[Repeater-Builder] Re: Mirage B-320-G as a Repeater Amp
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 Repeater-Builder@yahoogroups.com, 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
RE: [Repeater-Builder] Re: Mirage B-320-G as a Repeater Amp
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! What does the dummy load alone read? How about my other question - do you have grunge with the repeater transmitter NOT keyed (i.e. just listening on the local repeater receiver with the repeater transmitter disabled)? 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 Tried to go to the URL but it took me to some other web site and asked me to log in? Again, best wishes. I have a 1 year old and a 3 year old, they're my best buddies, I can't imagine what you're going through. --- Jeff WN3A
Re: [Repeater-Builder] Re: Mirage B-320-G as a Repeater Amp
throw away the duplexer and get another i seem to read everything you state it is fine until i plug in the duplexor inline at least if not, do you have another duplexer to try in its place Marcus On Sat, Aug 14, 2010 at 1:29 PM, Jeff DePolo j...@broadsci.com wrote: 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! What does the dummy load alone read? How about my other question - do you have grunge with the repeater transmitter NOT keyed (i.e. just listening on the local repeater receiver with the repeater transmitter disabled)? 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 Tried to go to the URL but it took me to some other web site and asked me to log in? Again, best wishes. I have a 1 year old and a 3 year old, they're my best buddies, I can't imagine what you're going through. --- Jeff WN3A
RE: [Repeater-Builder] Re: Mirage B-320-G as a Repeater Amp
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
[Repeater-Builder] Re: Mirage B-320-G as a Repeater Amp
The grungy audio isn't related to the amp. The TKR may be turned down to 20-30 watts and not trip the amp. 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. I like to use two 6 fans and they keep the amp cool. The 320 has its own fan on the bottom that pulls air in. 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. We tuned for maximum output and isolation. 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. The LMR will go when the antenna is replaced with either a DB-224 or a Telewave before first snow. As I've indicated time is not on my side at the moment but I have time to ask questions of more experienced repeater operators and learn whiloe sitting here. --- In Repeater-Builder@yahoogroups.com, Jeff DePolo j...@... wrote: Before adding a Mirage 320 our TKR 750 was putting out 50 watts into a 6 cavity Wacom WP-642 at the cost of 2-3dB loss on TX (as the spec sheet said.) The cans are tuned right on the money and the Hustler G5-144 fed with LMR-400 is 1.1:1. I'm guessing that's a G6...? This has worked for over a year just fine (except for grungy weak signal audio.) Is that grungy weak signal audio with the repeater transmitter keyed, unkeyed, or both? Now add the Mirage B-320-G 200 watt amplifier. Egads. If you have problems without a high-power amplifier, seems only prudent that you should deal with those issues first... Unless I'm mistaken, the B-320G isn't a continuous-duty amp, is it? But as soon as we tune it all up and connect it to the duplexer the Mirage SWR/Drive trips and the amp goes to sleep. A SWR meter between the repeater and the amp shows 1.1:1. The amp to the duplexer shows 1.1:1. How do you know the VSWR is 1.1:1 between the PA and the duplexer if the amp shuts down before you can measure it? In other words, how do you know the amp isn't shutting down because it's going spurious, resulting in high reflected power coming back from the duplexer, tripping the VSWR overload? At the risk of disparaging a particular manufacturer in a public forum, my experience with Mirage repeater amps has been horrific. I wouldn't expect the results of one of their non-repeater amps pressed into repeater service to be any better... Before we go spelunking into the dark underworld of making your Mirage play nice, let's work on fixing your original noise problem. Start by answering the above questions and we can go from there... And for the love of John, get rid of the LMR400 before this turns into a Holy War. --- Jeff WN3A
