If you have been reading this blog for any time, by now you know three things:  first, I'm fairly utilitarian when it comes to design -- how something works is more important than how it looks.  Second, I am skepical of marketing claims, especially when they are applied to consumer products for digital TV.  And third, I'm a guy -- which means that I love to take things apart to see what's inside (sometimes I even get all the parts back together again!).  So when I spotted a "low profile indoor/outdoor amplified HDTV antenna" from a major electronics chain sitting in the corner... well, you can guess what came next.  I'll skip over the manufacturer's name -- not to protect them, particularly, but because I have seen essentially the same product with different plastic cases sporting different "name" brands.  The reality is that only a couple of companies actually make this stuff, and none have names we would recognize in this country.

You wonder, dear reader, am I really going to destroy a $55 piece of HDTV electronic wizardry, complete with universal mounting bracket that is perfect for apartments?  You bet!  Besides, the thing doesn't work anyway -- it was dead, right out of the box.  Might as well get something useful from it!  Here's what it looked like, pre-op:

Hmmm... are the grey things on the side are part of the pickup elements, maybe?

Nope.  Just plastic trim to hide the seam between halves of the casing.  Let's press on and cut the case open -- what's to lose (other than a finger or two)?

Well!  That was not at all what I expected to find -- I was assuming it would be a loop antenna, but this is a single driven rod with a ground reflector rod... in effect, half of a Yagi with no director elements.  Let's grab a screwdriver and get a closer look.

Say... if this is amplified, where's the amplifier?  All I see here are passive components, and one of those coils is squished down so it can't possibly be at its designed value... maybe on the other side?

Lots of surface mount parts here, but still nothing that looks like an amplifier... no, there it is:

Looks like a tiny amplifier after all, surrounded by some atrocious soldering -- especially on the antenna rods.  In fact, if you look closely at the amplifier's leads, you see that there's an errant blob of solder between two of the wires, which is very likely why the thing didn't work in the first place.  (Sorry, my camera doesn't focus close enough to show that manufacturing faux-pas.)  Speaking of solder, I notice that this was assembled with old-style lead/tin solder -- it's soft and has the typical dull gray look, not the shiny silvery color of lead-free solder.  Apparently this product is only sold here, not in Europe where lead-based material has been banned for most electronics.

Okay... what can we tell from looking at this?  For one thing, the manufacturer claims that the antenna covers from channel 2 (47 Megahertz) to channel 69 (890 Megahertz)... but they never say how evenly it covers this range.  Based on the lengths of the rods and their distance apart, the best response will be around 550 Megahertz, channel 27... and from a theoretical standpoint, it will have, at most, just shy of 3 decibels of gain.  As you tune away from that sweet spot, the gain will be considerably less, actually below zero.  It will also be somewhat directional, though not enough to be terribly useful.  So we start off with a rather poor antenna that doesn't really discriminate between the signal we want, versus reflections from other directions that we need to avoid.

What about the amplifier?  My paperwork says it has 18 decibels of gain... and a noise figure of 6 decibels.  So we're taking a marginal signal, adding a lot of noise to it (a good amplifier will have a noise figure between 2 and 3 decibels), and making the whole mess stronger.  But we lose a lot of it (I measured about 6 decibels of loss) in the power inserter.  Basically, our $55 box could give us an ideal net gain of about 15 decibels at best, and probably less than half of that over most of the band.  Plus it's adding all that noise that your TV or converter has to sort out from the signal... so in real terms, this really isn't much better than a pair of rabbit ears.

But isn't this the best of the breed?  Isn't this a special design for HDTV?

Not hardly -- this is merely another instance of cobbed-together junk assembled in a fancy case with lots of hype on the outside of the box.

Often the best solutions are also the simplest. Take a look at several "real" UHF antennas -- for instance, the Channel Master 4228, the Winegard HD8800, or the Terrestrial Digital DB4.  None of the three have an amplifier, yet each provides 12 decibels of gain across the band.  All of them are directional enough to focus on the signal you want, and minimize interfering reflections.  And none of them add noise to the signal.  Best of all... all of this real-world performance costs about the same as that Chinese piece of plastic-fantastic.

So what is to became of that antenna, now that I've cut it apart?  Well, I suppose I can always make the mounting bracket into a pencil cup... might as well get something useful for all that money, after all.

-- Jeff