Now that I am home from the hospital I can respond a bit better. The amp does fine without the duplexer inline. Full power and it follows the Mirage chart. But I had a thought (that's SCARY) I pulled out my seldom used MFJ 259 and dialed in my output. I plugged it into the duplexer TX side and noted that it reads 39 ohms. I disconnected the remaining two cans and attached a dummy load to the output of the can and still read 39 ohms.
I'm not sure what conclusion to take from this. I mean, low tech! To your question about tripping, the amp has a relay when activated that deactivates when the SWR/Load light illuminates. One can then read the exciter power on the Mirage meter. Yes, it does not fault with a lower exciter level. We never intended to run the amp beyond roughly 40%. Thank you for your best wishes re: my daughter. She has had a tremendously bad week. The high dose chemo has burned her body and worse that I won't share. But she's a sick little 8 year old. http://princessrachael.com --- In [email protected], "Jeff DePolo" <j...@...> wrote: > > > The grungy audio isn't related to the amp. > > Yes, I know, you said that. My question was whether the grunge was there > whether or not the repeater transmitter was keyed. > > > The TKR may be turned down to 20-30 watts and not trip the > > amp. > > By "not trip", do you mean "not key" or "not cause the amp to fault"? I'm > guessing the latter. What power output do you measure at 20-30 watts drive? > > > > The amp may easily be made continuous duty by driving it > > at a lower level and adding fans and blowing on it from an > > inch or so away, or by sucking on it. > > For the heck of it, I looked at Mirage's specs on their web site. They have > a handy-dandy chart showing power in to power out. They're showing that > with 25 watts of drive it puts out 165 watts. Doubling the drive to 50 > watts, it puts out 200 watts. In other words, a 3 dB increase in drive is > yielding only a 0.8 dB increase in output. That tells me you're way into > saturation at 200 watts output. Now, saturation in class C is generally "a > good thing", but that's kind of pushing it. Looking at the power saturation > profile, it seems to me that somewhere in the 150-175 watt range is really > where that amp would seem to want to be run. And that's based on the > intermittant mobile/HT kind of use it was designed for. I think you're only > asking for trouble trying to run that amp continuous duty at 20-30 watts of > drive no matter how much forced air cooling you push through the fins. > > > We know that the repeater, amp and antenna play nicely and > > show a 1.1:1 SWR. It's just the duplexer and it appears that > > the tuning was not done based on the reference I was given > > earlier. > > But you said that the VSWR from the "amp to the duplexer shows 1.1:1" and > "the cans are tuned right on the money", so why do you think the duplexer is > the problem? > > > Yes, it's a G6-144 and I typed in a state of near exhaustion. > > I'm living in a children's hospital with a seriously ill daughter. > > My best wishes for your harmonic. > > Again, without being there with a spectrum analyzer, it sure sounds like > your Mirage is off wandering in the weeds. There's more to building a > repeater-grade amplifier than just being able to make gobs of power... > > --- Jeff WN3A >
