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Author Topic: Alpha Delta DX-EE (Attic Installation Question)  (Read 4302 times)
KD6OZF
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Posts: 5




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« on: March 25, 2011, 09:28:16 AM »

All,

Looking for some advice here...I think I have decided on this antenna to install in my attic due to restrictions in my community. However here is my dilemma, (murphys law all the way).  The antenna is a dipole but it is 40 ft in length overall. My attic space lengthwise is only about 31 ft, where I can sneak this guy in there. I have about a 8ft high roof, but has a heavy steep on it. My question is can I still install this, and allow the wires to touch the rafters in the attic, sort of zig zag around until it fits, without worrying about a fire? I will never run more than 100watts into it, but wondered if anyone had any suggestions on how to secure this to the wood frame in the attic with additional matierials besides the supplied insulators at the end and center feedpoint? I have some concerns here, but maybe some of you have some experience, can shed some light on the subject for me.

Thanks

73

Mike
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W8AD
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« Reply #1 on: March 25, 2011, 09:50:29 AM »

Hi Mike,

We have many customers who have Model DX-EEs installed in attics and have heard from several who have worked 100+ country DXCC with it in attics. Last was from a fellow who had worked 140 countries. Don't know his exact attic set up though. However, and this is the biggie, each attic site is unique with regard to attic wiring, HVAC ducting outside metal gutters, height above ground and roofing materials. Some attic installations work quite well and some are problematic due to all this.

As a minimum, you'd need to use a wide range (10:1) separate antenna tuner to compensate for all the reactances such an installation would pick up. Also, we recommend to never let the antenna wires come closer than two feet from any rafter material and at least three feet from any metal such as attic wiring or HVAC ducting material. With a good tuner, you can snake the wires around a bit, but keep it away from these other things for safeties sake.

Also, based on your situation, you may need to run less than 100 watts to keep RFI from home electronics, phones, burglar alarm systems, garage door opener electronics and security systems. It's a matter of trying it out, as these things cannot be predicted.

It's worth a try, based on your house and attic configuration. It could work out OK but we always give these cautions!

73,

Don, W8AD, Alpha Delta Communications, Inc.
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W0FM
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« Reply #2 on: March 25, 2011, 02:09:14 PM »

Hi Mike,  (hey Don!)

I am one of the guys that Don is talking about who has had very good success with the DX-EE in my attic.  I hung the center insulator dead center along the peak of the roof, down a couple of feet, with Dacron cord.  Then I ran both legs out following the peak of the roof.  When I ran out of space, I put in an insulator (nylon tie wrap) hung down by the same type cord, then let the remaining five feet of each element (40 meter section at that point) just dangle straight down on the ends weighted with a small insulator in case I needed to zig zag it.  It's been like that for over 10 years and I have 230+ DX entities in the log, all with 100 watts or less.  I designed this house so there is no HVAC, low voltage or house supply wires in the attic.  If you have any of those issues, work the elements well around them and keep the elements from contacting any wood.

Yes, it is a compromise antenna situation, but it has been very effective for me.

73,

Terry, WØFM
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W8AD
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« Reply #3 on: March 25, 2011, 03:01:55 PM »

Hi Terry,

Holy Cow. Didn't know you are up to 230 countries with the DX-EE attic set up now. That's got to be a record. And, with the sunspots finally coming up, the higher bands are going to yield some good DX now too.

Thanks for checking in Terry, Always nice to hear from you!

73 and GOOD DX,

Don, W8AD
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VA2FSQ
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« Reply #4 on: April 05, 2011, 08:04:01 AM »

This thread comes at a good time for me...I bought a DX-CC a few months ago and now realize that the only place this could be connected is to a power pole and the tree in the front.  The tree in front will upset my neighbour and the power pole will upset my power company.  So I have just decided to buy a DX-EE.  My attic has no metal (other than shingle nails) not wires nor poles anywhere except at the two ends which are aluminum siding.  It is also 48 feet long.
I do have a couple of questions though.  I plan to run the coax outside to the basement shack.  It will be going through a lightning arrestor just near the entrance.  Should I remove the one on the center of the dipole or is it ok to leave it there?
Also, what effect do you think that the aluminum siding will have?
Finally, the end of the antenna will be about 10 feet away from a living area.  I plan to use up to 100W.  Is this too close for rf and people?

Thanks
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VA2FSQ
W8AD
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« Reply #5 on: April 05, 2011, 09:33:33 AM »

Hi Tom,

Since the ends of the house with the aluminum siding would be perpendicular to the antenna, based on your description, they shouldn't affect the operation of the antenna. There may be some coupling but it should be minimal.

Leave the Model SEP ARC-PLUG installed in the center insulator. It's purpose is to bleed off static voltage build up on the antenna and is not an actual "lightning arrestor" as such. The actual lightning arrestor is to be connected directly to a single point ground bus and/or ground rod at the point of entry to the house, so it serves a different purpose for protection of the equipment.

10 ft. above your room is OK for people when you run 100 watts, or less. Sort of like a mobile environment. However, you'll need to test if RFI will get into your home electronics. You may need to reduce your power a bit more or use RFI chokes on speaker leads and that sort of stuff. That will be an experimental project.

In any case, I would advise using a good wide range antenna tuner to adjust things. We have many successful attic installations like Terry reported, but some are problematic depending on the installation and attic site.

Hope these ideas help out. You might be amazed at the good stuff you can work!

Don, W8AD, Alpha Delta
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VA2FSQ
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Posts: 511




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« Reply #6 on: April 05, 2011, 11:01:10 AM »

Thanks Don.  The attic works pretty well for tv antennas in the past so I'm hopefull.  Just got my license so I am eager to get started...I just need to finish my HW-101 build!
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VA2FSQ
VA7CPC
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« Reply #7 on: April 21, 2011, 05:58:10 PM »

I run an attic-mounted DX-EE, 100 watts from an FT-450. [I think that's the 40m-10m antenna, yes?]

I tied it to my rafters with nylon cord -- you don't need anything fancier, IMHO.   The antenna wires aren't _touching_ the rafters.   It's crammed in (like yours); the overall shape is a "Z".  The center section is straight, the ends are at 90 degrees.

In the attic, I put an LDG Z-11 Pro tuner, in "full automatic" mode -- apply power, it tunes.  It's about 8' from the antenna feedpoint.   My shack is on the second floor, under the attic.   The antenna is usable on 40m (but not very good), and comes alive on higher bands.

It doesn't help that I have metal rain gutters!

Be ready to put ferrite cores on _every control wire and DC power wire_ if your shack is close to the antenna.  And be ready to check for sources of RFI in the house.

                     Charles
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VA7CPC
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« Reply #8 on: April 21, 2011, 06:05:21 PM »

. . .
Finally, the end of the antenna will be about 10 feet away from a living area.  I plan to use up to 100W.  Is this too close for rf and people?
. . .

There's an RF exposure calculator here:

http://www.arrl.org/fcc-rf-exposure-regulations-the-station-evaluation

My gut feel:

. . . Don't worry about it.

But the warning about burglar-alarm systems (in a previous post) -- _that_ can be real trouble.   Ferrites may help.

                  Charles
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