Old Radio Shack Antenna in Attic

[lkruper]

Here are my TV Fool results for my location.

I have a 20+ year old Radio Shack Antenna, UHF, VHF, FM in my attic that is 12'6" long. I found the specs here which is for a 21.5db gain.

*** Edit ***
I cannot find an antenna with as high of gain as the Radio Shack Specs. Is it possible that the specs are not realistic?
*** End Edit ***

I went up into the attic and "remembered" that I had put the mast up with duct tape years ago. After a few earthquakes, etc it may have shifted. It was pointed pretty good, but after tweaking it with my TV diagnostics I was able to get channel 7.1 from 85% to 95% and channel 5.1 came in at about 10% which I did not get before. I would really like to get channel 2.1

I get 5.1, 7.1, 9.1, 11.1, 13.1 now all the time and intermittently 28.1 and 56.1.

I have the following equipment between the antenna and the TV receiver.

1) Antenna
2) 25-30 feet of coax
3) A joiner to join my Dish Network Receiver to the antenna
4) About 10 feet coax down the wall to the TV which would be hard to replace.
5) A splitter which takes the signal to the Dish Network Receiver and another to my Slingbox.
6) A short coax from my Slingbox to my TV

Please forgive the formatting, below are my results. I think I can raise the antenna about 3-5 feet. It is currently supported by cross beams in the attic and duct tape around a vertical beam. I have no amplifier. I tried an old Radio Shack amp a few years ago and took it back because I did not see any difference, but I did not have a TV with diagnostics then either.

The last entry in brackets is the new NM(db) and Pwr(dBm) from raising the antenna from 18 to 23 feet. I am not 100% positive I have enought clearance through the support beams to do this. I may only get 2-3 feet at best.

Callsign Real (Virt) Netwk NM (db) Pwr (dBm) Path Dist miles TRUE (Magn) Ant Ht Act TV Signal Ant Ht Max PWR
KVCR-DT 26 (24.1) PBS 56.8 -34.1 LOS 27.9 93 (81) 18 0 23 NC
KABC-TV 7 (7.1) ABC 35.8 -55.1 2Edge 23.5 314 (301) 18 95 23 [40.8 / -50.1] *
KTTV 11 (11.1) Fox 35.7 -55.1 2Edge 23.3 314 (301) 18 Y 23 [40.8 / -50.1] *
KCOP-TV 13 (13.1) MyN 36.8 -54 2Edge 23.3 314 (301) 18 Y 23 [39.9 / -50.9] *
KCAL-DT 9 (9.1) Ind 33.9 -57 2Edge 23.5 314 (301) 18 Y 23 [38.9 / -51.9] *
KTLA-TV 31 (5.1) Cw 26.8 -64 2Edge 23.5 314 (301) 18 2-10 ** 23 [34.9 / -56.0] *
KDOC-DT 32 (56.1) Ind 10.7 -71.1 2Edge 23.5 314 (301) 18 Pix (Int) 23 [27.8 / -63.0] *
KCET 28 (28.1) PBS 16.9 -74 2Edge 23.2 314 (301) 18 Int 23 [24.7 / -66.2] *
KCBS-TV 43 (2.1) CBS 19.5 -71.3 2Edge 23.5 314 (301) 18 0 23 [27.9 / -62.9] *

I will be happy to replace the antenna if it seems prudent, along with coax and add a good powered amp as I have power in the attic. I know the address is not 100% precise, but in taking the height from the existing 18 feet to 23 feet it went from 2Edge to 1Edge. From the DB gain and comparing channel 2.1 to the weakest channel that comes in (5.1) it looks to me that I might get channel 2.1 this way.

One question I had was whether or not I could use a two-input amp and two antenna to get the PBS 24.1 which is line of sight in another direction and should be very powerful at my location, but which I don't get at all. I really need to get either PBS or CBS to get the datastream needed for the Rovi TV guide on my google TV.

Thanks in advance.

My initial plan was to start with new coax where I can replace it and then to add a pream-amp and then finally replacing the antenna with either one or two antennas if necessary. I would be happy with my existing line-up if I could get CBS on 2.1 which antenna web says I cannot get.

[GroundUrMast]

21.5 dB forward gain does not seem plausible... I've seen gain figures like that, only on a pair of 8' diameter parabolic antennas ganged together, weighing about 150 lbs. I suspect that that figure may be the Front-to-Back ratio. Radio Shack has never been known to hire the top of the class from MIT's electrical engineering department.

My first thought re. reception is, try the antenna outside, above the roof line.

[lkruper]

Originally Posted by GroundUrMast

21.5 dB forward gain does not seem plausible... I've seen gain figures like that, only on a pair of 8' diameter parabolic antennas ganged together, weighing about 150 lbs. I suspect that that figure may be the Front-to-Back ratio. Radio Shack has never been known to hire the top of the class from MIT's electrical engineering department.

My first thought re. reception is, try the antenna outside, above the roof line.

Thanks for the reply. I was actually looking at the roof line this evening. Problem is that it would not fit in, in my neighborhood, not to mention the cost and labor of installation. I am sure, though, that at that height I could achieve what I need as it might even be LOS there.

Do you think that a newer antenna of a brand like Channel Master or Winegard would give better performance in the attic?

[GroundUrMast]

If the attic is your only option, I'd err on the side of caution and go big. If it will fit, a Winegard HD7698P is not overkill. You need to overcome the edge path impairments and also deal with the penetration losses and reflections of the attic/roof construction.

[lkruper]

Originally Posted by GroundUrMast

If the attic is your only option, I'd err on the side of caution and go big. If it will fit, a Winegard HD7698P is not overkill. You need to overcome the edge path impairments and also deal with the penetration losses and reflections of the attic/roof construction.

Thanks, I looked at the specs on that and it is about 1.5 feet longer than my existing antenna. Not sure about width, etc. There is a good chance it will fit. I wish I knew the real specs on the Radio Shack antenna to know how much more gain I will get from this one. In 20 years or so, and considering broadcast was analog at the time, have their also been improvements in design/technology? Also, would you recommend an amplifier?

[GroundUrMast]

Without knowing the exact performance of the RS antenna I can't tell you what the difference will be either. Here is the published spec. sheet for the HD7698P: http://www.winegard.com/kbase/upload/HD7698P.pdf. Currently, the HD7698P offers the highest gain performance available in a combination h-VHF/UHF antenna.

Most SoCal attics get way too hot for any active electronics. If you use any amplifier, I think it best to protect it from extreme heat. A Channel Master CM-3414 or CM-3418 depending on the number output ports needed would be my suggestion.

In the analog days, a signal from an attic mounted antenna would be a bit 'snowier' and have a bit more 'ghosting' but you'd be able to watch it without pixelation or complete loss of signal. The 'cost' of digital TV's 'perfect' picture is that once the signal is too weak or there's too much interference, the picture on the screen goes from 'perfect' to gone as if a switch had been flipped. If we were neighbors, You'd see an antenna or two on my roof.

[lkruper]

Originally Posted by GroundUrMast

Without knowing the exact performance of the RS antenna I can't tell you what the difference will be either. Here is the published spec. sheet for the HD7698P: http://www.winegard.com/kbase/upload/HD7698P.pdf. Currently, the HD7698P offers the highest gain performance available in a combination h-VHF/UHF antenna.

Most SoCal attics get way too hot for any active electronics. If you use any amplifier, I think it best to protect it from extreme heat. A Channel Master CM-3414 or CM-3418 depending on the number output ports needed would be my suggestion.

In the analog days, a signal from an attic mounted antenna would be a bit 'snowier' and have a bit more 'ghosting' but you'd be able to watch it without pixelation or complete loss of signal. The 'cost' of digital TV's 'perfect' picture is that once the signal is too weak or there's too much interference, the picture on the screen goes from 'perfect' to gone as if a switch had been flipped. If we were neighbors, You'd see an antenna or two on my roof.

Thanks for the info. What do you think of the 8-bay antennas like Channel Master 4228HD? I found this site that compares antennas.

*** Edit 1/5/2012 ***
My current thinking is this:

Since the stations I am currently pulling in strong are real channels 7,9,11,13 I propose to leave the Radio Shack Antenna in place and add a Channel Master 4228 mounted as high as possible in the attic with a UHF/VHF Combiner.

This will give me three pieces of hardware that could reduce the signal:

1) New UHF/VHF combiner
2) Existing Satellite Mixer combines Dish Network and Antenna
3) Existing Splitter for Satellite to Dish and Antenna to TV

Would it make sense to replace items 1-2 which are 20+ years old with newer items or items with better specs and if so what would these be?

*** End Edit ***

[lkruper]

I have an antenna in the attic and then a diplexer to join the Dish Network to the antenna in the attic and then another diplexer to split the signal back to those two sources. I do not have power in the attic and I know some of the amplifiers send power up the coax to the preamp near the antenna. I think I know the answer but need to confirm. I cannot power the preamp downstream of these diplexers, can I? I understand that there is also power between my dish network receiver and my dish as well.

[GroundUrMast]

I'll continue to recommend an outdoor antenna as opposed to an attic mounted solution.

Re. multiple antennas in the attic; If you can place the antennas so one is not in front of the other, this may work. You should strive to maintain at least 4' of separation form other metal, so if you're mounting one above the other... you need to maximize the distance, at least 4'.

Metal pipe, roof flashing, duct work, etc will all skew the antenna's pattern (aim). This effect can vary from one channel to another.

If you are not using the satellite receiver as your terrestrial OTA/DTV receiver, I would recommend you run the OTA antenna separate of the satellite coax. The losses in the Satellite/TV diplexers are not great, but if they can be avoided, avoid them. Both your OTA and satellite receivers will be that much better off.

If you connect the RS antenna to the VHF port of the UVSJ, the UHF capacity of the RS antenna will be blocked. All of your UHF reception will be the responsibility of the antenna connected to the UHF port of the UVSJ. If it will fit, a single maximum performance combination antenna still seems more viable to me.

[lkruper]

Originally Posted by GroundUrMast

I'll continue to recommend an outdoor antenna as opposed to an attic mounted solution.

Re. multiple antennas in the attic; If you can place the antennas so one is not in front of the other, this may work. You should strive to maintain at least 4' of separation form other metal, so if you're mounting one above the other... you need to maximize the distance, at least 4'.

Metal pipe, roof flashing, duct work, etc will all skew the antenna's pattern (aim). This effect can vary from one channel to another.

If you are not using the satellite receiver as your terrestrial OTA/DTV receiver, I would recommend you run the OTA antenna separate of the satellite coax. The losses in the Satellite/TV diplexers are not great, but if they can be avoided, avoid them. Both your OTA and satellite receivers will be that much better off.

If you connect the RS antenna to the VHF port of the UVSJ, the UHF capacity of the RS antenna will be blocked. All of your UHF reception will be the responsibility of the antenna connected to the UHF port of the UVSJ. If it will fit, a single maximum performance combination antenna still seems more viable to me.

Thanks for the additional information. The channels that are true VHF (7.1, 9.1, 11.1, 13.1) come in really strong. The accessible portion of my attic runs north to south and is about 12' wide but has rafters, etc cutting through the space. I think I can relocate the existing antenna much farther than 4' away from its current position which has the best angle and least interference from the attic walls and roof. I did not know the distance necessary to keep between them. Thanks for filling in that part of the equation.

I would really like to have two separate runs for the Dish Network and antenna, however I don't have good access to the single cable that runs to the location where my TV is located. It looks like the diplexers reduce the dB by about 0.5 each and the ones I see advertised as low-loss don't say how much that is improved.

I do have another possibility that I may try after reading your discussion of using the hdhomerun devices. There are cables in the attic that are not currently being used for other devices. I may consider some other antennas to be used with them in order to record OTA to a NAS device that can be viewed over the network connection.

Thanks for the additional information. I am cursed with the personality that requires me to analyze (over analyze?) things before I take the first steps.

[GroundUrMast]

0.5 dB insertion loss is not going to be improved on enough to spend more money. If your NM/SNR budget is that tight, you need more antenna or a better antenna site.

I am cursed with the personality that requires me to analyze (over analyze?) things before I take the first steps.

Ah!

The first thing that looks good on a menu... "I'm ready, let's order."

My wife needs to read the entire menu... twice, then ask if the server thinks it's a good choice.

I'm not right, she's not wrong, we seem to be wired different. (That's good!)

[Electron]

http://forum.tvfool.com/showthread.php?t=6829