Hi:
I just use a resistor.
http://www.prc68.com/I/DAGR.shtml#PS
and here is the Cable TV power divider were Type-F DC blocks are added to all
but one of the output ports.
http://www.prc68.com/I/4GPS.shtml
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
-------- Original Message --------
Hi
Hitting the inductance required is relatively easy. Doing so and not hitting
self resonance is a bit more tricky.
Even a zero ohm reactance likely will work ok (in series with a 150 ohm
resistor). It’s tough to know
what you have done without a network analyzer. It is even possible that your
resistor has enough stray C
to mess things up. Of course it might also have enough stray L to get you back
in business.
A somewhat less critical approach is to use ferrite beads on both sides of the
resistor. They generally are a
bit less critical (= more likely to do what the data sheet claims). The trick
there is to find some that are set up
to work at L band …. they aren’t common in my junk box.
Bob
On Jun 21, 2017, at 4:16 PM, Attila Kinali <att...@kinali.ch> wrote:
On Wed, 21 Jun 2017 15:03:54 -0400
Bob kb8tq <kb...@n1k.org> wrote:
The typical answer is: The largest one I could that 1) Would handle the short
circuit current expected and
2) was self resonant at or above 1.6 GHz.
I found out, by experiment, that any "large enough" inductance is ok.
A simple "a few dozen windings of AWG30, air core and a tiny bit of
epoxy to keep the windings apart, yet stable" does the trick quite well.
At least it does for the bias-T I used it in. As a rule of thumb,
at the frequency you are using it, the inductor should have an
impedance much larger then the 50Ohm. And for 1.5GHz you get there
pretty quickly. E.g. 20-30 windings on 3mm spread to a length of 20mm
give you something in the order of 150 to 350nH, which translates
to 1k5 to 3k5 impedance at 1.5GHz.
I recommend reading [1] and [2] for the design of bias-T's
(there are probably better sources, but these are those
that I stumbled upon, some time ago)
Attila Kinali
[1] "Design of Bias Tees for a Pulsed-Bias, Pulsed-RF Test System
using Accurate Component Models", by Baylis, Dunleavy, Clausen, 2006
http://www.microwavejournal.com/articles/3912-design-of-bias-tees-for-a-pulsed-bias-pulsed-rf-test-system-using-accurate-component-models?v=preview
[2] "Wideband Bias Tee". by Johnson, 2008
http://wb9jps.com/Gary_Johnson/Bias_Tee_files/Bias_Tee_Design_V2R.pdf
--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering. -- The Doctor
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