Quiz time

Is a duplexer required to build a repeater?

  • Yes

    Votes: 4 26.7%
  • No

    Votes: 11 73.3%

  • Total voters
    15
  • Poll closed .
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KC0QNB

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It was a quiz wanted to see other opinions, now then I will be nice and not get an attitude, what the hell, ever take a quiz Grog? You know one of those pesky little things that people do to find out what others know and feel about a particular subject.
 

KC0QNB

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Now I will force myself to be nice, If I wanted to know if I needed a duplexer for a 2 meter repeater I would have phrased the question in that manner, and wouldn't have posted it on this forum, there are better places to ask those kind of things, reread the op.
 

Grog

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So you admit there are more technical places to ask a duplexer question, are you just wanting to feel smarter than most RR users?


Saying the alphabet without singing it would be enough for that :D
 

kb2vxa

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Gee, you guys love to chew your food, not to mention each other! The short answer is "yes and no" being if the transmitter and receiver are at the same site you need a duplexer if they use a common antenna or a cavity notch filter on the receiver if they use separates. (A duplexer also consists of a notch filter.) If the receive site is remote there is enough physical separation between them the transmitter won't desense the receiver.

Now I have a related question just to goof on you. Resonant cavities used in duplexers are called cans. What other device used with a radio is called cans?

Speaking of goofs, I just love this one.
"Why would you bother to ask a question you already know the answer to?"
When the teacher pops a quiz do you think he doesn't know the answers? It's a QUIZ you dope! (;->)
 
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KC0QNB

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That would take us back to how far apart the antennas needed to be.

It could be anything from twisted pair to microwave.
Ok Don, from what I have found out the antennas if on the same tower, need to be vertically separated by a minimum of 100 feet at vhf, agree or not?
If horizontally separated something on an order of a half mile, agree or not?
If the receive antennas are a half mile minimum from the transmit antenna, then twisted pair would be real pricey, so that is not an option grantend I said if cost was not a factor, but at least be realistic.
Ok a uhf "link" would work ok, if you had a data channel, and a voice channel, yea you could do a digital thing and combine the two onto one channel, which would be a good option, agree of not?
I have been thinking about this the past few days this is the basic concept I have come up with. Now if one was really into making a concept like this work, he would also have a electronically, controlled antenna system at the transmit site, that would "rotate" as needed to provide the best signal for the user,so say in a 4 point system E,W,N,S the receiver on the south hears the better signal, and selects the south direction on the transmit antenna array, and then goes into "normal" repeater mode. that is my take on the idea.
 

Don_Burke

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KC0QNB said:
Ok Don, from what I have found out the antennas if on the same tower, need to be vertically separated by a minimum of 100 feet at vhf, agree or not?
I do not agree.

That would depend on several things including the receiver performance, the power output of the transmitter and the antenna patterns.

The frequency split would be a factor, although I would stick with 600kHz and deal with the consequences.
KC0QNB said:
If horizontally separated something on an order of a half mile, agree or not?
See above.
KC0QNB said:
If the receive antennas are a half mile minimum from the transmit antenna, then twisted pair would be real pricey,
Not so much.

3000 feet or so of Cat 5 would not be a deal breaker. I would use something else for that, though, maybe fiber optic, more likely 2.4 GHz.

Both would be cheaper than your typical UHF system.
KC0QNB said:
so that is not an option
see above
KC0QNB said:
grantend I said if cost was not a factor,
You said cost aside.

I am not sure what you meant by that.
KC0QNB said:
but at least be realistic.
That would be a first.
KC0QNB said:
Ok a uhf "link" would work ok, if you had a data channel, and a voice channel, yea you could do a digital thing and combine the two onto one channel, which would be a good option, agree of not?
No, I do not agree.

I see no need for a data channel.
KC0QNB said:
I have been thinking about this the past few days this is the basic concept I have come up with. Now if one was really into making a concept like this work, he would also have a electronically, controlled antenna system at the transmit site, that would "rotate" as needed to provide the best signal for the user,so say in a 4 point system E,W,N,S the receiver on the south hears the better signal, and selects the south direction on the transmit antenna array, and then goes into "normal" repeater mode. that is my take on the idea.
I would use a voting system for that.

There is no "electronic control" of the antenna system and it does not rotate.
 
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KC0QNB

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I do not agree.

That would depend on several things including the receiver performance, the power output of the transmitter and the antenna patterns.

The frequency split would be a factor, although I would stick with 600kHz and deal with the consequences.See above.Not so much.

3000 feet or so of Cat 5 would not be a deal breaker. I would use something else for that, though, maybe fiber optic, more likely 2.4 GHz.

Both would be cheaper than your typical UHF system.see aboveYou said cost aside.

I am not sure what you meant by that.That would be a first.No, I do not agree.

I see no need for a data channel.That is a voting system.

There is no "electronic control" of the antenna system and it does not rotate.
Antenna separation refer here
for maximum isolation.
I haven't figured out the multi quote thing yet so bear with me
I have found a site that discusses the voter system I will read it when I have time.

OK forget the steerable transmit array, they don't exist for vhf, and it wouldn't work if more than one user was on the system.
Gotta get ready for work, later
 

n5ims

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Now I have a related question just to goof on you. Resonant cavities used in duplexers are called cans. What other device used with a radio is called cans?
I've also heard of tubes (most often the metal cased ones) and electrolitic capacitors (especially those that plugged into sockets) called 'cans'. I may be showing my age here though.
 

kb2vxa

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No Gort, er, Steve; crystal ovens are simply called ovens.

John, you hit upon the old chassis mount electrolytic can capacitors, good answer but not the one I'm looking for. I'll give you a clue, they don't even resemble cans although kids use cans to make one.
 

Don_Burke

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KC0QNB said:
Antenna separation refer here
for maximum isolation.
The webpage you quote gives only part of the answer because it takes into account only part of the problem.

Antenna pattern and transmitter power are the two big ones I see right off.
 

Don_Burke

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If you know of a better one post a link please
I know of no such link.

The bottom line is what is happening at the receiver.

Some receivers deal with fundamental overload and desensing better than others.

The patterns for the two antennas will affect how much of the transmitter signal gets to the receiver.

The power output of the transmitter will directly affect the level of the transmitter signal that the receiver needs to deal with.

Nearby (and sometimes not-so-nearby) objects can affect the amount of signal.

Wecome to real-world RF design. :)
 
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