divxhacker

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Aaron62

Real world comparison and results. Subscribed Divx. That background on their product picture is sooooooo cheesy.

Piggie

It fails my approval rating because it's has too high a noise figure. Anything above 3db just doesn't cut the DTV world. Numerous examples on this board alone where people ditched their old amp and bought a low noise amp that improved their reception.

ANT-1008
ANT-1008Frequency Range : 40-862MHz
Gain : VHF:18dB UHF:26dB
Impedance : 75Ω
Noise figure : ≤5.0dB
Power Supply : AC110V 60HZ AC220V-230V 50/60HZ

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Plus marketing wise that site flunks over and over for me.

Busted on this antenna

ANT-2075
ANT-2075No. of Elements: 32
Frequency Range : 174-230Mhz & 470-862MHz
Channels: Ch. 5-12 & Ch. 21-69
Antenna Gain: 7.5-8.5dB
Beam Width H/V: H 45-55/ V55-65
Front-back Ratio: 20-30 dB
Impedance: 75Ω
Antenna Length: 750mm

First 174-230Mhz are channels 7-13 but 13 ends at 216 MHz
And no those aren't the Chinese frequencies either
They are the CCIR European channels. Europe TV Frequency Table
Same with the UHF range they market.

The problem is they are marketing to the US and Canada that have different but about the same frequencies. Big deal? Well what if a US or Canadian thinks it will pick up channels 5 or 6 ? It won't. Or not buy the antenna because they have a channel 16 like I do on UHF.

There is also no way to get that much gain from a 29.5 inches. That much gain at UHF takes at least a 40 inch boom and at VHF a 60 inch boom.

More gizmo stuff.

Plus if you value your job you can still buy American antennas from Winegard, Antenna Craft. I know Channel Masters are now Chinese. Not sure about Antennas Direct, but I don't like them either except their XG-91.

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divxhacker

well, I don't have that big a budget, not without holding out my pencil cup first... (don't look in there now, there's no pencils in there, yet.)

it'll just be a quickie experiment, then back into the box it goes. When I get rid of it, I'll include the cable I'll cut and throw in one F-to-F adapter.

Looks like Digiwave didn't put much thought into the box design - it's not gonna be kept by an end-user like a treasure, would it?

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Piggie

I see I didn't get a thanks for my rave response.

The one thing it has that all amps should have is a gain control. And the gain control could be inside and outside if you want to adjust VHF vs UHF to balance them, then an over all gain inside the house. It is very possible to do, just no one does it.

Even the cheapest commercial amps have a gain control for each band. For long cable runs in particular if you cascade amps for long runs it's essential for separate gain controls because coax attenuation is not linear, and goes up with frequency.

Ok, I will bite what did it cost? I could not find a price on the web site.

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divxhacker

A quick search on eBay reveals the Canadian seller: eBay Store - satellitestorecom:
and one item:
VHF UHF HD TV HDTV ANTENNA AMPLIFIER - eBay (item 250448237791 end time Jul-19-09 19:38:26 PDT)

I wonder why their store listing shows a different VHF gain number. Typo, I hope.

Anyways, it was the most strongest best-looking and correct looking amplifier on eBay. The amplification looks better than this Australian one, which gives only 10 db per split:

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Don_M

There's your thanks, Piggie. I owe you that much: I'd taken a quick look at this thread yesterday, then got distracted. So, you got to play the "heavy" ... this time!

Still, I'm gonna do a little bit of quibbling re gain controls. I was under the impression they're not such a good idea:

This entry was posted in a blog called Plugged In: The DTV Switch by Jeff Hartman, chief engineer at WSYR-DT/Syracuse, NY, and a slew of smaller Central NY stations owned by the same chain. The guy usually makes a lot of sense, and his posts are very entertaining.

cowboyup4christ

digiwave stuff is real cheap but the shipping is a killer it is all Canadian stuff I have a dealership but can't afford to buy because of the shipping. their Sat. stuff does look pretty good though.

Piggie

I agree with Jeff Hartman's Rule 5 given the constraints he stated.

1) Noise level is a fixed quantity of the type of components and design of the amp.

2) Radio Shack made some 2 stage TV amps. They had a preamp on the mast powered by an indoor box inside that was not only a power supply but a small 10 db or so amp with a gain control. This is exactly I think what Jeff eludes to in no point in adjusting the gain on the inside amp in no way affects overload on the top amp.

3) Rule one of anything, fewer parts means less failures. Any technician of any kind, from automotive to electronics knows that cold.

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I should have added to make my point clear is adjustable gain at the initial mast head amp (despite the more parts to fail theory) is not into itself a bad idea, and could be adjusted to reduce overload.

But noise figure is the deal killer in this amp. 5db is way too high.

3 db is acceptable these days for DTV. For those that can't relate to the difference between 3 and 5 db, well it's 2 db, but what is 2db to someone that isn't used to thinking db?

Here is a good example of db in the real world.

Lets say you have the biggest antenna you can buy, but want more signal, so you stack two of them together to increase reception. The resulting advantage of two identical antennas over one is 2.5 db though a common combiner.

Or lets say own an antenna with a 60 inch long boom. To get 2 db more, you would need to buy an antenna with a boom 2/3's longer or 100 inches.

So if you save $10 bucks on a cheap amp, and have a 100 inch boom antenna on the roof, you just reduced the antenna to one that would have reception of one that is only 60 inches.

High noise amps are absolutely a no no for DTV.

There is no point in buying one.

That said, if you already own an older high noise amp, it may work ok for you if you have strong signals, and need the gain of the amp to over come long runs of coax.

This does beg an idea or though to you Don. Take a CM7777, it already has 2 switches on it. One for combined or separate and one to add or remove the FM trap filter.

I wonder if it would not be a good idea, since a switch is more reliable than a pot to add a switch to something of the gain and low noise of a CM7777 that drops the gain in half, if and only if that drop also gives an increase in the dynamic range of the amplifier.

The reason I add that last constraint is if you look at holl_and's evaluations of amps, even though the CM7778 has 10 db or so less gain than the CM7777, it apparently has no better dynamic range.

So I will add to Jeff's rules, that without an increase in dynamic range, there is no point in lowering the gain of an amplifier.

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Don_M

That's what I took away from his chart, too -- dynamic range doesn't necessarily have an inverse relationship to gain, so this capability must be due to something else in pre-amp design. What that might be, I can't say: I only roomed with an EE in college, I didn't major in it!

Unless you were thinking out loud here, I see little advantage to having a switch for selectable gain if it wouldn't also mean greater dynamic range. The only benefit I can imagine is that a switch might bail the buyer out in situations where a higher setting causes amp or tuner overload, but the lower setting doesn't. That's a pretty narrow circumstance that can be avoided through careful pre-amp selection.

I read a post not so long ago from a knowledgeable source asserting that a) most people who think they need an amp need a better antenna instead and b) of the few who do need a pre-amp, almost none of them need look any further than the high-input Winegard HDP-269, because its 12 dB gain was all just about any household within roughly 50 miles of the transmitters and with fewer than five TVs really needed. (He wasn't a Winegard shill, AFAIK.)

A CM 7777 makes sense in the deep fringe because its noise figure is 1 dB lower than that of the HDP-269. It's not really due to the high gain at all. That lonely little dB becomes crucial in weak-signal areas that are close to the noise floor in the first place.