Checking duplexer

[FreddyM]

I'm not sure if I'm in the correct spot to ask this......


I have a sinclair duplexer Q2220E hooked up to a kenwood TKR-D710 repeater
At my disposal I have a NanoVNA meter and a 50 watt digital SWR meter
The duplexer ports are marked low pass and high pass
The repeater ports are marked Tx and Rx
I am transmitting at a lower frequency than I am receiving
Im wondering if there is a way to check how the duplexer and the repeater should be interconnected?
Is there a way for me to check the SWR on the repeater and if so how would I connect my meter?
Is there a way to see if the duplexer is tuned correctly with those 2 meters?

And just because the duplexer is marked low pass and high pass I have lost all faith in the company that sold
the equipment to me so I am assuming it might be marked incorrectly.

All help is appreciated>

 

[mmckenna]

I'm not sure if I'm in the correct spot to ask this......


I have a sinclair duplexer Q2220E hooked up to a kenwood TKR-D710 repeater
At my disposal I have a NanoVNA meter and a 50 watt digital SWR meter

The duplexer ports are marked low pass and high pass
The repeater ports are marked Tx and Rx
I am transmitting at a lower frequency than I am receiving

The lower frequency (your repeater transmit frequency) ~should~ go to the low pass port on the duplexer.
The higher frequency (your repeater receive frequency) ~should~ go to the high pass port on the duplexer.

Im wondering if there is a way to check how the duplexer and the repeater should be interconnected?
Is there a way for me to check the SWR on the repeater and if so how would I connect my meter?
Is there a way to see if the duplexer is tuned correctly with those 2 meters?

Ideally you want a spectrum analyzer with a tracking generator if you wanted to try tuning the duplexer.
Since it sounds like you just want to confirm what should be connected where, you could use the SWR meter connected to a proper 50Ω load, or at least a known good tuned antenna, and look at the power output. Look up the specs for the duplexer, it should show a maximum loss through it. You could could then connect the watt meter between the repeater transmitter port and the duplexer low pass port and compare the transmit output to the duplexer output. The manufacturer specs should tell you how much loss you should see.
If you see a whole lot of loss, then try checking the other port. Could be it's hooked up backwards or so far out of tune that the TX power isn't getting through.

Specs for that duplexer seem to suggest around 1.5dB of loss.

Duplexers are fragile, and if you think it may be out of tune, banged around, mistreated, or not hooked up right, I'd contact a professional to come out and tune it on site for you.

And just because the duplexer is marked low pass and high pass I have lost all faith in the company that sold
the equipment to me so I am assuming it might be marked incorrectly.

I would recommend not calling that company to tune your duplexer.

 

[FreddyM]

Since it sounds like you just want to confirm what should be connected where, you could use the SWR meter connected to a proper 50Ω load, or at least a known good tuned antenna, and look at the power output. Look up the specs for the duplexer, it should show a maximum loss through it. You could could then connect the watt meter between the repeater transmitter port and the duplexer low pass port and compare the transmit output to the duplexer output. The manufacturer specs should tell you how much loss you should see.
If you see a whole lot of loss, then try checking the other port. Could be it's hooked up backwards or so far out of tune that the TX power isn't getting through.

Are you saying I should connect the SWR meter between the antenna and the duplexer antenna port first and than between the duplexer low pass port and the repeater transmit port and compare results?

I checked the SWR on the antenna with the VNA meter and it showed around 1 to 1.1 so that should work instead of a 50 ohm load


On my SWR meter it says 120 watt measurable range.
What if I exceed that with the repeater.
I'm not an expert on laws governing max watts repeaters can have.

 

[buddrousa]

What does you Radio Station License for the Frequency you have say?
Just a hint 100 Watts ERP is the Output Power out of the Duplexers Minus the Feed Loss Multiplied By the Gain of the Antenna Equals ERP.
That is why you need all the tools that a Radio Shop has to set the Frequency, to set the Power, to tune the Duplexers, and to check the Power and SWR. Not a Hobby Toy VNA Meter that sells for $50.

 

[prcguy]

A hobby VNA can be used to verify ports and give a good indication if its tuned to the correct frequency. A cheap VNA can sometimes do final tuning on a flat pack notch only or a 1/4 wave pass only duplexer depending on VNA dynamic range. They cannot tune an 85 to 120dB isolation duplexer, not enough dynamic range for that.

The instructions for verifying ports or tuning are too much to type here and there is probably a YouTube video that covers it.

 

[davidgcet]

is it working now, or totally unknown? if totally unknown then do NOT connect the repeater rx just yet. those sinclairs can dump power back out the rx port if badly out of tune and cause front end damage. this is also why you don't tune them under power, i've seen more than one blow out a receiver when someone tried to tweak it a little too much. if it works and you just think it could be better, then hire a pro to come check it out. there is more to it than just peaking the pass and dipping the notch.

BTW, it is possible to tune either side as high or low pass. it "should" be as marked but i have had to retune them opposite before when the plunger was pitted right at the desired spot so we flipped them to make them work. not for a customer, but several times for some of our own stuff.

 

[mmckenna]

Are you saying I should connect the SWR meter between the antenna and the duplexer antenna port first and than between the duplexer low pass port and the repeater transmit port and compare results?

That's what I'd do. Plug your SWR meter directly to the repeater TX output port and your antenna into the other side (leave the duplexer out of it for now). That'll tell you how much power is coming directly out of the repeater.

Then reconnect the duplexer to the repeater, low pass to your TX, high pass to the RX and connect the SWR meter to the antenna port. Connect the antenna to the other side of your SWR meter.
Then read the power output again.

The specs say that the duplexer should have around 1.5dB of loss. That's about 25% loss. So if your repeater was putting out 100 watts and you saw 75 watts or so out of the antenna port, then you'd know you had the duplexer connected correctly.
If the power output of the duplexer was zero, then you'd know you had it backwards.

I did this on one of our repeaters the other day just to check to see I had it all connected right. 10 watt repeater, 7.5 out of the duplexer.

I checked the SWR on the antenna with the VNA meter and it showed around 1 to 1.1 so that should work instead of a 50 ohm load

It should. If it wasn't low, you'd have reflected power that would throw your readings off. That's close enough for testing.

On my SWR meter it says 120 watt measurable range.
What if I exceed that with the repeater.
I'm not an expert on laws governing max watts repeaters can have.

You don't want to do that. But I'd be surprised if your repeater was putting out more than 100 watts. What kind is it?

 

[FreddyM]

You don't want to do that. But I'd be surprised if your repeater was putting out more than 100 watts. What kind is it?

It is a Kenwood TKR-D710.

I forgot to mention that the repeater was programmed by the company it was bought from so the output power would have been set correctly according to the laws governing repeater output power in Canada.
I did go online to try to find what that law states but seeing as I'm not quite sure what I'm looking for I didn't find it.

As for the duplexer, it was tuned as well by the same company. I did try to be gently when moving it but from what I learned online they are fairly fragile.

At this point what I'm trying to do is figure out if I am hooking the interconnecting the repeater and the duplexer correctly.

That's what I'd do. Plug your SWR meter directly to the repeater TX output port and your antenna into the other side (leave the duplexer out of it for now). That'll tell you how much power is coming directly out of the repeater.

Then reconnect the duplexer to the repeater, low pass to your TX, high pass to the RX and connect the SWR meter to the antenna port. Connect the antenna to the other side of your SWR meter.
Then read the power output again.

With the above information, would you still go ahead and check it this way?


Once I figure out the correct termination setup what I would like to do than is see if the duplexer tuning is grossly out with the VNA meter.
Again I did watch some youtube videos and I did get the message that I can't tune the the duplexer with the VNA meter but it seems like I could get an idea how the tuning is.

Not a Hobby Toy VNA Meter that sells for $50.

I paid 75 for it.

 

[mmckenna]

It is a Kenwood TKR-D710.

I forgot to mention that the repeater was programmed by the company it was bought from so the output power would have been set correctly according to the laws governing repeater output power in Canada.
I did go online to try to find what that law states but seeing as I'm not quite sure what I'm looking for I didn't find it.

TKR-D710 is capable of 50 watts. It is possible to set them lower.
Your license should state what your maximum Transmitter Power Output is, and/or your Effective Radiated Power.

As for the duplexer, it was tuned as well by the same company. I did try to be gently when moving it but from what I learned online they are fairly fragile.

At this point what I'm trying to do is figure out if I am hooking the interconnecting the repeater and the duplexer correctly.



With the above information, would you still go ahead and check it this way?

Yes. Reading the power output directly off the back of the repeater with the duplexer removed and the other side of your watt meter connected to a 50Ω dummy load or at least a properly tuned antenna should give you an idea of what the repeater is putting out.

Then, reinstall the duplexer and test power on the antenna port as I mentioned above. You'll either see something around 35 watts if things are hooked up correctly. If you see 0 watts, then it's hooked up backwards.

 

[FreddyM]

Okay Thank's for the information.
I need to get some coax adapters and than I will check it out.
I will report back how it turned out for me.

 

[speedway_navigator]

Another test is to use a male to male N adapter and put your Wattmeter on the repeater output to measure power, then use your jumper to see how much line loss it has. It's not duplexer related but does show the quality of your jumper and cable from the output port to the duplexer.
I had an RG-142 jumper from the repeater to a transmitter combiner flake out and cause what sounded like intermod.