I had a quite much longer reply in the
buffer and decided to shorten it.. .. but 19
miles for any tx to rx coupling would seem to
make the band unusable in a metro area.. due to
every radio would swamp every receiver in the
market...This is just not the case..
The only influence the tx could have on the rx
(500khz spacing) at over maybe a mile or two
would be white noise.. as the carrier would be
well below desense levels itself at that
range.... The implication is every white noise
generator within 19 miles would disrupt the rx
site.... aka every mobile in the band..... or base or other repeater......
I can say I am aware of a system that a group
here operated a 6m repeater site to site at .5
miles at 300khz with modest filters on the TX
end.. The RX site actually had 3 repeater receivers for 3 different clubs...
Proper engineering would put at least a single
bandpass can and maybe an isolator if possible on
the TX site.. to minimize white noise to other
users...and by itself should make the system
useable within a mile let alone 8...or 19...
Doug
KD8B
At 08:59 AM 1/22/2010, you wrote:
Boy, that seems excessive to me, even at 500 kHz. My hunch is that you'll
have acceptable performance much closer in distance. 1 MHz spacing was
mentioned which would obviously be even better.
Chuck
WB2EDV
----- Original Message -----
From: "Eric Lemmon" <<mailto:wb6fly%40verizon.net>[email protected]>
To:
<<mailto:Repeater-Builder%40yahoogroups.com>[email protected]>
Sent: Friday, January 22, 2010 12:19 AM
Subject: RE: [Repeater-Builder] 6 Meter Repeater spacing (no duplexers)
> Tim,
>
> I use CommShop for Windows, a handy package that does much more than
> duplexer isolation calculations. Go here for more info:
> <www.dcico.com/dcilmr.htm>
>
> It calculates that you'll need about 93 dB of isolation, which requires
> more
> than 19 miles of horizontal separation. This can be reduced by using
> lower
> power output, a better receiver and PA, and perhaps directional antennas.
> Bear in mind that CommShop and similar programs make many assumptions to
> come up with these estimates, and some or all of those assumption might be
> invalid. YMMV...
>
> 73, Eric Lemmon WB6FLY
>
>
>
> -----Original Message-----
> From:
<mailto:Repeater-Builder%40yahoogroups.com>[email protected]
> [mailto:[email protected]] On Behalf Of Tim Ahrens
> Sent: Thursday, January 21, 2010 7:21 PM
> To:
<mailto:Repeater-Builder%40yahoogroups.com>[email protected]
> Subject: RE: [Repeater-Builder] 6 Meter Repeater spacing (no duplexers)
>
>
>
> Hi Eric/all,
>
> Since this is just a curiosity at this time, let's figure 50 watts,
> 0.25uV, & 500khz split.
>
> I figured that was the case about the vertical separation, but
> threw it in anyway.
>
> One site would be a solar site, so it would make sense to
> make it the RX. Guess it might require a notch can at
> the rx site, based on what Chris said.
>
> BTW, what software package are you using?
>
> I've been using Radio Mobile for coverage, & it works
> pretty good.
>
> Thanks,
>
> Tim W5FN
>
