> mch <[EMAIL PROTECTED]> wrote:
> I wonder if anyone using the high-out low-in
> method considered the intermod concerns from
> having two high power transmitters 'beside'
> each other while the receivers are on the
> 'ends'.
Yes, we do. It's all about proper planning of
the master antenna scheme. The master antenna
system might have more than two antennas in
service. Close spaced transmitters get different
antennas or combine through hybrids. Mixing
problems are "managed".
Computer software is part of the planning
process, along with the ever present gremlins.
Every single site is different. So many wild
cards are in the deck.
> Not only would the mixing put both TXs on
> your receiver, but it would put it on the
> commercial/public safety repeater inputs
> as well!
If you don't keep your thinking cap on, poop
happens. Quite often in someones' receiver.
> Let's face it - this same problem exists
> in the commercial band as well - 460 MHz
> TXs beside 459 MHz RXs, and 470 MHz TXs
> beside 469 MHz RXs.
Yes it does, but I/we Engineer Antenna Systems
to manage and avoid said mixing problems.
> Now, you want to turn the ham repeaters
> upside down which will really screw up
> the current balance. As it stands with
> everything right side up, most mixing
> products will all be on repeater outputs
> rather than inputs (except for 473-475
> MHz, but that would be the products from
> the 450 and 460 MHz TXs mixing, not the
> ham TXs).
I don't want to change anything...
There is a commercial site solution to the
most common repeater bandplan problems,
just add 10dB min to the cost.
> As I said before, the New England panhandle
> (down to MD) has an every-other-pair-inverted
> bandplan on UHF (real fun during band openings
> when repeaters lock up with each other).
We have a similar scene from Northern to Southern
California. Doesn't even take much of a band
opening to hear the Mountain Top Repeater Systems,
many hundreds of miles away.
> I understand that was done to minimize adjacent
> channel interference, but now where do you put the
> splinter repeaters? They are going to be 12.5 kHz
> away from a repeater on one side and 12.5 kHz away
> from an upside-down repeater on the other.
> Joe M.
We already have them going both directions... adds a
whole new can of worms to site receiver systems, which
use preamps having poor IP3 preformance. It's a
managed mess out there.
cheers
skipp
www.radiowrench.com
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