDF7-50A (1 5/8") at 2450 MHz has a loss of
1.28 dB List price (cable only) is $9.33 per foot. This cable is very
heavy so figure in a lot of freight as well. The connectors are $153.22
each
Now if you would like to use a very efficient feed line, you can use EW20-25
Elliptical waveguide, which is technically the correct cable for microwave
frequencies like these. It will cost you $33.40 per foot. The connectors
are only about $1570.00 each, but you will have onlt .45 dB of loss in 100
feet!
Remember that these numbers are only for 2450 MHz. 5.2 and 5.8 loss is
higher, but waveguide for that frequency is lots smaller and lighter and has
only 1.35dB loss at 5200MHz. $23.5 per foot and only $500.00 per connector.
I'm not going to justify my statements on amplifiers either. You can (and
should) read Part 15 for yourself. Go try to get Teletronics to give you an
FCC waiver, or go ask your AP manufacturer, assuming they are even building
certified equipment.
An amplifier manufacturer cannot grant an "FCC waiver" for anything.
And the AP manufacturer must submit the combination to the Part 15 cert
lab for combined "package" certification as a system... I know that is
the case because this was discussed with Commission representatives
directly when we were in Washington a couple of years ago. I think
marlon still has the pictures........ Right Marlon???? :-)
The problem I see with many of today's WISPs is that they are making up
their own rules to suit themselves. Recently I saw a WISP post a
recommendation to another WISP to set up a device to intentionally interfere
with Wal-Mart's 900 MHz RFID systems.
Frustration will make people say things that at times they either don't
mean, wish they could take back or trying to get a laugh....
Nothing I say can stop or even sway any of you- that will have to come from
someone with that kind of clout. Maybe a competitor who follows the rules
will come into your market, or maybe you'll cause a problem with something
licensed and you'll have a white Ford Explorer with a government tag and
antennas hidden in the headliner pull up at your tower- but why would it
even have to come to that.
Wow.....Every guy I ever dealt with from the enforcement division was
always riding around in some ratty pool car. And he was lucky if the
radio and air conditioning worked...The guys in the Atlanta field office
must be spoiled....
Personally if 3-5 dB of cable loss is going to make or break your system
you need to re-engineer it. While it is great to have zero dB of loss it
is not always practicle. As such, system where climbers are not readilly
available or where weather dictates access to your equipment then cable
loss is a reality and the system should be designed to accomodate those
losses.
I am sure you took the time to research your pricing and attenuation
factors that you outline above but to me, you shoot all credibility when
you tell people they can use 1 5/8 at 5 Ghz. You need to do just a
little more research.......
Not bashing here.........Just my opinion....
Gotta take a nap now.....I'm tired from all this typing today..
-B-
WISPS are taking technology that was designed for in-building LANS and doing
remarkable things with it. A few years ago it was a pipe-dream to be able to
do this stuff. Now we do it with off the shelf devices and do a damn good
job.
Let's just make sure we set the good example!
(wow- I feel like Patrick) <grin>
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of JohnnyO
Sent: Saturday, March 17, 2007 8:32 AM
To: 'WISPA General List'
Subject: RE: [WISPA] LMR600, LMR900, Heliax
Importance: High
Jeez Ralph - your post is misleading to EVERYONE that is reading this.
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