I've got a UHF GR1225 45 watt repeater that is programmed for continuous duty at 25 watts and that has the built-in Celwave duplexer rated up to 50 watts. I've heard a lot of good comments on this repeater and took the advise of setting the output at the lower wattage for continuous duty. I'd like to use the GR1225 as an exciter to drive a 50 watt amp that is rated for continuous duty. I am licensed to operate at 50 watts and would like to find something that can be used between the TX source and duplexer. Is this increase in power worth my trouble?? or should I just be satisfied at the lower wattage? Will I notice any difference from 25 to 50 watts output?
Thanks for your input
Repeater Amp Question...
Moderator: Queue Moderator
Its very hard to notice a 3 dB difference. Its really not worth the trouble. If you really want higher power, go to hardware that is really made for continuous duty at high power (Micor, MSR, Quantar, etc). Most people will not recommend adding an "external" amp to the setup you describe.
I am betting even at 25 watts you GR gets REAL hot. Spend a small amount on muffin fans, or trade up to better hardware.
I am betting even at 25 watts you GR gets REAL hot. Spend a small amount on muffin fans, or trade up to better hardware.
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MSS-Dave
- Posts: 770
- Joined: Mon Jun 30, 2003 6:02 pm
- What radios do you own?: Harris XL200M. XPR7550E, NX300
Speaking from LOTS of experience of changing out PA's toasted by running at high power, run it at lo power (and check it at the radio, not at the duplexer output..), don't exceed 25 watts output. If you have the later power supply with the fan control switch, make sure it's on continuous. If you don't, wire up the fan direct to the power supply to bypass the thermistor control.
A much better alternative to your power problem is to increase the gain of the antenna. You will see a night and day difference between, say a short stick like a 0 or 3 dB Maxrad or Antenex and a big stacked dipole (DB 420) or fiberglas stick like a PD 201 or bigger like a PD 455. Your gain will work on receive and transmit. Of course, there will be issues with using a big antenna like costs, mounting considerations and your desired coverage area.
Dave
A much better alternative to your power problem is to increase the gain of the antenna. You will see a night and day difference between, say a short stick like a 0 or 3 dB Maxrad or Antenex and a big stacked dipole (DB 420) or fiberglas stick like a PD 201 or bigger like a PD 455. Your gain will work on receive and transmit. Of course, there will be issues with using a big antenna like costs, mounting considerations and your desired coverage area.
Dave
If you have ever seen a serious communications receiver, like the ICOM R7000, you will see a received signal strength meter (sometimes known as an "S Meter"). The lower end of the scale is numbers from 0 to 9. Each of the gradations represents a 6 dB increase in received signal strength. So increasing your power would have the effect at any given receiver location of increasing the needle on this meter by one half of one gradation. Not much.
I second the recommendation that you spend your time and money looking at antennas, feedline improvements, and site improvements.
I second the recommendation that you spend your time and money looking at antennas, feedline improvements, and site improvements.
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raymond345
- Posts: 268
- Joined: Sat Sep 22, 2001 4:00 pm
We need input on location and height.
we need to know what model the duplexer is?
what the feed line and Lenght are?
What do you have for an antenna?
What height is the antenna.
This helps with good replies.
Did anyone do a HAAT calculation?
what the feed line and Lenght are?
What do you have for an antenna?
What height is the antenna.
This helps with good replies.
Did anyone do a HAAT calculation?