[Motorola] UHF MICOR Base
Glenn Little
[email protected]
Sun, 20 Jan 2002 17:09:51 -0500
Jim
Thank you for your timely response!
Our transmitter is now on 441.450. When it was abandoned it was on
463.775. I am the one that did most of the work in getting the transmitter
converted. We have never been able to get more than 30 Watts from the
duplexer. The transmitter power on the original frequency is
unknown. During the retuning, I measured the power levels at diffrent
points that I could get to. The Tripler/Amp was putting out 1.6W when we
put it into service on our ham frequency. The filter was not retuned, as
the manual says 1.0 W minimum here.
Now we are getting 0 W at this point. This is with the PA disconnected
from the tripler/Amp. I had the person at the site check the power from
the exciter. He does not know how to use his equipment well and did not
have all of the adapters he needed. He told me that he could see the 150
MHz signal on his spectrum analysez. His watt mete would not go down low
enough to measure the power.
He said that he could just see the display move on the spectrum analyzer
when he looked at the output of the tripler. The manual does not give
(that I could find) a power level out of the tripler before the amplifier.
My plans are to power up the module on the bench and feed a 400 mw signal
into the tripler and see if I can get something out. I will check the
filter on a spectrum analyzer / tracking generator and see what it looks like.
Since we are operating outside the band that this MICOR was designed for,
could a filter be mistuned enough to cause the tripler problems and still
allow the amplifier enough signal to meet specs for drive?
The fact that we met drive specs to the PA, led me to believe that we were
ok on the stages previous to this.
When we got this repeater, it was still attached to the antenna. The
antenna that it was attached to was a VHF antenna! The low overall power
out of the transmitter is caused by a 3dB loss through the circulator. Not
knowing a lot about circulators, I think that this one was damaged by
heat. I think that the VHF antenna presented a mismatch to the
transmitter. The circulator routed the reflected energy to the load. The
load heated up. The heat, over time, changed the magnetics of the magnets
in the circulator. This changed the tuning of the circulator.
Does this make sense?
Would a mistuned UHF filter have caused a problem with the tripler?
Thanks for your help
73
Glenn
WB4UIV
At 01:26 PM 1/20/02 -0800, you wrote:
>You most likely will need to tune the filter that is part of the low level
>amplifier.
>
>There is a thin metal cover soldered over the tuning screws and this is not
>"field tunable".
>
>You should use a tracking generator to look at the filter before you tune
>it. Then tune for 440-450 range.
>
>Do some logical troubleshooting before you assume that there is a bad part
>in the low level amp section. They rarely fail. BE SURE to check the power
>control section! I have 20+ years working on the Micor UHF (and other
>bands), the don't fail that often!
>
>
>What frequency are you transmitting on ? When I was using a Micor and
>transmitting on 444.725, you need to tune it!
>Good luck!
>
>73
>Jim W7RY
>
>----- Original Message -----
>From: Glenn Little <[email protected]>
>To: <[email protected]>
>Sent: Sunday, January 20, 2002 12:43
>Subject: [Motorola] UHF MICOR Base
>
>
>| Our radio club has a UHF MICOR repeater that was donated to us. After a
>lot
>| of work, we got it on the air. This only lasted a day. After
>| troubleshooting the transmitter problem, we feel that we have a
>| Tripler/Amplifier (TLE1603B) problem. We have zero power out of this
>| module, where we had 1.6W out when the repeater was working. We have
>about
>| 400mw input at VHF into the tripler.
>|
>| Does anyone have any experience with repairing this module? The manual
>| lists it as not field repairable. The module is currently inroute from
>the
>| site to my house for investigation as to repairability.
>|
>| Does anyone know where a spare might be obtained?
>|
>| Thanks
>| 73
>| Glenn
>| WB4UIV
>|
>|
>| --------------------------------------------------------------------------
>-
>| Glenn Little [email protected] QCWA LM 28417
>| Amateur Callsign: WB4UIV [email protected] AMSAT LM 2178
>| QTH: Goose Creek, SC USA (EM92xx) ARRL TAPR
>| --------------------------------------------------------------------------
>-
>|
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>| Motorola mailing list
>| [email protected]
>| http://mailman.qth.net/mailman/listinfo/motorola
>
>
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Glenn Little [email protected] QCWA LM 28417
Amateur Callsign: WB4UIV [email protected] AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) ARRL TAPR
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