I have a duplexer mounting question

[KevinJ]

Hello everyone, I hope you are all having a good evening after a good day! I have been looking for a few weeks now and googling and searching the interwebz, and I can not find information on duplexer mounting do's and don'ts. I want to know what options I have for mounting/securing my duplexer. I will use two ra87s in a powered desktop cabinet made for them that comes as a kit. But how far apart should the duplexer be from any electrical devices including the radios? Do I mount it vertically or should it be lying down? I read somewhere that changing their orientation from how it was sitting when tuned can cause them to change their tune slightly. It is an 8-cavity cheap Chinese notch style. I was either going to make a stand and mount it vertically above and behind the radio set, or possibly make a small cover-like shelf and then bolt the duplexer to it in a flat horizontal position either on the top or even upside down underneath the top of said cover/cabinet.  I am just trying to reduce any interference it may get from household items and appliances as well as making sure I don't accidentally mess the thing up and have to get it re-tuned or replaced.

[BoxCar]

For the cheap "flat pack" duplexers it probably won't make any difference. The duplexer was probably lying flat when tuned though.

[nokones]

My EMR Corp Duplexer mounted to a backboard. The cables were custom made by me.

If you're going to use a cheap Chinese duplexer I would be more concern about burning out the plastic inserts at each connection port rather than the mounting orientation. The cheap Chinese duplexers have a habit of burning out the plastic inserts in the ports from RF.

[KevinJ]

21 hours ago, nokones said:

My EMR Corp Duplexer mounted to a backboard. The cables were custom made by me.

If you're going to use a cheap Chinese duplexer I would be more concern about burning out the plastic inserts at each connection port rather than the mounting orientation. The cheap Chinese duplexers have a habit of burning out the plastic inserts in the ports from RF.

so if this happens is the unit junk? or is it serviceable/repairable?  Should I check it periodically when I get it all together and running? Or is it something that I will know because it just stops working or works very poorly? Mine is a Jiesai?(weird label design) model SGQ-450K strait outta Guangzhou CHYNA

[BoxCar]

Reduce the power going into the duplexer as the losses caused by the duplexer is turned to heat. The loss in dB remains the same but the amount of heat created is reduced.

[WRKC935]

A large VHF set of tubular aluminum can's might change tune based on how they were sitting when tuned.  Anything built from extruded aluminum is going to have enough rigidity to be mounted in any configuration without it being an issue.

A small 'flatpack' duplexer like the EMR pictured is probably the LEAST prone to it flexing from it's orientation.  But mounting them on an uneven surface MAY cause issues.  But, on the flip side of that, a flatpack duplexer is a NOTCH only type of filter and the bandwidth of the notch is wide enough that even if they were lightly tweaked, I seriously doubt that you would be able to see a difference on a tracking generator or a VNA. 

 

[nokones]

10 hours ago, KevinJ said:

so if this happens is the unit junk? or is it serviceable/repairable?  Should I check it periodically when I get it all together and running? Or is it something that I will know because it just stops working or works very poorly? Mine is a Jiesai?(weird label design) model SGQ-450K strait outta Guangzhou CHYNA

It is my understanding most of them are serviceable. When the inserts start to burn out, you will see a reduction in your Farz. You can stay on top of this by periodically by  checking your coverage footprint. I don't know if the VSWRs would get worst or not because it is mostly a desense issue rather than RF being reflected back.

[Lscott]

11 hours ago, WRKC935 said:

A large VHF set of tubular aluminum can's might change tune based on how they were sitting when tuned.  Anything built from extruded aluminum is going to have enough rigidity to be mounted in any configuration without it being an issue.

A small 'flatpack' duplexer like the EMR pictured is probably the LEAST prone to it flexing from it's orientation.  But mounting them on an uneven surface MAY cause issues.  But, on the flip side of that, a flatpack duplexer is a NOTCH only type of filter and the bandwidth of the notch is wide enough that even if they were lightly tweaked, I seriously doubt that you would be able to see a difference on a tracking generator or a VNA. 

 

See attached file for a guy who tested one.

Chinese Mobile Duplexer Measurements.pdf