[Repeater-Builder] Re: mobile duplexers
These type of duplexers are also, only good for about 5MHz split, and will not work in the ham 2M band with a 600Khz split. Dick---N7ZH --- In Repeater-Builder@yahoogroups.com, Mike Morris WA6ILQ [EMAIL PROTECTED] wrote: At 10:12 AM 3/28/05, axe1990 [EMAIL PROTECTED] wrote: I have what I think is an old vhf mobile phone duplexer. It has four cavities. The cavities are marked with three as TX and one as RX. Can anyone tell me are these all pass type cavities ? Or could any of them be notch type ? This seems to be the common pattern of cavity set- up for these mobile phone duplexers. Thanks If it's the kind I'm thinking of it's a notch-only device, and only works with lower powered TXs. There is absolutely no pass functionality, thereby allowing any and all nearby RF complete and free access to the RX front end. This means that they are only practical at a repeater site unless you are the only system there. The 4-cavity units come in both three-and-one and two-and-two designs. I've also seen 6-cavity units in four-and-two and three-and-three arrangements. Mike WA6ILQ 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/
Re: [Repeater-Builder] Re: Mobile Duplexers
Bob Dengler wrote: A 5 watt signal is +37 dBm. *Typical* transmitter sideband noise with a good radio set is likely -90 to -100 dB below the carrier at 2.5 mHz spacing. Many receivers intended for repeater service will hear a signal at -125 dBm. +37 minus 90 is negative 53 dBm. Now take -125 and subtract -53, and the duplexer will have to provide 62 to 72 dB of isolation. That sounds right. Still significantly lower than what's required for 600 kHz spacing. Now, use a PLL exciter and your right at that -40 number for both. Kevin Custer Interesting. I know about PLL exciters for Mastr IIs but never seen one for an MVP; do they exist? They do not. One from a Mastr II would have to be scabbed in, and there may not be enough room. Kevin 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 the Yahoo! Terms of Service.
Re: [Repeater-Builder] Re: Mobile Duplexers
At 1/15/2005 12:06 PM, you wrote: skipp025 wrote: Hi Jim, I really don't want to argue with you, but it can be done and I've done it numerous times. It all comes down to a number game (the specs) and a reasonable approach. no6b wrote: I'd like to see the specs on what you've come up with. A key advantage of the 2.5 MHz split that I use is that at that spacing the G.E. RX front end has significant rejection: over 40 dB at the TX freq., so it can work with as little at 40 dB of duplexer rejection at the TX freq. 40 dB of rejection of the transmitter power may be enough to make it duplex, but I doubt 40 dB would be enough rejection of the transmitter sideband noise number. Yes. I forgot to emphasize that the rejection savings was only for the RX side notch at the TX freq. But with so many mobile duplexers having asymmetrical responses, it's worth noting the above RX observation when shopping for mobile duplexers for this application. A 5 watt signal is +37 dBm. *Typical* transmitter sideband noise with a good radio set is likely -90 to -100 dB below the carrier at 2.5 mHz spacing. Many receivers intended for repeater service will hear a signal at -125 dBm. +37 minus 90 is negative 53 dBm. Now take -125 and subtract -53, and the duplexer will have to provide 62 to 72 dB of isolation. That sounds right. Still significantly lower than what's required for 600 kHz spacing. Now, use a PLL exciter and your right at that -40 number for both. Kevin Custer Interesting. I know about PLL exciters for Mastr IIs but never seen one for an MVP; do they exist? Bob NO6B 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/
Re: [Repeater-Builder] Re: Mobile Duplexers
"skipp025" wrote: Hi Jim, I really don't want to argue with you, but it can be done and I've done it numerous times. It all comes down to a number game (the specs) and a reasonable approach. no6b wrote: I'd like to see the specs on what you've come up with. A key advantage of the 2.5 MHz split that I use is that at that spacing the G.E. RX front end has significant rejection: over 40 dB at the TX freq., so it can work with as little at 40 dB of duplexer rejection at the TX freq. 40 dB of rejection of the transmitter power may be enough to make it duplex, but I doubt 40 dB would be enough rejection of the transmitter sideband noise number. A 5 watt signal is +37 dBm. *Typical* transmitter sideband noise with a good radio set is likely -90 to -100 dB below the carrier at 2.5 mHz spacing. Many receivers intended for repeater service will hear a signal at -125 dBm. +37 minus 90 is negative 53 dBm. Now take -125 and subtract -53, and the duplexer will have to provide 62 to 72 dB of isolation. Now, use a PLL exciter and your right at that -40 number for both. Kevin Custer 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 the Yahoo! Terms of Service.
[Repeater-Builder] Re: Mobile Duplexers
Jim can you give me more details, like what model # to look for. The only time it will be portable will be 2 times a year, for 2 one day events where no one repeater will get into. But setting it up on this one site covers the entire we need communications. Then it goes back to it normal site. This is a small Motorola GR 300 repeater mounted in a 42 tall GE cabinet. This unit puts out 15 watts - not high power. Rod KC7VQR Hi Jim, I really don't want to argue with you, but it can be done and I've done it numerous times. It all comes down to a number game (the specs) and a reasonable approach. I've used surplus Decibel mobile duplexer's in narrow split operation for years. If properly set up and secured, they should not detune. Portable two meter repeaters can work pretty well, if you approach the project with reasonable expectations. Many/most of the common flat-pack VHF duplexers are designed for wide splits. Some combinations of the small mid size Harris, Decibel, Sinclair and Phelps-Dodge packages can be set up or modified to operate narrow splits. The preformance will not be spectacular, but the repeater will work ok. cheers, skipp skipp025 at yahoo.com www.radiowrench.com/sonic 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/
[Repeater-Builder] Re: Mobile Duplexers
--- In Repeater-Builder@yahoogroups.com, russ [EMAIL PROTECTED] wrote: Some of the newer flat pack duplexers will do it. they will go down to 400 kHz but you are limited to 50 watts and you only get 60 to 70 DB but if you are using a couple of HT's it will work OK around a Hamfest. 73 Russ, FWIW, I tried substituting a pair of Icom HTs in place of my VHF MVP for my 2.62 MHz split portapeater. Didn't work at all even at only 1 W TX power: too much TX noise poor RX dynamic range. You need a real radio. Bob 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/
[Repeater-Builder] Re: Mobile Duplexers
--- In Repeater-Builder@yahoogroups.com, skipp025 [EMAIL PROTECTED] wrote: Hi Jim, I really don't want to argue with you, but it can be done and I've done it numerous times. It all comes down to a number game (the specs) and a reasonable approach. I'd like to see the specs on what you've come up with. A key advantage of the 2.5 MHz split that I use is that at that spacing the G.E. RX front end has significant rejection: over 40 dB at the TX freq., so it can work with as little at 40 dB of duplexer rejection at the TX freq. Bob NO6B 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/
[Repeater-Builder] Re: Mobile Duplexers
--- In Repeater-Builder@yahoogroups.com, [EMAIL PROTECTED] wrote: Does anyone know if there is even a mobile duplexer made for the 2 meter HAM split? ... __ Portable 2 meter duplexer? Closest thing is probably the Sinclair Special Compact Q-E-P. The -P version is intended for portable applications and has a special heavy duty protective cover with carrying handle. It measures 16.7 wide X 4.4 high X 17 deep. Minimum separation 0.5 MHz, insertion loss 2.3 dB, isolation 75 dB. Cost? Over $1K 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/
Re: [Repeater-Builder] Re: Mobile Duplexers
There are a couple of MFG. making a flat pack duplexer. That will work 600 kHz. It is larger then the mobile duplexer but no where near as large as a station duplexer. - Original Message - From: nj902 [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, January 12, 2005 11:19 PM Subject: [Repeater-Builder] Re: Mobile Duplexers --- In Repeater-Builder@yahoogroups.com, [EMAIL PROTECTED] wrote: Does anyone know if there is even a mobile duplexer made for the 2 meter HAM split? ... __ Portable 2 meter duplexer? Closest thing is probably the Sinclair Special Compact Q-E-P. The -P version is intended for portable applications and has a special heavy duty protective cover with carrying handle. It measures 16.7 wide X 4.4 high X 17 deep. Minimum separation 0.5 MHz, insertion loss 2.3 dB, isolation 75 dB. Cost? Over $1K Yahoo! Groups Links 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/
[Repeater-Builder] Re: Mobile Duplexers
Hi Jim, I really don't want to argue with you, but it can be done and I've done it numerous times. It all comes down to a number game (the specs) and a reasonable approach. I've used surplus Decibel mobile duplexer's in narrow split operation for years. If properly set up and secured, they should not detune. Portable two meter repeaters can work pretty well, if you approach the project with reasonable expectations. Many/most of the common flat-pack VHF duplexers are designed for wide splits. Some combinations of the small mid size Harris, Decibel, Sinclair and Phelps-Dodge packages can be set up or modified to operate narrow splits. The preformance will not be spectacular, but the repeater will work ok. cheers, skipp skipp025 at yahoo.com www.radiowrench.com/sonic Jim B. [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: Does anyone know if there is even a mobile duplexer made for the 2 meter HAM split? Make? Price? This is for a portable GR 300 repeater. Thank you. Rod KC7VQR No. Can't be done. To get the isolation you need for the 600Khz split on the 2M ham band, the cavities must be much larger, too large to be called 'mobile'. Plus the tuning adjustment will be touchy enough that the bouncing around will de-tune it. Portable repeaters for the 2M ham band don't work well. Getting rid of the desense takes some doing. It's not imposssible, but it ain't easy. Jim Barbour WD8CHL 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/
