Antenna Selection (includes some VHF-HI)

DarkNova

DTVUSA Rookie
#1
I'm trying to pick out an antenna to install and am hoping someone who knows the models out there can help with some advice. My TV Fool plot is here. I'm interested in real channels 7, 9, 16, and 31 (channel 38 could be substituted for 16 if it would be easier to receive, which I doubt). So you can see I have a couple of VHF-HI to deal with. I plan on mounting the antenna outside, on a pole, above the roof line. I'd like to avoid a rotor if possible, and also would lean towards something without a super long boom if I could make it work. I'm just not sure how feasible that is for the VHF-HI. I've been looking at the RCA ANT751R and that seems like it has potential, although I'm not sure if that would be the best choice or not. Thanks for the help.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#2
:welcome: DarkNova!

After reviewing your antenna survey, I highly doubt an ANT751R would work very well for you unless it was mounted significantly higher than 30 feet above ground. You might get away with using a Channel Master CM-3018 but I suspect you will need to use a deep-fringe antenna like a CM-3020 pointed SE. Since you want to avoid using a rotor, a second antenna could be pointed at NBC-16 to the NE, but it cannot be combined on the same coaxial downlead and an A-B antenna switch would be required. Remotely controlled A-B switches are available, as are manual switches.

Your antenna survey is very similar to mine and I was forced to install three seperate antenna systems and 3-way antenna switches to each TV in the house. Stand by and let's see what others here suggest.

Jim

PS to the mods and contributors: I wonder if this is a situation where a Jointenna-16 could be used (assuming one could be located)?
 

Jim5506

DTVUSA Member
#3
Your main problem is that 16 is 90 degrees off the two vhf channels.

I would use a 2 antenna solution, an Antennas Direct YA10-7-13 or Winegard Y1713 for VHF and a 4 bay vertical stack Like the Winegard Pr-4400 or equivalent for the UHF channels, pointed just slightly south of east, although the 60 degree spread of the 2 UHF channels may be a challenge.

Connect them with a UVSJ (UHF/VHF signal joiner).

A pre-amp may be necessary to pull in the UHF's 24/7, your strongest station is 39 miles away, no overload problem.

Depending on your tuner, using a rotator might be a problem if your tuner cannot add stations to its current database, but recreates it each scan.
 

dkreichen1968

Moderator
Staff member
#4
My guess would be an Antennas Direct C2 (Clearstream 2) pointed east (98 degrees magnetic) and a C5 (Clearstream 5) or Antennacraft Y5713 pointed at 147 degrees magnetic (need a UVSJ for the Y5713) may give your the best chance of not having to use a rotor or A/B switch. In my experience yellow TVfool indications are in general fairly strong.
 
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DarkNova

DTVUSA Rookie
#5
Thanks for the responses. Before I go about trying to decide which of these antenna sets to buy, I have some additional information and a question:

First, I was playing around with TV Fool and noticed that if I change my antenna height from 30 to 31 feet, channel 16 goes from 1 Edge with a 24.7 NM to LOS with a 36.4 NM. So it appears this height is just on the edge. The "30 feet" I used originally was an estimate, as I can't really figure out the exact mounting setup until I have the antennas picked out -- but I could possibly go a little higher, within reason, if it could improve the situation a lot. I do doubt though that the TV Fool elevation data is that exact, though, so I suppose I can't really know without just testing. But if I can get channel 16 high enough to be LOS, would that change the antenna selection?

Second, I've been reading about what the noise margin figures mean (here and here for example) and I'd appreciate if someone can read my logic and make sure I'm understanding things correctly. The basic conclusion, at least in my limited understanding, is that you need a 0 NM after adding the antenna gain and subtracting all losses, to get reception. It seems like a 10 NM figure is recommended for stable reception, as things sometimes change slightly. So, say I got a CM7777 preamp and mounted it within a few feet of the antenna. Then I would need to subtract 3 dBd from the NM figure because that's the approximate loss on the CM7777. After that, I don't really have to worry about any downstream coax or splitter loss (at least if I stay within the 30 dBd or so of gain the preamp provides).

So, according to TV Fool, the weakest station I'd like to receive has a 18.6 NM. If I subtract 3 then that's 15.6. Assuming things would work fine down to 10.0 NM, that means that my antenna could actually have a -5.6 dBd gain for this station and I'd still have reception, right?

I feel like I'm probably missing something, as most antennas have positive gains, so it should be relatively straightforward to have reception. Is my logic flawed? Thanks.
 

dkreichen1968

Moderator
Staff member
#6
I feel like I'm probably missing something, as most antennas have positive gains, so it should be relatively straightforward to have reception. Is my logic flawed? Thanks.
It sounds like you have a pretty good handle of it actually. The only real question is how close the prediction from TVfool is to your actual situation. In my case I know that the predicted NMs for many of the Denver stations I get are lower than my actual NMs or I'd have many more issues receiving them than I do. In other cases I'm sure TVfool is wrong the other direction. Part of it is how it uses average terrain heights to do the propagation maps. It also can't take into account things like buildings and trees in your area.
 

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