[Motorola] UHF MICOR Base
Komljanec
[email protected]
Sun, 20 Jan 2002 19:19:20 -0500
Blown triplers are a common thing with UHF Micors. Exciter is no problem
usually with 400 mW out. The PA is another story. I've never had a full
110W UHF PA, so I pulled the final transistors and their ceramics out of
110W mobiles to transplant them (a 3 hour operation with a BIG soldering
iron) into the 45 W pa. Unfortunately they never last long... a common
issue is hairline cracks on the flat caps.
I've also had UHF Micor receivers with differing sensitivites in the 447 MHz
area ... everything from -100 dBm to -118 dBm... and lots in between. No
idea why.... won't tune any better no matter how expensive the
communications analyzer and complete tuning was... by the book or a la
carte, if she tuned -110 dBm best, that was it. LO injection appears in
spec. Any suggestions out there?
If you have lost the tripler, but your PA still works, you may want to find
an old UHF HT... improve the heat sink, get 2W out of it, and drive the PA
directly.
Good Luck and '73,
RFdude
----- Original Message -----
From: "Glenn Little" <>
To: <[email protected]>
Sent: Sunday, January 20, 2002 5:09 PM
Subject: Re: [Motorola] UHF MICOR Base
> 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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> >-
> >|
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> >
> >
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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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>
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