How to build a UHF antenna... - Page 131 - AVS Forum
Forum Jump: 
 1Likes
Reply
 
Thread Tools
post #3901 of 4798 Old 04-25-2010, 11:02 AM
AVS Special Member
 
300ohm's Avatar
 
Join Date: May 2008
Location: Somewhere in Delaware
Posts: 1,823
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
The build looks good, but you may be picking up noise from the power lines. VHF/FM is more sensitive to power line noise than UHF.
300ohm is offline  
Sponsored Links
Advertisement
 
post #3902 of 4798 Old 04-25-2010, 01:04 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Liked: 48
Is it power or just cable/phone???

Tie-wraps don't last very long outdoors....even the black ones....
Suggest you use nylon or polyester cord or rope....or whatever....
When the wind whips it around, it's going to break the stub mount.
Suggest you figure some way to brace it so it doesn't twist in the wind,
such as some more of that cord tying the plastic uprights to the pole,
or better yet, something non-conductive and RIGID....
holl_ands is offline  
post #3903 of 4798 Old 04-25-2010, 02:01 PM
AVS Special Member
 
dr1394's Avatar
 
Join Date: May 2002
Location: Mizar 5
Posts: 3,139
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 19
Quote:
Originally Posted by 300ohm View Post

VHF/FM is more sensitive to power line noise than UHF.

That's a poor choice of words. A UHF receiver (with the same noise figure as a VHF receiver) is just as sensitive to man-made noise as the VHF receiver. What's really going on is that power lines produce more noise at lower frequencies.

Ron

HD MPEG-2 Test Patterns http://www.w6rz.net
dr1394 is offline  
post #3904 of 4798 Old 04-25-2010, 03:02 PM
AVS Special Member
 
300ohm's Avatar
 
Join Date: May 2008
Location: Somewhere in Delaware
Posts: 1,823
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:


What's really going on is that power lines produce more noise at lower frequencies.

Yep, thats exactly what I meant.

Quote:


Is it power or just cable/phone???

Those are 600 volt AC lines going into the house. Not exactly the safest of places, heh. Look at 004.jpg


The folded dipole does look like its aiming a bit towards the ground. You might want to adjust that.
300ohm is offline  
post #3905 of 4798 Old 04-25-2010, 04:33 PM
AVS Special Member
 
ProjectSHO89's Avatar
 
Join Date: Feb 2009
Posts: 2,522
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 60
That installation has GOT to be in violation of NEC!
ProjectSHO89 is online now  
post #3906 of 4798 Old 04-25-2010, 05:16 PM
Advanced Member
 
johnpost's Avatar
 
Join Date: Mar 2008
Posts: 783
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
it is a hazardous location for both installation and use. an antenna is above the power line if that came down it could become energized.
johnpost is offline  
post #3907 of 4798 Old 04-25-2010, 07:36 PM
Member
 
jstarling82's Avatar
 
Join Date: Jan 2010
Posts: 124
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I went up on the roof with the horizontal mount this evening around dark and walked around while my wife manned the TV remote. I actually found a spot on the roof where all my stations came in at at least 35%! The two lowest were 3 (NBC) and 39 (ABC), of course, but I was at least able to lock onto a fairly reliable picture.

In this spot, the antenna sits above the roof line, and I can't help but wonder if the vertical stack might give me a bit better picture, now that the reflector is on there.

I'm going to move the short mount up to my hot spot tomorrow and see if I can get it turned and tilted for the best signal. Then, I guess I'll shop for a pre-amp and get that on the way.

Once I get this mounted, is it still ok to run my coax to the grounding block the satellite company used, or is there more required than that?
jstarling82 is offline  
post #3908 of 4798 Old 04-26-2010, 12:03 AM
Member
 
nepaeric's Avatar
 
Join Date: Dec 2008
Location: Scranton/Wilkes-Barre area, Northeastern Pennsylvania
Posts: 150
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Yes, those are power lines. (The upper ones) The lower line is telephone. I'm not sure how legible the photos are, but let me explain a little better. I have a 4-bay mounted on the pole above the power lines, another 4-bay below them and just above the phone line. The FM dipole just below the power line, but above the lower four-bay, on the opposite backside of the pole. All 3antennas are constructed of PVC conduit (3/4" and 1") reinforced with wood. They are all screwed into the pole with heavy duty deck screws about 3" long, and held with galvanized conduit clamps. They've been up there over a year, and I haven't had any problems with any of them yet. No wind is going to blow those down.

I'm wondering how much effect the power lines would have on all of these antennas, because the TV antennas do perform well there, and every bit as good as two other antennas on the other side of the house.

I have never had any outdoor FM antenna anywhere else besides the pole. When I used a twinlead dipole indoors, performance was poor. At the very bottom of the pole is where the line enters the house through the wall is exactly where the stereo is. I couldnt run a shorter length of cable for the stereo, getting the antenna that high.

The pole seemed a logical place for mounting these antennas due to it's height and close proximity to two bedrooms' TV's and the stereo. It also avoids a lot of aggravation of needing to construct, (in this case) three separate masts for the three antennas. I had a huge Radio shack corner reflector yagi with a 6 foot boom, an Archer rotator and 6 foot mast mounted at the very top of the pole, and it was up there for nearly 20 years without any issues or problems.

How much effect can those electrical power lines have on FM reception, and is it anyone's opinion that it would be any better if I moved the antenna a few feet, and put it on a mast instead of the pole? (Or even raise the antenna higher, on a mast, above the power lines)
nepaeric is offline  
post #3909 of 4798 Old 04-26-2010, 12:11 AM
Member
 
nepaeric's Avatar
 
Join Date: Dec 2008
Location: Scranton/Wilkes-Barre area, Northeastern Pennsylvania
Posts: 150
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Holl_ands, would it be acceptable to drill out the dipole, and attach it directly to the PVC with perhaps, (4) #10 brass screws, washers and nuts, for a more secure mounting than the "zip-ties," currently holding it up? I thought about that idea of using nylon rope, too, and also thought that might be a better alternative to the tie wraps, but I'm thinking hardware fasteners would be even better, as long as it wouldn't skew the antenna's design, or interupt the dipole's function as an antenna. I figure brass would hold up better outdoors than steel, and avoid galvanic corrosion with copper.
nepaeric is offline  
post #3910 of 4798 Old 04-26-2010, 02:55 AM
 
BCF68's Avatar
 
Join Date: Apr 2009
Posts: 2,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 19
Quote:
Originally Posted by ProjectSHO89 View Post

That installation has GOT to be in violation of NEC!

Yeah I'm surprised the electric company hasn't come out on said anything about that. Not to mention that was extremely dangerous place to install that. Could very easily get yourself killed.

Also if the folded dipole is supposed to be for FM radio shouldn't it be vertical?
BCF68 is offline  
post #3911 of 4798 Old 04-26-2010, 06:54 AM
Advanced Member
 
johnpost's Avatar
 
Join Date: Mar 2008
Posts: 783
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
nepaeric,

your tv antennas are going to take periodic work, those elements will get bent and you will have go up there every few years. working that close to an energized line is hazardous for a skilled person.

you have all that on a single support now and you could put it all on a single metal mast with a base on the ground and wall support brackets.

usual safety thought is that you don't put up antenna at a height or position that if they fell they would contact a power line or while raising it would come in contact with the power line. almost any sturdy installation in that same area would be safer than your current one.
johnpost is offline  
post #3912 of 4798 Old 04-26-2010, 11:07 AM
AVS Special Member
 
300ohm's Avatar
 
Join Date: May 2008
Location: Somewhere in Delaware
Posts: 1,823
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:


How much effect can those electrical power lines have on FM reception,

That depends on how noisy your power lines are. As close as the FM antenna is now to the power line, its also acting as a poorly placed reflector, most likely decreasing gain.
300ohm is offline  
post #3913 of 4798 Old 04-26-2010, 12:13 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Liked: 48
Quote:
Originally Posted by nepaeric View Post

Holl_ands, would it be acceptable to drill out the dipole, and attach it directly to the PVC with perhaps, (4) #10 brass screws, washers and nuts, for a more secure mounting than the "zip-ties," currently holding it up? I thought about that idea of using nylon rope, too, and also thought that might be a better alternative to the tie wraps, but I'm thinking hardware fasteners would be even better, as long as it wouldn't skew the antenna's design, or interupt the dipole's function as an antenna. I figure brass would hold up better outdoors than steel, and avoid galvanic corrosion with copper.

Not a problem.

BTW: As discussed earlier, in FM Band you have a choice of mounting
Horizontally (like you did), resulting in a bi-directional antenna pattern
or Vertically, resulting in an omni-directional antenna pattern...but the
pole and the wires along the pole are going to degrade this orientation.
There is also a rare possibility that there is an FM station that choses to
broadcast in only/mostly Horizontal....or only/mostly Vertical....YMMV....

Wires strung in the air pick up interference and route it directly to the
vicinity of your antenna cluster....you would be better off....and SAFER
if you moved them as far away as possible...
holl_ands is offline  
post #3914 of 4798 Old 04-26-2010, 12:23 PM
Member
 
jstarling82's Avatar
 
Join Date: Jan 2010
Posts: 124
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by jstarling82 View Post

I went up on the roof with the horizontal mount this evening around dark and walked around while my wife manned the TV remote. I actually found a spot on the roof where all my stations came in at at least 35%! The two lowest were 3 (NBC) and 39 (ABC), of course, but I was at least able to lock onto a fairly reliable picture.

In this spot, the antenna sits above the roof line, and I can't help but wonder if the vertical stack might give me a bit better picture, now that the reflector is on there.

I'm going to move the short mount up to my hot spot tomorrow and see if I can get it turned and tilted for the best signal. Then, I guess I'll shop for a pre-amp and get that on the way.

Once I get this mounted, is it still ok to run my coax to the grounding block the satellite company used, or is there more required than that?

Also, if I were to add a pre-amp to this setup, with my VHF stations already coming in very nicely, could I damage that reception with a combo pre-amp? Would it be possible to pass VHF through a UHF pre-amp without amplifying that particular signal?
jstarling82 is offline  
post #3915 of 4798 Old 04-26-2010, 12:45 PM
Advanced Member
 
johnpost's Avatar
 
Join Date: Mar 2008
Posts: 783
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by jstarling82 View Post

Also, if I were to add a pre-amp to this setup, with my VHF stations already coming in very nicely, could I damage that reception with a combo pre-amp? Would it be possible to pass VHF through a UHF pre-amp without amplifying that particular signal?

you might amplify your VHF signal too much and have that cause problems.

you could split the signal into VHF and UHF with a UVSJ (UHF VHF splitter joiner), amplify the UHF signal and rejoin with another UVSJ.
johnpost is offline  
post #3916 of 4798 Old 04-27-2010, 01:15 AM
MBS
Member
 
MBS's Avatar
 
Join Date: Apr 2010
Location: Copenhagen, Denmark
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi
I have now build a CM4221 and hoped it could work well on the attic ( did not wanted it to be visible outside, but it seemed to loose a lot of gain. It works fine outside :-)
Do you know if there have been measurements of how much signal you loose through different building materials?

I my case the roof is made of 1 layer of red clay tiles (approx. 2 cm thick) and then a "underroof" made of strong plastic (2 - 3 mm thick, to keep the rain, snow wind out)

BR
MBS
MBS is offline  
post #3917 of 4798 Old 04-27-2010, 05:46 AM
Advanced Member
 
johnpost's Avatar
 
Join Date: Mar 2008
Posts: 783
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by MBS View Post

Do you know if there have been measurements of how much signal you loose through different building materials?

I my case the roof is made of 1 layer of red clay tiles (approx. 2 cm thick) and then a "underroof" made of strong plastic (2 - 3 mm thick, to keep the rain, snow wind out)

you can loose 30% to all of your signal depending on your materials. clay tiles may attenuate on the heavy side. if you could aim your antenna out a gable end instead of through the roof deck that may help a lot if you aren't sided in metal. if you relocate the antenna near the gable in the direction you want you will get a greater field of view if needed.

if you look at a plot of tv signal strength for your location then multiply the distance by 2 or 3 then that might be your effective distance. you need a higher gain antenna or amplifier to get that.
johnpost is offline  
post #3918 of 4798 Old 04-27-2010, 06:04 AM
MBS
Member
 
MBS's Avatar
 
Join Date: Apr 2010
Location: Copenhagen, Denmark
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by johnpost View Post

you can loose 30% to all of your signal depending on your materials. clay tiles may attenuate on the heavy side. if you could aim your antenna out a gable end instead of through the roof deck that may help a lot if you aren't sided in metal. if you relocate the antenna near the gable in the direction you want you will get a greater field of view if needed.

if you look at a plot of tv signal strength for your location then multiply the distance by 2 or 3 then that might be your effective distance. you need a higher gain antenna or amplifier to get that.

Thanks
I have already added an amplifier, but the signal varies a lot and in 1% of the time I have problems with the image (pixelize). I have also added a reflector with a distance of approx 11 cm to the CM4221. The reflector is made of multiple layers of alu/silver-foil.
Would it be better to use metal fence or similar?

So I am afraid I need to put the antenna outside which will give me a very low WAF. Are there any thumb rules about how many dB sensitivity you get when you increase the height of the antenna?

BR
MBS
MBS is offline  
post #3919 of 4798 Old 04-27-2010, 06:12 AM
Advanced Member
 
mclapp's Avatar
 
Join Date: Apr 2008
Location: Delaware Co. ,NY
Posts: 717
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by jstarling82 View Post

Also, if I were to add a pre-amp to this setup, with my VHF stations already coming in very nicely, could I damage that reception with a combo pre-amp? Would it be possible to pass VHF through a UHF pre-amp without amplifying that particular signal?

It takes a very strong signal or 2 to overload a decent amp, if you already have an amp give it a try it won't damage anything. If you think your vhf signal is that strong and you don't have an amp yet get one that just passes VHF and amps UHF as already mentioned.
mclapp is offline  
post #3920 of 4798 Old 04-27-2010, 06:25 AM
Advanced Member
 
mclapp's Avatar
 
Join Date: Apr 2008
Location: Delaware Co. ,NY
Posts: 717
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by MBS View Post

Thanks
I have already added an amplifier, but the signal varies a lot and in 1% of the time I have problems with the image (pixelize). I have also added a reflector with a distance of approx 11 cm to the CM4221. The reflector is made of multiple layers of alu/silver-foil.
Would it be better to use metal fence or similar?

Probably not, there's mot much more you can do to an antenna like that to make up for the huge loss from putting it inside.
Quote:


So I am afraid I need to put the antenna outside which will give me a very low WAF. Are there any thumb rules about how many dB sensitivity you get when you increase the height of the antenna?

BR
MBS

Maybe you should make a 2 bay it should be nearly invisable outside if painted the right color and it will most likely get better reception than about anything you can put in your house unless you can find a better inside location.

If we do the math, a 4 bay has about 12 - 16 db gain depending on channel and construction, and indoor locations can kill the signal by 20db more or less depending on house construction materials and antenna location. That's a net of minus 4 - 8 db compared to what's available outside with a zero db gain antenna. A 2 bay should have around 6 -10 db of gain without a reflector so you should have a net gain of 10 - 18 db over the 4 bay mounted inside and the WAF should go up some too.

Keep in mind these are ball bark figures and we are assuming a lot but it's all very possable.
mclapp is offline  
post #3921 of 4798 Old 04-27-2010, 09:11 AM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Liked: 48
Quote:
Originally Posted by MBS View Post

Hi
I have now build a CM4221 and hoped it could work well on the attic ( did not wanted it to be visible outside, but it seemed to loose a lot of gain. It works fine outside :-)
Do you know if there have been measurements of how much signal you loose through different building materials?

I my case the roof is made of 1 layer of red clay tiles (approx. 2 cm thick) and then a "underroof" made of strong plastic (2 - 3 mm thick, to keep the rain, snow wind out)

BR
MBS

Bricks (like clay roofing tiles) had considerably higher loss than wood in NTIA lab
measurements for different materials. BUT actual Attic Loss is considerably higher
than what the lab measurements would indicate....so YMMV.....a LOT.....

Here are some REAL WORLD MEASUREMENTS and a link to those NTIA lab measurements:
http://www.avsforum.com/avs-vb/showt...php?p=14035356

I figure 13dB +/- 7dB (or more) for most situations.....but YMMV....a LOT....
You could be on the upper side of that range....

And if you have A/C and Heating ductwork in your attic, it may have metal spiral wires,
which can wreck havoc on reception.....again YMMV.....a LOT...

PS: I've seen 50% loss mentioned before....and now 30%....
A 50% power loss is only 3 dB and 30% is a mere 1.5 dB....NOT EVEN CLOSE!!!
holl_ands is offline  
post #3922 of 4798 Old 04-27-2010, 11:13 AM
MBS
Member
 
MBS's Avatar
 
Join Date: Apr 2010
Location: Copenhagen, Denmark
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
mclapp&holl_ands, thanks for great info.
I will go for the 2 bay now placed outside, but can I still use the same balun, for the 2 bay? is the impedance the same or smaller? I am using an approx 17 cm long U shaped coax.
MBS is offline  
post #3923 of 4798 Old 04-27-2010, 02:11 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Liked: 48
With a few notable exceptions (Yagi's, Log-Yagi's & LPDA's), most antennas are
matched to 300-ohms, which would employ a 4:1 300/75-ohm Balun to a 75-ohm coax.

I've seen Yagi's & Log-Yagi's (e.g. RCA ANT751 & W-G YA-1713) matched
to 28, 50, 75 and even 300-ohms, depending on the intent of the designer
(K7MEM's on-line Yagi calculator is close to 50-ohms).
Characteristic impedance of LPDA's & Zig-Zag LPA's are also adjustable.

======================
Differences between VHF & UHF Penetration Loss and a summary of
results for a European measurement program can be found here:
http://www.avsforum.com/avs-vb/showt...php?p=17343477

Penetration Loss vs Frequency Lab Test for a Windowed wall can be found here:
http://www.realwireless.biz/publicat...20pdfs/142.pdf

More info re Indoor Penetration Loss and Height Gain:
http://www.digitalhome.ca/forum/showthread.php?p=918798
http://www.digitalhome.ca/forum/show....php?p=1062381

An extensive Literature Survey and Summary of Results:
http://alexandria.tue.nl/extra2/afstversl/E/560768.pdf
holl_ands is offline  
post #3924 of 4798 Old 04-27-2010, 03:58 PM
Advanced Member
 
johnpost's Avatar
 
Join Date: Mar 2008
Posts: 783
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by MBS View Post

I will go for the 2 bay now placed outside, but can I still use the same balun, for the 2 bay? is the impedance the same or smaller? I am using an approx 17 cm long U shaped coax.

are you using a balun that you made from coax?
johnpost is offline  
post #3925 of 4798 Old 04-27-2010, 04:00 PM
Member
 
jstarling82's Avatar
 
Join Date: Jan 2010
Posts: 124
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by mclapp View Post

It takes a very strong signal or 2 to overload a decent amp, if you already have an amp give it a try it won't damage anything. If you think your vhf signal is that strong and you don't have an amp yet get one that just passes VHF and amps UHF as already mentioned.

I wasn't too sure about this point. So a UHF only amp would still pass VHF?

The main one I'd be worried about is channel 9, which is still almost 30 miles away. I found a good deal on a PA-18 from AntennasDirect. Medium gain and very low noise...I thought I'd give it a try, considering the length of cable I'll be using.

On another note, I officially mounted the antenna yesterday. I didn't get the spot quite right because I lost channel 39 again, where I had it during my tests a few nights ago. I also miscalculated the height of the mount, and this thing sticks way up above the roof line right in the middle of the house. Time to try again.
jstarling82 is offline  
post #3926 of 4798 Old 04-27-2010, 09:11 PM
Member
 
nepaeric's Avatar
 
Join Date: Dec 2008
Location: Scranton/Wilkes-Barre area, Northeastern Pennsylvania
Posts: 150
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I figured many of you guys would have reservations about mounting those antennas on the pole by the power lines, and I also thought about some of those comments, so I'm considering, even though it hasn't posed any problem in several years, maybe I've just been lucky, and I have decided to move them over away from the power lines.

On one of those 4-bays, I could actually move it about 10 ft away from the pole, and cut the 20 ft coax down to about 15 ft, saving loss on the slightly longer cable run, and possibly eliminating any problems caused by interference with the power lines and the large pine tree you see in the photos. The other 4-bay, on the other hand, I would have to lengthen the cable run from about 20 ft to about 25-30', in order to move it. The FM Dipole, I am also going to have to increase the 300 ohm twin-lead length, so I have decided to build 14 guage ladder wire to replace it, and even possibly mount it even higher.

I've devised a mast mounting idea, and I'd like some opinions regarding my strategy. I was at the Home Depot, and Lowe's doing some brainstorming, and this is what I came up with for what I think might be overkill, but a seemingly stealth, weatherproof, strong installation:

Looking at EMT conduit, which is super strong, I found that 3/4" will slide nicely and fairly snug inside of 1" PVC. I thought it might look better, not rust, and add strength. Even though EMT is galvanized, it will rust after a lengthy period of time outdoors exposed to the weather. Knowing that ordinary PVC is not UV resistant, I figured 1" PVC gray electrical conduit would work best, and the gray seems to hide well against a cloudy or blue sky better than the white.


I found galvanized, 1" female thread floor flanges for about $4, which are stronger than hell, and could be mounted about 2' below the eve, on an exterior wall, through the siding and plywood with lag bolts. I could thread a 1" male to glue fitting inside, glue on a length just enough to clear the eve, slide in a cut to length piece of 3/4" EMT, glue on an elbow, continue up to the top, slide in another length of EMT, and either glue on a cap, or silicone it closed on top. Mount the antenna to the mast with ordinary U-bolt clamps, and secure a piece of steel strap just under the eve around the mast, and secure it to the side of the house, above the flange with deck screws.

Interested in thoughts or opinions on this. Thanks.

Best Regards,
Eric
nepaeric is offline  
post #3927 of 4798 Old 04-27-2010, 09:20 PM
Member
 
nepaeric's Avatar
 
Join Date: Dec 2008
Location: Scranton/Wilkes-Barre area, Northeastern Pennsylvania
Posts: 150
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
We should probably start a new thread in this forum: "How to build a mast for your UHF antenna, and mount it on your house."

....or "Antenna Mounting for Dummies," (like me) so others here building thier own antennas don't electrocute themselves when they go to mount them on thier roofs!

Furthermore, I also found an ordinary broomstick will also slide inside of 1" PVC just as nicely as 3/4" EMT. Thanks for your opinions on my plans.
nepaeric is offline  
post #3928 of 4798 Old 04-28-2010, 02:41 AM
MBS
Member
 
MBS's Avatar
 
Join Date: Apr 2010
Location: Copenhagen, Denmark
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by johnpost View Post

are you using a balun that you made from coax?

Yes, same principle as from this website: http://www.arcticpeak.com/antennapages/dipol.htm - look at the bottom of the page. Sorry it is in norwegian, but you will get the idea.
MBS is offline  
post #3929 of 4798 Old 04-28-2010, 03:46 AM
MBS
Member
 
MBS's Avatar
 
Join Date: Apr 2010
Location: Copenhagen, Denmark
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by holl_ands View Post

With a few notable exceptions (Yagi's, Log-Yagi's & LPDA's), most antennas are
matched to 300-ohms, which would employ a 4:1 300/75-ohm Balun to a 75-ohm coax.

I've seen Yagi's & Log-Yagi's (e.g. RCA ANT751 & W-G YA-1713) matched
to 28, 50, 75 and even 300-ohms, depending on the intent of the designer
(K7MEM's on-line Yagi calculator is close to 50-ohms).
Characteristic impedance of LPDA's & Zig-Zag LPA's are also adjustable.

======================
Differences between VHF & UHF Penetration Loss and a summary of
results for a European measurement program can be found here:
http://www.avsforum.com/avs-vb/showt...php?p=17343477

Penetration Loss vs Frequency Lab Test for a Windowed wall can be found here:
http://www.realwireless.biz/publicat...20pdfs/142.pdf

More info re Indoor Penetration Loss and Height Gain:
http://www.digitalhome.ca/forum/showthread.php?p=918798
http://www.digitalhome.ca/forum/show....php?p=1062381

An extensive Literature Survey and Summary of Results:
http://alexandria.tue.nl/extra2/afstversl/E/560768.pdf

OK, so if I use the same balun (4:1) to match the 2 bay it should be ok?
I can see from the simulations at http://imageevent.com/holl_ands/mult...oay9u4.panda_s that the impedance also varies along the frequencies.

Thanks again for more info on transmission loss, which convinces me again to put it on the roof.
MBS is offline  
post #3930 of 4798 Old 04-28-2010, 05:45 AM
AVS Special Member
 
ProjectSHO89's Avatar
 
Join Date: Feb 2009
Posts: 2,522
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 60
Quote:
Originally Posted by MBS View Post

Yes, same principle as from this website: http://www.arcticpeak.com/antennapages/dipol.htm - look at the bottom of the page. Sorry it is in norwegian, but you will get the idea.

LOL! Here's Google's translation: http://translate.google.com/translat...tm&sl=no&tl=en

A bit easier to follow...
ProjectSHO89 is online now  
Reply HDTV Technical

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off