I've just bought a CM 4221, a four-bay, UHF antenna. CM 4221 (http://www.warrenelectronics.com/Antennas/4221.htm)

I am considering installing this antenna on the top of my old Radio Shack VHF/UHF antenna. I don't know the exact model number, but I think it is close to Radio Shack VU-90 XR. VU-90 XR (http://www.radioshack.com/product/index.jsp?productId=2103085&cp=2032057.2032187.2032189.2032205&parentPage=family) I need a VHF-lo antenna now to receive WBBM-DT (channel 3, my zip code is 60062) and will need a VHF-hi antenna to receive channel 7 (WLS-DT) and 12 (WBBM-DT) after Feb 2009.

What would be the minimal distance required for optimal signal reception between the two?

What about installing the RS above CM? Is it better or worse than the above?

OK. The 4221 won't help you one lick to getting you WBBM -- the Radio Shack already installed will give you more of a shot. The VU90's also going to be better than the 4221, and should be quite good in of itself, at getting digitals 7 and 12 in 2009. It'll also probably do well at the UHFs, including WLS-DT (on channel 52), today.

OK. The 4221 won't help you one lick to getting you WBBM -- the Radio Shack already installed will give you more of a shot. The VU90's also going to be better than the 4221, and should be quite good in of itself, at getting digitals 7 and 12 in 2009. It'll also probably do well at the UHFs, including WLS-DT (on channel 52), today.

I am afraid that you did not understand what I wanted to do. I wanted to keep my Radio Shack to get WBBM-DT now and VHF-hi later. CM 4221 is for UHF, that is for the rest of HDTV channels. :mad: You answer does not help me a bit.

Does not the UHF part of the VU-90 work well enough? As far as I can tell, it should be somewhat close in performance to the UHF-only RS U-75R (since it's literally EXACTLY the same, and made by the same company). I have the U-75R, and I can't imagine the 4221 being much better. I get stations from over 60 miles away with the U-75R.

I would think something like the 4228 would be a more noticable step up. I seriously doubt if you're going to get anything more with the 4221 than you already are with the VU-90 - unless your using the 4221 to get channels in another direction or something like that. Or hoping to pick up channels from the back of it - in which case I'd say just get a rotor.

Does not the UHF part of the VU-90 work well enough? As far as I can tell, it should be somewhat close in performance to the UHF-only RS U-75R (since it's literally EXACTLY the same, and made by the same company). I have the U-75R, and I can't imagine the 4221 being much better. I get stations from over 60 miles away with the U-75R.

I would think something like the 4228 would be a more noticable step up. I seriously doubt if you're going to get anything more with the 4221 than you already are with the VU-90 - unless your using the 4221 to get channels in another direction or something like that. Or hoping to pick up channels from the back of it - in which case I'd say just get a rotor.

Rest assured that CM 4221 is a lot better for UHF reception than my old antenna. I have CM 4221 set up in my second floor study and compared its signal strength with that of my old antenna. So let's not argue whether I need CM 4221 or not. By the way, I did not say I have VU-90 XR but something close to it. :cool:

How are you planning to combine the two antennas? I would install the 4221 above the combo at least 3.5'

Are you using a pre-amp? Do you have a VHF/UHF joiner?

Once a digital signal locks, there's no "better" picture to get, unlike analog. If the Radio Shack antenna can provide a strong enough digital signal to lock the UHFs you want, you don't need the 4221 installed at all.

What would be the minimal distance required for optimal signal reception between the two?

What about installing the RS above CM? Is it better or worse than the above?
All these replies and no one answers the actual questions! My understanding is that you ideally want a gap of several feet between the antenna to keep UHF signal reflections from the big antenna interfering with the reception on the CM 4221. I would install the CM 4221 above the big Radio Shack antenna. It will probably balance better with the torque from long VHF antenna lower down on the pole. In principle, UHF is more line of sight than low VHF, so a little more height for the UHF antenna would be preferred.

As for why a CM 4221, the CM 4221 is an excellent UHF antenna which can pick up stations over a wide spread in azimuth. The UHF part of the big RS antenna is likely far more directional, especially at the higher UHF channels.

Once a digital signal locks, there's no "better" picture to get, unlike analog. If the Radio Shack antenna can provide a strong enough digital signal to lock the UHFs you want, you don't need the 4221 installed at all.

Do you think I am stupid or something? The current setup I have does not work for me. That is why I bought a new antenna. If you cant' make useful replies, why don't you keep your mouth shut?:mad:

How are you planning to combine the two antennas? I would install the 4221 above the combo at least 3.5'

Are you using a pre-amp? Do you have a VHF/UHF joiner?

I am not going to use a pre-amp because I have CM 4221 set up in my second floor study and the HD signals I get are satisfactory. I am planning to have the HDTV in the family room downstairs. So I will mount the antenna on the roof and bring a RG6 coaxial cable to the family room, which is seperate from the old antenna RG59 because the latter is impossible to replace with RG6 in my hand.

I will use a indoor joiner I have now (inside the family room), but I am willing to get a VHF/UHF jointer later. I have read about some Channel Masters joiners. Would you recomment any particular one for my setting?

pinenut,
Put the 4-bay 4ft above the 90.You could get by with 3ft if you knock the reflectors off the UHF section of the 90.
As far as a V/U seperator/combiner,most perform about equal.I use the RS "gold" one.

I've just bought a CM 4221, a four-bay, UHF antenna. CM 4221 (http://www.warrenelectronics.com/Antennas/4221.htm)

I am considering installing this antenna on the top of my old Radio Shack VHF/UHF antenna. I don't know the exact model number, but I think it is close to Radio Shack VU-90 XR. VU-90 XR (http://www.radioshack.com/product/index.jsp?productId=2103085&cp=2032057.2032187.2032189.2032205&parentPage=family) I need a VHF-lo antenna now to receive WBBM-DT (channel 3, my zip code is 60062) and will need a VHF-hi antenna to receive channel 7 (WLS-DT) and 12 (WBBM-DT) after Feb 2009.

What would be the minimal distance required for optimal signal reception between the two?

What about installing the RS above CM? Is it better or worse than the above?

you are confusing this poor guy. he has a great plan.

The separation required between both antennas is about 3.5 feet from the bottom of the cm 4221 to the vu90. there is no need to dismantle the vu90 and the cm4221 will out perform the uhf on the vu 90. The setup will even work on 2 separate masts. you do not need to be concerned about equal lengths of coax.

A cm0549 vhf / uhf antenna combiner works great to combine both antennas and is available for about $10. I use a ton of them for the exact application as you described above. do NOT use a standard combiner. the cm 0549 has electronics within which will isolate the vhf and uhf of both antennas while a standard combiner will not. The cm0549 only has .5 db insertion loss.

http://www.starkelectronic.com/cmjoiner.htm

there is alot of flexibility with this setup. you can pass vhf and amplify uhf, amplify both uhf and vhf, use separate preamps if you desire, or even combine both antennas inside running separate coax from each antenna.

you can also use a cm 7777 preamp which has dual inputs. in your case , use a cm0549 combiner and a winegard hdp269 preamp if an amp is necessary. the cm7777 would overload your setup since you are less than 20 miles from the towers and most stations are yellow based on your antenna web profile.

if you need a wiring diagram let me know.

most would suggest the uhf on top but lo band vhf may benefit with the vhf on top. try the setup both ways and see which works best for you. two separate masts with the 2 antennas may work even better if that does not bother you.

great idea by the way.

Many thanks to those who have given me intelligent and insightful answers.

Rick0725, where do you buy cm0549 vhf / uhf antenna combiners? My zip code is 60062.

http://www.warrenelectronics.com/Antennas/joiners.htm

$8.74

1-800-397-5301

Rest assured that CM 4221 is a lot better for UHF reception than my old antenna. I have CM 4221 set up in my second floor study and compared its signal strength with that of my old antenna. So let's not argue whether I need CM 4221 or not. By the way, I did not say I have VU-90 XR but something close to it. :cool:Sorry if you took what I said as an insult, but I wouldn't even have said it if you had mentioned in your OP that you had actually TRIED the 4221.

It was just meant as a legitimite question.

The thing that concerns me about your proposed setup is the wind load.

The 4221 is a fairly big wind load and you're talking about putting it at the top of a fairly tall mast since it has to go at least a few feet above another antenna, which makes the problem even worse.

If I was doing this, I'd make sure and buy the heaviest mast material and mount from a ham radio outlet rather than the cheap weak mast material sold at someplace like RadioShack.

Plumbing pipe is good.

I don't actually use my antenna anymore, but I did something like this about 2 yrs ago.

I had an old (about 7 yrs) Radio Shack antenna on the roof too, on a rotor. I had about a 7 ft mast mounted to an eaves mount on the peak of my garage roof, and the rotor was at the top of this, with about a 2 foot length of mast between the rotor and the RS antenna.

I got crappy reception of the local Fox affiliate, so I thought I would try the Antennas Direct DB4 (essentially a CM 4220) in combination with the old antenna.

Due to the constraints of the mast that I had, I flipped the mast segments around, so the rotor was on the 2ft mast attached at the roof, and the long mast became the rotating element on the top of the rotor. I then mounted the DB4 below the RS antenna. This isn't ideal, since that tall mast and its long moment arm puts a lot of strain on the rotor bearings during high wind events. It is still standing though, knock on wood!

I removed the UHF reflectors on the RS antenna so they wouldn't block the signal to the DB4. I did the combining with a CM preamp - I can't recall the exact model, but it might have been 7778? This had separate inputs for UHF and VHF on the mast.

To be honest, it didn't help much for me - I live in a heavily wooded area, and there is a pretty tall stand of trees in the direction of the UHF station I was struggling with. These trees are also quite close to my house, on the neighboring lot.

I can take a picture if you want to see what it looks like. I don't recall the spacing I used, but I would guess that it is close to 3-1/2 feet below the original antenna.