Syncronizing 2 UHF antenae for HD TV reception

Apparently you do not, since that it not the topic here.

In terrestrial reception, the ground emits noise at about 300 K noise temperature (noise figure 3 dB), thus the receiver noise figure does not have to be that good. Receiver noise figures of 3 dB are not uncommon, thus contributing the same amount of noise as the warm earth.

These days, the main purpose of antenna mounted preamps is to compensate for the feedline (and splitter and connector) losses. Thus the preamp gain should be larger than the feed line losses. By increasing the gain with a further 5-10 dB, the receiver front end noise can be eliminated from the equation.

The gain should not be increased above this, since the generation of spurious signals goes very quickly up, either in the antenna preamp or in the receiver.

I did not find any device directly suitable for UHF TV masthead preamps. Perhaps the wide band 0.5 dB noise figure device would be nice, but it would absolutely require proper high pass (450 MHz) and low pass (850 MHz) filtering at the input, thus, the insertion losses of these filters would have to be added to the system noise figure, but still be well below 3 dB.

OTOH, for terrestrial reception, I do not see much point in trimming off the last decibel. The signal variation due to various kinds of fades can be more than 10 dB.

You'd win! Let me know where to mail the nickel and the five vintage box tops :-)

Thanks!

a rotator

Is it "antennae" or "antennas"? A pet peeve of mine I guess. May just be a US thing.?

My dictionary lists both, although at least in my experience people use "antennas" for the things that send or receive EM radiation and "antennae" for what's found on the top of insects.

Are you in the US? Do you think extra height on the antenna can help? Nothing beats line of sight coverage!

-mpm

You should go away and attempt to plug all of your ofrifii with superglue.

Just get a 2-to-1 splitter/combiner, and use two of the same length pieces of coax. Plug these antenna leads into the combiner inputs and the combiner output to the downfeed.

Good Luck! Rich

Probably not a good move. Firstly, best reception requires freedom from multipath reception (i.e. your best steering might be to null a reflection rather than to peak a signal strength). So, a 'better' antenna is not one with higher signal power, but with a well defined null direction. Secondly, a good four-element Yagi has one dipole and three directors or reflectors; two two-element antennae is not similar to a good four-element one. It's a rather small gain for the cost of multiple antennae and downleads.

There is a fairly good bargraph signal strength indicator in most modern TVs; look at it carefully, 3 dB is a TINY bit of difference.

Usually have dozens of elements and are very directional.

Off axis, reflected signals are ignored.

... Phil