I was wondering if I go for a signal diode (presumably low inductance but also low capacitance) or a beefy power diode with a hunk of capacitance. I suppose a signal diode and chip cap is the best solution.
-----Original Message----- From: "Tom Miller" <tmil...@skylinenet.net> Date: Mon, 30 Jul 2012 20:06:01 To: <li...@lazygranch.com>; Discussion of precise time and frequency measurement<time-nuts@febo.com> Reply-to: "Tom Miller" <tmil...@skylinenet.net> Subject: Re: [time-nuts] Active antennas for a Thunderbolt... Put a capacitor across the diode. 0.01 uF should be fine. ----- Original Message ----- From: <li...@lazygranch.com> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Monday, July 30, 2012 7:58 PM Subject: Re: [time-nuts] Active antennas for a Thunderbolt... Are you considering lumped components? At that frequency, you really need to be doing a stripline design. There are also COTS SAW filters. I have this US Navy GPS active antenna with integral SAW filter, but never got around to using it due to the 4.3VDC spec. A separate power supply, DC insert and DC block is kind of clumsy. I have considered a series diode to take 5V down to what the active antenna requires, but I don't know how well that would work. -----Original Message----- From: "Ron Ward" <n6idl...@comcast.net> Sender: time-nuts-boun...@febo.com Date: Mon, 30 Jul 2012 16:32:46 To: 'Discussion of precise time and frequency measurement'<time-nuts@febo.com> Reply-To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] Active antennas for a Thunderbolt... Hi: What is the GPS bandwidth at 1575.42 MHz? For a band-pass filter / amplifier would a Butterworth response be acceptable? Thanks, Ron -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: Monday, July 30, 2012 1:17 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Active antennas for a Thunderbolt... I use a small power supply to feed the antenna (use a bias tee) and a DC block for the analyzer input. I have made a quadrifilar helix for the analyzer output. Set a suitable frequency range (1400-1700) and test. Yes, I have (at work) an analyzer with the S-parameter test set, so that no directional coupler and no problems, moreover I have new antennae to test to make comparisons but the results are clearly visible and you can recognize a defective antenna. Usually customers send in questionable antennae and we can tell weather or not they are really unusable: lightning is the killer. On Mon, Jul 30, 2012 at 9:54 PM, Chuck Harris <cfhar...@erols.com> wrote: > Hi Azelio, > > How would you use a network analyzer to test an active antenna > like these? I have the ANA, but I am not sure how to couple > the input to the antenna effectively. > > -Chuck Harris > > Azelio Boriani wrote: > >> Have you any other GPS unit to test your antennae? You can test GPS >> antennae with a network analyzer or a spectrum analyzer with the tracking >> generator... yes, first you have to find one. >> >> On Mon, Jul 30, 2012 at 5:12 PM, Hal Murray <hmur...@megapathdsl.net> >> wrote: >> >> >>> cfhar...@erols.com said: >>> >>>> I suspect that I have just had the bad luck to buy two bad antennas, but >>>> >>> I >>> >>>> am naturally curious what happens when the sample set gets larger. >>>> >>> >>> I have 2 TBolts using the small Motorola antenna from TAPR in a not-good >>> location. The sheet says 24 dB of gain. I have 6 or 9 or ?? feet of >>> RG-6. >>> >>> They work as expected, that is they work, but not well. The holdover >>> logic >>> gets tested frequently and surveys take a long time. But they do work. >>> >>> -- >>> These are my opinions. I hate spam. >>> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
