Hi ,
I am trying to tune an APCOR duplexer using the watt meter method (just to get the basics)
Problem: this radio is known (or at least thought) to be putting out somewhere in the neighborhood of 12 watts. so I place an in-line power/swr meter between the transmitter output and the antenna and when I key-up I get NO movement on the power meter whatsoever! NOTHING, not even a little bounce, I know for a fact that the radio is transmitting- even if not at the full/correct power, so I thought I would get SOME kind of reading?
The reason I messed with the duplexer at all is because I just got a channel element back from ICM and it works (tx/rx is correct with correct 5mhz split)
I am at a loss here, ONE NOTE and I don't know if this makes a difference or not but I am using the supplied radio antenna as opposed to a dummy load as I could not find anyone that carries a 50watt-----I wouldn't have thought that this should make any difference but I figured I'd include that info.
Any thoughts? NO fluctuation of the power meter needle AT ALL! yet radio is putting out enough to work at (at least ) close- range.
and yes, the settings are correct on my cheap little radio shack meter (switched to watt setting)
<<<<<<<<< I assume that a power meter is the same thing as a watt meter? >>>>>>>>>>>>>>>>>>
Thanks,
John
duplexer/power out problem
Moderator: Queue Moderator
Just a qestion :
Is your Radio Shack meter usable in the freq range your txing at ?
Its not a CB swr/watt meter by chance ?
What freq area are you trying to tune into with the duplexer ?
Whats the duplexers brand and model number ?
Whats the radios brand and model number ?
Just wondering if by chance you have a mismatch or something else going on here.
EKLB
Is your Radio Shack meter usable in the freq range your txing at ?
Its not a CB swr/watt meter by chance ?
What freq area are you trying to tune into with the duplexer ?
Whats the duplexers brand and model number ?
Whats the radios brand and model number ?
Just wondering if by chance you have a mismatch or something else going on here.
EKLB
Thanx EKLB,
Well, the power/swr meter I'm usung is a little R/S type, its branded as being for use with 440mhz,
the duplexer is a 7 can mobile sinclair built specially for the moto apcor medical (paramedic) radio. the radio is 450-470 capable and I recently installed a recrystalled channel element in the GMRS range (rx @ 462.xxx) the radio uses an offset to acheive a 5 mhz higher transmit freq.
Although I realize that 440mhz is not 467 mhz I figured (?) it would at least give me some indication of the power out.
so basically I'm trying to tune the duplexer for 467.xxx out and I can even get so much as a "blip" on the power meters' needle. I'm beginning to wonder if the power amp is shot but the radio does tx at close range (to a scanner) and the incandescent bulb dims asthough the power amp is sucking power from the battery (and the tx led glows) so I don't know where to go next.
I even went as far as to touch the tip of my tongue (yes, I know- retarded) to the antenna side of the in-line power meter, and not so much as a tingle- never mind an rf burn ;(
I'm at a loss-
-J
Well, the power/swr meter I'm usung is a little R/S type, its branded as being for use with 440mhz,
the duplexer is a 7 can mobile sinclair built specially for the moto apcor medical (paramedic) radio. the radio is 450-470 capable and I recently installed a recrystalled channel element in the GMRS range (rx @ 462.xxx) the radio uses an offset to acheive a 5 mhz higher transmit freq.
Although I realize that 440mhz is not 467 mhz I figured (?) it would at least give me some indication of the power out.
so basically I'm trying to tune the duplexer for 467.xxx out and I can even get so much as a "blip" on the power meters' needle. I'm beginning to wonder if the power amp is shot but the radio does tx at close range (to a scanner) and the incandescent bulb dims asthough the power amp is sucking power from the battery (and the tx led glows) so I don't know where to go next.
I even went as far as to touch the tip of my tongue (yes, I know- retarded) to the antenna side of the in-line power meter, and not so much as a tingle- never mind an rf burn ;(
I'm at a loss-
-J
-
jackhackett
- Posts: 1513
- Joined: Tue Jun 10, 2003 8:52 am
Are you just putting the meter in between the duplexer and antenna, or have you tried putting it from the transmit output to the antenna, without the duplexer being in the circuit? That would at least tell you if it's the duplexer causing the problem or not.
Oh.. and the sticking the coax on your tongue thing? VERY stupid... have you never had an RF burn? Quite painful on a finger, I can only imagine what it would be like on a tongue.
Oh.. and the sticking the coax on your tongue thing? VERY stupid... have you never had an RF burn? Quite painful on a finger, I can only imagine what it would be like on a tongue.
I'm putting the meter at the rf out source - where the antenna connects, I have left the duplexer in place - the radiio is full duplex operation but I have been usung the "ptt" function when testing the transmit portion of the radio. I know- very stupid tongue thing - I was just so frustrated to find if there was ANY rf out (tried the finger)jackhackett wrote:Are you just putting the meter in between the duplexer and antenna, or have you tried putting it from the transmit output to the antenna, without the duplexer being in the circuit? That would at least tell you if it's the duplexer causing the problem or not.
Oh.. and the sticking the coax on your tongue thing? VERY stupid... have you never had an RF burn? Quite painful on a finger, I can only imagine what it would be like on a tongue.
Lets see what you have for answers for these qestions.
The duplexer you have is used to seperate the incoming signal from the intended out going freq. ( Im pretty sure you knew that though)
So a legal GMRS repeaters rx in signal will be your 467.xxx freq and it takes this signal and puts it into the repeaters 467 rx and the repeater retransmits it back out as the 462.xxx freq.
So the duplexer would be tuned at the rx input side to pass a 467.xxx freq but not pass any others.
The duplexers tx out put would be tuned to pass the 462.xxx freq but not pass any others.
If your txing with your mobile into the antenae input the duplexer when tuned will on the rx side pass a 467.xxx freq and the duplexers tx output will pass a 462.xxx freq when properly tuned and not allow any others to pass other than what they are tuned for.
The above only applies if your trying to tune the duplexer for use in a repeater.
Are you attempting to use the duplexer with your mobile to become full duplexed or just wanting to learn a bit about doing a tune up for a duplexer ?
I do have a sheet that explains the steps for tuning a duplexer if youd like to have it PM me your email address and ill scan it and email it to you.
This sheet tells you how to tune each cavity one at a time then after you have them all done you conect them back up with there cables and you should see the signal then.
But in your case the cables may actualy be hard solder copper tubed coaxil which will not allow you to seperate the cans for individual tuning which would be much easier for you.
The reason you may be experiencing so much trouble in tuning the duplexer is that you only need one can to be tuned wrong and you get nothing.
And since you stated a 7 can duplexer im assuming that means 4 cans on tx or rx and the remaining three are on the oposite = but my point is that if you have 4 cans tuned wrong your gonna have a helluva time finding even a close tuning if you have to pass through all four cans without a service monitor or the instruction sheet telling you how to tune it to get close for fine tweaked tuning.
So be aware that proper tuning procedure will sneak you into the duplexer cans pass band so that you would be able to further tune onto the pass freq properly as you go to each can for tuning.
PS : jackhakett has a valid point - your tounges is not a watt meter and the rf burn well lets just say you wont do it again.
My younger brother once while standing in the middle of a small creek took on a dare to pee on the weed chopper electric fence and when he did it knocked his butt back side down in the creek and left his whanger peeing up into the air down onto himself= Dont know if him being the best endowed one of the four brithers had anything to do with that incident but he sure as H will not pee on another electric fence.
And that is a true story :
EKLB
The duplexer you have is used to seperate the incoming signal from the intended out going freq. ( Im pretty sure you knew that though)
So a legal GMRS repeaters rx in signal will be your 467.xxx freq and it takes this signal and puts it into the repeaters 467 rx and the repeater retransmits it back out as the 462.xxx freq.
So the duplexer would be tuned at the rx input side to pass a 467.xxx freq but not pass any others.
The duplexers tx out put would be tuned to pass the 462.xxx freq but not pass any others.
If your txing with your mobile into the antenae input the duplexer when tuned will on the rx side pass a 467.xxx freq and the duplexers tx output will pass a 462.xxx freq when properly tuned and not allow any others to pass other than what they are tuned for.
The above only applies if your trying to tune the duplexer for use in a repeater.
Are you attempting to use the duplexer with your mobile to become full duplexed or just wanting to learn a bit about doing a tune up for a duplexer ?
I do have a sheet that explains the steps for tuning a duplexer if youd like to have it PM me your email address and ill scan it and email it to you.
This sheet tells you how to tune each cavity one at a time then after you have them all done you conect them back up with there cables and you should see the signal then.
But in your case the cables may actualy be hard solder copper tubed coaxil which will not allow you to seperate the cans for individual tuning which would be much easier for you.
The reason you may be experiencing so much trouble in tuning the duplexer is that you only need one can to be tuned wrong and you get nothing.
And since you stated a 7 can duplexer im assuming that means 4 cans on tx or rx and the remaining three are on the oposite = but my point is that if you have 4 cans tuned wrong your gonna have a helluva time finding even a close tuning if you have to pass through all four cans without a service monitor or the instruction sheet telling you how to tune it to get close for fine tweaked tuning.
So be aware that proper tuning procedure will sneak you into the duplexer cans pass band so that you would be able to further tune onto the pass freq properly as you go to each can for tuning.
PS : jackhakett has a valid point - your tounges is not a watt meter and the rf burn well lets just say you wont do it again.
My younger brother once while standing in the middle of a small creek took on a dare to pee on the weed chopper electric fence and when he did it knocked his butt back side down in the creek and left his whanger peeing up into the air down onto himself= Dont know if him being the best endowed one of the four brithers had anything to do with that incident but he sure as H will not pee on another electric fence.
And that is a true story :
EKLB
Tuning of a mobile duplexer
I may have missed it but I don't remember you saying what kind or model of radio your using on this hookup. If by some chance you have one of the transmitters that looks at reflected power, the transmitter may be cutting back on the output power.
With a duplexer out of tune, it is not a good load for a transmitter. It will show up as a fairly high reflected power. I have seen some people try and use refected power to tune a duplexer. This also is not the right way to do it.
You may be better off using a receiver with some attenuation pads and connecting it to the antenna port of the duplexer. Set it to the same frequency as your transmitter and start tuning the cans for max signal. Change the radio ports to the receiver side, change the radio your using to generate a signal and put it on the receive frequency. Change the test receiver to the receive frequency and start tuning the RX cavities for max signal.
This methode should get you in the ball park. As you get the cavities close to the correct position, you will have to reduce the level by lowering the transmit power or adding more attenuation pads on the receiver side.
It is also a good idea to keep the unused port of the duplexer terminated with a 50 ohm pad while your doing the tuning. An unterminated port will effect the tuning.
Jim
With a duplexer out of tune, it is not a good load for a transmitter. It will show up as a fairly high reflected power. I have seen some people try and use refected power to tune a duplexer. This also is not the right way to do it.
You may be better off using a receiver with some attenuation pads and connecting it to the antenna port of the duplexer. Set it to the same frequency as your transmitter and start tuning the cans for max signal. Change the radio ports to the receiver side, change the radio your using to generate a signal and put it on the receive frequency. Change the test receiver to the receive frequency and start tuning the RX cavities for max signal.
This methode should get you in the ball park. As you get the cavities close to the correct position, you will have to reduce the level by lowering the transmit power or adding more attenuation pads on the receiver side.
It is also a good idea to keep the unused port of the duplexer terminated with a 50 ohm pad while your doing the tuning. An unterminated port will effect the tuning.
Jim
My two bits worth:
I think that you have a notch type duplexer.
You NEVER tune one of these for max power out.
The resonators on the receive side reject the transmitter energy, the transmit side rejects the receive frequency.
One side is designed for high reject, the other for low freq reject.
The duplexer does not care if a port is connected to a receiver, or transmitter.
I mention this because a portable repeater is usuially "up side down"
That is they transmit high, just like a mobile, so don't go by the "rec" marking on the duplexer.
To tune the duplexer you will need a good 50 ohm load, as well as a signal source, as well as a receiver for each frequency.
There is no end of equipment that can be used for alignment from net work analyzers, tracking generators, to a signal generator and a multi channel receiver.
It depends what you have at hand.
Tuning:
I prefer to lubricate the threads of the tuning screws with Caig D-5.
Use a properly fitting screw driver. Don't "booger the threads"
Terminate the antenna port with a good 50 Z load.
Generate into the transmit port on the transmit frequency, tune screws on the receive side for minimum signal as measured on the receive port.
Be sure that each tuning adjustment causes a change, the distance of the screws from the end plate should be about the same for the same frequency.
Generate the receive frequency into the transmit port, adjust screws on the transmit side for minimum signal as measured on the receive port.
Use an iso tee to measure the receiver desense.
There should be no difference between the signal received on the repeater
when the transmitter is keyed.
That is the answer to wether the repeater is working properly or not.
You also have to do this test after installation.
I think that you have a notch type duplexer.
You NEVER tune one of these for max power out.
The resonators on the receive side reject the transmitter energy, the transmit side rejects the receive frequency.
One side is designed for high reject, the other for low freq reject.
The duplexer does not care if a port is connected to a receiver, or transmitter.
I mention this because a portable repeater is usuially "up side down"
That is they transmit high, just like a mobile, so don't go by the "rec" marking on the duplexer.
To tune the duplexer you will need a good 50 ohm load, as well as a signal source, as well as a receiver for each frequency.
There is no end of equipment that can be used for alignment from net work analyzers, tracking generators, to a signal generator and a multi channel receiver.
It depends what you have at hand.
Tuning:
I prefer to lubricate the threads of the tuning screws with Caig D-5.
Use a properly fitting screw driver. Don't "booger the threads"
Terminate the antenna port with a good 50 Z load.
Generate into the transmit port on the transmit frequency, tune screws on the receive side for minimum signal as measured on the receive port.
Be sure that each tuning adjustment causes a change, the distance of the screws from the end plate should be about the same for the same frequency.
Generate the receive frequency into the transmit port, adjust screws on the transmit side for minimum signal as measured on the receive port.
Use an iso tee to measure the receiver desense.
There should be no difference between the signal received on the repeater
when the transmitter is keyed.
That is the answer to wether the repeater is working properly or not.
You also have to do this test after installation.
Aloha, Bernie
-
jackhackett
- Posts: 1513
- Joined: Tue Jun 10, 2003 8:52 am
Ok, first we need to do is get some terminology straight so we're on the same page here, 'where the antenna connects' is not the 'rf out source', it is the antenna port. For the sake of this discussion we'll call the port where the transmitter connects the transmit port, and where the receiver connects the receive port.
The way you have it set up now, the transmit RF comes out of the transmitter, and passes through the duplexer to your meter and the to the antenna. Several things could be be causing you to not get a reading.
1) the transmitter could not be putting out any power.
2) the duplexer could be attenuating so much of the power that there's not enough left to measuse.
3) the duplexer could be causing the transmitter see high reflected and shut down.
4) the antenna could be causing the transmitter see high reflected and shut down.
5) your meter could be bad (I think the tongue test rules this out though)
So the first thing you want to do is find out if the transmitter is actually putting out power. To do that you need to eliminate the duplexer from the circuit, disconnect the cable from the transmit port of the duplexer and connect it to the input of your meter, then connect the antenna to the other side of your meter (should use a dummy load, but you say you don't have one). Now key the transmitter and see if you get a reading. If you don't, you've probably got a bad transmitter, and you need to get that fixed before going any further with the duplexer.
There you have it, Troubleshooting 101 lesson 1, divide and conquer.
The way you have it set up now, the transmit RF comes out of the transmitter, and passes through the duplexer to your meter and the to the antenna. Several things could be be causing you to not get a reading.
1) the transmitter could not be putting out any power.
2) the duplexer could be attenuating so much of the power that there's not enough left to measuse.
3) the duplexer could be causing the transmitter see high reflected and shut down.
4) the antenna could be causing the transmitter see high reflected and shut down.
5) your meter could be bad (I think the tongue test rules this out though)
So the first thing you want to do is find out if the transmitter is actually putting out power. To do that you need to eliminate the duplexer from the circuit, disconnect the cable from the transmit port of the duplexer and connect it to the input of your meter, then connect the antenna to the other side of your meter (should use a dummy load, but you say you don't have one). Now key the transmitter and see if you get a reading. If you don't, you've probably got a bad transmitter, and you need to get that fixed before going any further with the duplexer.
There you have it, Troubleshooting 101 lesson 1, divide and conquer.
One needs to remember that APCOR and other bio-phones are backwards, they TX high on the 467.9 and receive in the 462.9 mhz.
The duplexers in the bio-phones may not tune up on the reverse frequencies you are using. And with 462 mhz on the TX port the output would be NONE, the duplexer notches out 462 on the TX port! These are special "mobile duplexers" made for Med freqs.
The duplexers in the bio-phones may not tune up on the reverse frequencies you are using. And with 462 mhz on the TX port the output would be NONE, the duplexer notches out 462 on the TX port! These are special "mobile duplexers" made for Med freqs.
-
jackhackett
- Posts: 1513
- Joined: Tue Jun 10, 2003 8:52 am
I might have remembered that, had i ever known itOne needs to remember that APCOR and other bio-phones are backwards, they TX high on the 467.9 and receive in the 462.9 mhz.
never dealt with apcor stuff myself.So, knowing this, #2 from my list seems likely to be the problem. Question is, can you just switch the connections to the receive and transmit ports around and have it work, or are the duplexers non-symetrical?