I thought about this. Not really sure it’s worth the effort. And then there’s the issue of the Antop getting power for its amp and the CS4 … not amped, but if I put them into a combiner they’ll both get power even though the CS4 has nothing to power and will the combiner alter the power that’s supposed to be going to the Antop and… see? 
It would be kinda cool if I could just mount them back to back on the mast. hehehe
I’ve never seen an SNR higher than 31. I suspect that both antennas are near the upper limit so that one or the other wouldn’t exceed the other by much. It’s the longitudinal design of the Antop that gives it a wider beamwidth.
Anything within the 30 to 31 range I consider 100% (27 being 90%, 24 being 80%).
Gonna put the ladder up and go up there before the wife gets up and wants to watch TV.
The one I got must be defective had to return it some channel just pixel every couple minutes not bad just annoying, move it in different location in the attic still same result went back to the old antenna got better result because of all the different location of experimentation guest it’s not a waste of time and effort now the old antenna works better in a different location
Finished just in time
I removed the CS4 and raised the Antop. Signal level on our NBC station dropped significantly. (RF 33)
Tweaking the aim didn’t do much at all. LOWERING it about a foot brought the signal back up.
I remember reading on one of the sites that talks about digital TV and RF signal travel, etc… about how RF sort of has “layers” according to wave length… something like that. I’m not an RF engineer but I think I just experienced the effect of that.
Here is what I ended up with on the channels I actually care about…
Channel 2 (RF33) SNR 29.8 - 30.3 NBC
Channel 4 (RF36) SNR 29.75 - 30.10 CBS
Channel 7 (RF38) SNR 29.5 - 30 ABC
Channel 17 (RF43) SNR 30.5 - 30.8 PBS
Channel 23 (RF36) SNR 29.75 - 30.10 CW
Channel 29 (RF32) SNR 25 - 26 FOX
Channel 49 (RF49) SNR 30 - 31
With the Antop they seem a bit more stable. Probably because the beam width encompasses all of the tower locations well, rather than having them just at the fringe as was the case with the CS4.
We’ll see how this plays out over time. The trees should be leafed out here in about 2 weeks.
Where did you get the SNR readings? Was that from a TV readout, or from somewhere else? If from a TV, what manufacturer was it?
I replaced my Antop 400-BV with two RCA ANT751E Antennas. I found the reception to be similar on both, but the Antop had a couple of advantages. The pre-amp and LTE filter the Antop comes with is very good. Even though the short coax cables that is hardwired to it are thin, it is still a very functional device. I use it for one of my RCA’s, and it works well. The other advantage of the Antop is the reception width (beam width?) is greater, or at least that was my impression. I really didn’t want that for my setup, but it would be useful in certain situations.
Not sure I would pay the extra cost in the end. You can get the RCA antenna for $35 and purchase Antop’s pre-amp separately. In fact, using two of the RCA’s allows me to get more channels than the one 400-BV did, but every situation is different. My stations are pretty easy to pickup, it’s very possible the 400-BV is better in every way, it just wasn’t necessary in my situation. The 400-BV certainly looks better though.
The SNR readings are coming from my Samsung TVs. I have 2 different ones and I go into Signal Information on both and see if they agree… and they do.
Yeah, my situation is a bit challenging. I have 3 towers out 38 miles to the southeast, and then a small “tower farm” only 8 miles out to the southwest. AAaaand… trees in both directions
Not a forest, but still.
With the CS4’s beam width, aiming had to be super precise to catch both sets of towers and then they were at the edges of the effective beam pattern. The Antop is a LOT less picky about direction but seems more sensitive to small variations in height. On that same mast, if I slide the Antop up a foot, I lower the signal from one of those distant towers a ton. Like it goes from showing a nice strong 90% signal to having a sort of wobbly 50 or 60%. Lower it back down and signal comes back strong. So… I guess higher isn’t always better (somewhere I think Cheech Marin is cringing…)
The RF signal patterns also change with time of day. An optimal location for an antenna in the morning may not be the optimal location for the antenna in the evening. My antennas vary by time of day as much as 15%.
Also the angle at which the RF wave patterns come in will vary from location to location on a roof or in an attic. NBC may come in better higher at the eastern part of the house and better lower at the western part. And vice versa for CBS.
One is really playing with averages in placing an antenna. You may also find that the leaves divert a signal, not necessarily block it. Suddenly NBC is better a few inches to the left…
Because the Antop receiving elements are one above the other (a column), it’s the up and down location of this antenna that matters.
Thanks, Mark. That makes sense about the orientation of the elements. And if the wave length of that channel is 20 inches, then I basically moved it about a half wave down. Interesting that it didn’t seem to have any effect on the other channels as far as I can tell.
2, 7, and 49 are the 3 distant towers. 33 to 38 miles.
RF 33 at 161 degrees
RF 38 at 169 degrees
RF 49 at 149 degrees
The rest are at 204 to 206 degrees and only 8 miles
Each channel has a different frequency, wave length and RF cloud pattern. Antenna placement is quite an effort… I live in a forest in a valley!
Yessir… I started out on the south side of my house. Same 20 ft mast. Had issues with variability. I was about 25 feet from the treed lot next door. Moved it to a chimney mount about 20 feet farther back from the trees and maybe 6 feet higher. Wasn’t really any better.
Now I’m on the north end of the house (same 20 ft mast) and a good 75 feet or more from the trees. Reliability of the signal went WAY up. Very little discernible difference with time of day, big swings in temperature, trees swaying in the wind.
Yup, temperature is a big variable. I can predict what my SNR will be on a cool 70 degree day as opposed to a humid 90 degree day. It will drop by 6 db.
Thanks. I think I have a 32" Samsung TV around somewhere. I will have to check to see if that has that feature.
Interesting. I didn’t realize that the temperature can have such a big impact. Hopefully I don’t start having issues once summer roles around. I don’t have many trees in the way, but I didn’t realize that just the temperature can cause that much of a db loss. I’m going to record my SNR now and then again once it gets warm and see if it has much effect.
This Splitter/Combiner will do a “Power Pass” on only 1 Port, with the rest having DC-blocking (series capacitor, I’d imagine)
https://www.amazon.com/SHIELD-SPLITTER-COMBINER-3-WAY-PASSIVE/dp/B00EIAFWBA
Done… almost… it’s mounted and fine tuned. Every station I care about has SNR 29.5 to 30.5.
Rescanned Tablo. Now just gotta do a little more work hiding the cable and I’ll call this one done… for now. 
Nice work. Looks really good! 
(that looks a lot like a sat mount - with extension)
It’s a channel master mount. I’m glad I got the adjustable extension since this antenna is sensitive to small height adjustments .
I have been using the AT400BV for over a week now and did not have to mess with it all. Just pointed it in the general direction of the towers and it works.
Note, I am only ~20 miles from most of the towers so it is not much work for this antenna 
I did note great improvement in the VHF-H (NBC) channel that is now a solid signal.
Cable and ground wire tucked in and hidden.
I’ve had the opportunity to check signal levels now during the day, at night, at 32 degrees, and today at 70.
This morning we had a heck of a downpour so I checked then too.
I’m just not seeing any change.
So right now, if this all stays pretty much as it is, I will have achieved a goal of being able to just watch TV… not fiddle with the setup. And while I do, admittedly, enjoy the techy stuff and new toys… I have other stuff to do. Get the boat ready to back in the water, build my outdoor cooking area, build the wife a new kitchen table, start building new cabinets for the bathroom remodel she’s gonna spring on me 
I do like this antenna though… heheh
