Skipp, You made a comment about your local 440 Amateur repeaters using the High in and Low out plan and by doing this you suggest that your area in California is a "trend setter". I thought that I would share some information about the logic that went into our band planning and actions here in Utah.
In Utah and neighboring States, our 440-450 repeaters use low in and high out. Most of our long standing repeaters chose this plan because they were co-located on mountain top radio sites with commercial equipment. The commercial repeaters transmitted in the 450-455 Mhz band. As an example, we did not want to have our amateur 449.500 Mhz receiver next to a 450.250 Mhz transmitter that was used by the local TV stations remote pickup broadcast repeater. Our our antennas were restricted to have only 40 ft or less horizontal separation from each other. The desense would have been difficult and expensive to cure with only 750 khz of frequency separation between the transmitter and receiver at 450 Mhz. We chose to put our receiver inputs low in and by using the 444.500 Mhz frequency to receive, we gained 5 more megahertz of frequency isolation from the commercial transmitters. We still have to use bandpass type duplexers with band reject on our repeater to co-exist with the commercial transmitters. Yes, we do have a dual isolator in our transmitter output to the duplexer to keep the IM products down to acceptable levels.. This is only one of several examples I could show you as to why Utah chose the Low in and Hi Out Plan for our 440 Repeaters. Maybe you do not have this kind of problem in your local area. I'm sure that's one of the reasons why the band plan is different in other parts of the country. On our 420-435 Mhz band, we have links that use a 10 Mhz or wider split. Some links use the 5 Mhz split. We chose this because this lowers the cost of Duplexers and Cavity filters. We planned our 420-450 amateur band frequencies to work the best in our local RF environment without having costly solutions. John, K7JL Utah VHF Society http://www.ussc.com/~uvhfs/ http://www.ussc.com/~uvhfs/frqcoord.html >Message: 6 > Date: Wed, 10 Mar 2004 22:09:11 -0000 > From: "skipp025" <[EMAIL PROTECTED]> > >Most 440 to 450MHz Amateur Repeaters in my >area use 5MHz offsets, with the transmitter >on the lower frequency. I believe much of >the country uses the reverse. But we here in >Northern California are always the "trend setters". >:-) > >Linking 420-425MHz range amateur duplex links in >Northern California use a 3MHz offset, as does >the 480-490 range "T Band" repeaters. > >cheers >skipp > >www.radiowrench.com 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/
