[Motorola] UHF MICOR Base
[email protected]
[email protected]
Sun, 20 Jan 2002 17:39:20 -0600
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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> >| [email protected]
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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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