View Single Post
Old 16-Sep-2015, 11:15 AM   #2
4.6 Explorer
Junior Member
Join Date: Jul 2015
Posts: 8
Originally Posted by rabbit73 View Post
We need some more information to make a good analysis.

Please tell us the town or city where you are located and give us a tvfool report using your exact address (which will not show) or coordinates (which will be shortened) using this:

I live in Hamilton Ontario. As seen below CHCJ is the one western transmitter I'm after. Its Tx Total distance: 4.49 km (2.79 mi) miles away but the escarpment is 850 meters (Google maps).
On my north are all the Toronto stations; no issue there. I even pick many of those up off the side of my eastern facing two 8 bays

If you have a problem with that page determining your location, use the interactive map browser with exact coordinates, or move the cursor to you antenna location and generate a report by clicking on Make Radar Plot >> at the upper right corner of the map and give us the URL link in bold type near the top:

Does that mean you have combined the two 8-bay antennas into a 16-bay that is connected to the 7778? Is it the old 7778 with separate VHF and UHF inputs or the new 7778 with only one antenna input?

That is all correct. I created my own 16 bay from two 8 bays and it's a CM 7778 with one UHF input and between the preamp power inserter and the TV is my combiner
You have more than one yagi?
No just one UHF Yagi and the station is CHCJIs it a VHF or UHF yagi? What is the callsign of that station?

Combining two antennas aimed in different directions, using a splitter in reverse as a combiner, doesn't always work because when the same signals arrive at the combining point they will interfere with each other if they are not in phase.

When the coax lines need to be the same length
All the 8 bay connection lines to each combiner (on their own antenna) are carefully made the same length, In essence 4x4 bays with identical lengths. I DONOT recall how exact the feed from the two 8-bays antennas to the preamp is. Is that crucial? If you have two identical antennas, aimed in the same direction, and are using a splitter reversed as a combiner, the coax lines must be the same length for maximum gain. You will be able to get up to 2.5 dB more, 3 dB because of doubling the signal minus the 0.5 dB internal loss of the combiner.All the combiners that I used are copycats from that original combiner that I found with the one 8-bay. They do seem to work, how well needs to be determined

When the antennas are aimed in the same direction, the incoming wave front arrives at both antennas at the same time, and the signals arrive at the combiner at the same time, so they add in phase.

This only works if the wave front is uniform across both antennas. If the wave front is not uniform across both antennas (like thru trees), you don't get the gain you expected. I do have a tall 80ft poplar tree about 50ft away from the 16-bay [2x8 bay combination] in direct line of sight for the eastern facing NOTE: Full foliage now no leaves in the winter. I tried to take all that into consideration. Consider my tower is in a fixed location and I'm not cutting down that beautiful tree This explains why a 4-bay bowtie antenna sometimes works better than an 8-bay bowtie, like 4221 VS a 4228, because it has a smaller capture area.

And when they don't need to be the same length

If the two antennas are NOT aimed in the same direction, the incoming signals do not reach each antenna at the same time, so it is not necessary to have the coax lines the same length, because the same signals aren't going to arrive at the combiner at the same time anyway. This means that they might interfere with each other because they aren't in phase.

It is possible to adjust the lengths of the coax lines to different lengths so that one desired signal arrives at the combiner in phase, but that often harms the other signals that might have been OK before adjusting the lengths.
My answers are highlighted in red
Any further questions please ask or if I wasn't clear enough re-ask
4.6 Explorer is offline   Reply With Quote