HTNut

Don_M

Nosiree, none whatsoever. The FTC regulated power claims in stereo equipment for a while back in the 70s and 80s, but never got around to promulgating antenna-testing parameters. No standard-developing organization (IEEE would be the likeliest candidate) has ever issued any kind of guidance, either. It's all left up to the makers.

Each manufacturer sets their own procedures for determining range, so the claims are valid only within each product line. Evaluating range claims of competing products against one another, OTOH, is like comparing apples to oranges. The difference between a CM 4221 (45 miles) and a CM 4228 (60 miles) has some meaning because it's safe to presume both models were measured using the same yardsticks. But a comparison of the 4221 claim with that for, say, the DB4 (55 miles) isn't valid.

TonyT

alywas wondered that myself. There should really be some independant studies done to verify or establish real numbers. I'm sure in a perfect world, some of those antennas can receive up to 225 miles.

HTNut

Thanks for that answer Don, it's something that's always stuck in the back of my head, but never really had a chance to look up. Figured I'd ask on one of the slower days here.

My thoughts exactly.

Mr. Know it all

Digital UHF is line of sight.

In engineering terms, if you placed your transmitter antenna with a height of 100 m above average terrain in the middle of the ocean, the horizon distance is 35.7 km. Thus an observer on a beach can see the tower as long as it is not more than 40.35 km away

Anything beyond the horizon and you have a hard time receiving the signal.

Analog VHF was like sound vs light.

If you make a sound, it will go through buildings, around corners, down holes - valley's, and up one hill and down the next.

Digital UHF is like a pin point of light. It does not go up one hill and down the next and it does not go down a hole when you shine the light into the air.


Heavy rain and snow also affect microwave reception.

The earth is round and eventually the beam of light, UHF tv the beam will no longer touch the earth but go up into the sky.
Here is some information concerning line of sight and how it effects TV
http://www.softwright.com/faq/suppor...re_values.html

http://www.ian-ko.com/ET_Surface/Use...Discussion.htm

http://en.wikipedia.org/wiki/Horizon

Mr. Know it all

on 6/12/2009 most all analog VHF transmissions stopped by 11:59 Pm.

At approximately 11:45 AM on that day, several large transmitters in Pennsylvania shut down their analog transmitter.

At that time, using a Winegard 8200U antenna and a run of about 50 feet of quad shield RG 6 wire and 50 feet of plain RG 6 tv cable wire and no amplifier.
I was able to receive as many as 3 stations at any one time on any one channel from 2 - 6 analog by just turning the antenna rotor.

The furthest was a toss up between a station in Detroit Mich and Boston Mass.

Several stations from West Virginia and Ohio also came in that morning.

In Pennsylvania that was a one time occurrence and will never happen again in my lifetime.

All stations had a semi clear - watchable picture and clear analog signal.

Piggie

To take this to the next level even the db ratings can't be believed.

Lets assume the db gain ratings on the antennas are all the same. Some manufacturers use dbd and some use dbi. Where dbi = dbd + 2.15, rating an antenna in dbi inflates it's ratings while remaining legally correct. In my opinion any company that used dbi is not to be trusted. Moreover I like dbd because that is compared to a real world antenna a dipole, similar to your rabbit ears spread out horizontally which is dipole. The i in dbi is an isotopic radiator, an imaginary point source that receives or

Here is a simple and advanced paper on dbd vs dbi
Field Intensity Units

----------------

Well that is a perfect world. They all don't use the same testing ranges, and they all have marketing departments. So you can't just believe ratings, you just about have to know antennas well enough to know about how much gain you get if you have x number of elements arranged in a certain way.

Now some companies you can trust more than others. I have found AntennaCraft and Winegard to be the most consistent with their db numbers and use dbd. But I can quote from both companies dbd ratings on some models that absolutely can't be true in both directions for it's not always exaggerating.

However overall even though Channel Master uses dbd I find their gain figures high over all.

But the worst of the worst is Antennas Direct. Not only do they use dbi but always take any of their claims with a ocean of salt.

But then everyone of those companies makes at least one good antenna and every one of them make bad antennas.

There is no pattern. I have the advantage of playing with antennas for 30 years seriously on at least a weekly basis.

__________________
The more I understand, the less I know.

Piggie

I watched it also from Florida. There was a strong E-Skip that day that could not have happened at a better time to see what several of us saw. In Florida that day as locals shut off, we were seeing stuff out of the mid west on low band analog.

__________________
The more I understand, the less I know.

Eureka

There are exceptions to this, called "knife-edge refraction".

I know of folks getting UHF perfectly, 65+ miles from the transmitters, with a huge hill in the way, about ¼ mile away. Their reception scenario is almost identical to this situation. Google Earth maps, TVFool and antennaweb.org all show no signal at the addresses. They have tried VHF-Highband antennas all over the yard and at a many many different heights, but can not get VHF to make the trip. The UHFs are all received with only a 4221 4-bay and 7777 preamp.

YMMV (and will).