Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Should I hang Ladder Line from the floor joists under my house?  (Read 1655 times)
N4NOO
Member

Posts: 106




Ignore
« on: August 11, 2012, 12:14:00 PM »

My ladder line path is down through the floor and the under my house to the back of the house and out. Then straight up to a fan dipole I am building.  Should I "hang" the ladder line down about 3" from the floor joists?  Also should I put twists in it as it passes near HVAC ducts?  My tuner (Palstar AT4K) has a balanced output which I would like to try.  But generally speaking am I setting myself up for problems?  Like RF in the house, problems being near duct work, any house electrical wiring under the house and such.   Should this type of installation even be tried or just use coax and a balun of some type at some place before the antenna? And if so where and what type of change over from unbalanced to balanced is the most efficient?

Looking forward to your thoughts,

Rick - N4NOO
Logged
W4VR
Member

Posts: 1194


WWW

Ignore
« Reply #1 on: August 11, 2012, 12:39:16 PM »

Most folks use coax inside the house, connect to a remote balun outside, and then use open wire line from that point to the antenna.  However, the coax portion can't be too long of a run. 
Logged
AE5QB
Member

Posts: 269




Ignore
« Reply #2 on: August 11, 2012, 12:50:15 PM »

Yes go ahead.  I have ladder line run through my attic and it works just fine.  Cross any power cables, pipes, or AC ducting at right angles and try to keep it at least 6 inches away from those things or any metal.  There is no problem drooping it down to go around these things.  Yes go ahead and twist it.  You should have pretty good results. 
Logged
WB6BYU
Member

Posts: 13287




Ignore
« Reply #3 on: August 11, 2012, 01:44:12 PM »

Quote from: N4NOO

Should I "hang" the ladder line down about 3" from the floor joists? 



That should work.  I've run it through the attic and the crawlspace under the house
before with no problems.


Quote

 Also should I put twists in it as it passes near HVAC ducts? 



Cross them at right angles.  Twists aren't necessary unless you are running parallel
to another conductor of some sort, but they don't hurt.



Quote

Should this type of installation even be tried or just use coax and a balun of some type at some place before the antenna? And if so where and what type of change over from unbalanced to balanced is the most efficient?



The most efficient point is either at the tuner, or at a point where the SWR on the coax
is low.

If you are using ladder line because it has low loss, then going through a remote balun with coax
from into the house to the tuner, you may find that the loss in that short length of coax is higher
than if you ran coax all the way to the antenna, because it is operating at a high SWR.  In fact,
the losses in 15' of RG-213 used that way can be twice as high as running 75' of RG-58 to the
antenna, and that doesn't include possible tuner losses (which are often, but not always, fairly
low.)  If the ladder line is an electrical half wavelength (or multiple thereof) on each band, it
may work fine.  If it is a quarter wave (or odd multiple) on some bands, and the antenna is
50 ohms, you can have a very high SWR on the coax.  The impedance that the coax sees
is a function of the antenna, the ladder line length, and the operating frequency.

You're building a fan dipole.   Usually that is done to provide a low SWR with coax feed
across multiple bands, so no tuner is needed.  Unless you have a very lossy feedline, there
usually isn't much benefit to using ladder line in that situation.  On the other hand, using
ladder line allows you to operate multiple bands on a single doublet.  For example, a 20m
dipole can be used on 20m through 10m, and possibly on 30m or 6m.  (You do have to
watch the radiation patterns when covering more than a 2 : 1 range.)


There may be some specific reason why you are using a fan dipole with ladder line feed,
but it isn't common.  Usually multiple dipoles on a common feedpoint are used with coax
feed, and ladder line is used for a single wire used on multiple bands.  Not that other
combinations won't work, but it is good to be clear why you're choosing that particular
combination.
Logged
WA4FNG
Member

Posts: 162




Ignore
« Reply #4 on: August 11, 2012, 07:21:23 PM »

Interesting that your using ladder line and tuner for a fan dipole. I'd like to hear more about the antenna. What bands are you including in the dipole? Are you trying to use it for other bands for which it is cut?

-Milt
Logged
N4NOO
Member

Posts: 106




Ignore
« Reply #5 on: August 12, 2012, 10:34:12 AM »

Interesting that your using ladder line and tuner for a fan dipole. I'd like to hear more about the antenna. What bands are you including in the dipole? Are you trying to use it for other bands for which it is cut?

-Milt

No, actually I was not well informed about fan-dipoles.  After discussions with other, more informed operators, I have now decided to use a 6 band (40, 20, 17, 12, 10, 6) fan-dipole with a current balun and coax hung from a halyard on a 30' mast.  Yes, that's a lot of bands but it easy to remove a wire if not needed.  And no worries about running ladder line inside (under) the house.

Many, many thanks to all who helped!

Rick - N4NOO
Logged
AA4HA
Member

Posts: 1451




Ignore
« Reply #6 on: August 12, 2012, 12:51:52 PM »

Interesting that your using ladder line and tuner for a fan dipole. I'd like to hear more about the antenna. What bands are you including in the dipole? Are you trying to use it for other bands for which it is cut?

-Milt

No, actually I was not well informed about fan-dipoles.  After discussions with other, more informed operators, I have now decided to use a 6 band (40, 20, 17, 12, 10, 6) fan-dipole with a current balun and coax hung from a halyard on a 30' mast.  Yes, that's a lot of bands but it easy to remove a wire if not needed.  And no worries about running ladder line inside (under) the house.

Many, many thanks to all who helped!

Rick - N4NOO

I love the idea that you are using ladder line, the much besmirched of feedlines out there that did so well for so many decades. I would be interesting to hear how well you can get a fan to work on 6 meters.
Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!