I get to stick my neck out first again...
I've cut out mucho and added some comments.
> ... 6 Motorola MTR2000 100W repeaters,
I'd probably Cut the repeater power output
down a bit. Since you have narly antenna gain,
I'd probably back the repeaters down to 80
watts to possibly improve the unwanted products
from the power amplifiers (which can be measured).
> Also part of the system are a factory tuned Telewave
> M101-150-6TRM TX Combiner
Did you check the combiner for proper tuning? All
is rarely plug and play in the real world. "Trust
but verify".
> (Cavity/Dual Isolator type), and a Sinclair
> RM201-112S1B RX Multicoupler fitted with a BP
> Preselector (with 1MHz pass-band, and factory
> tuned to 165.625), a "Hi Level" Bipolar preamp
> (Angle Linear brand / anglelinear.com),
Crap, I just took a look at it.
Not enough protection... by a long shot. You need
to boot the 1 MHz band pass filter and get a real
serious vhf preselection network.
As mentioned before, you should also add some
serious receiver protection in the transmit
combiner side/path.
> and a 12 port power divider.
Using 6 ports..? Every other coax jack should be used
to balance the internal dividers better and "mo
isolation".
> Between the preamp output and the power divider there
> is a 2dB pad fitted.
Not good, the horse is already out of the barn...
> Since we only use 6 output ports of the 12 available, the
> remaining ones have been fitted with 50-ohm terminators on them.
Should be every other port as I described above.
> Antenna system consists of two Decibel DB228 8-dipole
> arrays, mounted on a 90ft self supporting tower.
Nice...
> RX antenna is at the top, TX is
> mounted from about mid-tower down. Vertical separation between
> antennas is not much due to tower height limitations, and each
> antenna's length, but each DB228 is mounted on a separate adjacent
> tower leg. Feedlines are 7/8 hardline running on separate tower legs
If the site is on a hill, you might do better with a bit more
vertical seperation trade. Lower the tx antenna if possible.
Increasing the vertical seperation from 45' to say... 65' will
help a lot.
> up until the point where they start to get horizontal to be routed
> into the building next to the tower. At this point they run parallel
> to each other for about 40ft.
Parallel as in right next to each other? A big no-no even
for 7/8 Hardline. The two lines had better be min 6 inches
away from each other in the the inbound tray.
> Combiner to repeater TX port jumpers are made of Belden 9913,
>From Telewave..? or you made them up? You need to boot the
9913 and use RG-214 min or 1/2 inch superflex hardline typical.
> and between RX Multicoupler and RX ports we were using 100%
> shield RG58.
Crap... boot the RG-58 right away. There is no real 100%
shielded rg-58 that I've ever measured.
> Since at least one person expressed concern over the usage
> of said cables, we changed the RX jumpers to RG142.
Most of the pro repeater sites out here also use RG-214 for
the receiver side, unless they use hard line or older RG-9.
> TESTS
>
> One of our first tests was to look at the combiner output with a
> spectrum analyzer trough a "Lossy T". It looked pretty clean
> with only two or three smaller peaks on the sides of the main
> carrier, all between 40-50db down or more.
Not good enough... did you use any main signal notch cavities
with the test set up described below? You are not going to see
the problem using what you describe above.
Lunch takes me away (I like to eat)... more later on.
cheers,
skipp
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