DUPLEXER For CDM Repeater!!!

[ResqChief201]

Goodmorning Guys!

Im in the processes of building a VHF Repeater with two CDM750s. I have acquired my frequency pair and have programmed one CDM for Rx only and the other for TX only. I purchased a RA-1 One-Direction Repeater Adaptor Cable from MRE1032 to link the two radios together as an alternative of using a RICK. I got two Rg142 Mini-UHF to N pigtails to go into the duplexer.

Next i need to know which duplexer will work for this project. I know cellwaves are good but they are pricey. I was looking at a Jiesai VHF Duplexer. it was $109.00 from ham-radio2008. I know its cheaper and you get what you pay for but i am restricted on money at the moment. Im not sure if anyone has any experience with these cheaper duplexers. Let me know

-Ray

 

[prcguy]

The frequency split will determine what kind of duplexer you can get by with. A 600KHz split will require at least a large expensive, probably 6 cavity pass/reject duplexer that's going to cost a lot, maybe $2k on up new. Even used these run about $450 on up.

If you can use a 1MHz or greater split then a 4 cavity pass/reject will be fine but the cost is still high new, probably $1.2k on up. I have one of these tuned up on the portable repeater pair of 144.930/147.585.

A mobile VHF 4 or 6 cavity reject only duplexer (like the Jiesai) is usually rated for a 5MHz split and some will do 4MHz with degraded specs. Bottom line, there is no cheap alternative unless you use seperate tx and rx antennas with lots of vertical spacing and adequate band pass cavaties in both the tx and rx path.
prcguy

Goodmorning Guys!

Im in the processes of building a VHF Repeater with two CDM750s. I have acquired my frequency pair and have programmed one CDM for Rx only and the other for TX only. I purchased a RA-1 One-Direction Repeater Adaptor Cable from MRE1032 to link the two radios together as an alternative of using a RICK. I got two Rg142 Mini-UHF to N pigtails to go into the duplexer.

Next i need to know which duplexer will work for this project. I know cellwaves are good but they are pricey. I was looking at a Jiesai VHF Duplexer. it was $109.00 from ham-radio2008. I know its cheaper and you get what you pay for but i am restricted on money at the moment. Im not sure if anyone has any experience with these cheaper duplexers. Let me know

-Ray

 

[kayn1n32008]

Is this for ham radio? If so you will need a duplexer that is able to do a 600 KHz split. Mobile duplexers generally will not go closer than 3-5MHz seperation.

You are gointlg to need something like a Q2330 resloc or a proper 6 can pass/reject duplexer. A mobile duplexer will NOT work for a standard 600KHz amateur repeater pair.

Edit: What PRCGuy said as well.

 

[ResqChief201]

I have a 4.6 Mhz spacing between the two freqs. It is actually being used for Search and Rescue on a PW license. Trying to make a portable repeater for the field. I was looking at the Jiesai Mobile Duplexer but wasn't sure if it was junk or not. Thats really all i wanted to know was if they are reliable even tho they are from china lol.

-Ray

 

[kayn1n32008]

Having been involved in testing some mobile, no name, Chinese mobile duplexers, they seem to be decent for what they are. The ones i have seen will tune up as good or better than the Sinclair mobile duplexers they are copied from. Small warning though. Tune them once you have possesoon of them.

Also if this is going in to a high RF sote a mobile duplexer will not be enough.

Also make sure it is designed for minimum 4.5Mhz split.

 

[ResqChief201]

The one i found is a 3.5 minimum split. Also are these capable of more than one freq? i was planning on putting two repeater pairs in the cdms. Do i use the lowest freq of the four as my low and the highest as my high? or is it low and high for each pair?. For example if I'm using 150.430 and 154.025 as one and then 151.684 and 156.145 as a second….is the duplexer tuned to each pair or to 150.430 and 156.145?

 

[jim202]

The one i found is a 3.5 minimum split. Also are these capable of more than one freq? i was planning on putting two repeater pairs in the cdms. Do i use the lowest freq of the four as my low and the highest as my high? or is it low and high for each pair?. For example if I'm using 150.430 and 154.025 as one and then 151.684 and 156.145 as a second….is the duplexer tuned to each pair or to 150.430 and 156.145?

Most repeater duplexers are a very narrow frequency devices and as such can not be used on frequencies more than one or two channels apart. So in your case, don't plan on being able to change channels.