[Repeater-Builder] Re: Duplexer isolation/Antenna separation
What does CommShop say would be needed for a 25-watt GMRS repeater (5 MHz split) with 0.35 uV RX sensitivity? George, KA3HSW / WQGJ413 - Original Message - From: Eric Lemmon [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: Repeater-Builder@yahoogroups.com Sent: Saturday, August 30, 2008 1:52 PM Subject: [Repeater-Builder] RE: [EMAIL PROTECTED] VHF Duplexer Tom, According to my CommShop duplexer isolation calculation software, a 600 kHz split at 2m with a 50 watt transmitter and a receiver with a (my assumption) sensitivity of 0.35 uV, about 87 dB of isolation is necessary to achieve no desense. If you intend to use two antennas, be aware that they will need to be separated by about 202 feet vertically or over three miles horizontally. Neither of these separations is practical for a portable repeater.
RE: [Repeater-Builder] Re: Duplexer isolation/Antenna separation
George, I plugged in 25 watts at 462.500 MHz and 0.35 uV at 467.500 MHz, and got 67.83 dB of isolation needed, which could be provided by 30 feet of vertical antenna separation or 619 feet of horizontal separation. Keep in mind that CommShop, like all other similar programs, makes many assumptions about the receiver and transmitter and its calculations should be used with care. Nevertheless, the creator of the CommShop program based its algorithms on known characteristics of commercial-grade radios, and I have found it to be remarkably accurate. Information about this program is available here: www.dcico.com/dcilmr.htm 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of George Henry Sent: Sunday, August 31, 2008 12:55 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Duplexer isolation/Antenna separation What does CommShop say would be needed for a 25-watt GMRS repeater (5 MHz split) with 0.35 uV RX sensitivity? George, KA3HSW / WQGJ413 - Original Message - From: Eric Lemmon [EMAIL PROTECTED] mailto:wb6fly%40verizon.net To: [EMAIL PROTECTED] mailto:radio-programming%40yahoogroups.com Cc: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, August 30, 2008 1:52 PM Subject: [Repeater-Builder] RE: [EMAIL PROTECTED] VHF Duplexer Tom, According to my CommShop duplexer isolation calculation software, a 600 kHz split at 2m with a 50 watt transmitter and a receiver with a (my assumption) sensitivity of 0.35 uV, about 87 dB of isolation is necessary to achieve no desense. If you intend to use two antennas, be aware that they will need to be separated by about 202 feet vertically or over three miles horizontally. Neither of these separations is practical for a portable repeater.
RE: [Repeater-Builder] Re: Duplexer isolation/Antenna separation
Good grief! Only $89? I assumed this software was pretty pricey, but that sounds like a real deal for what it does! Thanks for posting that link, Eric. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Sunday, August 31, 2008 4:31 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Duplexer isolation/Antenna separation George, I plugged in 25 watts at 462.500 MHz and 0.35 uV at 467.500 MHz, and got 67.83 dB of isolation needed, which could be provided by 30 feet of vertical antenna separation or 619 feet of horizontal separation. Keep in mind that CommShop, like all other similar programs, makes many assumptions about the receiver and transmitter and its calculations should be used with care. Nevertheless, the creator of the CommShop program based its algorithms on known characteristics of commercial-grade radios, and I have found it to be remarkably accurate. Information about this program is available here: www.dcico.com/dcilmr.htm 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of George Henry Sent: Sunday, August 31, 2008 12:55 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Re: Duplexer isolation/Antenna separation What does CommShop say would be needed for a 25-watt GMRS repeater (5 MHz split) with 0.35 uV RX sensitivity? George, KA3HSW / WQGJ413 - Original Message - From: Eric Lemmon [EMAIL PROTECTED] mailto:wb6fly%40verizon.net mailto:wb6fly%40verizon.net To: [EMAIL PROTECTED] mailto:radio-programming%40yahoogroups.com mailto:radio-programming%40yahoogroups.com Cc: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, August 30, 2008 1:52 PM Subject: [Repeater-Builder] RE: [EMAIL PROTECTED] VHF Duplexer Tom, According to my CommShop duplexer isolation calculation software, a 600 kHz split at 2m with a 50 watt transmitter and a receiver with a (my assumption) sensitivity of 0.35 uV, about 87 dB of isolation is necessary to achieve no desense. If you intend to use two antennas, be aware that they will need to be separated by about 202 feet vertically or over three miles horizontally. Neither of these separations is practical for a portable repeater. image001.jpgimage002.jpg
