Need antenna selection advice

[Gillez]

Hi everyone,

Here are the details concerning my location: http://www.tvfool.com/?option=com_wr...b7c8424056344f

I would like to get as many available channels as possible, but the ones I really want are the American networks (CBS, NBC, PBS, FOX and if possible ABC).

I'll be using an Apex DT250 converter box since my TV doesn't have an atsc tuner. I think it has an analog pass-through, will that make it possible to view both the digital and analog channels?

I'm looking at making a DIY antenna. My roof is high and quite steep so a roof mount isn't good for me. It will be installed in the attic which is quite high so I can install a large antenna there (a 2 bay Gray-Hoverman or 8 bow-tie antenna will easily fit).

Thanks in advance for your advice and help.

Your location has both VHF and UHF digital television channels. I always go to the >>Start MAPS<< part of tvfool.com

[mtownsend]

Originally Posted by Gillez

I'll be using an Apex DT250 converter box since my TV doesn't have an atsc tuner. I think it has an analog pass-through, will that make it possible to view both the digital and analog channels?

Hello and welcome!

Yes, if your converter box has analog pass-through, it means that it will directly connect the RF input to the RF output when the converter box is powered off. This will allow you to use your TV's built-in tuner to watch analog stations when the converter box is off.

When the converter box is on, you have the option of watching the digital stations via RF channel 3 (or 4), or via the composite video / S-Video connections.

I'm looking at making a DIY antenna. My roof is high and quite steep so a roof mount isn't good for me. It will be installed in the attic which is quite high so I can install a large antenna there (a 2 bay Gray-Hoverman or 8 bow-tie antenna will easily fit).

Most DIY antennas are really UHF-only antennas. Some of them work a little bit in VHF, but that's only good enough if you have some pretty strong local VHF stations. Even the SBGH or DBGH antennas that have been modified for some high-VHF gain will not perform as well as an antenna specifically designed to cover VHF frequencies.

In your case, you have some strong local VHF channels and also some weaker ones further away. If you go with a DIY antenna, you will probably not be able to pick up the more distant VHF stations. If you are serious about picking up the weaker VHF stations, you are better off getting a true VHF capable antenna.




Some of the weaker US digital stations are pretty weak (NM in the single digit range). There will be some signal loss going through the building if you install the antenna in the attic (typically between 3-10 dB, depending on roof construction). You will want to get as much gain as you can muster to maximize signal robustness (fewer dropouts). You will also need an antenna rotator to pick out the different Canadian and US transmitter clusters. And finally, I'd recommend NOT using any kind of amp. The Canadian analog stations are too strong for most amps to handle, so you're better off not using one.

If you want a good full-band (low-VHF, high-VHF, and UHF) antenna, I'd recommend something like the Winegard HD8200U. It occupies a lot of horizontal space (unlike stacked 8-bay bowties or a DBGH) so you'll have to check if it will fit in the space you have. Most antennas with good VHF gain end up being quite large due to the long wavelengths involved.

If you don't care so much about VHF, then the DIY options will work well. You just need to decide if that's acceptable or not.

If you want to make your own UHF antenna, you can also add a VHF-only antenna like the Winegard HD5030, and join the two with a UVSJ.

[Gillez]

Thank you so much for the advice. That's exactly what I'm looking for.

The channels I'm most interested in are the US networks so they're digital, in the UHF range but a little weak. At least they're all coming from the same direction.

What would be my best chance at getting them? (especially ABC which is the furthest)

For the other local channels, I can wait until next summer when Canada goes digital and I assume those channels will move into the UHF range also.

[mtownsend]

Originally Posted by Gillez

What would be my best chance at getting them? (especially ABC which is the furthest)

ABC is on channel 13, which is VHF. Furthermore, you have a stronger Canadian analog broadcast (CKTM) that is going to make reception of WVNY very difficult or impossible. I think you may end up with no ABC at least until the Canadian analog broadcasts go off the air.

For the other local channels, I can wait until next summer when Canada goes digital and I assume those channels will move into the UHF range also.

I wouldn't necessarily count on it. A lot of US broadcasters kept their high VHF channels (for brand recognition and RF propagation reasons). Some Canadian broadcasters may choose to do the same. You might be fine with UHF-only antenna for US digital channels for now, but you may end up adding a VHF antenna later if some of your local broadcasters decide to remain there.

The antennas mentioned in the previous post will give you the best chance of receiving the more distant channels.

[Gillez]

Thanks again for your precious advice.

I think I will try to build a DIY antenna and follow your recommendations and add a separate VHF antenna if I'm pleased with the results of the first.

I'll post once I have some results.

[Gillez]

I finally got around to setting up my home made 4 bow-tie antenna in the attic this afternoon. After much aiming, I actually managed to get WCAX-DT (just barely). That station is 84 miles away from my home, so I'm sort of encouraged.

Would a different type of antenna with more gain let me get these distant US digital channels? I'm toying with the idea of a double-bay Grey Hoverman. Would something else be even better?

Thanks again for all your help

[mtownsend]

In very rough terms, the DBGH ought to have about 6 dB more gain than a 4- bay bowtie.

I would not have expected WCAX to be that difficult to receive with a 4-bay bowtie in the attic. What dimensions did you use for your 4-bay antenna? Do you have a screen behind your antenna? I wonder if your current antenna could be tweaked to give you better performance on channel 22.

Another possibility is that there is something in the building materials of your house (e.g., wire mesh, foil-backed insulation, ducts, metal bracing, etc.) that is interfering with your reception.

[Gillez]

The antenna I made is has 7 inch 'legs' with a 3 inch gap, which seems to be the standard DIY measurements I found. I haven't yet installed a screen behind it, I was looking for some cheap 'mesh' material but since it's indoors I guess plywood and foil would do.

The only metal I could think of in the attic would be the nails used for the wood structure and shingles. Not much else besides that. I'll have to try and move around in the attic to see if thing improve.

Thanks for the advice. If you have any other suggestions, they're very much appreciated.

[Dave Loudin]

Your bowties are too small, and probably too close together. Gain at the lower end of UHF will suffer and high-VHF performance will be disappointing. Read the information here for better design information.

Good luck!

[Gillez]

Wow! I made a model off the site you gave me, the one with the 10-inch whiskers and 9 1/2 inch spacing. Without a back reflector, I get all the channels I want except for ABC (WVNY). I've read it's hard to get in my area, lots of people use a dedicated yagi to get it. I'll try curving the whiskers and adding a back reflector and report my results.

[Dave Loudin]

I'm very glad to hear that it worked for you. The author of that site started from the "Youtube design" when it was first brought up over at avsforum. Modeling, measurement, and verification by others led to what you find at his site.