[Motorola] UHF MICOR Base
Jim
[email protected]
Sun, 20 Jan 2002 16:29:36 -0800
Great info...
I did not tune the circulator in my Micor repeater....I obtained full output
without tuning it. My repeater was a 450-470 MHz model.
73
Jim W7RY
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Sunday, January 20, 2002 15:39
Subject: Re: [Motorola] UHF MICOR Base
| Glenn:
|
| There are several tuning steps that you can take that should help
| the radio.
|
| Regarding the tripler/amp, it requires a certain minimum power
| before it will work. There must be something that has killed the output
| of the exciter or maybe there is a loose connection or something.
|
| As Jim suggested, you can tune that first prefilter. Sweat the metal
| cover off and tune. I did not use a tracking generator or anything, I
| just tuned for maximum output out of the filter. I used a couple
| of IFR -1000 to peak. Mine were on the very end of the tuning slugs.
|
| The power will all of a sudden just appear as the driver comes up
| to power.
|
| The circulator can be tuned also, but you have to be a little careful
| about it. I doubt that the VHF antenna "ruined" the circulator. But
| here is what I did. I carefully measured the location of the six
| capacitors in the circulator, marked the cover, then drilled holes in
| the cover. The tuning will change when the cover is put on the
| circulator,
| so it is best to try to tune it with the cover on. I did not find the
| holes
| affected the operation. If you are concerned dust will get in the
| circulator-
| isolator (perhaps critical if in an elevator room where carbon dust
| is prevalent), you can put tape across the holes.
|
| I tuned the circulator-isolator by putting an IC-27 turned down to
| 10 watts on the frequency in question, then tuned the input
| and output capacitors (both legs) for maximum throughput. I then
| turned the isolator-circulator around and tuned the two capacitors on
| the load for minimum power on the input. This means that most of the
| power is shunted to the dummy load. It has been awhile, but
| it seems to me that I could touch up the reverse by also tuning
| the input and output capacitors. I did this a couple of times
| to get acquainted with it, then finally settled for a tuning setting
| where it seemed to have about 1.0 - 1.2 db forward loss and
| about 30 db isolation in reverse. My Micor was a 470 -490
| Mhz version and it would not tune as well as a 450 - 470 Mhz.
| However, when it was all over with 80 watts out of the amp
| (a Mirage Repeater Amp), I was getting 40 - 42 watts out of
| the duplexer and sometimes a little more.
|
| I did touch up the isolator-circulator when I reinstalled the
| repeater, but I would not necessarily recommend this as
| the power control changes the power with differing loads. Of
| course, I guess you could put a jumper in to make the repeater
| power independent of the antenna condition, but I would
| turn down the power and not use more than 10 watts.
|
| I have some other notes about this and could probably find
| them if you still have trouble.
|
| I think the Micor is great equipment. I hope this is helpful.
|
| Micheal Salem N5MS
|
|
|
| On Sun, 20 Jan 2002 17:09:51 -0500 Glenn Little <[email protected]>
| writes:
| > 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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| >
| >
| -------------------------------------------------------------------------
| --
| > 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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