The Official AVS Antenna and Related Hardware Topic! - Page 496

I agree completely. I was only illustrating that there are situations where antenna gain is not the most important factor. My 9 local stations have about 20 to 35 dB noise margin, strong enough for every one of them to have an SNR >30 dB. But not a one is that good. Most run in the mid 20's, in the ballpark of F/R ratio of the antennas. I can throw away 10 dB and and see no change in Signal Quality at all. Signal Quality at my location is entirely dependent on F/R of the antennas.

Chuck

Just to make sure we're talking the same RS 75R antenna, is this yours pictured here ? :
http://www.hdtvprimer.com/ANTENNAS/VU-75XR.html

The 75R antenna gets about 4 dbi in Raw Gain at channel 6, on par with most combo antennas, even some that are much bigger. But Net Gain is about zero, which means the SWR on it is over 8.5:1 at 300ohms. Not good for digital which should be 2.7:1 SWR or less. http://www.hdtvprimer.com/ANTENNAS/comparing.html
(I have that NEC model of the 75R from Ken Nist so I could play around with it to try to get more Net Gain on channel 6, but it will take some time)

To get a significant increase, youll need something like the 190R or YA-1026 or 3671 etc which are much much bigger antennas.

The most compact channel 6 antenna, with significant gain increase over what you have now, is the no longer made Wade Delhi 5Y6S single channel antenna.
You can make your own from plans here: http://www.digitalhome.ca/forum/show...ght=delhi+5Y6s
(Note that measurements are in centimeters in the first post, and the boom length is 184 CM not 84 CM, which makes it a little over 6 feet long. It has 9.29 dBi Raw Gain with a SWR of 1.69 at 85 mhz, Net Gain of about 8.9 dbi. http://www.digitalhome.ca/forum/show...4&postcount=22)

I think the easiest thing to do is to move the antenna high outside, either with a mast or a chimney mount. That will improve your uhf stations too. Im surprised those uhf stations are doing so well in the attic with that RS antenna.

Another thing you could quickly try is moving the antenna in the attic, it may be near big metal or close to electrical wiring.

Do you already have a CM4228 ?

First Off I want to thank everyone that has responded to my questions and are trying to help me get my channels. The antenna I am using now is a old RS Model U-75R that is mounted in the attic. My house is a Two Story with Vinyl Siding and a end lot with no electric lines or trees near bye. These are original specs of antenna. At the time it was cheap as heck and was just experimental to try.They no longer sell it separate but from a readers image it looks like they now incorporate it into a complete set-up. It worked but when Comcast finaly came marching in I said Goodbye to Dish and antenna. Now with the internet and FTA I am coming back. I am also open to try another antenna but it has to go in the attic and not on the house.I do not have the 4228 I just remember they were reliable in 06. Wife is cooperating with me migrating back and ditching cable but draws the line with antenna hanging off the house ;-)

Dimensions
Product Length 40 inches
Product Height 32 inches
Product Width 16 inches
Product Weight 2.55 pounds
General Features

Model U-75R
Product Type UHF only
Enclosure Color Gray
Body Material Multi
Radio Shack site claims 75 miles

Quite often, vinyl siding has foil-backed insulation behind it. If yours does and if you have to aim through it (instead of through asphalt shingles), your attic reception may be greatly hampered. Even if not aiming directly through it, the foil, if present, may still cause significant reflection/multipath problems.

It is not very likely your existing UHF-only antenna will get WJZ, WPVI, WHYY or WBAL very well, all of which are VHF channels. And WPVI is lowband VHF, requiring an antenna with even longer elements, typically over 100" in width, tip to tip.

You will likely need a fairly large, VHF-LO, VHF-HI, UHF (aka all-channel) antenna for attic reception. Or, you might combine a VHF antenna with your existing UHF antenna.

The mileage claim is meaningless. They quote a conservative 9.5 dBd (11.65 dBi) in their specs. http://support.radioshack.com/suppor...oc19/19192.htm It probably has a peak gain of just below 14 dBi.

I originally thought you had the VU-75R, which has vhf elements on it.

Youll need to connect a vhf-low antenna to it with a UVSJ.
For channel 6, the AntennaCraft (who makes RS antennas) Y5-2-6 is about the cheapest way to go ($28) if you just want to add channel 6.
http://www.solidsignal.com/pview.asp...u=716079000949
and a UVSJ for about $2
http://www.solidsignal.com/pview.asp...r-%28Z-UVSJ%29

Of course, if you get a quality preamp (which you should since youre using 50 ft of coax) with separate UHF and VHF inputs, you can skip the UVSJ.

But dont you also want WHYY PBS 12 ? If so, then youll need a full combo antenna. The AntennaCraft C290 is about the cheapest at $38.
http://www.solidsignal.com/pview.asp...0Antennas&sku= The AntennaCraft C490 would be better still, but at a higher price.

And since the uhf section on it looks to be about as good as your U-75R, you can skip the UVSJ. (a quality preamp is still recommended with 50 ft of coax)

Generally, AntennaCraft/RS antennas arent as durable outdoors as Channel Master or Winegard ones. But in an attic, it doesnt matter.

Hi,

Does the store get some money when they sell a Cable / Dish ... subscription?

Most stores here in Silicon valley know nothing about OTA, or will say incorrect things. They want their commission!

I had a huge problem getting Fry's to admit that they had FM HD Radios.

Then the one station I wanted in FM HD went off the air. Well it's back with a 16 Watt translator which fights with one of their other translators on the same frequency.

SHF

300Aohm, antennaCraft-C29 & AntennaCraft -C490 Wuld these be one stop shopping for all my digital phily stations? I could always shoot my U-75R at Baltimore as a backup in case phily pixalates. Now just have to see how i can cram one of these in the attic through a 3x4 hatch and into the A frame. Thanks, Rick

Assemble it in the attic.
On a cool night.

Yes, the C490 would. The picture in the Solid Signal ad for the C290 is wrong, it has way less elements. So, the C290 would be very weak to use in an attic.
The AntennaCraft C490 can also be purchased at Radio Shack, but I dont think most stores would have it on hand, so it would have to be delivered.


Consistently without pixelation, I think ABC WMAR RF 38 (2.1 virtual) is the only Baltimore channel youll get with the U-75R. The next strongest Baltimore channels are RF 11 and 13, which need a vhf-hi antenna.

Yes, the C490 would. The picture in the Solid Signal ad for the C290 is wrong, it has way less elements. So, the C290 would be very weak to use in an attic.
The AntennaCraft C490 can also be purchased at Radio Shack, but I dont think most stores would have it on hand, so it would have to be delivered.


Consistently without pixelation, I think ABC WMAR RF 38 (2.1 virtual) is the only Baltimore channel youll get with the U-75R. The next strongest Baltimore channels are RF 11 and 13, which need a vhf-hi antenna.


Yes, assemble in the attic on a cool night or in the morning before the attic heats up. You should have no trouble getting it into the attic as the box will be approx around 18 inches by 12 inches or so, but it will be long. You should do some think ahead planning, knowing were the front of the antenna is in the box and the direction it will be finally pointed at. In some cases you may have to take it up back end first. Turning around a large antenna in an attic is no easy task, heh.

Uh... From my perspective (deep southeast Texas), any morning in Delaware would be a "cool morning" wouldn't it???

300ohm, Well Crash and Burn. I got the AntennaCraft-C490 from RS and installed the behemoth in my Attic with 18 inches of blown insulation & much finagling. I aimed it at 18* North and got little to no signal. Only ones coming in are UHF but no VHF. Just 3 phili channels and I don't see any other? I removed it from the splitter put in a barrel coupling because cable was a little short and still no good at around 30ft of run? It is laying supported on my A frame truss and wired up at the rear and level. Now I have no idea why this large antenna gets worse signal than the little AC U75? Thanks,Rick


KYW-DT 3.1 10%
WPVI-DT 0%
WCAU 10-01 10%

Reception in the attic is very unpredictable, especially VHF. With those signal strengths, you likely need something mounted outside to ensure reliable reception of the desired channels.

Not sure why some women are so against a neatly installed antenna if it means saving hundreds/thousands of dollars a year??? Hmmm, may be part of the reason more men are coming out of the closet these days.

Agreed. 58 miles out with 1 and 2 edge reception is a lot to ask for an indoor antenna. You need to put that antenna outside. Doing so will not only vastly improve reception, but also might not require an amp since the signals are stronger.
And if you really want to see the Baltimore stations , you can attach on a rotor.

If you haven't, I think you need to try a preamp like the C.M. 7777. At your distance it surely should help, and unless there are local stations of some kind that could overload it, I doubt that it could hurt. Unless you're in a big hurry, order a 7777 and try it before you go to the trouble of moving the antenna.

KYW is on real channel 26 and WCAU is on real channel 34, both of which are UHF channels. WPVI (6.1) is real channel 6 VHF-Low.

That said, since the UHF gain of the U-75 and the C490 antennas are nearly identical, and they both were in the attic, you should not have seen a drop in signal from 70-80% to 10% on KYW and WCAU. Something is terribly wrong.
Common errors in assembling combo antennas include:
Not correctly connecting up or shorting out the phasing lines between the UHF and VHF sections.
A broken balun. When installing, dont overtighten because it can break the little wires inside. (RS baluns are notorious for being bad. You can pick up an outdoor style Phillips or RCA balun at Walmart or Lowes)
A short or open in the coax line, usually at the F connectors.


Just checking, was that the same direction the U-75 was pointed at ?

BTW, you could also post your experience as to getting the large antenna in the attic so that others could benefit from your experience.

Just a follow up.As for the experience of the attic C-490 Antenna install etc. It got a little hot up there and I thought I was going to get heat exhaustion. You Figure with all the blown insulation and temps getting into the high 70's it got cooking above that. Wear a dust mask because blown fiberglass is no joke in the lungs. As for the antenna itself I put it together on the ground first temporarily to see how everything went together and to make sure assembly was correct. It goes together in 3 large pieces and stretches out to about 12' by 8' It goes together fairly easy with wing nuts and bolts and nuts with fold out locking pieces. Make sure you have this amount of fairly clear space before install. I had about 5' of height to install with cross brases etc.and I am 6'-2" so it made it a tight experience for me. It took about 2 hours of feeling like quosimoto and clear thinking about went out the door with the heat involved. So as stated before do it early morning or at night with a good drop light. Try to get a helper if you have one around just to hand you parts or tools ;-) I had no one to help which took a little longer than expected. You might not want the wife around because my house was littered with snow like insulation that sticks to you and everything around you. Had to Break out the vacuum every time :-) I went back up the other day changed out the Transformer and check all connections and brought up a compass to realign to transmitters. All was OK and rechecked signals. Now UHF was pegged but no VHF channels? This was the only Antenna hooked up for testing. I had my other Antenna disconnected at the time to have a comparison. Finally went back up and disassembled the behemoth brought it down to the garage and lugged a flat screen TV to the garage and different RG6 cables for testing.Resembled the Antenna again and pulled it outside re-aimed and checked signals. Note to self maybe do this first before actual install ;-) Once again only UHF and no VHF channel 6 phil. Brought my little antenna down hooked it up and signals about the same as the larger one so packed up the C-490 & back to RS it went. Called Cmcst. lowered tier of Internet and TV (Digital Economy) for now at around $90 including taxes so will suffice until I either find another antenna just for channel 6 or look for something a little smaller for my application.Or just get an antenna for ABC Balt.I do wonder if maybe I just got a lemon of an antenna.Oh well we will never know. I hope my experience may help someone else with there decision on this type of install ;-) Thanks,Rick

I would have tried an FM trap before giving up. Looks like you have a few strong FM stations very close to you.

Yep channel 6 is right next to the FM band

It sure looks like strong FM signals might be causing a problem. Even a good full-band FM trap might not cut sharp enough to attenuate FM signals just above 88 MHz without affecting CH6. There are tunable notch FM traps that might knock out the most troublesome FM signal.

His FM fool report in attrachment.

I agree with 300ohm:

Your RF6 reception is shown as 2-edge from TVFool. You are trying to receive the signal via diffraction. If you have diffractions coming from different locations then you have skyline multi-paths. This would result in weak signal spots and strong signal spots. You could be located in a weak signal spot. Unfortunately, at VHF, these weak and strong signal spots could be up to 50 to 200 feet apart. So there is not much you can do if you happen to be in a weak signal spot.

FM signals may be affecting RF6 and you could try a filter. However, analysis I've seen so far indicate it's the second order harmonics that causes problems and they usually only affect RF7 to RF13, not the lower RFs.

Your reception range and weak signals definitely requires use of a preamplifier. You'll be surprised what a preamplifier can do.

Channel 6 ends at 88 MHZ. He has two strong stations within 5 MHz of that at 91.7 and 92.9 and a VERY VERY strong station within 7 MHz at 94.7

2006 was pre-transition and your station on RF 6 was on another channel back then, probably UHF but I have no way to research that. You can't compare 2006 to 2012.


Then I guess you don't really want free TV. There's no magic here. You need to put up a good enough antenna to do the job. I've seen the difference between an attic antenna and one 40' high outside. It's dramatic, especially on low VHF.

A preamp will likely do more harm than good. Those strong FM stations will probably overload it. The Winegard AP8700 has a fixed FM trap and a narrow tunable trap which might be able to reduce that one really strong signal but you don't really need a preamp on channel 6 with your short run of cable.

Chuck

I agree that for short runs of cable, you don't need a preamplifier. But another reason for using a preamplifier is to compensate for the noise figure (NF) of the TV. I haven't seen what the NFs are for the latest HDTVs since they don't publish that number but I believe it is much higher than the NF of a preamplifier. Higher NFs are equivalent to additional signal loss.

I agree 100% but he's not receiving the station at all now so picking up let's say 4 or 5 dB isn't going to make 0% reception into 100% reception. It might make 90% reception into 99% reception.

I have that situation here with a 2 edge VHF station where I improved the system noise figure by about 3.5 dB and the station went from about 75% reception to 90% reception, still not as good as I'd like but better.

Chuck

Have you considered the possibility that interference is the problem? This discussion refers to RF3.

http://www.avsforum.com/avs-vb/showp...postcount=5610

Interference could certainly be a problem. Power line noise could be a problem even if he doesn't have any very close by. The best chance for reception is putting the antenna 40' up in the air to get the most signal possible.

Chuck

Thanks for all the replies and suggestions. I just read all the reviews on this Antenna on RS and one in particular stands out. All the reviews were favorable except for this one. The review is dated FEB 25 2010 and states that after being installed that they received all channels except for VHF. Sounds familiar doesn't it, I remember looking at the Transformer Balun and it also had a date of 2010 something on it. I wonder if they just had a bad run around that time? All your suggestions sound interesting but with no obstructions laying in the driveway shouldn't I have seen at-least a weak Signal on VHF channel 6? Rick

I got good Signal back on the UHF side after re-aiming. I know my post was rather long but it was in there. I made it long because I didn't want to hijack the thread with little replies,Rick

What do you mean by a weak VHF signal? In the analog TV days, you could see weak signals, but with digital TVs, weak signals don't appear until the signal strength is greater than 15.2 dB above receiver noise. It's the cliff affect. A preamplifier helps if the weak signal is just below this threshold (15.2 dB). However, your mileage may vary. The preamplifier may or may not help at all. You will just have to give it a try.