Originally Posted by jwwm_2
I had fun looking at this. A blast from the past. I can't decide if I should smoke Lucky cigarettes, or Prince Albert. The articles and ads are remarkable, well worth looking at.
I'm glad that you enjoyed the references. Some of the old ideas are still good and have withstood the test of time.
Now, it just so happens that I made a video for Youtube which more than 12,000 people have watched, and it grows by a few hundred daily. I get a lot of questions from people regarding that video, I kid you not. I answer all of them.
Your Youtube video is a big improvement over the previous videos, especially the ones that claim that 7" whiskers and vertical spacing of the bays is optimum.
Also, on the cm4228 they use wires to connect the 2 4bays. I copied that design once, but I admit it only worked marginally well for me.
I actually made signal level measurements at my location comparing a 4221 with a 4228. The 4228 gave one channel that was 1 dB stronger than the 4221, most were about the same, and a few were a little weaker than the 4221.
The main advantage of the 4228 is that its horizontal beamwidth (because of its horizontal stacking) is narrower than the 4221 which helps with multipath problems (the signal strength might not be better, but the signal quality ((BER)) is improved, which helps the tuner maintain lock).
I also found that which balun is used can make a difference with certain channels. In my case, a Magnavox outdoor balun was better than the CM outdoor balun for one of my channels.
The latest question I couldn't answer with authority had to do with combining 2 4 bay antennas using splitters. I advised the guy that one properly made 4 bay would probably work better than 2 4 bays connected by splitters. My answer was that splitters aren't a good choice for combining antennas. I also advised him to look at some commercial designs for ideas.
What do you think? Did I get it right?
You gave a good answer.
One well designed 4 bay can be better than 2 4 bays combined with a splitter especially if the smaller antenna is placed in your best location, which is why mclapp
has been focusing on designing his 4 bays with the optimum element lengths, larger reflectors, and curved reflectors.
In my case, using a signal level meter, moving my 4221 to a better location gave me more gain than if I had combined FOUR 4221s. If I didn't have a signal level meter, my second choice would be the Apex DT502 CECB and my third choice would be the signal level percent scale on a DTV.
Using a splitter to combine two 4 bays is an "iffy" solution. When I combined two 4 bays with a splitter for CH 15 I got 2.5 dB more gain, using baluns that gave the highest readings for CH 15. I didn't, at the time, check the other channels, because a friend needed an antenna optimized for CH 15 (PBS). The point that mclapp
made about the two baluns needing to be phased correctly is right. If you end up with much less gain with two 4221s, then reverse one of the baluns.
Tests have been made by others, using better equipment than I have, showing that many factors are involved, like the actual length of the two identical coax lines from the two 4 bay antennas (a null might appear just where you don't want it):http://www.hdtvtruckee.com/http://www.hdtvtruckee.com/CombinerMeasurement.htmwww.hdtvtruckee.com/CombinerComparison.htm
So my order of priorities would be (in increasing difficulty):
1. Find the best location for your present antenna. This will often give more gain than combining two identical antennas that are aimed in the same direction, and the smaller antenna is easier to handle.
2. Make sure that your antenna is the best for the channels that you want. If not, modify your DIY antenna or buy a better one.
3. Try AGAIN to find a better location. With UHF sometimes a few feet up or down, left or right, or even forward or backwards (which I noticed when I mounted a 4221 on my car---a lot like when listening to FM in a parked car, it is sometimes necessary to move the car a few feet to get out of a "dead spot" null in the wavefront) can make a big difference.
4. Stack/combine more than one antenna and use any device available to you to measure the improvement. (Can you tell that I'm hung up on measurements?)
5. Give up on your marginal channels.
6. Sign up for limited cable or a dish.
7. Move to a better OTA signal location.