Draped over the roof?

[mm3148]

I am trying to find a good place to put up my dipole antenna temporarily, the problem I have right now is that I only have 50 ft of coax and for me to get this up into a tree run the coax across my yard and get it hooked up I am going to need much more than that. I have to save pennies right now.

I live in a single story ranch and was going to hang this from the rafters in my attic but I did read that because all my duct work is up there and its all aluminum that would not do well. (is there anyway to take advantage of all that metal up there to boost the antenna performance?)

would just draping it over the roof work until I can get the proper amount of cable to get this up higher? also what would the effects of snow cover be on any RX/TX?

Thanks in Advance

Jon

[MDYoungblood]

I would give it a try, asphalt shingles normally don't contain any metals. I have a friend that has a dipole on the roof, fashioned a short 4x4 to fit the peak (dipole's center)and 2 bricks on each end to give the dipole some tension, all that holds it about 2" off the roof shingles. It is horizontally polarized but he does get out.

3's

Greg

[Scipio Kid]

Hey MDYoungblood,
Do you know if your buddy had a lot of trouble tuning the thing? I had so much trouble with mine I gave up. (Well, 2 feet of snow had a little to do with it too). Before I go back up, I'd like to get as much info as possible. I have a bar-tile roof so I'm hoping if I can get the lengths of cable right, it might be good. I'm also in a canyon or cove so transmitting south is useless, only mountains there but North I'm wide open. If I were to drape it over the roof, like mm3148 suggested, it would be with the vault, so both poles would be on an incline down, one running east and the other west. Wouldn't that tend to make my signal stronger in those directions but weaker to the north and south? I'm also wondering, since I have the mountains blocking me to the south, if there is a good recommendation for making it directional, toward the North but still keeping it close to the roof (one complaint to the HoA and you get a 45 dollar fine ... bunch of dummies). I'm thinking if I drape it over the vault but run the poles on a 45 degree angle from the peak down either side but on an angle to the north or south, rather than keeping them aligned with each other.

These questions are for everyone, not just MD. Experience is far better than trial and error.

And mm,
How'd yours end up working for you?

Thanks.

[MDYoungblood]

He borrowed my analyzer, I think he ended up with the wires at 8' 5" and the SWR was 1.5:1 at 27.2050 and 1.7 at 26.5/27.7 . Getting on his roof is just from his deck using a step ladder so he plays with it all the time. He recently added a a old Archer (RS) ground plane.

3's

Greg

[Scipio Kid]

Thanks,
It may be a couple weeks before I dare get up on the roof (it's still snowing here every other day) to experiment but I'll report back on what works and what doesn't.

[nk14zp]

I have had far better results feeding dipoles with balanced line. Buy or make some. Now this will need a balun. I'm running the balun built into my mfj tuner for now but will be building a link coupled tuner soon.

[Scipio Kid]

Hey nk,
Your solution sounds interesting. Give us some details and pics and keep us up on what you're doing.

Thanks

[nk14zp]

Right now I am just useing 300 ohm tv flat leed in wire from the tuner to the dipole. Otherwise refered to as a doublet antenna.

[nk14zp]

edu6-1.gif

Heres a pic.

[Scipio Kid]

Somewhere, I have an old Realistic antenna matcher (I think that's what it was called) I bought back in the 70's when I was having trouble getting a good match on a big 5/8th wave antenna we put on the roof of our shop. It didn't work at all but it turned out the antenna was fine, the coax was junk. Once we replaced it, we had a perfect match and didn't need the matcher so it's been in a box ever since. Is that "matcher" some sort of tuner like you mentioned? I'll dig it out and try it if you think it's worth it. Otherwise, some recommendations on a good one would be helpful when I get around to installing mine.

Also, we just got a new yard and I'm putting in a base for the security guard there in his trailer. I was simply going to use a mobile whip on his trailer but I've got a 30' steel pole there and thought I'd put up a di-pole on it instead.

I'm thinking though that the steel pole will interfere with the antenna and /or the coax. I was planning to have a mast above the top of the pole and an insulated wire hanging down from that point for the second pole. But that wire would be hanging along side the steel pole and so would the coax. I don't want to go to all that trouble just to find out it won't work.

So, those of you who know, what do you think?

[nk14zp]

The pipe wont affect the coax. That would be a problem with ladder line.

[Scipio Kid]

The pipe or the coax?

I still think a vertical di pole with the lower radial grounded (or not grounded) running parallel with the steel pipe would radiate off that steel pipe and throw your SWR's out of kilter. It seems to me, if it were possible, that a horizontal dipole would work very well because the coax would be coming into the center of it at a right angle. Maybe that might work as an inverted 'V'. I've heard they work pretty good. Hmmmm, still thinking on it.

[Bobcat]

I can't actually vouch for this thing but the guy in the YouTube video makes it sound usable.

39" tall, no ground plane needed.

Workman B100


as always, YMMV but..... it might be better than nothing.

I am trying to find a good place to put up my dipole antenna temporarily, the problem I have right now is that I only have 50 ft of coax and for me to get this up into a tree run the coax across my yard and get it hooked up I am going to need much more than that. I have to save pennies right now.

I live in a single story ranch and was going to hang this from the rafters in my attic but I did read that because all my duct work is up there and its all aluminum that would not do well. (is there anyway to take advantage of all that metal up there to boost the antenna performance?)

would just draping it over the roof work until I can get the proper amount of cable to get this up higher? also what would the effects of snow cover be on any RX/TX?

Thanks in Advance

Jon

[Scipio Kid]

Now that little Workman is impressive for the cost and ease of installation but wouldn't work in a lot of cases (such as mine) where HoA rules prohibit noticeable antennas above the roof line. I can see several ways one might hide it since the antenna itself is so small. I also wonder if it gets out as well as it receives. It's one thing to pull in far off signals but it's another to talk back to them.

Questions for the experts;
The video makes it look very simple, just run a lot of coax to your antenna and screw it on. However, he has a bunch of other stuff up on his mast that he never mentions. What is it? Some kind of balun? How might it contribute to the function of the antenna and how necessary would it be to novices trying the same thing? If I just run coax straight to the antenna, will it get as good a match and work as well as his? Also, I think I (and maybe others with restrictive HoA rules) could mount this thing on top of the roof without getting dinged. The coax however, wouldn't run vertical, down the mounting pipe. It would have to run horizontal along the rooftop to some access point to the house. Wouldn't that screw up the ground plane and thus the SWR match?

Thanks for your thoughts.

[295 antenna]

I have the Tram browning which is basically the same as the workman and it works better than nothing but like you said to be heard any distance i had to get a full size antenna. one of the videos for the workman the antenna is high which works better . If you cannot put it up at least 20 feet it will only be good for talking to someone close by. Anyway thats been my experience. I have not tried side band though.

[MDYoungblood]

Years ago that antenna was called "Saturn", here is the spec and install instructions,

Mine is about 30yo and never been used, sitting in the garage collecting dust. Use the "search" and see who all here has one. Think we are getting a little off the topic.

3's

Greg

[The DB]

I also wonder if it gets out as well as it receives.

Their is something called reciprocity, which states that signals traveling in both directions will be effected equally. It doesn't matter which antenna you use, this is always the case.

It's one thing to pull in far off signals but it's another to talk back to them.

If you are transmitting with the same power as they are, and you can hear them, you can talk to them, assuming their is no interference preventing your response, say someone much closer talking to the same station.

The video makes it look very simple, just run a lot of coax to your antenna and screw it on.

Run a lot of coax... This is the first hint of band antenna design.

However, he has a bunch of other stuff up on his mast that he never mentions. What is it? Some kind of balun?

Looks like a couple of dipoles, one appears to be 2 meters, and the other is about the size of 440 MHz ham bands. They could be for MURS/FRS/GMRS as well as those have similar frequency ranges to said ham band frequencies.

How might it contribute to the function of the antenna and how necessary would it be to novices trying the same thing?

Should be near invisible to CB frequencies.

If I just run coax straight to the antenna, will it get as good a match and work as well as his?

That is a very good question, as this antenna is dependent on the coax for the antenna to function. The downside is different lengths of coax may yield different results. This is why I stated above that this is a bad design.

Also, I think I (and maybe others with restrictive HoA rules) could mount this thing on top of the roof without getting dinged. The coax however, wouldn't run vertical, down the mounting pipe. It would have to run horizontal along the rooftop to some access point to the house. Wouldn't that screw up the ground plane and thus the SWR match?

The "ground plane" doesn't actually exist with this antenna. In this case running the same antenna two different routs can cause the SWR to change. Their is as much if not more signal being radiated from the coax than their is from the antenna itself.

Thanks for your thoughts.

Not a problem.

With this antenna, if it is really the only thing you can do then go for it, but if you have a mast to mount it on get a longer base antenna. The only reason this one seems to work as well as it does on the video is because of the height it is as.


The DB

[Scipio Kid]

Thanks DB,
Sorry to take so long to respond, been out of town. I really appreciate the detailed response(s). Given your assessment of the antenna and design, I think I can do better myself and stay within the HoA restrictions. I've got a dipole up a tree now and no one is bothered by it. But I've got my coax running across the lawn and we almost chopped it up with the mower a time or two! Got to get that changed. Now, what you said about reciprocity ... The antenna that gets the best reception will also do the best transmitting, right? My dipole (as it sits currently) does a lot better on receive than my other antennas but it's got a borderline SWR match. I figure it pulls in far off signals better simply because it's 20' higher in the air, and will do even better once I get the SWR's down ... Am I thinking in the right direction here?

It finally stopped snowing out here (I hope) last week and getting on the roof is now an option. I'm going to try the "draped over the roof thing and see where it goes. I have a three story house so it's up there, out of the mix (will actually be 8 feet higher than the tree) and hopefully will be better than anything else I've tried so far.

[The DB]

Thanks DB

Not a problem.

Now, what you said about reciprocity ... The antenna that gets the best reception will also do the best transmitting, right?

If you are using an antenna for two way communication, this is true. Their are other antenna designs like the rhombic antenna that have other desirable receiving properties, but those you don't transmit on, or do so very rarely, they simply don't work well for that purpose.

My dipole (as it sits currently) does a lot better on receive than my other antennas but it's got a borderline SWR match. I figure it pulls in far off signals better simply because it's 20' higher in the air, and will do even better once I get the SWR's down ... Am I thinking in the right direction here?

As far as height is concerned, yes you are on track. When it comes to performance, the phrase "height is might" when referring to antennas exists for a very good reason. A lesser antenna that is not much higher than a superior antenna will generally outperform said superior antenna. With height, almost every aspect of antenna systems get better.

What SWR are you getting on that antenna? Getting it down, in and of itself, isn't going to affect performance enough that you will notice. Dipoles are naturally about 1.5 SWR so as long as you are somewhat close to that you are fine.

It finally stopped snowing out here (I hope) last week and getting on the roof is now an option. I'm going to try the "draped over the roof thing and see where it goes. I have a three story house so it's up there, out of the mix (will actually be 8 feet higher than the tree) and hopefully will be better than anything else I've tried so far.

In the tree is the antenna vertical? If it is draping it over a roof might be detrimental depending on what you are tying to do with it. You will change the polarization of the antenna, which for DX work will likely not be so noticeable, but with local contacts I bet you will see a difference...


The DB

[Scipio Kid]

Again, thanks for your insight DB,
The dipole is vertical and the SWR isn't good, about a 2.5 to 2.7 so I don't transmit on it. I've been fiddling with it some, got it up higher and set up a coax balun on it and did some fixups to the coax run to the tree. I've still got some work to do so things might be better later. Funny thing, I set this antenna up away from the tree Horizontally and it really pulled in the skip and had a good SWR reading but it was only up for a week or so before the HoA gave me a call to say it was against code. When I switched it to vertical and put it in the tree, the SWR went up. I mounted it on a PVC pipe to make sure there wasn't ground interference but I wonder if that pipe and the tree itself might have something to do with the higher SWR.

I haven't had time to try anything with the roof dipole except some measurements. It'll end up being an inverted V on a 35 degree angle top to bottom running right on the roof ridge. That'll only give the same 35 degree separation between poles and I read somewhere that might not work, but I'll try it and see what happens. I can widen the angle if necessary but it'll be harder to do. We'll see what happens.

[Scipio Kid]

Oh, I've also wondered if the coax, running parallel with the lower pole might be the reason for the bad match. I'm trying to route the coax farther from the antenna and bring it in horizontally to the middle without it being too obvious and having the HoA get on me again. It's a stand-alone tree so suspending the coax from the house makes it stand out.

[The DB]

Oh, I've also wondered if the coax, running parallel with the lower pole might be the reason for the bad match.

Yes it can. That will be at least part of the problem. 1/4 wavelength is the absolute minimum distance that you want the coax to go directly away from the antenna.

When running a vertical center fed dipole most people use the t2lt design.


The DB

[Scipio Kid]

Thanks again DB,

I was all fired up to get this done and run the coax out to the house (figured a way to do it so they neighbors won't mind) and test it out and then I was reminded where I live, Utah. When you have a week with an average temperature of 50 it's only because it's 0 the first half of the week and 100 the last. It's snowing again and supposed to keep it up through Friday. Got a phone call from my son in Hawaii, he laughed and said he was going spear fishing later today. Then I got emails from my daughters in Oceanside Cal and Midland TX. They're laughing at me too. Both are at 80 degrees and loving it.

I know I'm not supposed to sell here but I'm thinkin' any one of you could buy my antenna and the house would come with it and I could go spear fishing with my boy on O'ahu.

P.S. anyone with suggestions or info on setting up a good skip station in Hawaii, my son is very interested, so am I. I want to see if we can skip back and forth some. He's shopping for equipment now but doesn't know quite what to get. (He's new at this and needs a little more experience ... I had to show him how to key a mic last time he was up for a visit. The 'squelch' concept also gave him a headache ... sometimes I wonder what that college degree of his is good for ... ) Oh well.

[Scipio Kid]

Oh yeah, DB,

My design is exactly like the t2lt you suggested (uhhh, except for the part where it doesn't work).

[Blue Ox2]

didn't quite get the Patriot all the way up today. Gotta get another set of arms to help hoist it up while the bolts are tightened. Replacing the TRAM 1499 with the Patriot 12.

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