How to combine two repeaters to one antenna?

[Hawk5000]

Hello all, new to the forum. I am trying to combine 2 icom repeaters so the use one antenna.

Can this be done using an RF power spliter like the one in this link ?

or do I have to use a Tx/Rx Multicoupler like this one?

Thank You.

 

[Captain Kilowatt]

You need cavity filters tuned very precisely to the frequencies of interest, both RX and TX. A basic repeater is bad enough but combining two or more ESPECIALLY on the same band is a migraine waiting to happen. :headbang

 

[ok1mx]

It is not so problematic. Description is here: Radioklub OK1OMX
Unfortunately it is only in Czech language. (Try google translator ) To complete the picture: KZ circulator is made of coaxial cable, called a "rat racing". Used it as a World War II. The biggest problem are the IM3 products. I solve it by using circulators and it works without problems even at 25 kHz spacing. IM3 is better than-90dB.

73 Milan OK1MX

 

[Wire Weasel]

What exactly are you trying to do with your setup?

 

[Hawk5000]

What exactly are you trying to do with your setup?

I am working on communication system on a ship consisting of icom hand held radios and 2 repeaters. I have 2 repeaters so i can support 2 groups of hand held users on separate frequencies.

I need to combine the to repeaters so they use the same antenna.

 

[ke7vvt]

Hawk,

The multi-coupler link you provided is what you need. It is commonly referred to as a duplexer, there are two types, bandpass (passes only the tuned frequency) and band notch (does not pass the tuned frequency).

That will allow multiple radios on one antenna, the cavity filters stop the RF from one radio going into the other radios.

 

[Hawk5000]

Hawk,

The multi-coupler link you provided is what you need. It is commonly referred to as a duplexer, there are two types, bandpass (passes only the tuned frequency) and band notch (does not pass the tuned frequency).

That will allow multiple radios on one antenna, the cavity filters stop the RF from one radio going into the other radios.

And if I where to try and do it using the splitter device instead of the multicoupler would you expect to work at all? would I risk damaging the repeaters?

 

[Captain Kilowatt]

And if I where to try and do it using the splitter device instead of the multicoupler would you expect to work at all? would I risk damaging the repeaters?

 

[Captain Kilowatt]

It is not so problematic. Description is here: Radioklub OK1OMX
Unfortunately it is only in Czech language. (Try google translator ) To complete the picture: KZ circulator is made of coaxial cable, called a "rat racing". Used it as a World War II. The biggest problem are the IM3 products. I solve it by using circulators and it works without problems even at 25 kHz spacing. IM3 is better than-90dB.

73 Milan OK1MX

That will work but it appears that you are not using much power,only 12 watts?? It still uses tuned cavities in the combiners too I believe. Maybe I am wrong and if I am I'll just balme it on Google Translator.

 

[ok1mx]

In my concept ( http://www.hamradio.cz/prevadece/ok0bna/ok0bn-bna.gif ) is not used any cavities. When you combine two signals with close frequencies, must be of high quality cavities large and expensive. 25 kHz spacing of 70cm band is impossible to make with cavities. It's very close. When I counted the minimum distance for the possibility of splitting with cavities is about 400 kHz in the 70 cm band.

Circulator does inhibit reverse power to neighboring transmitters. It is therefore not a problem with IM3. KZ

is a circulator, and sends the output from the two transmitters to the antenna only. The disadvantage is that it is the loss of about 3.5 dB. (Separation between the TXs is more than 22 dB) This is a major advantage in contrast to the hybrid Combiners. Both the transmitter to see each other through two circulators in the closed direction.

I'm combining two repeaters, one with a 12W power, the other 27W.

 

[ke7vvt]

Hawk,

Radios have their own built in signal isolation, it is not much but it usually is enough to have two radios using different antennas and tuned to similar frequencies to ignore eachother. But since you want to tune your radios to similar frequencies but use the same antenna, that built in ability to ignore the other radios probably won't be enough.

The RF power splitter is probably for a different application than you are trying to do.

Can you provide these specs on the radios you are using
Receive frequency radio 1
Transmit freq radio 1
Transmit power radio 1
Sensitivity and selectivity radio 1
Receive freq radio 2
Transmit freq radio 2
Transmit power radio 2
Sensitivity and selectivity radio 2

ICOM 208H Specifications

I have a cool spreadsheet I'll look for that we can use to find out the amount of isolation needed too.

 

[Captain Kilowatt]

The BIG problem is going to be eliminating desensing of one RX while the other TX is on. You need a LOT of isolation for that.

 

[Hawk5000]

I know it has been a long time but this project got sidelined for a while.

Now I am back to trying to figure this out.

Here are the answers to your question.

Receive frequency radio 458.875 MHz
Transmit freq radio 468.875 MHz
Transmit power radio 1 = 50W
Sensitivity and selectivity radio 1 = 0.25µV typ. (at 12dB SINAD)

Receive freq radio 458.575 MHz
Transmit freq radio 468.575 MHz
Transmit power radio 2 = 50W
Sensitivity and selectivity radio 2 = 0.25µV typ. (at 12dB SINAD)

Both radios have duplexer to combine there Rx and Tx signals.

Hope you all are still interested in helping out.

Hawk,

Radios have their own built in signal isolation, it is not much but it usually is enough to have two radios using different antennas and tuned to similar frequencies to ignore eachother. But since you want to tune your radios to similar frequencies but use the same antenna, that built in ability to ignore the other radios probably won't be enough.

The RF power splitter is probably for a different application than you are trying to do.

Can you provide these specs on the radios you are using
Receive frequency radio 1
Transmit freq radio 1
Transmit power radio 1
Sensitivity and selectivity radio 1
Receive freq radio 2
Transmit freq radio 2
Transmit power radio 2
Sensitivity and selectivity radio 2

ICOM 208H Specifications

I have a cool spreadsheet I'll look for that we can use to find out the amount of isolation needed too.