Hi Everyone... =)
I have a QC I decoder at my fire station. We have been having some problems being activated with our tones. What I would like to do is determine a procedure to test the reeds to make sure they are working properly. Does anyone have any suggestions on how to do this? I would appricate it =) Thank you!
-Bob
Tone Reed Tests?
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It is a Quik Call I decoder that activates our siren when our dispatch sends our tones. I dont have the model number as they numbers and lettering have pretty much fully warn off. What I need is the ability to test the individual reeds in the decoder...There are four reeds (2+2 since its QCI). Any other questions feel free to ask! =)
-Bob
-Bob
That sounds like the OLDDD QCI. Does it have the old 'gold' long reeds in it? TU333 comes to mind, and yes there was a test procedure for those reeds, even a box to test them in. (but that was a loooong time ago!!)
The TU series reeds have mechanical contacts in them that do go intermittent, two pins are the coil, the other two are the contacts.
Think of a tuning fork, and the vibrating element has a contact on it, the other contact is fixed. So every cycle of the correct frequency the contact makes for a small portion of the cycle.
The TU series reeds have mechanical contacts in them that do go intermittent, two pins are the coil, the other two are the contacts.
Think of a tuning fork, and the vibrating element has a contact on it, the other contact is fixed. So every cycle of the correct frequency the contact makes for a small portion of the cycle.
Re: Tone Reed Tests?
Sounds like a job for a service monitor. This way
you could generate the signal to test that the
receicer has the required signal sesitivity and decodes
the tones.
Another problem that may be effecting this is a bad
coax cable and or a bad antenna. The antenna
system doesn't last forever and does tend to need
some tender loving care after a number of years.
Many times the antenna may be a yagi that may
have got moved from the original direction. If it is
an omni, then I would look at the coax and what
condition the cable and antenna are in.
Jim
you could generate the signal to test that the
receicer has the required signal sesitivity and decodes
the tones.
Another problem that may be effecting this is a bad
coax cable and or a bad antenna. The antenna
system doesn't last forever and does tend to need
some tender loving care after a number of years.
Many times the antenna may be a yagi that may
have got moved from the original direction. If it is
an omni, then I would look at the coax and what
condition the cable and antenna are in.
Jim
USSZulu2 wrote:Hi Everyone... =)
I have a QC I decoder at my fire station. We have been having some problems being activated with our tones. What I would like to do is determine a procedure to test the reeds to make sure they are working properly. Does anyone have any suggestions on how to do this? I would appricate it =) Thank you!
-Bob
The test procedure was basically to drive the reed coil at the proper level with an audio signal at the proper frequency and see if the output contacts
closed.
I am not sure what level was required to drive the reed but you could probably test it with just an audio oscillator on the coil and an ohmmeter on the contacts.
closed.
I am not sure what level was required to drive the reed but you could probably test it with just an audio oscillator on the coil and an ohmmeter on the contacts.
Sort of, you have to be very carefull with the current and voltage on the contacts tho. An ohm meter most likley puts too much current on the contacts. You need to look for a contact on-off ratio pattern, and it requires a scope.k2hz wrote:The test procedure was basically to drive the reed coil at the proper level with an audio signal at the proper frequency and see if the output contacts closed.
I am not sure what level was required to drive the reed but you could probably test it with just an audio oscillator on the coil and an ohmmeter on the contacts.
I would not want to see the reeds damaged by using the wrong test procedure as they are very hard to find.
I am not sure they even have solid state decoders that do the old QC1 format. Of course that would be a lot less expense and more reliable than the old 'reeds'.
Yes, you have to be careful with levels on the reed. As I recall from maintaining a QC system back in the 60's, our reed test setup was a socket for the reed with terminals to connect an audio oscillator to the input. A scope and counter could also be bridged to the input to check audio frequency and level. There was a battery and resistor on the contact circuit to provide a controlled current and terminals to connect the scope across the resistor to check the contact pattern.
We determined what levels and frequency tolerance were normal with good reeds and then a suspect reed would be checked be seeing if it worked at normal frequency and level and also the effects of variations of frequency and level for drop out limits.
A solid state ohmmeter should not be a problem for a go/no-go test on the contacts but overdriving the audio input could probably cause some damage so caution is certainly advised.
I think there was an "official" Motorola test set but I never saw one.
We determined what levels and frequency tolerance were normal with good reeds and then a suspect reed would be checked be seeing if it worked at normal frequency and level and also the effects of variations of frequency and level for drop out limits.
A solid state ohmmeter should not be a problem for a go/no-go test on the contacts but overdriving the audio input could probably cause some damage so caution is certainly advised.
I think there was an "official" Motorola test set but I never saw one.
If you are dispatched by Allegheny county 911, good luck getting a 2+2 decoder to work. We throw these away in Allegheny & Westmoreland counties and use a modern decoder.
If 911 is sending 2+2, as they do for some companies, you will alway get errors as their 2+2 tones are waaaay too hot and won't properly decode. This has been a problem in both counties- especially in Westmoreland since the new center went in a few years ago.
If you are using 2+2 "chord" tones, dump them and go with QCII and get a modern decoder (and not a POS Minitor in a amp charger).
If 911 is sending 2+2, as they do for some companies, you will alway get errors as their 2+2 tones are waaaay too hot and won't properly decode. This has been a problem in both counties- especially in Westmoreland since the new center went in a few years ago.
If you are using 2+2 "chord" tones, dump them and go with QCII and get a modern decoder (and not a POS Minitor in a amp charger).
Thanks for the help everyone...
and yes...our decoder is working properly, according to the tests that I have done...
and yes...we use Allegheny 911. I believe now that they might not be sending the tones with enough audio level to activate the older reeds. We are going to get a modern decoder, however I am not sure if it is going to be QC I or II. We shall see. Thank you everyone for your help! =)
-Bob
and yes...our decoder is working properly, according to the tests that I have done...
and yes...we use Allegheny 911. I believe now that they might not be sending the tones with enough audio level to activate the older reeds. We are going to get a modern decoder, however I am not sure if it is going to be QC I or II. We shall see. Thank you everyone for your help! =)
-Bob