coax filter dilemma
 

"Frank" wrote in message
news:HMKhk.1277$nu6.889@edtnps83...
well, yes, but actually the design started with the shorts at 98 MHz
which are easy, then the only unknown variable becomes the series stub
that gives a 50 ohm match at 70 MHz, I still don't get why the
matching section appear to be 3/8 wl on a smith chart and actually is
1/8 like if I inverted the sense of load/generator (yes, I worked with
admittances for shunt stubs).


Let me know if you would like to see my results, will be glad to e-mail
them
as JPEGs.

sure, my email address is valid, thank you very much.

73
Francesco IZ8DWF

Francesco, I will be e-mailing my results for your interest. We seem to
have arrived at the same conclusions.

I think I understand where you are confused. Initially, starting at the
center of the Smith Chart, the shunt open stub moves down, along the
constant conductance circle (0.2S). At 0.175 WL at 70 MHz (0.25
WL at 98 MHz) - 62 cm, the input impedance is 10 - j 20 ohms.
Next; the series section of transmission line moves clockwise along
the 10 ohm resistance circle. At 0.125 WL (70 MHz) - 44 cm, the
impedance
reaches 10 + j 20. The final shunt section then moves the impedance
to the center of the Smith Chart along the 0.2 S circle.

73,

Frank (VE6CB)

Hi Frank

When describing the path on the Smith Chart from the "load" Z to the "rig"
Z, you write "along the 10 ohm resistance circle". I would have refered
to that circle as the circle of constant VSWR.

Jerry KD6JDJ

coax filter dilemma
 

Hi Frank

When describing the path on the Smith Chart from the "load" Z to the
"rig" Z, you write "along the 10 ohm resistance circle". I would have
refered to that circle as the circle of constant VSWR.

Jerry KD6JDJ

Of course you are correct Jerry. I realized what I had done after I posted
the comments.

Frank, VE6CB

coax filter dilemma
 

"Frank" wrote in message
news:RH1ik.1379$%b7.1159@edtnps82...
Hi Frank

When describing the path on the Smith Chart from the "load" Z to the
"rig" Z, you write "along the 10 ohm resistance circle". I would have
refered to that circle as the circle of constant VSWR.

Jerry KD6JDJ

Of course you are correct Jerry. I realized what I had done after I
posted
the comments.

Frank, VE6CB

Hi Frank

My reply was delayed because I had anticipated that someone might ask you
for clarification on Smith Chart use. I was sure you'd clear up the
confusion. I even thought I might learn something new. Smith Chart use is
so valuable to my thinking that I just couldnt let this thread finish
without checking in with you.

Jerry KD6JDJ