RE: [Repeater-Builder] simple repeater
Are you going to cross band, or stay in the same band? Your radios should be fine as long as they are not subject to temperature extremes, or doing a lot of transmitting. You may some receiver desense if you are staying in one band and do not have sufficient spacing between the two antennas. We did something like you did several year ago at a hamfest. Had a 1.9MHz split and the antennas were about 20 feet apart for use on 2m. It worked well and other amateurs found it and used it as well. ~Benjamin, KB9LFZ From: Repeater-Builder@yahoogroups.com on behalf of chris Inos Sent: Thu 13-Dec-07 05:26 To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] simple repeater I have access to IC 28h mobiles and intend to make a repeater out of two mobiles. ...not for heavy use...but casual ...club use...5-10 watts tx. will be sufficient ...will be powered by solar ...not too sure whether to use duplexer or two antenna ...to make it portable to readily move to another location and access (program directly by dial) other repeaters. any idea from this group...whether this radio is reliable for this application.? thanks chris Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://us.rd.yahoo.com/evt=51733/*http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ winmail.dat
Re: [Repeater-Builder] simple repeater
At 06:26 PM 12/12/07, you wrote: I have access to IC 28h mobiles and intend to make a repeater out of two mobiles. ...not for heavy use...but casual ...club use...5-10 watts tx. will be sufficient What duty cycle? ...will be powered by solar No, it will be powered by batteries, which are charged by solar. There's a big difference. For one, the battery bank will probably cost as much or more than the radios did new, and about as much as the solar panels. See http://www.repeater-builder.com/tech-info/some-thoughts-on-solar-power.html ...not too sure whether to use duplexer or two antenna Depends on the physical site, and the tower. Two antennas means purchasing two GOOD antennas, and two GOOD feedlines, one antenna means purchasing one GOOD duplexer, one GOOD feedline and one GOOD antenna that can duplex See http://www.repeater-builder.com/antenna/cracking.html. ...to make it portable to readily move to another location and access (program directly by dial) other repeaters. Having a frequency agile repeater means having synthesized radios, and no duplexer. There are very few good repeater grade synthesized radios. any idea from this group...whether this radio is reliable for this application.? thanks chris You will be very dissatisfied with the 28 series receiver because the 28 and similar 220 and 440 series of radios were in the DC-to-Daylight front end family. In other words, there was little to no off-frequency rejection. The transmitter has the typical no-heat-sink problem... adding more metal would have increased the size of the radio, and raised the price of the radio (more metal cost, more shipping,cost, etc.) The lack of a heat sink has the same effect as described on the Maxtrac index page: http://www.repeater-builder.com/maxtrac/maxtrac-index.html All in all, I think that you should look hard at your need for frequency agility, and if you can get by with a fixed frequency system you would be happier with a radio that has a real front end. One of these is the GE Custom MVP which can be thought of as an under-dash, low power Mastr II http://www.repeater-builder.com/ge/mvp/no6bmvpconversion.html http://www.repeater-builder.com/ge/mvp/mvpstepbystep.html Mike WA6ILQ
Re: [Repeater-Builder] simple repeater
As others have posted, I think you will be disappointed using that setup. Here are things to consider: There are fairly standard graphs available from several sources giving guidance as to need for duplex isolation, isolation curves for cavities, freq offset, antenna separation, etc. GE, Motorola, most of the duplexer manufacturers have these graphs posted, so go do some looking and you will find them. For example, at 600 Khz, in the two meter band the TX-RX Tech-Aid says you need 98 dB of isolation with a GOOD receiver and a 100 watt transmitter. If you are going to run less power, correct that to about 90 dB.(just estimating 8 dB less TX power) If you use a weird split, and make that 2 mhz offset instead of 600 Khz, the 100 watt figure is down to about 76 dB. (again correct for low tx you are around 68 dB). Again, going to a TX-RX Tech-Aid chart, you can get about 56 dB of isolation between two antennas perfectly aligned, 30 ft separation.. So, somewhere you need to get a LEAST 12 dB of isolation to even run 2 mhz. And thirty some for 600 Khz spacing. And one of the ways to get that isolation is to just suffer some receive desense. A few dB is not that big of deal in a portable set up. But if you start out with a system that suffers more that say 6 or 8 dB, you will be disappointed. Weak signals get clobbered, and the repeater just goes kerchunk a lot. As other posters said, those particular radios have very wide front end receivers. If you have a radio that hears a -125 dB signal, as compared to an older more selective radio that is more like -117 you will need that additional 8 dB somewhere. Not to mention the wide band noise the Tx would make somewhere off the Rx freq. A little disclaimer here: These figures from the various charts are not precise. (altho the charts are all pretty close to the same from one manufacturer to another) I am just quickly estimating, and not covering all variables(like cable and connector differences, losses, etc) With many radios to choose from, and performance differences frequency to frequency there are even more variables. I am not trying to talk you out of experimenting, just suggesting things that will help you be more successful (and less disappointed). Generally, you may have more success with Commercial radios ( I like the Maxtrac, Radius GM300 lines, others I know use the Midlands and Kenwoods) If you don't really need frequency agility, use the separate antennas, and a single small cavity on each. There are several combinations that may work, but try not to start out with something that won't work good enuf to satisfy your need. Do that little bit of math and get a duplex budget figured out. Then shoot for about 10 dB better than you think you need. And last but not least, if it is easy enuf, TRY it.
RE: [Repeater-Builder] simple repeater
Steve, You did a great job of hitting all of the key points, and I agree with the majority of your estimates. One point that should be clarified is that when dual antennas are used, they must be separated vertically, one over the other, by no less than 30 feet to achieve about 55 dB of isolation. A similar isolation would require more than 450 feet of horizontal separation which is, of course, impractical due to line loss. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Steve Kometz Sent: Thursday, December 13, 2007 10:12 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] simple repeater As others have posted, I think you will be disappointed using that setup. Here are things to consider: There are fairly standard graphs available from several sources giving guidance as to need for duplex isolation, isolation curves for cavities, freq offset, antenna separation, etc. GE, Motorola, most of the duplexer manufacturers have these graphs posted, so go do some looking and you will find them. For example, at 600 kHz, in the two meter band the TX-RX Tech-Aid says you need 98 dB of isolation with a GOOD receiver and a 100 watt transmitter. If you are going to run less power, correct that to about 90 dB.(just estimating 8 dB less TX power) If you use a weird split, and make that 2 MHz offset instead of 600 kHz, the 100 watt figure is down to about 76 dB. (again correct for low tx you are around 68 dB). Again, going to a TX-RX Tech-Aid chart, you can get about 56 dB of isolation between two antennas perfectly aligned, 30 ft separation.. So, somewhere you need to get a LEAST 12 dB of isolation to even run 2 MHz. And thirty some for 600 kHz spacing. And one of the ways to get that isolation is to just suffer some receive desense. A few dB is not that big of deal in a portable set up. But if you start out with a system that suffers more that say 6 or 8 dB, you will be disappointed. Weak signals get clobbered, and the repeater just goes kerchunk a lot. As other posters said, those particular radios have very wide front end receivers. If you have a radio that hears a -125 dB signal, as compared to an older more selective radio that is more like -117 you will need that additional 8 dB somewhere. Not to mention the wide band noise the Tx would make somewhere off the Rx freq. A little disclaimer here: These figures from the various charts are not precise. (altho the charts are all pretty close to the same from one manufacturer to another) I am just quickly estimating, and not covering all variables (like cable and connector differences, losses, etc) With many radios to choose from, and performance differences frequency to frequency there are even more variables. I am not trying to talk you out of experimenting, just suggesting things that will help you be more successful (and less disappointed). Generally, you may have more success with Commercial radios ( I like the Maxtrac, Radius GM300 lines, others I know use the Midlands and Kenwoods) If you don't really need frequency agility, use the separate antennas, and a single small cavity on each. There are several combinations that may work, but try not to start out with something that won't work good enuf to satisfy your need. Do that little bit of math and get a duplex budget figured out. Then shoot for about 10 dB better than you think you need. And last but not least, if it is easy enuf, TRY it.
RE: [Repeater-Builder] simple repeater
Eric, good point. I put ...perfectly aligned... where I really MEANT to have vertically in there, I missed it. Too many interuptions.
[Repeater-Builder] simple repeater
I have access to IC 28h mobiles and intend to make a repeater out of two mobiles. ...not for heavy use...but casual ...club use...5-10 watts tx. will be sufficient ...will be powered by solar ...not too sure whether to use duplexer or two antenna ...to make it portable to readily move to another location and access (program directly by dial) other repeaters. any idea from this group...whether this radio is reliable for this application.? thanks chris - Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now.
Re: [Repeater-Builder] simple repeater controller for handhelds
[EMAIL PROTECTED] wrote: Not sure it was mentioned, but a VOX will work. It isn't the best solution necessarily, especially if you have to I'd (and you probably do). If you need a simple VOX, e-mail me off list. Michael Yeah-it might slightly more reliable then a tin can and string...maybe. -- Jim Barbour WD8CHL Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * 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/
Re: [Repeater-Builder] simple repeater controller for handhelds
Not sure it was mentioned, but a VOX will work. It isn't the best solution necessarily, especially if you have to I'd (and you probably do). If you need a simple VOX, e-mail me off list. Michael -Original Message- From: taglyons [EMAIL PROTECTED] Date: Sat, 23 Sep 2006 16:06:07 To:Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] simple repeater controller for handhelds Hi all just wondering if you have used any controller that would work off of a handhelds audio and mic port without having to go inside the radio. Thanks TAG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * 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/
