Hi Bruce,
Here's your answer...
Your receive distribution systems doesn't look too hard.
Here's one good method to build a basic system.
You have about a 3 Mhz receive window, the desired bandpass
"Window Filter" would be a min qty 2 High-Q bp-cavities,
I prefer 3 to 4 min and a best high performance (bp window
filter) would be up to 6 series cavities typical.
Setting up the window filter is a trade-off of what you
have available and what you're willing to take the time to
properly align. The filter window is all about a trade
off of the number of series cavities and their adjusted
insertion loss. The typical Motorola T-1500 series band
pass cavities has only step adjustments for insertion loss,
so you'd probably like to preset the lower values... say ½ dB.
The stock T-1500 duplexer loops don't make good 3 MHz pre-
selector loops as supplied.
A totally adjustable (Decibel brand) repeater site window
filter has each cavity set for near minimal insertion loss,
but the filter window takes shape (squares off/down) as you
series more cavities into the path. A typical 6 cavity window
looks really good for 3 Mhz pre-selection. If you don't have 6
adjustable cavities, use what you have and increase the
insertion loss up slightly. Less cavities - add more insertion
loss for protection when using minimal series cavity systems.
Of course the end "as built" values are a trade-off.
Next from the pre-selector window you follow the band-pass
window filter (if possible) with a paralled cavity notch
filter or two set to the transmit frequency. If you have
one transmitter, you probably need only one notch set to the
single tx frequency.
It would be really nice (but possibly not really required)
to place a notch, two, three or four cavities in the transmit
path, (especially if you don't use a preamp) set as a notch
out window on the receiver.
If you have enough receive frequency pre-selection and
protection, you can use a Phempt or Gasfet preamp before the
final receiver signal divider. Greatly improved hand held
coverage...
Some repeaters are "all alligator", big mouth no ears.
Actually many repeaters are alligator machines...
>From your series cavity preselection window, through any
additional paralleled notch cavities, through a decent
preamplifier (ARR, Angle Linear or similar) to a power or
signal divider. Mini circuits sells about the best low
cost high performance 4 way divider. You can also buy new
and used power dividers on the web, which includes Ebay.
You will also see a number of surplus dividers on Ebay,
up to 12 port units pop up once in a while. Just remember
to avoid the higher number (12) output port device unless
you can get it cheap or will use all the outputs (I've
seen it done). All unused ports still present or receive
a portion of the available energy, which is real world
signal energy stolen from the ports you would be using. A
twelve port divider can be quite lossy...
Good quality coax from the power divider output to each
receiver and you're good to go. Some receiver distribution
systems route the signal (power) divider BNC jack output
to a rear panel mounted N bulkhead connector. Where possible
in new constructed layout, it's a good idea to go direct
to the power divider with a BNC cable. Consider each BNC
to N bulkhead assembly will add an undesired fractional dB
loss, which really can get out of hand at the high end of
the UHF Band.
Hope this helps you a bit...
cheers,
skipp
skipp025 at yahoo.com
www.radiowrench.com
> "Bruce Nanney" <[EMAIL PROTECTED]> wrote:
> OK skipp here goes, TX freq. is 442.675. Rx freq. are
> 447.675, 449.075, 446.775, 449.875. TX antenna is a
> set of stacked 6 element beams pointed at remote 2
> meter TX site. Is 30' side mounted under rx antenna
> in which is on top of tower. Rx antenna is G6-2/70 R.
> I have Bp filter on 447.675. Tx is @ 40 watts. If I need
> to put Bp on other receivers I have them. They are
> Sinclairs. All radios are Micors. Thanks Bruce.
> ----- Original Message -----
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
