Comet CF-413B duplexer specs

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W4KRR

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The comet CF-413B duplexer specs say 1.3 to 460 MHz low pass and 840 to 1400 MHz high pass. My question is would it be usable slightly outside this frequency range, say up to 470 MHz?
 

cmdrwill

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Comet CF-413B DIPLEXER.

Low Pass Frequency Coverage: 1.3-460 MHz

High Pass Frequency Coverage: 840-1400 MHz
 

KevinC

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I can sweep mine again tomorrow, but as I remember it went up to around 500 MHz or so...but don't hold me to that.

And each individual unit may act differently at the band edges.
 

W4KRR

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I can sweep mine again tomorrow, but as I remember it went up to around 500 MHz or so...but don't hold me to that.

And each individual unit may act differently at the band edges.
I was thinking that the upper cutoff might not be so sharp as to preclude going up to 470MHz or so, it's not so far above upper limit.
 

KevinC

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Just swept it. SWR of less than 1.5:1 up to 501 MHZ.

But like I said, individual units may be different.
 

IdleMonitor

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I'm glad I came across this thread. This is exactly what I've been needing for so many years, not sure why I've never actually seen this model before. My other ones similar to this don't do what I need it to do.
 

iMONITOR

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That depends on how it's connected. It will function as both.
I agree with the function buy I believe the amount of insertion loss is much less with a diplexer. Everything I've read says they are different in their internal circuitry.


What is the difference between a Diplexer and Duplexer?

8569085691
 

iMONITOR

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What’s the Difference Between a Diplexer and a Duplexer?

RF Diplexers and Duplexers are very common RF components in transmitters, receiver, and transceiver circuits for communications, radar, and other sensing applications. As the terms are similar, they are sometimes mistakenly used interchangeably, which isn’t appropriate. Diplexers and Duplexers perform very different functions, though they are located in similar areas in a circuit block diagram. This blog will explain the basic functions of Diplexers and Duplexers, and detail the differences in operation.
Diplexer
A diplexer is a 3-port RF device, which enables the use of two signal paths on the same antenna or transmission line. This is done by frequency division using filters, either high-pass, low-pass, or band-pass filters. Hence, signals at two different frequencies could be sent and received from the same antenna. For a diplexer to function well, the quality and attenuation of the filters must scale with how close the signals, what power levels they operate at, and what nonlinearities are expected.
Diplexers are commonly used in telecommunications, where multiple modulation methods and carriers may operate on the same antenna. For example, cellular base stations may need to transmit and receive CDMA, LTE, or GSM signals on the same antenna, as a cell site may have limited availability off tower space for additional antennas.
Duplexer
A duplexer is also a 3-port RF device, and its purpose is to separate transmit and receive signals from an antenna to two different signal paths based on direction. These transmit and receive signals may be operating at the same frequency, and hence a duplexer enables true two-way communication from a single antenna. For example, a duplexer may be used in a radar system were the high power transmitter signals need to be isolated from the sensitive receiver circuitry, but operate on the same antenna.
Either switched systems or magnetic circulators are used to create the isolation between the incoming and outgoing signals within a duplexer. Duplexers are limited by how well they can isolate the receive path from the transmit path, as well as their bandwidth of operation. With radar transmit/receive (TR) modules, the transmit and receive frequencies are typically very close, and can only reasonably be separated through duplexing. Duplexer and circulator is sometimes used interchangeably, which is a common simplification, though not always accurate.
Diplexer versus Duplexer
Simply put, a duplexer separates a transmit and receive path based on signal direction and can be used for same frequency signals, and a diplexers separates signals based on frequency with filters. Their operation is not interchangeable, and a diplexer could not replace a duplexer in common circuits. Duplexers may become more common in telecommunications applications and future 5G technologies may benefit from having transmit and receive signals at the same frequency for greater spectrum utilization.
 

900mhz

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I agree with the function buy I believe the amount of insertion loss is much less with a diplexer. Everything I've read says they are different in their internal circuitry.


What is the difference between a Diplexer and Duplexer?

View attachment 85690View attachment 85691
Insertion loss on the Comet is the same, whether you use it to combine two antennas to one radio, or use one antenna to feed two radios of different bands. The diagram comparison you have is irrelevant to this Comet.
 

iMONITOR

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Insertion loss on the Comet is the same, whether you use it to combine two antennas to one radio, or use one antenna to feed two radios of different bands. The diagram comparison you have is irrelevant to this Comet.
That's my point. I'm talking about the difference between using a true diplexer vs a duplexer. You're talking about using the same device for either function.
 

prcguy

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The Pasternack and other Wikipedia descriptions do not fit in the two way radio world. In radar terms a diplexer is simply a circulator when used to separate a receiver and transmitter off one antenna. For radio people a circulator is usually configured as an isolator and has nothing to do with connecting a transmitter and receiver to the same antenna. A circulator is not a filter and only allows RF to flow in one direction around its circular construction.

In general terms for us radio folks, a diplexer combines two different frequency bands to one port and used to feed to different band antennas to a single radio or two different band radios to a single multiband antenna.

A duplexer combines two different frequencies within the same band for connecting a transmitter and receiver to the same antenna. You could never use a two way radio type duplexer to combine a transmitter and receiver on the same frequency. To the photocopy world a duplexer means something completely different.

What’s the Difference Between a Diplexer and a Duplexer?

RF Diplexers and Duplexers are very common RF components in transmitters, receiver, and transceiver circuits for communications, radar, and other sensing applications. As the terms are similar, they are sometimes mistakenly used interchangeably, which isn’t appropriate. Diplexers and Duplexers perform very different functions, though they are located in similar areas in a circuit block diagram. This blog will explain the basic functions of Diplexers and Duplexers, and detail the differences in operation.
Diplexer
A diplexer is a 3-port RF device, which enables the use of two signal paths on the same antenna or transmission line. This is done by frequency division using filters, either high-pass, low-pass, or band-pass filters. Hence, signals at two different frequencies could be sent and received from the same antenna. For a diplexer to function well, the quality and attenuation of the filters must scale with how close the signals, what power levels they operate at, and what nonlinearities are expected.
Diplexers are commonly used in telecommunications, where multiple modulation methods and carriers may operate on the same antenna. For example, cellular base stations may need to transmit and receive CDMA, LTE, or GSM signals on the same antenna, as a cell site may have limited availability off tower space for additional antennas.
Duplexer
A duplexer is also a 3-port RF device, and its purpose is to separate transmit and receive signals from an antenna to two different signal paths based on direction. These transmit and receive signals may be operating at the same frequency, and hence a duplexer enables true two-way communication from a single antenna. For example, a duplexer may be used in a radar system were the high power transmitter signals need to be isolated from the sensitive receiver circuitry, but operate on the same antenna.
Either switched systems or magnetic circulators are used to create the isolation between the incoming and outgoing signals within a duplexer. Duplexers are limited by how well they can isolate the receive path from the transmit path, as well as their bandwidth of operation. With radar transmit/receive (TR) modules, the transmit and receive frequencies are typically very close, and can only reasonably be separated through duplexing. Duplexer and circulator is sometimes used interchangeably, which is a common simplification, though not always accurate.
Diplexer versus Duplexer
Simply put, a duplexer separates a transmit and receive path based on signal direction and can be used for same frequency signals, and a diplexers separates signals based on frequency with filters. Their operation is not interchangeable, and a diplexer could not replace a duplexer in common circuits. Duplexers may become more common in telecommunications applications and future 5G technologies may benefit from having transmit and receive signals at the same frequency for greater spectrum utilization.
 

thinbluebbq

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The Pasternack and other Wikipedia descriptions do not fit in the two way radio world. In radar terms a diplexer is simply a circulator when used to separate a receiver and transmitter off one antenna. For radio people a circulator is usually configured as an isolator and has nothing to do with connecting a transmitter and receiver to the same antenna. A circulator is not a filter and only allows RF to flow in one direction around its circular construction.

In general terms for us radio folks, a diplexer combines two different frequency bands to one port and used to feed to different band antennas to a single radio or two different band radios to a single multiband antenna.

A duplexer combines two different frequencies within the same band for connecting a transmitter and receiver to the same antenna. You could never use a two way radio type duplexer to combine a transmitter and receiver on the same frequency. To the photocopy world a duplexer means something completely different.
Late to the party on this post but this is where I am at. I am confused with your response as to whether or not the Comet Duplexer could be used to combine the signals from two antennas into one scanner? I have the BCD325P2 and in my area I need a yagi to hit the 800mhz system Indianapolis Metro Police uses, but I also need a discone to monitor my county systems, milair, civil air etc. I have two antennas going up and need to combine them. Is the insertion loss going to be too great you're saying? Without the Yagi I am not close enough to get the IMPD system.
 

oracavon

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Late to the party on this post but this is where I am at. I am confused with your response as to whether or not the Comet Duplexer could be used to combine the signals from two antennas into one scanner?
Yes, you can. Here is a link to the original manufacturer's spec sheet, showing the connection options:


Edit: Here's a clearer view of it:


Note that the manufacturer no longer makes this model:

 
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