Originally Posted by ProjectSHO89
But the signal I get with the PA-18 is the same as with no amp at all, so the amp isn't working as far as I can tell.
That doesn't mean the amp wasn't working, it usually means the amp wasn't needed in the first place and its installation neither harmed nor helped reception.
If it was faulty, it would have bricked your signals by anywhere from 20 -30 dB causing a loss of your weaker, distant signals. You can test this idea by hooking it up, checking reception, unplugging the power supply without disconnecting anything else, then checking to see if your weaker signals were lost. If so, the amp was working just fine.
If I were installing an amp for the first time into a previously unamplified system, I'd agree with you. But if you check the last several posts, you'll see that's not the case.
You should know I'm dividiing my OTA signal four ways, with about 50' of RG-6 cable from the antenna to any given TV. With no amp, that works out to about 8 dB signal loss (probably a bit more at the top of the UHF band), which would wipe out most of my CM-3020 antenna's gain. In that environment I can receive most full-power stations with some dropouts, but not all, and low-power stations are effectively nonexistent.
I had been using one of the old Channel Master CM-7777 preamps, which cleared up full-power reception and also allowed me to receive all low-power stations in the DFW area. Unfortunately, last month this preamp failed, and I discovered the new version of the CM-7777 was much less suited to my needs (too much gain, way too much noise). So instead, I replaced it with an AntennaCraft preamp with variable gain and a somewhat higher, but still reasonable, noise figure. (Model 10G212 I think)
As I've explained before, the AntennaCraft preamp works reasonably well. However, it's not quite as good as the old CM-7777: a few weak low-power stations no longer come in. So when I learned that Antennas Direct also makes reasonably inexpensive preamps, and that they advertise a better noise figure than even the old CM-7777, I decided to try one (the PA-18) just to see if it'd bring back those weak stations.
Unfortunately, the PA-18 acts as if it's not present at all. I get the same reception as with no preamp. Since the AntennaCraft preamp, in contrast, does
significantly improve reception, I can only conclude that my PA-18 doesn't work, or at least, doesn't work well enough to notice.
I admit that I'd expect a non-working preamp to attenuate the signal, as you said. My CM-7777 did attenuate the signal when it failed, and I'm surprised the PA-18 doesn't seem to do that (at least not much; certainly not 20-30 dB). However, as far as I could tell, unplugging the power had no effect.
I did test the power injector. It puts out 15 volts. And since the working 10G212 also uses a power injector, I know the cable will carry power up to the preamp OK.
My best guess is that there's a break within the amp that prevents power from reaching the transistors. It might actually be a simple fix, like a cold solder joint; but the box is sealed so I'll leave more detailed testing to someone else.Edited by JHBrandt - 2/7/13 at 8:43am