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.
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