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] 2 Next   Go Down
  Print  
Author Topic: Ladder Line question  (Read 22471 times)
KJ4TRI
Member

Posts: 4




Ignore
« on: July 09, 2012, 01:38:12 PM »

Hello all,

I picked up an FT-817ND as my first “shack” radio (yea, yea bad first choice with QRP, but I am looking forward to the challenge). I do not have an auto tuner but plan on picking one up. The long term goal is to become familiar enough with the 817 to turn it in to a pack radio and eventually “upgrade” to something slightly more powerful (for this layout no more than 200 watts).

Due to HOA I have to go stealth in the attic.

I want to conceal the ladder line between the wood and corner molding of the plastic siding. This would run, approximately, 3 stories from a walk out basement to the soffit where I can handle any stand offs that may be needed once it enters the attic. My question is, how much heat/interference (radiated or inducted interference) will I have to be concerned with.  I am still not sold on the ultimate attic design but it will probably be a dipole.

Again the question is, can I run Ladder Line, up to 200W in such close proximity to vinyl siding and wood or is my shack location a no-go from the start.

Any advice would be appreciated.

Tim
KJ4TRI
Logged
K5LXP
Member

Posts: 4465


WWW

Ignore
« Reply #1 on: July 09, 2012, 02:20:36 PM »

I picked up an FT-817ND as my first “shack” radio
...
Due to HOA I have to go stealth in the attic.

Yeah,  you'll have a challenge alright.


Quote
My question is, how much heat/interference (radiated or inducted interference) will I have to be concerned with.

Heat won't be a problem.  Interference is another question and depends a lot on your specific installation.  It could be totally quiet or RFI hell.  No way to know until you try it.


Quote
I am still not sold on the ultimate attic design but it will probably be a dipole.

Consider a loop too.


Quote
can I run Ladder Line, up to 200W in such close proximity to vinyl siding and wood

Feedline should never get hot.  The energy is delivered to the load and radiated.  (Ideally) nothing will even get slightly warm and if it does, it will be a lumped component and not the wire.

At high voltage nodes there is an opportunity for arcing.  The fix for that is to keep conductors a safe distance from combustibles.

Another option is to put a remote ATU in the attic and use coax from your shack to the attic.  I think it would be easier to mitigate common mode that way.


Mark K5LXP
Albuquerque, NM

Logged
N4UM
Member

Posts: 465




Ignore
« Reply #2 on: July 09, 2012, 03:31:36 PM »

I like K5LXP's suggestion about running coax to the attic and having a remote autotuner close to the antenna feedpoint. 

If you're really set on the ladder line idea, consider whether or not you can run it inside PVC conduit up the side of the house.

I have a dipole in my attic and it really picks up a lot of electrical noise on 80 and 40 meters.

My main antenna is a 23 foot "flagpole" in my back yard with 50 20-foot radials that works well on 40 thru 10.  I feed it thru 13 feet of buried coax going to an autotuner inside a Rubbermaid cabinet on my back porch with about 75 feet of coax going from my rig to the autotuner.
Logged
KJ4TRI
Member

Posts: 4




Ignore
« Reply #3 on: July 10, 2012, 03:27:45 AM »

Thank you both for your opinions and help.

Am I missing something with the coax? I thought the point of ladder line was for low loss? Is the loss factor somehow negated between the auto tuner and the radio (yes the auto tuner adjusts for the overall length but why make it work harder)? I was going with a 5W output and approximately 50 feet from the station to the antenna. I do data cabling (fiber and copper) design and installation, so I have no problem picking up some LMR400 (not sure about adequate pathway but that is my problem).  Even with LMR400, it was my understanding that I was looking at between 0.35db and 1.35db of loss. Granted not much but again if I am starting with 5W I will be looking to make the system as efficient as possible.

It never occurred to me to place the tuner at the antenna location, just one of those “should have been obvious” brilliant ideals. Now you’re going to make me consider a radio with a separation kit and research the maximum separation distance.

Thank you both for your input on this.

Tim
KJ4TRI

Logged
N3WAK
Member

Posts: 274




Ignore
« Reply #4 on: July 10, 2012, 04:16:46 AM »

Jim--I like the idea of coax to a remote tuner, with ladder line from there to your dipole. 

If you run coax, even excellent, low loss coax like LMR 400, to an antenna that is not resonant on the frequency on which you want to operate, you'll have an elevated SWR, as you know.  So, feeding a 20 meter dipole with coax will work great on 20 meters, but there'll be a lot of signal loss on 17 or 15 meters, for example.  However, as you know, ladder line is very low loss, so if you run a length of coax from your transceiver to a tuner (whether manual or automatic), and use ladder line from your tuner to your antenna, you need to realize that you have two discrete parts to your antenna feedline.  The part from your transceiver to your tuner is coax, but there's relatively very little loss in the transmitted and received signal between the two because the SWR is low (your tuner sees to that).  The second part is the ladder line from the tuner to the antenna.  The SWR is high on the ladder line side, but that doesn't matter (relatively speaking) because even with high SWR your loss will be miniscule at HF. 

A lot of people feed their resonant dipoles with coax because the SWR that the transmitter sees is low.  With a low SWR, on HF with a reasonable length of good coax, feeding a 40 meter dipole with coax will work great--as an example.  But because you can't use a 40 meter dipole on 20 meters if you're feeding it with coax (or, more aptly, you wouldn't want to because of horrendous losses in the coax even if you were using a tuner to make the transmitter happy), people instead feed their 40 meter dipole with ladder line and, with a tuner, happily use it between 40-10 meters. 
You just have to locate a tuner somewhere between the transmitter and the antenna. 

Some people use a 3' coax jumper from their transmitter to a manual tuner located in the shack, with LL from there.  Others use a 50' length of coax to a remote, autotuner, with LL from there.  It makes no difference in your signal--it's all up to you how you want to arrange your shack and antenna system.  The nice thing about a remote autotuner is that it gives one a lot of flexibility, since it is easier for most people to run coax into their shack than ladder line--but either way works fine. 

One last thing--as a general rule, because LL has lower losses at HF than coax, it's better in a technically pure sense to have more ladder line and less coax as your antenna feedline.  However, in the real, every day world, using coax at HF if your SWR is less than 3:1 (decent coax of a reasonable length--say, less than 100'), you'll be fine.  You'll have next to no losses on 160 meters even with a 5:1 SWR (IMHO), but you'll have higher losses on 10 meters since coax loses more signal (even with a low SWR) the higher you go in frequency.

So, keep your SWR <3:1 at HF if your antenna feedline is all coax.  (Often, by the way, your 40 meter 1/2 wave dipole will work fine on 15 meters as a 3/2 wave dipole, with a low SWR, even with coax.)   If you're using a tuner and feeding your antenna with LL, don't worry about SWR.  Relax and be happy. 

Good luck and 73!  Tony
Logged
WB6BYU
Member

Posts: 13112




Ignore
« Reply #5 on: July 10, 2012, 05:05:57 AM »

Quote from: KJ4TRI

Am I missing something with the coax? I thought the point of ladder line was for low loss? Is the loss factor somehow negated between the auto tuner and the radio (yes the auto tuner adjusts for the overall length but why make it work harder)?



The loss depends on the SWR on the line.  If you are feeding a single antenna on multiple bands,
likely the SWR will be high on some bands, which increases the losses in the coax.

The ladder line has lower losses, especially when operated at high SWR.  (Usually, but not always.)
So if you have to use an antenna that isn't matched on some bands with a tuner in the shack,
ladder line is often a good choice.

But if the SWR is low, most sorts of coax will have reasonably low losses at HF.  By putting your
tuner in the attic, it should provide a good match to the coax.

Here is a great calculator to see the relative losses of various sorts of cables:

http://www.vk1od.net/calc/tl/tllc.php

For example, even using RG-58 coax on 10m, the loss in 50' is just over 1dB when the coax has
a low SWR, and it will be less on the lower frequencies).  It is only 0.34dB using LMR-400 if you
can run that without it being too noticeable.  Those losses will hardly be significant on HF.

Logged
KG4NEL
Member

Posts: 373




Ignore
« Reply #6 on: July 10, 2012, 11:47:19 AM »

Icom's integration with the AH-4 tuner sounds like it would work perfectly for you Smiley I used a 706MKIIG for a while with an attic loop - tough going with an indoor antenna, definitely. Using Morse or a digital mode would be a huge advantage under these compromises.

If you don't want to be tied down to a single brand of transceiver, SGC would be one to look at too.
Logged
AB4D
Member

Posts: 298


WWW

Ignore
« Reply #7 on: July 10, 2012, 03:30:45 PM »

As others have suggested, use a tuner at the antenna feed point and feed it with coax. I did this for several years to feed a delta loop antenna with an SGC 239 auto tuner. The antenna worked great for what it was.  However, I mounted my antenna outside with the tuner and feed line contained out of sight inside the attic. I used 18 gauge copper weld for the antenna, extended out to each corner and across of the back yard, which was nearly invisible.  A next door neighbor once asked what it was for, I told him SW reception.  He indicated that he used to listen to short wave too when he was a teenager. I never heard another word about it from anyone else for the 5 years I was there.

73
Logged
W5DQ
Member

Posts: 1209


WWW

Ignore
« Reply #8 on: July 12, 2012, 02:36:11 PM »

At high voltage nodes there is an opportunity for arcing ---- FT-817ND Huh

Now chew on that for a minute  Grin
Logged

Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
K5LXP
Member

Posts: 4465


WWW

Ignore
« Reply #9 on: July 13, 2012, 07:20:52 AM »

At high voltage nodes there is an opportunity for arcing ---- FT-817ND Huh    Now chew on that for a minute  Grin

Per the original question:

eventually “upgrade” to something slightly more powerful (for this layout no more than 200 watts).
Logged
W5DQ
Member

Posts: 1209


WWW

Ignore
« Reply #10 on: July 13, 2012, 08:43:03 AM »

At high voltage nodes there is an opportunity for arcing ---- FT-817ND Huh    Now chew on that for a minute  Grin

Per the original question:

eventually “upgrade” to something slightly more powerful (for this layout no more than 200 watts).

I know that ... where's your funny bone ... it was just funny hearing it said in a thread about a FT-817  Grin
Logged

Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
KC4MOP
Member

Posts: 731




Ignore
« Reply #11 on: July 14, 2012, 03:56:57 AM »

The Ladder Line will not like being run near any electrical wiring or passing near metal objects. You mentioned plastic siding, but what is behind this wall as you run the OWL??
OWL is better coming out of the shack and going directly to the antenna.

Here is a boring link to a Youtube movie of my mess............but it works!!
http://www.youtube.com/watch?v=95goqNmJFTQ

In my new QTH , I thought I could run OWL over the drop ceilings in the basement to the shack and was disappointed with S-9++ of trash from the fluorescent lights. So a re-design of coax to the tuner mounted on the basement wall and the OWL goes out through a hole in the wall to the antenna.

Your situation seems better for the coax and auto tuner at the antenna.

Fred
Logged
KC4MOP
Member

Posts: 731




Ignore
« Reply #12 on: July 14, 2012, 07:21:31 AM »

I went past the time to edit my previous.
I think I know where you are trying to go with the OWL and antenna, and your attic antenna.

The OWL will have to be spaced away from any part of the structure about 6 inches. Entering into the attic will be the same hassles of clearances. Window line might be a little easier than the OWL. But still needs to be spaced away from other objects. I would not know how you can test to be assured of no metal whatsoever near the Ladder line. I realize that the vinyl siding will not bother the ladder line, and you hope that there is nothing behind the vinyl that will induce noise into your antenna system (RX) or cause imbalances.
Once in place you hope that the tuner can handle the wide range of impedances involved. I'm assuming 40M and up?? 80M is going to be a lot of problems, but as long as the wire is up there and doesn't double back on itself too much, it might work. 
Good luck
Fred
Logged
KH2G
Member

Posts: 252




Ignore
« Reply #13 on: October 28, 2012, 01:24:48 PM »

Running ladder line flat on the side of a building is never good at best. I suggest you snake some coax up a rain gutter and pull out and under the eaves to your attic. Get matching paint to coat the visible under eave part.
Good luck
Dick KH2G
Logged
K1ZJH
Member

Posts: 947




Ignore
« Reply #14 on: October 31, 2012, 09:56:36 AM »

The SWR at the FEEDPOINT is the critical issue, and determines which feedline will work the best, under ideal conditions.

Pete
Logged
Pages: [1] 2 Next   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!