TV Antenna question

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
Status
Not open for further replies.
John From Detroit said:
It is simple. your understanding of AC is improper
Click to expand...

You'll have to take that up with the Illinois Institute of Technology in Chicago.  They are the ones who apparently lied to me for four years.  Remind me to return their worthless degree next time I pass through town.

John From Detroit said:
AC means the POLARITY of the signal goes from positive to negative and positive
Not that the directions reverse (though in truth the directions of the electron flow DO reverse) but that the polarity, as viewed on a 'scope. goes up and down
Click to expand...

Hmmm, wonder why they they didn't call it  POSGFPTNAP  for  (POLARITY of the signal goes from positive to negative and positive). 
Could it be because AC means Alternating Current ???  Nah!  that's too simplistic.

John From Detroit said:
In the case of the coax cable DC flows one way
RF (Which is ultra high frequncy  ac) the other
Click to expand...

Sorry, I can't make this comment make sense. ??? ???

RF includes about six other (Radio Frequency) bands between LF 540Khz and EHF 300Ghz, not just UHF.

I can't remember if they all flow up a coax cable in the same direction or not? ;) :D ???

;D ;D ;D ;D ;D ;D

John, I'm just funnin' with ya.. but like Ned says we're getting way too silly.....
 
You are right on, Ned. The DC bias component is simply removed by a capacitor is series with the line, as Lou pointed out earlier.

carson FL

 
As a non-techie I have had to work hard to keep up with this discussion.

You all have finally succeeded in "losing" me.

I'm almost sorry I started this thread.......though I do appreciate the help I received.

Don

 
Ned said:
If the RF is biased by a DC voltage on the coax, as it is when using an amplified antenna, then the RF doesn't alternate polarity but oscillates between high and low values around the DC bias.

The term AC is usually used in reference to power distribution and not when discussing RF frequencies.

This whole discussion has gotten silly with all the mis- and disinformation being bandied :(
Click to expand...

Ned,

Does this oscillation mean that the voltage is considered DC as has been suggested?

I don't know how silly the thread has become BUT it sure is getting CONFUSING, at least, to me.
 
Don,

I have an electronics background, including some years working on TVs, but I finally had to resort to using the attached button.
 

Attachments

  • Translation2.gif
    Translation2.gif
    2.3 KB · Views: 15
English translation:

The are two different types of electrical currents, AC and DC. Direct Current (as championed by Thomas Edison) has a constant polarity. In other words the positive terminal on your batteries always stay positive, the negative terminal always stays negative and this never changes. With Alternating Current (as championed by Nicolas Tesla) the voltage produced by an electrical outlet in your house changes polarity 120 times a minute. It starts at negative, goes to full positive voltage then back to zero, then back to negative then to full negative voltage then back to zero. It does this 60 times per second (hence it is called 60 cycle or 60 Hertz (only in America and a few other countries, other countries can use other cycle rates)). Radio waves (RF signals that come from your antenna) vary in voltage but don't go from + to -, they remain the either positive or negative all the time. This creates confusion. Is it DC since it doesn't change from + to - or is it AC since it varies. As a retired electrician I tend to think of AC only in the classic definition whereas a radio engineer has a different view. So whether or not RF waves are AC or DC really depends on how you look at it. This should make everything clear as mud.
 
the voltage produced by an electrical outlet in your house changes polarity 120 times a minute
Click to expand...

Typo alert - that would be per second, but we knew what you meant Tom  ;D
 
Lou (onaquest) said:
LOL Tom, but is it pulsating or oscillating ???
Click to expand...

It could be called either pulsating or oscillating. But it definitely isn't alternating and that is why I don't think it is AC. OC would be a better term.

Yep, it was a typo, it should be 60 times per second. I am going rather slow today, I had to break in a new laptop. ;D
 
RLSharp said:
Tom,

So we agree that they are not both DC, I think.

Richard
Click to expand...

I still think they are both DC. Alternating Current is called Alternating because the current alternates between plus and minus. That ain't happening so I think it is better called DC. But as Ned said it is a silly discussion. You call it what you want and I will call it what I want.
 
I do agree I should have said "DC" and "RF" but the problem is he was tinking DC/DC

And for the record it is not uncommon for a coax cable to carry MANY different signals all at the same time, it's up to the hardware at the end to figure out which signal or signals are desired.

For example: Some cables in your motor home can carry up to five different DESIRED signals at the same time (Up to 3 going one way and 2 the other) in fact they can do more, and in some installs do.

One of those,, JUST ONE, is DC
 
John From Detroit said:
For example: Some cables in your motor home can carry up to five different DESIRED signals at the same time (Up to 3 going one way and 2 the other) in fact they can do more, and in some installs do.
One of those,, JUST ONE, is DC
Click to expand...

John, I understand that this would be child's play, as far as coax technology is concerned, but just what five signals in a typical  RV would you expect to find on a single run of coax?
 
Lou (onaquest) said:
John, I understand that this would be child's play, as far as coax technology is concerned, but just what five signals in a typical  RV would you expect to find on a single run of coax?
Click to expand...

Odd transponder, Even transponder, 22KHZ tone, DC power for LNB, DC power for Dome, control signals for Dome motors.  (Oh, I went over five)
 
John From Detroit said:
Odd transponder, Even transponder, 22KHZ tone, DC power for LNB, DC power for Dome, control signals for Dome motors.  (Oh, I went over five)
Click to expand...
Hardly typical of the average RV configuration, but very impressive.  You are da man. :D :D
 
Status
Not open for further replies.

Latest posts

Members online

Total: 804 (members: 23, guests: 781)

Forum statistics

Threads
132,129
Posts
1,390,777
Members
137,849
Latest member
Moore1947
Back
Top Bottom