Amplified Antenna Question

[Kenkong586]

Is there a difference between buying an amplified indoor antenna and hooking up a drop amp to a standard indoor antenna?

[Jim5506]

They both amplify all the stray reflections and garbage you usually get with an indoor antenna.

[Scott in FL]

I'm not sure what you mean by a drop amp.

An amplified indoor antenna is an indoor antenna with an pre-amp built into its enclosure. It has the benefit of putting the amplifier as close to the antenna as possible, sometimes taking advantage of the most efficient match between the antenna and pre-amp's first stage.

An indoor antenna with a pre-amp attached to it is essentially the same thing, with a bit of loss contributed by the balun or cable (but not much, as long as the cable is kept short) between the antenna and the amplifier.

The important thing is: an amplifier can not increase the gain of an antenna. An amplifier can only be used to make up for any loss after the amplifier. A pre-amp can't "pull in" distant stations. So I really don't understand why they even sell amplified indoor antennas.

As far as reception is concerned, the carrier-to-noise ratio (C/N) is the most important parameter, and it will always be highest at the antenna. An amplifier can not increase the C/N, because it amplifies the carrier and the noise equally. So the ratio doesn't improve. In fact, the amplifier's noise floor contributes to the noise, therefore degrading the C/N. That's why the most important spec for an amplifier is its noise figure. In short, an amplifier can only degrade the C/N ratio.

So why use a pre-amp? If the cable length from the antenna to the tv is long, or the signal is split, this adds loss. If there is too much loss in front of the tv tuner, then the tv tuner's noise floor contribution will be significant. But if the overall level (C as well as N) is high, then the tuner's noise floor contribution will be insignificant. So a pre-amp is useful at the antenna to compensate for loss after the amplifier. Outdoor antennas in fringe or near-fringe reception areas are a good example. The overall C and N levels will be low, and the cable run into the house will add loss, so a pre-amp can be used to increase the C and N (but not the C/N ratio) so that the tv tuner's noise floor does not contribute excessively.

Sorry for the long post, but I hope it helps.

[Kenkong586]

I'm not sure what you mean by a drop amp.

An amplified indoor antenna is an indoor antenna with an pre-amp built into its enclosure. It has the benefit of putting the amplifier as close to the antenna as possible, sometimes taking advantage of the most efficient match between the antenna and pre-amp's first stage.

An indoor antenna with a pre-amp attached to it is essentially the same thing, with a bit of loss contributed by the balun or cable (but not much, as long as the cable is kept short) between the antenna and the amplifier.

The important thing is: an amplifier can not increase the gain of an antenna. An amplifier can only be used to make up for any loss after the amplifier. A pre-amp can't "pull in" distant stations. So I really don't understand why they even sell amplified indoor antennas.

As far as reception is concerned, the carrier-to-noise ratio (C/N) is the most important parameter, and it will always be highest at the antenna. An amplifier can not increase the C/N, because it amplifies the carrier and the noise equally. So the ratio doesn't improve. In fact, the amplifier's noise floor contributes to the noise, therefore degrading the C/N. That's why the most important spec for an amplifier is its noise figure. In short, an amplifier can only degrade the C/N ratio.

So why use a pre-amp? If the cable length from the antenna to the tv is long, or the signal is split, this adds loss. If there is too much loss in front of the tv tuner, then the tv tuner's noise floor contribution will be significant. But if the overall level (C as well as N) is high, then the tuner's noise floor contribution will be insignificant. So a pre-amp is useful at the antenna to compensate for loss after the amplifier. Outdoor antennas in fringe or near-fringe reception areas are a good example. The overall C and N levels will be low, and the cable run into the house will add loss, so a pre-amp can be used to increase the C and N (but not the C/N ratio) so that the tv tuner's noise floor does not contribute excessively.

Sorry for the long post, but I hope it helps.

Thanks for the info. I live in an apartment/condo that has an antenna mounted on the building attached to mine, so the run from that antenna to my place is a nice distance. I just put drop amp because that's what it says on it, I know it as a pre-amp but thought I might be wrong. I have this amp because the wiring in the buildings is old and the Comcast Digital signal I had was horrible and causing tons of break up so they provied me with a 4 out pre-amp @ 7db. It helped with the cable and has helped with my OTA reception as well. I tried using the amp on a standard indoor antenna and it helped, but not much. I'm in an area that antennaweb shows as needing a small directional antenna for OTA reception. I've been messing with the OTA reception for months and I think I finally have it just right. The weird thing is that reception (split 2 ways) is affected by where and how the amp is placed. Can you explain to me why that matters? Example being I had to slide the amp along the floor to the right until I received a stable/stong enough signal from my NBC affiliate. The amp has to be in the floor and set in a certain position. So again, can you explain why that effects my reception?

[Scott in FL]

When the placement of an amplifier and cable affect reception it's usually caused by the shield of the coax acting as an antenna. That might be what's happening. The other possibility is the coax leading away from the antenna can affect the antenna's reception. The amp might affect it also. If you're using an indoor antenna that might be what's happening. If you're using the antenna on the building attached to yours, then I have no idea.

Sounds like you have a distribution amp which usually have higher noise figures than pre-amps and not too much gain. They're helpful in overcoming the loss of the splitter at the amplifier's output.

If the overall level out of an indoor antenna is too low for your tv tuner then an amplifier will help, but usually the C/N is too low as well.

It sounds like you have something that works. I'm not really sure why the amplifier's placement affects your reception though.

[eakes]

I would strongly expect that the coax is no longer connected to the antenna -somewhere it is broken. Thus the coax is actually the antenna. Moving the amp around on the floor also changes the position/location of the coax vis a vis the OTA signal which alters the received signal to the set.

You would likely get better results with rabbit ears for VHF or a simple loop antenna for UHF. A long piece of wire strung around the room can also work. I usually use a piece of zip cord (electrical lamp cord wire), separate the two wires at the 'antenna' end move each piece individually and thumb tack to the wall where I get a good signal.