Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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module: My Reflection Sucks - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
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sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Who Are We Afraid Of?
God 0% [ 0 ]
Evil 0% [ 0 ]
0% [ 0 ]
Ourselves 100% [ 1 ]
Total votes : 1
Post subject: module: My Reflection Sucks Posted:
Tue Mar 21, 2006 8:33 pm
Joined: Sun Aug
03, 2003 2:02 pm
Location: Erie, PA
NOTICE: I replicated
the post of user "module" while moving it to the database on the new
server. - Kirt Blattenberger
Posted: 21 Mar 2006 06:28 pm Post
subject: My Reflection Sucks
I have been a good person and tried to design
my PA around my load line. Our establishment has this bad habit of "just
dropping transformers in". I would actually like to try to match my
input impedance using that stuff called math. I have calculated my loadline
and designed my transformer using UT-34-50 semi rigid coax. Can someone
do a quick check on my equations? I hooked it up to my network analyzer
and I get nasty reflection. I am trying to match the input of a Polyfet
SQ721 to a 50Ohm source. I am using Amawave's UT-34-50 50Ohm semi-rigid
coax with a Amidaon BN-61-2402 with an AL=150. My math is here done
in Mathcad. Any feedback would be greatly appreciated.
- Kirt Blattenberger
RF Cafe Progenitor & Webmaster
Post subject: ReflectionPosted: Wed Mar 22,
2006 8:53 pm
Joined: Wed Feb 22, 2006 3:51
I guess I'm not clear on what you're
A quick trip to a Smith chart, matching 50 Ohms to 10-j65
Ohms at 88 MHz, yielded a two-inductor matching solution. One inductor
of 45 nH from the amplifier input to ground, and a 83 nH inductor from
the amplifier input to the power FET gate. I'm assuming the source is
Gnd ``` 83 nH
(ignore the ` characters -
PHPBB doesn't let me use spaces for ascii art - which I'm not good at
Maybe that's not what you meant. Maybe you meant something
like the series 45 nH inductor, with a shorted stub of about VF*10 inches
of 50 Ohm coax in parallel (in place of the 83 nH inductor)?
Or did you mean a 1:5 transformer, with approximately 517 nH inductor
in series with the input winding?
It doesn't look like I'm "getting
it". What configuration is your input matching network? Are we even
"on the same page"?