# Help on Electronics with Mathmatics

#### tklesel

Joined Jan 18, 2006
2
question #1

which of the following transmission lines may be classified as an "electrically long" line
a. any line more than one quarter mile lone
b. any line having distributed capacitance
c. a 30 foot line operated at 300 kilohertz
d. a 300 mile line operated at 30 hertz
e. a 30 inch line operated at 300 megahertz

question #2

a transmission of even-numbered harmonic frequencies may be minimized by placing accross the transmission line a
a. half wave shorted stub
b/ quarter wave open stub
c. quarter wave shorted stub
d. half wave open stub
e. full wave open stub

if any one can help it would be great and if you find the answer, where did you locate them

thanks

#### spork891

Joined Jan 17, 2006
3
Question 1:

I'd say the 30 inch line is a pretty good candidate. 300Mhz is awfully fast for a transmission line that long.

A and B are definitely wrong, and D is probably wrong as well. C is sort of a toss up IMO, someone else may like to weigh in.

I just happen to know this because I've taken an EM course, which is what it looks like you're in the middle of.

question #2

Don't really know much about filtering out even numbered harmonics with stubs.

-Jason

#### JoeJester

Joined Apr 26, 2005
4,390
In question number one, you can throw out any answer that doesn't specify a frequency.

Those with a frequency, find out the wavelength and then divide the length of line by the wavelength. The largest value is the answer.

In the second question, look for the current and voltage distribution about a wavelength. You will be looking for a way to minimize the signal.

Those answers can be found in NEETS module 10. visit http://www.phy.davidson.edu/instrumentation/NEETS.htm to get a copy.

#### tklesel

Joined Jan 18, 2006
2
THANKS FOR THE HELP.

Tim

Originally posted by spork891@Jan 18 2006, 02:35 AM
Question 1:

I'd say the 30 inch line is a pretty good candidate. 300Mhz is awfully fast for a transmission line that long.

A and B are definitely wrong, and D is probably wrong as well. C is sort of a toss up IMO, someone else may like to weigh in.

I just happen to know this because I've taken an EM course, which is what it looks like you're in the middle of.

question #2

Don't really know much about filtering out even numbered harmonics with stubs.

-Jason
[post=13206]Quoted post[/post]​