[Repeater-Builder] Low Band Micor mobile not making power
Hi all, Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. The tags on the PA cover indicate over 100 watts were once measured. Made most of the capacitor mods to the exciter, but it tunes up easy. (slugs not in wierd places). Oh, not gonna run it at full power, but wanted to make sure it was up to snuff. Thanks, Tim W5FN
Re: [Repeater-Builder] Low Band Micor mobile not making power
How much current is it pulling? At 53.7 I suspect you are well into the roll off on the output low pass filter. I forget exactly how it's implemented in this case. On 3/18/2010 9:06 AM, tahrens301 wrote: Hi all, Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. The tags on the PA cover indicate over 100 watts were once measured. Made most of the capacitor mods to the exciter, but it tunes up easy. (slugs not in wierd places). Oh, not gonna run it at full power, but wanted to make sure it was up to snuff. Thanks, Tim W5FN -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] Low Band Micor mobile not making power
On Thu, 18 Mar 2010, tahrens301 wrote: Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. The tags on the PA cover indicate over 100 watts were once measured. Made most of the capacitor mods to the exciter, but it tunes up easy. (slugs not in wierd places). Oh, not gonna run it at full power, but wanted to make sure it was up to snuff. IIRC Motorola usually used about 1W at the exciter to drive the PA to full power. 1.125W (+33dBm) will put a Mitrek amp up to 125W under certain conditions. The Micor may have a tripler though. -- Kris Kirby, KE4AHR Disinformation Analyst
Re: [Repeater-Builder] Low Band Micor mobile not making power
Oops, forgot to mention that this was directly out of the amp. The filter has been removed. (I already spread out the turns, but for this I wanted to make sure it wasn't affecting the power). Tim
Re: [Repeater-Builder] Low Band Micor mobile not making power
Kris Kirby wrote: IIRC Motorola usually used about 1W at the exciter to drive the PA to full power. -- Kris Kirby, KE4AHR Disinformation Analyst Not on the MICOR line. All are 400 mW out of the exciter regardless of band. Low Band exciters usually make 600 mW, but their spec is 400 mW. UHF Stations takes the 400 mW at the VHF exciter and makes 1 to 2 watts for the PA as a function of the tripler. The UHF MICOR mobile is similar, but different. Kevin
Re: [Repeater-Builder] Low Band Micor mobile not making power
tahrens301 wrote: Hi all, Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. I'd expect to only see 75 watts out of a 110 watt PA if you only have 300 mW of drive. Low Band exciters usually have about 600 mW leaving the exciter on frequencies within original specification, and it's common to see 150 watts out of a Low Band PA. Under drive can be a bad thing. I'd look at it with a spectrum analyzer and make sure it isn't spurious because of the 3 dB of under drive. It probably isn't, but I'd check it anyway... Kevin
Re: [Repeater-Builder] Low Band Micor mobile not making power
On 3/18/2010 10:45 AM, Kevin Custer wrote: tahrens301 wrote: Hi all, Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. I'd expect to only see 75 watts out of a 110 watt PA if you only have 300 mW of drive. Low Band exciters usually have about 600 mW leaving the exciter on frequencies within original specification, and it's common to see 150 watts out of a Low Band PA. Under drive can be a bad thing. I'd look at it with a spectrum analyzer and make sure it isn't spurious because of the 3 dB of under drive. It probably isn't, but I'd check it anyway... Kevin The other thing I would do is if you have the original tx channel element, or can get one that's in the right area, like around 47-49 MHz, put that in and tune it up there and see what you get, if you didn't do that when you first got it. If it makes spec, then it might be time for some mods or something. I know someone who put a Micor mobile on 53.77. It never did make full power up there (it was good on the original freq., 47-ish), and was set to run at abt 50W I think. At that point, it was clean, and stayed cool with a fan. 53.7 is pretty high for one of those.
Re: [Repeater-Builder] Low Band Micor mobile not making power
I would run it as is if it does not overheat and look for a Syntor X they are good to go on six for full power. tom wd8chl wrote: On 3/18/2010 10:45 AM, Kevin Custer wrote: tahrens301 wrote: Hi all, Working on a micor mobile to be used as a repeater (only using the exciter/control board/PA). Was going through it, and am only able to get about 75 watts out of it with the exciter on 53.7. The exciter is putting out 0.3 watts... a bit more than most exciters I've seen, but they were high band. I'd expect to only see 75 watts out of a 110 watt PA if you only have 300 mW of drive. Low Band exciters usually have about 600 mW leaving the exciter on frequencies within original specification, and it's common to see 150 watts out of a Low Band PA. Under drive can be a bad thing. I'd look at it with a spectrum analyzer and make sure it isn't spurious because of the 3 dB of under drive. It probably isn't, but I'd check it anyway... Kevin The other thing I would do is if you have the original tx channel element, or can get one that's in the right area, like around 47-49 MHz, put that in and tune it up there and see what you get, if you didn't do that when you first got it. If it makes spec, then it might be time for some mods or something. I know someone who put a Micor mobile on 53.77. It never did make full power up there (it was good on the original freq., 47-ish), and was set to run at abt 50W I think. At that point, it was clean, and stayed cool with a fan. 53.7 is pretty high for one of those. Yahoo! Groups Links
Re: [Repeater-Builder] Low Band Micor mobile not making power
Hi All, Thanks for the info. I had made about half the recommended mods here on RB... making the mods where the tuning didn't quite make it. I'll go and make the rest of the mods see what kind of power I can get out of it. I understand about the 'reduced-power' issues, so will re-tune it as the manual states for reduced power. I think it said 43 watts was the recommended. Thanks again! Tim
Re: [Repeater-Builder] Low Band Micor mobile not making power
Well, things are starting to get muddy! Since I was having some issues with both of the exciters, I started looking closely at them, and things didn't seem to be quite correct. I asked the guy I got them from if he had an extra exciter, as one of them seemed to have some parts missing. Anyhow, he said oh, that maybe one that was setup for digital. Evidently they came from an oil company, and they were a bit 'special'. Speaking of special, the number is TLB 8164 A2 SP4. It's really acting strange when I put a reed in it, and it doesn't do well with audio either. Just wonderin' if anybody has a clue about the SP4 what it may be. Thanks, Tim
Re: [Repeater-Builder] Low Band Micor mobile not making power
On Thu, 18 Mar 2010, Tim Ahrens wrote: I asked the guy I got them from if he had an extra exciter, as one of them seemed to have some parts missing. Anyhow, he said oh, that maybe one that was setup for digital. Evidently they came from an oil company, and they were a bit 'special'. Early DVP and DES systems used a 16KHz-wide data signal. To repeat these through the repeater required re-clocking modules. That may be what you're seeing, that or a DCS(DPL)-type module. -- Kris Kirby, KE4AHR Disinformation Analyst
