Fw: [Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question
But what the OP asked about was a multi-coupler, not a tower top amplifier. WalterH --- In Repeater-Builder@yahoogroups.com, John Sehring wrote: > > Let's never forget that ANY loss between the antenna and the receiver will > degrade the rx's noise figure.� That means feedline, duplexer, cavities, > connectors, Polyphasers, etc. > > Noise figure degradation means less sensitivity, period.� There's no way to > make up for that EXCEPT with a preamp at the antenna.� If that preamp's > gain just equals the losses downstream from it, you've got a wash.� > However, you will lose on strong signal performance, IM, 3rd order intercept, > etc., i.e. the preamp may be prone to overload by strong sigs. depending on > its design. > > --John > > > --- On Fri, 8/21/09, ka1jfy wrote: > >Long SNIP>
Re: Fw: [Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question
At 8/22/2009 07:49, you wrote: >Let's never forget that ANY loss between the antenna and the receiver will >degrade the rx's noise figure. That means feedline, duplexer, cavities, >connectors, Polyphasers, etc. In theory, yes. However, if the noise floor (antenna noise temperature) is much higher than the noise temperature/figure of the receiver, then some loss between the antenna & receiver will have a negligible affect on overall system sensitivity. This is often the case at 6 meters, & sometimes even on 2 meters depending on location & receiver sensitivity. At higher frequencies the antenna noise temperature is usually much lower than 300 K, so in those cases yes you want to minimize all loss between the antenna & RX. Bob NO6B
Fw: [Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question
Let's never forget that ANY loss between the antenna and the receiver will degrade the rx's noise figure. That means feedline, duplexer, cavities, connectors, Polyphasers, etc. Noise figure degradation means less sensitivity, period. There's no way to make up for that EXCEPT with a preamp at the antenna. If that preamp's gain just equals the losses downstream from it, you've got a wash. However, you will lose on strong signal performance, IM, 3rd order intercept, etc., i.e. the preamp may be prone to overload by strong sigs. depending on its design. --John --- On Fri, 8/21/09, ka1jfy wrote: From: ka1jfy Subject: [Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question To: Repeater-Builder@yahoogroups.com Date: Friday, August 21, 2009, 5:31 PM Not quite the whole story Eric. If the original poster is trying to use this in the ham 440 band, then the preselector will most definitely need tuning before use. Sinclair says their standard preselector is +/- 5 MHz. And it should be mentioned that the gain of the amp is set to make up for the losses in the resistive dividers and nothing more. To get 'gain', you'll have to bypass one or more stages of the divider network. 2x divider gives you 3dB loss, and a 4x gives you 6dB. Remove one of those for corresponding 'gain'. Lastly, all unused outputs should have 50 ohm terminations. WalterH --- In Repeater-Builder@ yahoogroups. com, "Eric Lemmon" wrote: > > Tony, > > Those Sinclair multicouplers are intended to serve as many as 12 separate > receivers from one antenna. Ideally, all receivers should be for > frequencies that are clustered within a few MHz of each other, and the > preselector will be tuned to pass a band that is perhaps 2-4 MHz wide. The > splitter that follows the amplifier will provide sufficient isolation > between receivers. No additional cavities are needed. > > 73, Eric Lemmon WB6FLY > > > -Original Message- > From: Repeater-Builder@ yahoogroups. com > [mailto:Repeater-Builder@ yahoogroups. com] On Behalf Of kt...@... > Sent: Friday, August 21, 2009 7:27 AM > To: Repeater-Builder@ yahoogroups. com > Subject: [Repeater-Builder] Sinclair UHF Receive Antenna Multicoupler > Question > > > > Good Day everyone, > Does anyone have experience or tuning info for a Sinclair UHF Antenna > Multicoupler? The model on the rack panel is "CR4-302CF" and contains a > power supply, pre-amp (or preselector) and BNC distribution box (1 to 12 > outputs). Looks like 450-470 range. > > I haven't hooked this up yet, but wanted to see what to expect from it.. Can > such a device be used directly to receivers, or do you still need to add > band-pass cavities between it and the receiver? > > Thanks for any information! > > Tony >
[Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question
Thanks Eric and Walter. I just wanted to see what to expect when I hooked this up, and so far it does only show about 3db gain, which makes sense to overcome the splitter. I was able to adjust it using the couple of tuning screws to center on the 450 band. Has a very sharp tuning slope though since as a test I tried pushing a 460 and 440 signal through it at much reduced levels. Tony --- In Repeater-Builder@yahoogroups.com, "kt...@..." wrote: > > Good Day everyone, > Does anyone have experience or tuning info for a Sinclair UHF Antenna > Multicoupler? The model on the rack panel is "CR4-302CF" and contains a power > supply, pre-amp (or preselector) and BNC distribution box (1 to 12 outputs). > Looks like 450-470 range. > > I haven't hooked this up yet, but wanted to see what to expect from it. Can > such a device be used directly to receivers, or do you still need to add > band-pass cavities between it and the receiver? > > Thanks for any information! > > Tony >
[Repeater-Builder] Re: Sinclair UHF Receive Antenna Multicoupler Question
Not quite the whole story Eric. If the original poster is trying to use this in the ham 440 band, then the preselector will most definitely need tuning before use. Sinclair says their standard preselector is +/- 5 MHz. And it should be mentioned that the gain of the amp is set to make up for the losses in the resistive dividers and nothing more. To get 'gain', you'll have to bypass one or more stages of the divider network. 2x divider gives you 3dB loss, and a 4x gives you 6dB. Remove one of those for corresponding 'gain'. Lastly, all unused outputs should have 50 ohm terminations. WalterH --- In Repeater-Builder@yahoogroups.com, "Eric Lemmon" wrote: > > Tony, > > Those Sinclair multicouplers are intended to serve as many as 12 separate > receivers from one antenna. Ideally, all receivers should be for > frequencies that are clustered within a few MHz of each other, and the > preselector will be tuned to pass a band that is perhaps 2-4 MHz wide. The > splitter that follows the amplifier will provide sufficient isolation > between receivers. No additional cavities are needed. > > 73, Eric Lemmon WB6FLY > > > -Original Message- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kt...@... > Sent: Friday, August 21, 2009 7:27 AM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] Sinclair UHF Receive Antenna Multicoupler > Question > > > > Good Day everyone, > Does anyone have experience or tuning info for a Sinclair UHF Antenna > Multicoupler? The model on the rack panel is "CR4-302CF" and contains a > power supply, pre-amp (or preselector) and BNC distribution box (1 to 12 > outputs). Looks like 450-470 range. > > I haven't hooked this up yet, but wanted to see what to expect from it. Can > such a device be used directly to receivers, or do you still need to add > band-pass cavities between it and the receiver? > > Thanks for any information! > > Tony >
