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Author Topic: Offset of Repeater under 100 KHz  (Read 2923 times)
JZ10HZY
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Posts: 7




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« Reply #15 on: February 15, 2017, 04:44:22 PM »

The power output is about 25 watt max.
We are still observing the repeater since the split is too close.  If there were no other problem, we will add the power up to 50 watt max.



Don't run a GM300 at 50w.  It'll last about a week max.  Even running at 25w is a tad high.  Use an external amp rated for 100% cont duty.

What would be your suggestion for the power? If we used gm388, would it be better in using power?
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K4JJL
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Posts: 657




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« Reply #16 on: February 16, 2017, 11:06:09 AM »

What would be your suggestion for the power? If we used gm388, would it be better in using power?

GE amps usually require an exciter down around the 500mW range.  Motorolas have an intermediate PA that gets them to the necessary 7W input.  There are several other companies that make a variety of amps (TE, TPL, Henry, etc.)  Just make sure you look for something with a large heat sink necessary to make it continuous duty.  Avoid the MFJ variety.  I haven't seen one survive in service long-term.

Something like this... http://www.solidsignal.com/pview.asp?p=pa6-1fem-rxrf-ps  Pricey, but that's just an example of what to look for.

I wouldn't run the GM300 as an exciter lower than 12 watts.  The PAs get weird and spur.
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K1ZJH
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Posts: 3030




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« Reply #17 on: February 16, 2017, 07:40:01 PM »

Considering the very narrow frequency spacing, and the broadband nature of the front ends in those radios, I am surprised you aren't having desen problems. Have you tested the system to see if there is any loss of receiver sensitivity when the TX is keyed?

Pete
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JZ10HZY
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Posts: 7




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« Reply #18 on: February 17, 2017, 10:16:43 AM »

What would be your suggestion for the power? If we used gm388, would it be better in using power?

GE amps usually require an exciter down around the 500mW range.  Motorolas have an intermediate PA that gets them to the necessary 7W input.  There are several other companies that make a variety of amps (TE, TPL, Henry, etc.)  Just make sure you look for something with a large heat sink necessary to make it continuous duty.  Avoid the MFJ variety.  I haven't seen one survive in service long-term.

Something like this... http://www.solidsignal.com/pview.asp?p=pa6-1fem-rxrf-ps  Pricey, but that's just an example of what to look for.

I wouldn't run the GM300 as an exciter lower than 12 watts.  The PAs get weird and spur.

Thanks for your information, we try to find on of the PA. How about the GM 388, is it the same power output??  Coz some says that GM 388 more stronger than GM 300.
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JZ10HZY
Member

Posts: 7




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« Reply #19 on: February 17, 2017, 10:21:47 AM »

Considering the very narrow frequency spacing, and the broadband nature of the front ends in those radios, I am surprised you aren't having desen problems. Have you tested the system to see if there is any loss of receiver sensitivity when the TX is keyed?

Pete

Hi Pete,

Well, so far we did not find any problem in receiver sensitivity. 
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K4JJL
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Posts: 657




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« Reply #20 on: Today at 09:45:37 AM »

Thanks for your information, we try to find on of the PA. How about the GM 388, is it the same power output??  Coz some says that GM 388 more stronger than GM 300.

They made GM300 in 2 different varieties of power levels.  One 15W and one 45W.  You're probably thinking that the GM388 (25W) is larger than the GM300 rated for the lower wattage.

Since the GM388 is rated for roughly 20% duty cycle, I wouldn't run it much over 7W.  You may have a hard time getting the PA to be stable at that wattage, though.
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