Jeff,
I think the LMR400 is a double shielded with each shield different
metals. One braid and one foil. This is a no-no for duplexed repeaters
for the higher TX RF will generate noise getting into receiver. I
recommend at least 1/2" heliax. Know cost, but well worth the cost.
7/8" even better, but with your 150 ft or so run 1/2" would be ok.
At 122 ft HAAT you can get 30 miles to a mobile, but this is assuming
flat terrain. To an HT not unless one is on a mountain or air plane,
hi.
However, your 3 db gain antenna is room for improvement. If possible
put up commercial grade 6 db like the DB224. Might find one used. They
go for about $450 new. 3 db gain antenna for repeater is low. Would
improve tx and rx. Some say only 3 db, but you will see notable
difference.
With you running 100 W on TX I am sure the portables can hear the
repeater, but trying to get back with 5 W 14 miles is pretty good.
Installing the pre-amp will help, but only if the tx does not cause
desense. Might try turn power down to say 40 W. Not necessary to run
100 W when listening to 5 W HT. However, if see little change with
100/40 W then leave at 100 W.
You may be to the limit of your system and it may be working well and as
good as one might expect.
The changes I recommend is improve antenna, 1/2" or larger heliax and
install pre-amp. Start with pre-amp. If tx don't over power it you
will see improvement and is easy addition. Otherwise I think the
equipment on the ground is good as is.
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 Thu, May 8, 2008 at 9:07 PM, jstechnicalservice wrote:
Thanks, Ron
Here is more information on what we have. The HAAT is 122ft., we
currently have a Maxrad MFB-1503 3db antenna and LMR400 coax. We are
using a ST2 Midland at 110W and there is some type of older pre-amp
installed with no tag, but has 6db hand written on it. Any
suggestions for improvement will be appreciated but we do have a
limited budget, especially with the impending rebanding. We want the
high-band repeater in place for backup when this happens and also as
our primary for the time being.
Jeff,
To really give advice here what HAAT is your antenna. At 100 ft
AGL 14 miles is about the expected range. Still depends on your
terrain.
As for feedline I think the LMR400 is a double shielded coax with 2
different shield materials. It has been found these generate noise
on the tx side from the high RF. This would affect rcv. Probably
good for rcv, but my standard is have nothing in a repeater that
causes problems.
I use either RG214 double shielded RG8 size and also 1/4" heliax.
Both give good shielding and with short pieces little loss. Also
RG142 which is a double shielded RG58 size cable often silver
shield. Motorola and others use this inside their equipment.
Never use double shielded cable with the 2 shields of different
material like 9913 or some of the LMR stuff. Again the tx high RF
will generate noise.
73, ron, n9ee/r
From: jstechnicalservice <[EMAIL PROTECTED] > Date: 2008/05/08 Thu PM
12:30:30 CDT To: Repeater-Builder@ yahoogroups. com
<mailto:Repeater-Builder@yahoogroups.com> Subject: [Repeater-Builder]
Best coax for short jumpers in
repeater cabinet?
I was hoping to get some opinions on the best coax to make jumpers
for
internal connections on a 152 Mhz public safety repeater. I'm
currently
using LMR400 and we can hit the repeater consistantly with a 5
watt
handheld at 14 miles. The problem is we sometimes need around 15
to 16.
I was hoping to improve performance as much as possible. Thanks
Jeff Skaggs Concord-Greene FD
Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64
repeater Tampa Bay, FL No tone, all are welcome.
<mailto:Repeater-Builder@yahoogroups.com>
