Source for VHF/UHF Diplexers?

Status
Not open for further replies.

iMONITOR

Silent Key
Premium Subscriber
Joined
Sep 20, 2006
Messages
11,156
Location
S.E. Michigan
I'm having difficulty finding a source for a good quality Diplexer.

VHF/UHF particularly for both air bands, commercial and mil-air. Preferably with Type-N connectors, and weather proof for outdoor installation. I've checked RR's Classifieds, Ebay, and Googled it to death, with no luck.

Thanks!
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
6,859
Thanks for responding. However these all appear to be duplexers, no diplexers. Duplexers are used to connect multiple radios to one antenna. The diplexer is used to connect multiple antennas to one radio.

It is a matter of semantics, that vendor calls them duplexers.

Just select the configuration you want. and, yes you can connect multiple radios to one antenna, or multiple antennas to one radio with same device. I have used them for that purpose.
 

KevinC

Big Dog...celebrating 10 years of abuse!
Super Moderator
Joined
Jan 7, 2001
Messages
11,340
Location
Home
It is a matter of semantics, that vendor calls them duplexers.

Just select the configuration you want. and, yes you can connect multiple radios to one antenna, or multiple antennas to one radio with same device. I have used them for that purpose.

From the link you provided...

They may combine the output of HF or HF/VHF transceivers and the output of a UHF transceiver so that both transceivers may be connected to the same antenna. They may also be used to separate HF/VHF transmissions from UHF transmissions so that one transceiver may be connected to two antennas.

(I'm agreeing with you BTW :wink:)
 

Project25_MASTR

Millennial Graying OBT Guy
Joined
Jun 16, 2013
Messages
4,164
Location
Texas
Thanks for responding. However these all appear to be duplexers, no diplexers. Duplexers are used to connect multiple radios to one antenna. The diplexer is used to connect multiple antennas to one radio.

Actually, duplexers are used for in-band application. Diplexers are for multi-band application. A neither are one-way devices. The add backfeed protection to a duplexer (in the form of a circulator) and it becomes a combiner. A diplexer can also be used to combine multiple band signal sources into a common feedline and them split them out to individual antennas once on top of the tower again (as long as you observer the combined signal levels are under the maximum power handling of the diplexer).

When it comes to amateur radio however, diplexers are often mislabled duplexers by the Chinese manufacturers.
 

cmdrwill

Member
Joined
Mar 30, 2005
Messages
3,984
Location
So Cali
DIPLEXER...

Comtelco DBD1 VHF 140-174 / UHF 440-512 N fe connectors $145

Triplexer

Comtelco DBD3 30-225 / 406-512 / 8/900 N fe connectors $230

I can say in critical applications the VHF / UHF Diplexer worked flawlessly. Not cheep, but not CC knockoff junk.
 

Project25_MASTR

Millennial Graying OBT Guy
Joined
Jun 16, 2013
Messages
4,164
Location
Texas
DIPLEXER...

Comtelco DBD1 VHF 140-174 / UHF 440-512 N fe connectors $145

Triplexer

Comtelco DBD3 30-225 / 406-512 / 8/900 N fe connectors $230

I can say in critical applications the VHF / UHF Diplexer worked flawlessly. Not cheep, but not CC knockoff junk.

It's a lower cost compared to offerings from Sti-Co and Panorama.
 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,601
Location
Sector 001
Thanks for responding. However these all appear to be duplexers, no diplexers. Duplexers are used to connect multiple radios to one antenna. The diplexer is used to connect multiple antennas to one radio.

So its name changes depending on what you are doing with it?
 

iMONITOR

Silent Key
Premium Subscriber
Joined
Sep 20, 2006
Messages
11,156
Location
S.E. Michigan
I'm certainly no expert on the subject, on the contrary. But I've been reading and attempting to learn and have a better understanding how diplexers work and how they differ from duplexers. For my application, I think the biggest advantage of using a diplexer introduces very little loss, where as a duplexer can introduce significant loss.

I found this:

Antenna RF Diplexer Tutorial

- the antenna diplexer or RF diplexer splitter / combiner used for combining and splitting RF feeders so they can be used by multiple transmitters or receivers and possibly on different frequencies.

An antenna diplexer or RF diplexer is a unit that in one application can be used to enable more than one transmitter to operate on a single RF antenna.
Sometimes these units may be called antenna duplexers. Typically an antenna diplexer would enable transmitters operating of different frequencies to use the same antenna. In another application, an antenna diplexer may be used to allow a single antenna to be used for transmissions on one band of frequencies and reception on another band.
Antenna diplexers find many uses. In one common example an antenna diplexer or RF diplexer is used in a cellular base station to allow it to transmit and receive simultaneously. The antenna diplexer enables the same antenna system to be used while preventing the transmitted signal from reaching the receiver and blocking the input. In another application a diplexer may be used by a broadcast station transmitting on several different frequencies at the same time using the same antenna. The use of the diplexer enables a single antenna to be used, while preventing the output from one transmitter being fed back into the output of the other.
Small antenna diplexers may be used in domestic environments to allow several signals to run along a single feeder. In one application this may allow a single feeder to be used for television and VHF FM radio reception, or to allow terrestrial television signals and this from a satellite low noise box (LNB) to pass down the same lead. These RF diplexers are normally relatively low cost as the specifications are not nearly as exacting as those used for professional RF diplexer installations.

Basic antenna diplexer concepts

There are a number of ways of implementing RF diplexers. They all involve the use of filters. In this way the paths for the different transmitters and receivers can be separated according to the frequency they use. The simplest way to implement a diplexer is to use a low pass and a high pass filter although band-pass filters may be used. In this way the diplexer routes all signals at frequencies below the cut-off frequency of the low pass filter to one port, and all signals above the cut-off frequency of the high pass filter to the other port. Also here is no path from between the two remote connections of the filters. All signals that can pass through the low pass filter in the diplexer will not be able to pass through the high pass filter and vice versa.
diplexer_concept.gif


Basic concept of a high / low pass filter diplexer
A further feature of an RF diplexer is than it enables the impedance seen by the receiver or transmitter to remain constant despite the load connected to the other port. If the filters were not present and the three ports wired in parallel, neither the antenna nor the two transmitter / receiver ports would see the correct impedance.

RF diplexer filter requirements

When designing an antenna diplexer a number of parameters must be considered. One is the degree of isolation required between the ports labelled for the high and low frequency transmitter / receiver. If the diplexer is to be used purely for receiving, then the requirement for high levels of isolation is not so high. Even comparatively simple filters give enough isolation to ensure each receiver sees the right impedance and the signals are routed to the correct input without any noticeable loss. Even levels of isolation of 10 dB would be adequate for many installations. For diplexers that are used to split and combine television and VHF FM radio along a single line, te levels of isolation are likely to be very low.
The next case is when the diplexer is to be used for transmitting only. It will be necessary to ensure that the levels of power being transferred back into a second transmitter are small. Power being fed into the output of a transmitter in this way could give rise to intermodulation products that may be radiated and cause interference. It is also important to ensure that the transmitters see the correct impedance, and that the presence of the second transmitter does not affect the impedance seen by the first. Typically levels of isolation between the transmitter ports of 60 - 90 dB may be required.
The final case is where one of the ports is used for transmitting, and the other for receiving simultaneously. In this instance very high levels of isolation are required to ensure that the minimum level of the transmitter power reaches the receiver. If high levels of the transmitter signal reach the receiver, then it will be desensitised preventing proper reception of the required signals. Levels of isolation in excess of 100 dB are normally required for these applications.

Band pass filters

Under some circumstances band pass filters may be used. These may be used where comparatively narrow bandwidth is required for either or both of the transmitter / receiver ports. Sometimes a very high Q resonant circuit may be used. By using this approach high degrees of rejection can be achieved. Often repeater stations which receive on one channel and transmit on another simultaneously use diplexers that utilise this approach.

Summary

Although antenna diplexers are mainly used in specialised applications, allowing a single Rf antenna to be used by more than one transmitter or receiver, they are nevertheless a crucial element of many installations. For example cellular technology would be significantly different if they could not be used and the cellular RF antennas for base stations would be considerably more complicated. Similarly antenna diplexers are used in many broadcast applications allowing a single large RF antenna to be used by more than one transmitter.
By Ian Poole

[source]
Antenna Diplexer | Duplexer Splitter / Combiner | Radio-Electronics.Com

 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,601
Location
Sector 001
Diplexers combine 2 different bands (HF+VHF or VHF+UHF or HF-VHF+UHF) to a single port.

For example the TM-V71A has a single antenna connector, if I had a distant VHF repeater I wanted to crossband repeat locally, I could split the VHF signal and the UHF signal to separate feed lines and use a VHF yagi and a UHF omni.

Another situation to use a diplexer is if you had a 6m mobile and a 2m mobile and wanted to use a 5/8wave 2m(resonant as a base loaded 1/4wave antenna on 6m) antenna because you only wanted one antenna. Another application I have used a diplexer for is to combine a UHF link radio and a VHF repeater onto a single feed line to a 210-c2 VHF antenna(resonant on 70cm) in installations we could not add any antennas, but were allowed to use a left over antenna from a bold LMR network.


Sent from my iPhone using Tapatalk
 
Status
Not open for further replies.
Top