Cutting the cord

[Keith]

Our home has three large antennas in the attic, they all happen to face exactly in the correct direction of our primary tv market. I've connected to one of the antennas and get a great signal, picked up 48 digital channels. Why would someone have three large antennas in the attic. Should I connect them all together to get a stronger signal? If so, anything special to consider as I do so? I loaded photos on post #4.

 

[MrPogi]

If you get 48 channels, you are doing pretty good. Just a guess, but sometimes people get a new antenna and leave the old one sitting in the attic.

I wouldn't connect them together but if you want to know what is best for your situation, just try all 3.

 

[Rickideemus]

Our home has three large antennas in the attic, they all happen to face exactly in the correct direction of our primary tv market. I've connected to one of the antennas and get a great signal, picked up 48 digital channels. Why would someone have three large antennas in the attic. Should I connect them all together to get a stronger signal? If so, anything special to consider as I do so?

If you connect two of them with a simple splitter, you lose 50% of the signal from each, and open yourself up to multipath problems. The classic way to to use two antennas is to point in different directions to catch more transmitters and combine with an A/B switch. Similar with three antennas, just a little more complicated. Can't tell you much more without a TVFool Report and specific makes and models on the antennas.

Rick

 

[Keith]

These were installed together, each are same model and pointed (hung) exactly the same in every aspect. Maybe they used them to feed different rooms. I'm going to post a photo and a cropped close up and will get back to post if I find any markings.

 

[Keith]

I'm unclear about the two rf wires. In the old days, used to hook up to a +/- on the back of the old TV. I can't tell which is which, and I just connected them to the two wires on a rf to coaxial converter. Does it make any difference, did I just get lucky?

 

[Rickideemus]

I'm guessing it's homemade. There are some long time antenna installers who lurk here, but I've never seen anything quite like it. Was it painted? Do you think there's an electrical connection with the big loop in the back? is the other antenna also attached to that big loop? Got any dimensions on the small loop? The big loop? Distance between the two?

It looks like dkreichen's VHF antenna in posts #1 and #17 here: http://www.dtvusaforum.com/dtv-hdtv...ion/47526-my-antenna-system.html#.U3fWHHaKS3Y

But not sure if you really have two elements connected. The size would tell us the frequency it's tuned to. Do you get all the UHF channels in your area? Here are detailed instructions on posting your TV Fool report (read post #2): http://www.dtvusaforum.com/dtv-hdtv...cussion/18368-how-ask-dtv-reception-help.html

Rick

 

[Keith]

It's difficult moving around up there with the blown in insulation. Home-made makes sense in context with the original owner. It may be a week or more before I get back up there, I'll take measurements and check the other two to see if wired differently. Are you saying the two loops should be connected by the joining wire? If so, only one of the two wires on this one is connected. Besides the two loops, there is a long straight tube in the rear. I assumed since the entire antennae is made of metal (I'm guessing aluminium) that all parts touching are in play. Is that not correct? More details will follow about specific stations, etc.., I had to move a tv in the hallway to check it with the temporary wire job I did. Thanks for your help.

 

[Fringe Reception]

Keith,

Rick, no way. That's not a home-brew antenna. The center element is supported by a complex aluminum casting that appears to insulate the lower part of the "loop" driven element from being electrically connected to the opposite side.

Stand by Keith: I'll zap your photos to an old-time antenna installer friend to see if he can identify them.

Since you receive 48 channels you are both lucky and blessed! I hope you aren't using the flat 'twin-lead' open wiring and you are now using a balun and coaxial cable.

Jim :thumb:

 

[Fringe Reception]

Keith,

You probably have the last three (nearly 70 years old) Amphenol Model 114-005 Folded Dipole Antennas remaining on planet Earth, manufactured between 1946 and 1949. As a novilty, Antique Roadshow might be interested because they still work well (48 FREE channels) for you.

* Special thanks to my friend Dan Kurts who researched and quickly found your antennas.

Here's the link (scroll down): 1946-49 Antennas ... the specifications (promises) and the assembly manual is there, too!

Jim

 

[Rickideemus]

Wow! Hat's off to your friend for the speedy research work!!
http://www.avsforum.com/u/7455615/dankurts

I'd still be curious to see the OP's TV Fool report. This antenna is only rated up to channel 13 (215 MHz), and gain appears to be headed toward zero at that point. Peak gain is only 7 dBd. It's very possible a modern antenna could double his lineup.

Rick

 

[Rickideemus]

Are you saying the two loops should be connected by the joining wire?

That's not what I meant, but it looks like that wire in your picture might be the "short transmission line 7" described in the specs. It has directions on how to attach it, if I'm right.

Besides the two loops, there is a long straight tube in the rear. I assumed since the entire antennae is made of metal (I'm guessing aluminium) that all parts touching are in play. Is that not correct?

The large and small loops are elements, which should be connected. The long straight tube in the rear is apparently a reflector (probably not the most effective reflector ever made), and should not be electrically connected.

Rick

 

[Fringe Reception]

I think this strange antenna has two driven elements and I have always found that concept very interesting, but I have not seen it practiced before. A gap (feed point) in the small dipole can be seen in the photo I posted, PLUS the second loop (Keith's photo) appears to have a feedpoint at a brown insulator (bakelite?) on the lower level of the large folded dipole. The long single element is a (parasitic) reflector. Per Keith's report, it works!

I guess it could be called a really simple VHF low and high band Yagi but I have no clue what its' impedence would be (as if anyone cared, 70 years ago).

Jim

PS If Keith supplies the details of this critter, measurements and the tubing sizes, is anyone here game to run it through the NEC-2 program to scrutinize the design? That sounds like a perfect project for our in-house mathematician, Riki ...

 

[Rickideemus]

If Keith supplies the details of this critter, measurements and the tubing sizes, is anyone here game to run it through the NEC-2 program to scrutinize the design? That sounds like a perfect project for our in-house mathematician, Riki ...

I'm willing, but it might take me a month or two to get to it. I'm working on another project for the forum that I think you'll like. The 4NEC2 program is complicated enough it will take weeks to get comfortable with all the input metrics. I'm pretty good at math, but I know next to nothing about electronics. The first half dozen times I use the simulator, I wouldn't have any confidence in my conclusions.

Definitely been wanting to get into the 4NEC2 program, but please understand the time frame. Somebody with experience could probably do it in a day or two.

Rick

 

[MrPogi]

It's hard to read, but they were made in the late 40's - yea, these are old antennas!

 

[Keith]

Rick, that's Amazing. That looks exactly like what I'm seeing. I'll be getting in the attic this weekend to get the specs. If this is correct, now would anyone know why there would be three up there, all lined up in a row? Would they have been working together to create a stronger signal of just used to feed different rooms individually?

 

[Keith]

Jim, I'll be running a coaxial from the antenna, but don't know if there are any special considerations of exactly how to do that. Right now, I have an old converter that was used to attach a tv analog RF input to a coaxial feed. My plan is to connect the antenna(s) to the whole house coaxial system. Currently, no amplifier is being used, not sure how much I'll lose be hooking into house system. My initial testing will be direct to one TV until I set up a permanent connection.

 

[Keith]

As for grounding, can I connect the ground to the ground wire in the electric outlet in the attic or run it all the way out to the ground spike? (Water pipes not an option, all PVC)

 

[Keith]

Here's my tv fool report link. Once I hook up again, I'll check this with what I'm getting and let you know. TV Fool

 

[MrPogi]

The TVfool report solves the mystery of how these antennas that were not designed for VHF get that many channels. Strong signals, so many in the green! With a report like this, almost any antenna would get something!

 

[Rickideemus]

Keith, when you say you get 48 digital channels, I'm pretty sure you're counting subchannels, like 3.2, 10.2 etc. So I think you're getting 18 or 19 separate stations, probably all marked LOS (line-of-sight) in the report. This makes perfect sense with that antenna installed in an attic. If you want to know whether a better antenna could improve your lineup, study up on the stations below those you receive in the Fool Report. Look at the stations at 344° (almost straight north by compass) down through all the yellow (NM = 15.4). Wikipedia is a good resource for that. If there's anything you just gotta have, then a better antenna might be a smart investment. Offhand, it doesn't look like there's much interesting below the green.

Possible reasons for three identical antennas in the attic:
- A previous owner sold those antennas.
- Previous owner had them hooked up to three separate receivers. (A perfectly reasonable solution, if there's enough room.)
- Previous owner thought he could improve reception by ganging them together with a three way reverse splitter.

If you gang carefully, with identical lengths of coax, combining antennas CAN sometimes improve reception. But I think the reason gain is moderate on this antenna is very wide beam width. That means they are going to talk to one another, i.e. multipath. Even if somebody had success combining them 30 years ago, that doesn't mean you'll have much luck now. I don't have any experience with ganging, but theoretically there's so many more stations today, you could get a massive traffic jam up there.

Still, it sounds like you want to do that, and it could be a fun experiment. There are probably people here with real world experience on that kind of thing, and it wouldn't cost much. Or you could get a more directional antenna with higher gain for less than $65, and sell the antiques on Craig's list or eBay.

Grounding to the outlet should be OK, as long as you're sure it's really ground you're connecting to. Technically, I don't think grounding is required for an attic antenna, but it's always a good idea.

Combining the two wires to the one coax with a converter is the way to go. Your converter must have a working transformer (balun) or you wouldn't get so many channels.

Rick