Reception better from my RV antenna ... ?

[mikebuild]

Hey all,

Newb's got a question ...

I just built a DB4 and mounted up on the roof. It sits about +40' off the ground, my RV's Wingard (model ?) sits about 12' off the ground and about 50' away from my new DB4. The RV will find 17 channels and the DB4 will only find 8 channels. I have an amp on the DB4 and the Wingard supposedly has an amp built in. How can the Wingard be getting better reception than the DB4 that's sitting so much higher. Is the RV just sitting in a hot spot? When the snow melts, I'm going to move the DB4 down by the RV and see what's what.

Which antenna model/style would you try here ( at my location)?
http://www.tvfool.com/?option=com_wr...dfaf44e4451727

Lots of people online claiming their home made antenna's perform better than the store bought versions, what's been your experience?


Thanks, Mike.

[ADTech]

The devil, as they say, is in the details, many of which are important are missing.

1. Which Winegard? They have two generations of RV antennas, very, very different. One is very good on VHF but lousy on UHF, even with their slip-on attachment. The other is fair on UHF but lousy on VHF.
2. Which stations are received by each? Not "channels" since that count is usually inflated by the presence of several sub-channels that are all part of the same station broadcast.
3. Which preamp is on your home made 4-bay antenna (please don't call it a "DB4", we already have dibs on that term).
4. What design was used for the 4-bay? The homemade 4-bay antennas are UHF designs, and some of them are lousy designs to start with.
5. What direction is each antenna facing?
6. What, if anything, is out in front of the 4-bay antenna? Trees, building, etc?

[mikebuild]

Originally Posted by ADTech

The devil, as they say, is in the details, many of which are important are missing.

1. Which Winegard? They have two generations of RV antennas, very, very different. One is very good on VHF but lousy on UHF, even with their slip-on attachment. The other is fair on UHF but lousy on VHF.

Sensar RV-2005

2. Which stations are received by each? Not "channels" since that count is usually inflated by the presence of several sub-channels that are all part of the same station broadcast.

RV- 9, 11, 13, 16, 20, 28 (and at one time 7, 33 and 64)
4-bay - 9 (weak), 11 (weak), 13, 20, 28 (weak)(never 7, 33 or 64)

3. Which preamp is on your home made 4-bay antenna (please don't call it a "DB4", we already have dibs on that term).

ONN, model ONA16AV004 (believe that to be the model)

4. What design was used for the 4-bay? The homemade 4-bay antennas are UHF designs, and some of them are lousy designs to start with.

like this: http://akschaefer.com/wordpress/wp-c...12/Picture.jpg (not mine, but same style). I have not yet installed any reflector on the 4 bay yet

5. What direction is each antenna facing?

I have rotated both 360 degrees, best reception facing NE (I would guess about 15 deg)

6. What, if anything, is out in front of the 4-bay antenna? Trees, building, etc?

Both antenna's are surrounded by trees and hill. We sit "down" a bit


Note: I actually seemed to get better reception with the RV antenna "before" the trees dropped their leaves. 7 would come in sometimes, now not at all.

Thanks again.

[WIRELESS ENGINEER]

Yes you can easily make a 4 bay bowtie antenna that works better than any commercial 4 bay

Since most commercial versions still have most of their gain above 700 MHz, (where no dtv stations exist) they perform poorly on the lower half of the UHF channels

I've found that whisker length of 10 inches produces excellent performance
Below rf channel 40 where most of my channels are

You should also use a screen reflector vs one made of wide spaced rods for better performance

Curving the reflector and sweeping the whiskers forward will also improve gain and narrow the pattern

Conversely, bending the whiskers back towards the reflector will widen the pattern and reduce gain

Spacing between the bowties and reflector is also a huge factor

1/4 wavelength (approx 5 inches) works well on lower channels

The Winegard TV antennas are amplified and omnidirectional while the 4 bay is directional so it won't pick up stations off to the sides or the rear

[mikebuild]

So in my case, to recieve all available chanels, the bowtie would work best with a rotator. Which antenna would you recommend that would not need a rotator?

[ADTech]

Originally Posted by WIRELESS ENGINEER

Yes you can easily make a 4 bay bowtie antenna that works better than any commercial 4 bay

The bowtie antenna is primarily a UHF-mostly design and usually has poor VHF performance. The only DIY 4-bay that I'd suggest investigating is the "M4" design which is well discussed in this thread over at DHC: http://www.digitalhome.ca/forum/186-...-featured.html This design features elements of a length and spacing pretty close to what WIRELESS ENGINEER suggested. This is an excellent design which was done by enthusiasts who were concentrating on performance, unfettered by concerns that must be present for a commercial design. Most of the You-tube coat hangers are based on a very poor design and should be avoided.

Since most commercial versions still have most of their gain above 700 MHz, (where no dtv stations exist) they perform poorly on the lower half of the UHF channels

I'll just note that our "e"-series of bowties, launched back in 2011, do not have this concern. They were designed specifically for the channel range of 14-51 and have only about a 2.5 dB gain differential from design band edge to design band edge. Data from other manufacturers regarding this performance is pretty much non-existent. Winegard discontinued their bowties several years ago without ever updating them. Channel Master redesigned their bowties back around the digital transition, but they publish a single gain number and then fail to even specify what what frequency it's at or which gain figure they're using, the just say "dB" which is not specific. The Chinese-made clones are typically of Euro-Asian specs and go up into the 860 MHz range (not optimized for North American UHF band).

I'll just say that I am not recommending our "e" series antennas for this location unless it is also paired with a suitable high-VHF antenna.

Sensar RV-2005

The Winegard Sensar, without the Wingman attachment, was designed decades ago and it's performance was concentrated in the channel 2-13 range. The clip-on Wingman was later added to offers a bit of UHF improvement. The built-in amp on older units was similar to the discontinued HDP-269 preamp. The Sensar is broadly bi-directional on VHF (hence the need to a rotating mechanism with their RV mounts).

ONN, model ONA16AV004 (believe that to be the model)

Ugh!

best reception facing NE (I would guess about 15 deg)

The expected aiming direction would indeed be almost due NE as per your plot.

Your best bet would likely be one of the medium-sized combo antennas (7-51 or 7-69) aimed at downtown Seattle. Note that any directional antenna aimed in this fashion would introduce the following concerns:

1. The primary transmitter for your Fox affiliate is located of to your northWEST. It's signal is quite strong so it probably will come in anyway. That station also operates a low-power UHF 22 transmitter from the downtown area, so there is a second opportunity to pick it up.

2. The PBS station in Tacoma, WBTC, will probably be lost as it's going to be in a significant null with any directional antenna. If this station is desired enough, you'd have to make special provisions for it.

3. You'll want to add a medium gain, high-input preamp to the system.

[rickbb]

You can make a 4 bay with better gain than you can buy.

BUT, the devil is in the details. You have to use the right plan and follow it exactly. Spacing and measurements are very critical. Wrong plan or poor spacing of elements and you might as well stick a coat hanger up in the air.

The Mclapp M4 that Adtech pointed you to is one of, if not the best DIY bow tie style design out there.

I've built a bunch of the 10 x 9 1/2 no reflector models using his plans and am very pleased with the results. I even get a Hi-VHF signal from 50 miles quite good.

Design, adherence to the design specs, aiming and obstacles in the signal path, (trees, buildings, etc.), all are factors.

Without knowing what plan you used or how well you followed it, or how you aimed it, you can't really say why it's not performing as well or better than the store bought model.

[mikebuild]

Thanks guys ... good info!

The bow tie plan I followed called for 9" elements spaced at 9" o.c. with 5.5" spacing at the element tips. The importance of all elements to be, "on plane" was noted. Elements were attached to a board separated by 1.25".