Use of an antenna amp. Signal weak without it, overloaded? with it, what to do?
I have a moderately large outdoor TV antenna in my attic.
On its own, it gets all of the Baltimore TV stations, but not DC.
So I bought an antenna amp. AntennaCraft 10G212 30 dB High Gain TV/FM Mast-Mounted TV Antenna Signal Amplifier
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though FTR I was dissatisfied with their customer service.
It has a gain control, which I set all the way at the top, so I wouldn't have to go into the attic again. but later I actually read the instructions and saw that I could (should) put 1/2 of the amp close to my TV**, so now it's on the floor in the bedroom.
Now I can get all the Baltimore and Washington DC TV channels, (except sometimes I can't get one or two of them) but sometimes channel 11 and
11.2 (Baltimore channels) don't come in, the screen is blank, or it goes from good picture to blank for a variable length of time, and then back to a good picture, then blank, and so forth. . I presume the tuner is overloaded, now that there is an amp, since those channels worked fine without the amp. I turned the gain down half-way and now down all the way and it still happens. There are several programs on 11.2 that I record, and I don't know until later that I have not recorded anything.
Am I amplifying the signal too much? Somewhere I have a signal attenuator with co-axial connectors and an adjustment knob that I could put between the amp and the DVDR. Should I try that first?
Or should I just buy a better amp? One that can be adjusted lower? Any suggestions of what to buy?
Thanks.
**FWIW, not actually using a TV for the tuner. Using a Philips digital DVDR with hard drive, with a digital tuner. Successfully running several analog TVs off of that.
You are in effect mixing strong signals with weak signals, causing cross-modulation and reception failure. Antenne amps are very "good" at that......... Get a separate areal for DC, one with high gain selectivity, to pull in those channels, and try aiming in such a way as to minimize the strong local, nearby ones.
Is your antenna on a rotator? Can you adjust its pointing direction on a per-station basis?
Reading between the lines, it looks to me as if this is actually two amplifiers - a fixed-gain 15 dB amplifier which goes up at the antenna, and a variable-gain amplifier in the "indoor" portion.
Unfortunately, I suspect that you may be dealing with a signal overload problem *before* the signal reaches your TV tuner. It's quite common for these consumer-grade TV amplifiers to have very poor strong-signal-overload resiliance. If you've got several strong local stations in your area, the first-stage amp (near the antenna) could very well be overloading and distorting. The distortion will cause intermodulation between these strong signals, and the intermodulation products are very likely to "bleed into" numerous stations and degrade the signal quality. Once this happens, your signal quality is ruined... turning down the gain of the second-stage "indoor" amplifier won't help... you can't make pig out of sausage :-(
Also, these cheap amps often have a high "noise figure" - the amp transistor or MMIC introduces enough noise of its own to degrade the signal significantly. The AntennaCraft is rated at under 4 dB VHF and under 3.5 dB UHF, which means that its output noise is roughly twice that of an unamplified antenna. Not terrible, but not state-of-the-art.
The "gotcha" about amps is that it's very likely that the tuner in your DVR has a *lower* noise figure in its front end, than any amplifier you can add at an affordable price. If you amplify the incoming signal, and then run it right to a single device (e.g. DVR), you actually aren't doing the DVR any favors. This is especially true for any amplification you do right down next to the DVR.
If it's possible, I would recommend that you address the problems "earlier in the chain". Get your antenna up out of the attic, mount it on a mast (as high as you can safely arrange, with proper guy-wiring) and try different aiming directions until you find the one which works best in practice. Hint: this might *not* be aiming directly towards the most-difficult stations.
Antenna height makes a huge difference with TV reception of "fringe" stations. The antenna can "see further" over the horizon, and by getting it up out of the "ground clutter" you will eliminate or reduce a lot of signal reflections ("multipath").
Unfortunately, since you're using a DVR which changes channels automatically, you may not be able to use one of the best "un-secret weapons" for TV reception - an antenna rotator. The higher the gain of the antenna, the more sensitive it will be to aiming.
If you do decide to use an amplifier, you're going to want one which is extremely resistant to overload, *and* has a very low "noise figure". A "professional-grade" CATV amplifier module might do the trick... or, it might end up boosting the strong local signals so much that they overload your DVR's tuner and you'd be right back where you are today.
So, I think your best bet is the classic one: as good an antenna as you can afford, mounted up as high as you can manage, wired down to your DVR with the lowest-loss 75-ohm coax you can locate (quad-shielded satellite-grade RG-6, rather than cheap RG-59), and aimed as well as possible. Since you're feeding the signal only to one device (the DVR) you won't need a splitter, hence you won't need amplification to overcome losses in the splitter.
This doesn't work well if you're recording several stations at once.
I went thru this hassle back when they converted the USA to ATSC. None of my stations are fringe. Mostly in the same direction.
I found that the ability to receive a given channel was far more sensitive to signal quality than signal strength.
One simple measure of quality is the flatness of the "bart's head" display on a spectrum analyzer. This appeared to be a function of multipath. But there does seem to be a relationship between signal strength and the ability of a tuner to resolve a low quality signal. I ended up with an amplified splitter and four separate attenuators to four tuner cards. Careful alignment of the antenna, careful adjustment of the attenuators and restricting the poorest quality channels to the best tuners gave me a system that mostly worked most of the time.
The situation improved over the years as tuners got better. I also moved the antenna further from the big metal building in my neighbor's yard. I no longer need the separate adjustable attenuators...but the whole system is right on the edge of not working.
Yes, it has one of those, and I switched it on and off while watching the picture, and I saw no change. However I didn't do this while watching the picture on either of the two stations that don't work well!
That was my intention with this antenna. And I used antennaweb.com or the other similar site to see what direction the DC stations were, and they were pretty much in the same direction, and by luck, my house points that way.
This is the antenna I have. Winegard HD 7696P High Definition VHF/UHF HD7696 Series TV Antenna (HD7696P)
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With over 80% of Local TV markets being on High Band VHF and UHF, the HD-769 Series has been specifically tuned for channels 7 - 69. Estimated Range: 50 miles VHF & 40 miles UHF Great mid range Directional antenna with an aproximate beam width of 30 degrees
Estimated Range: 50 miles VHF & 40 miles UHF Great mid range Directional antenna with an aproximate beam width of 30 degrees
*Note: This antenna can receive stations 2-6 in most areas due to the fact they are generally broadcast on higher unused UHF or VHF frequency numbers in the area. Our techs can verify this with your zip code information
************ Yeah, but maybe 11 is broadcast on a lower UHF Frequency. I have to check on that.
************
Active Elements: 41 UHF Elements: 26 VHF Elements: 15 Boom Length: 110.75" Maximum Width: 36" Element Diameter: 3/8" Turning Radius 70.6" Shipping Weight 10.8 lbs.
The local stations, at least channel 11 that I can't always get, is about 90^ in a different direction from the orientation of the antenna. I thought that would also make the signal weak, but this one station, probably the strongest in Baltmore (I got that idea somewhere) still seems to be overloaded.
Do they really do this? Especially for only 30 dollars**. I had assumed there was just one amp, at the antenna, and the indoor part was the power supply (since it plugs into the wall) and a rheostat.
**I was willing to spend more, but there were so many I coudln't make up my mind.
I have no place to keep a ladder and have to borrow one every time I need one. Plus I'm 68** and fat, and while I might have put an antenna on the roof 10 or 20 years ago, I know I'm not going to do it now.
** I don't feel old and I've managed to lose some of the weight, but still. And oh yeah, I have osteoporosis, because of hyperparathyroidism. Surgery is scheduled for 9 days from now, and the osteo may reverse itself without more drugs after they cut out the little benign-but-stiill-fouling--me-up tumor. No bigger than a plain M&M or a bean in Heinz baked beans. But the osteo hasn't reversed yet and might not do so completely. I think only one in a 1000 people get this. All this means I can't risk breaking a bone. (Though I've fallen twice in the last 6 months without breaking anything.)
I did start with the direction of the station and tnen tried re-aiming it, by bringing a TV into the attic, and using my RF relay and the remote to change stations on the DVDR in my bedroom. It seemed to make no difference, but I didn't spend time on the Baltimore stations. It's not too late to do that, in the attic.
But this one bad station is only 10 miles away, on "Television Hill", which has all but one or two Baltimore TV stations. It's actually a hill. ;-) Two or 3 miles north of downtown, and I live west and somewhat north of downtown. .
Absolutely. The longer I have it, the more even when I'm home I don't pay attention to when it starts recording. By watching the recorded version, I can fast forward through the commercials and through the annoying guy on the People's Court.
I'd hate to spend professional-grade momey and have results no better.
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