Question: question re: 1950s rooftop antenna

Eroc

DTVUSA Jr. Member
#81
Found a great deal on a 91xg for the same price as a HD7694P ($45). I know this is more than necessary but would it hurt? I could use my old antenna for the few vhf channels we get and use this to combine them.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#82
Eroc,

I wouldn't worry about having 'too much' antenna because too much signal strength can be attenuated. The antenna combiner you linked to is very expensive: I suggest a Radio Shack 15-2586 UVSJ which costs around five bucks.

Jim
 

Eroc

DTVUSA Jr. Member
#83
Yeah, I didn't think it would be a problem. I'd love to check out that UVSJ but cannot seem to find it for sale. I did find this and it has been recommended on other forums and seems comparable.
 

dkreichen1968

Moderator
Staff member
#85
Eroc,

I wouldn't worry about having 'too much' antenna because too much signal strength can be attenuated. The antenna combiner you linked to is very expensive: I suggest a Radio Shack 15-2586 UVSJ which costs around five bucks.

Jim
Does Radio Shack even have those anymore? I don't see them listed online ever. That doesn't mean that there aren't a few stores with one or two in stock. Solid Signal seems to be the only reliable source of low cost UVSJs.
 

FOX TV

Contributor
#87
With all of the programming you have in so many different directions, and if you are paying for any type of TV now, it is obvious to me that a one time investment into a modern antenna designed to deal with digital TV signals and an antenna rotor and new cabling would be a wise investment.

If I had access to all of those channels that you have, I would drop my pay tv in a NEW YORK minute. I have used an experimental indoor antenna I designed in a 2nd floor apartment in NEW YORK just a few months ago, and I could receive 35 "Channels" (Actually 35 program streams, not 35 RF Channels). If there were that many channels in my area, I would be determined to try and upgrade to receive them all with a better antenna and a rotor. Digital TV is even more directional than was analog, and a rotor is almost a must in your situation.

You may have some success with your old antenna, but I am sure you would not be able to receive all that were available with your old antenna. It will take repairing the old antenna, and at minimum replacement of the twin lead cable to achieve any decent results. Getting rid of the twin lead cable would be a big help in itself, as it is much more susceptible to interference reception of unwanted signals.

(This is a response to Terry not Eroc, DKR)
 
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Eroc

DTVUSA Jr. Member
#88
Please let us know how things work out.

Thanks,
Dan
Will Do! It is due Thursday and I am headed out of town that evening or the next morning. I already have all the "extras" I'm gonna need: 2 - 3ft rg6 cables, mast, and mount (both already installed). Next I have to see if I can mount them over under like I hope to.

When I do get it done I'll be sure to post pics of the setup!
 

Eroc

DTVUSA Jr. Member
#89
Got it installed. Here are some pics:
antenna1.jpg antenna2.jpg
Everything is clear for the most part. I can now pull in KHFD, but not some such as K31GL and K25FW.

Antennas are pointed roughly at 200 magn.

Someday may get a nicer VHF antenna like the Winegard YA1713, just to have it. Maybe point it E and get RF 7 or whatever.

Thanks again for all the help!
 

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Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#90
Ertoc,

Your second photo shows a Yagi-ish antenna that appears to be NOT designed for the current OTA spectrum. It was probably designed many years ago to receive Channel 83, but channels 83 down to 70 disappeared twenty years ago. Channels 69 down to 52 have also been "reclaimed" by the US Government.

I cannot see that Yagi as being very functional these days.

Jim
 

dkreichen1968

Moderator
Staff member
#91
Eroc,

Your second photo shows a Yagi-ish antenna that appears to be NOT designed for the current OTA spectrum. It was probably designed many years ago to receive Channel 83, but channels 83 down to 70 disappeared twenty years ago. Channels 69 down to 52 have also been "reclaimed" by the US Government.

I cannot see that Yagi as being very functional these days.

Jim
Jim,

That's an Antennas Direct 91XG. There is no way in the world it's a channel 83 antenna.

Dan
 

Eroc

DTVUSA Jr. Member
#92
If you are talking about the antenna on the bottom, that is the one I inherited with the house. It actually picked up UHF ok, but it would drop out more than I liked and I wanted a more up-to-date higher gain antenna for UHF reception. I have the older (lower) antenna hooked up to the VHF side of a UVSJ so it is effectively just a VHF antenna.

One thing, however. I still get some random breakup on KTVT (RF19). It is the worst channel as far as reception goes on my major networks. There are 2 channel 11.1: KTVT and KTVT-DT on my tvfool which are on different RF channels. I tested that 11.1 must be the RF19 channel by unplugging the UVSJ one band at a time. I lost the channel only when UHF was disconnected, so it must be the channel 19 UHF.

Anyway, it is 3rd on the list of highest NM and I am a little confused as to why it breaks up the most.
 

Eroc

DTVUSA Jr. Member
#93
Today had some real bad dropouts with KTVT again. It was windy out, which certainly didn't help. After aiming and changing heights/spacing of both antennas I decided to close the UHF corner reflector on the older antenna being used for VHF only. It seemed to help the most. The wind also died down so it is hard to tell which helped more.
 

dkreichen1968

Moderator
Staff member
#94
May easily be a strong multipath signal. The old antenna may be interfering. It might be a good idea to consider moving the 91XG to a location away from the older antenna.
 

Eroc

DTVUSA Jr. Member
#95
I measured about 28 inches between the antenna. Probably was not adequate with the fairly large corner reflector open so close to the 91XG. Since I closed it, it seems all good. If need be I can probably separate them a little more or move the 91XG if needed.
 

Eroc

DTVUSA Jr. Member
#96
More signal issues today but not as bad. The culprit....wind again. Looks like something I'll have to deal with, with my antennas being in an attic. May go roof mount, for stronger signal at the antenna, but that may not solve all the wind issues.
 

FOX TV

Contributor
#97
Wind loading effects Transmit antennas too !!

Unfortunately, the long boom style antenna in the picture is very prone to multi-path signals, simply due to the length of the boom and the excessive amount of driven elements needed to provide any decent gain.

Also, believe it or not, wind can move the transmit antenna too. This can cause dropouts on windy days, just as movement of a receive antenna can cause issues. Wind loading is always a consideration when designing a transmit antenna also.

The high mounting points of transmit antennas up to 2000 feet on some towers, and even much higher on mountains or tall buildings, puts them in a position to be subject to very high wind loading.

I have seen transmit antennas move as much as 1 foot off center in 50 mile per hour winds, even though they weigh as much as 10,0000 lbs or more in some cases, they are subject to wind movement also.

Look at the picture below, and know that this antenna is mounted on top of a 1,000 foot tower with about 25 1.5 inch diameter bolts on the bottom mounting flange, and the rest of it is free standing on top of the tower exposed to very high winds, so even it moves in the wind. Just a few inches of movement can change the radiation pattern in any direction until it moves back to center.

I have seen 70 mph winds on a 4,0000 foot mountain move a 10,000 lb antenna and cause flex and bending of the tower itself. The antenna below is nothing more than a 60ft section of schedule 120 aluminum pipe with the radiating element located in the center, with appropriate size slots machined in it according to the channel assignment to let the RF energy out of the pipe itself.

It has an orange PVC RADOME or cover that completely surrounds it to keep the rain out of it. It is known as a "SLOT" type transmit antenna, and was made by ERI (Electronics Research, Inc) for UHF channel 20.

242.jpg

Installation of a 60 foot, 8,000 lb antenna in 2009
 
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Eroc

DTVUSA Jr. Member
#98
Unfortunately, the long boom style antenna in the picture is very prone to multi-path signals, simply due to the length of the boom and the excessive amount of driven elements needed to provide any decent gain.
Excessive amount of driven elements? I think you mean parasitic elements aka directors. There is only one driven element (the dbl loop at the back in front of the reflector). It is hard to see this in the pictures, but I can get a close up of it. I thought that the combination of the directors and the reflector made this antenna more directive/smaller beamwidth with added rear and side lobe rejection.? I do agree, however, that the wind can still cause mutipath even for this antenna.

I do see what you mean about the transmitting tower moving in the wind, however. Not much I can do about that, heh.
 
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dkreichen1968

Moderator
Staff member
#99
Here is my latest though for something that you could try. KTVT is one of your strongest stations and you're using an antenna with about 14.5 dB of gain. I'm figuring the signal strength at about 70 dBs. It might not hurt to experiment with an attenuator on the 91XG like Jim suggested above.
 
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Eroc

DTVUSA Jr. Member
Could be, but, I thought overload would occur on all channels not just the offending channel. Also I have clear reception times such as tonight. No dropouts at all. Only during the day and during windy times. Granted I may still get an attenuator to test it out and just to have in case my situation changes.

Another idea would be to remove one of the booms extensions from the 91XG. The manual even states that this is an option, thereby, making it a 43XG and lowering the gain. This seems to be only about a 1db loss but may be all that is necessary.

I still think that is not the issue, but, it couldn't hurt and is not at all expensive for a piece of equipment that is nice to have around.

Thanks for all the input.
 
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