Gents,

I have a ladder line and balun question that I hope someone can guide me thru.

I had a good working antenna system with two antennas.  First being an Alpha Delta Dipole and the second a 2WL 160m loop antenna at 40 ft in the air strung in trees.  So the wire does touch the trees.

Dipole is fed with coax and choked at the feed point and the loop was fed with 60 ft of ladder line to a 1:1 current balun then 25ft coax to the shack tuner.  Then the amp and radio.   This combination was working real well no RF problems in the shack.

I was advised that I would obtain better results for better SWR at resonance and easier matching if I removed the 1:1 balun and went to a 4:1 balun.  I made this change with everything else being the same.  I now had RF in the shack again.

I then added an isolation balun to the system by adding 6ft coax from the output of the 4:1 to a balun designs 116du which is supposed to have 4500 ohms of choking impedance on 160m and over 5000 ohms choking impedance  on 80 and 40 meters.   This did not eliminate the RF and I am still having problems.

So here is the question, is it possible that with the combination of length of the ladder line at 60ft plus the 6 ft plus 25 ft of coax I am at a feed line length that will be a problem no matter what I do.    I keep looking at the internet to try and figure this out but I am confused as some information I find says it only applies to 1:1 baluns or other factors. 

So anyone who can help me understand this feed line question I will be greatly appreciative.

Thanks
Don
KD8NNU

What do you mean by bonding issues long term

KD8NNU

I just went thru a major issue with ground loops on the equipment side of my shack that appeared when I started to use an amp.

What I learned is that a single point ground of all the equipment, radio, tuner, amp, computer and so on helped my RF and dramatically improved my SN ratio.

So for SN ratio improvement a single point ground helps reduce noise.  I used 10ga wire as I did not have any braid for this grounding/bonding.   There are many articles on the net that describe single point grounds and how to implement them in your shack.   I am planning on braid for the ground in the future to get it even better.

Safety is another issue and if the equipment is AC powered then you need your neutral safety ground connected.  Don't confuse a safety ground with the equipment shield grounding/bonding.  It took me awhile to figure this out and had to re-read many articles and had some conversations with some EE's at work to get a good understanding.

So when guys say you don't need a ground, be careful as they are not saying that you don't need to single point ground or bond your equipment together.   This had me really confused for awhile but I finally got it sorted out.

Remember its more than just a good SWR at an antenna, its also SN ratio and in an attic I suspect you will want to get all you can out of the installation.

Also do research on Common Mode, if your antenna is not properly choked this could lead to problems.

This is a great article on chokes and the site has lots of info to help with the installation 
http://www.audiosystemsgroup.com/RFI-Ham.pdf

Also I am not an expert but I am learning and you can too, that is why its called amateur radio.

Have fun I hope to work you on the air.

KD8NNU
Don

Hi Tom

After a reread of your site I will state that my choke at the antenna feedline is not up to requirements.    I am planning on building a proper choke to kill the CM at the antenna feed .


Thanks for adding this reply.

Don
KD8NNU

Well I finally had time to work on the shack to fix my RF problem.

First thing was to get a dummy load that could run full power of the
amp.  This is done and guess what I had some problems with using the
dummy load.

After much research I determined that my ground was not correct.  What I
mean by not correct it was not a single point and the wires were
insufficient.  I now have 10ga single strand wire for my single point
ground with crimped and soldered ends.   After the grounding things were
fine from 40m on up.

Next all the short coax between all devices was replaced and the PTT to
the amp and on off switch lines were coiled and a #31 snap on ferrite
was used for each one.

Now I did a retest and now I can use the amp all the way down to 80m
with no issues with the dummy load.   I get the same results with the
antenna.  I did some QSO's on 75 and no issues at all.

I still have a bit of a hickup with 160m but research of the amp and the
date of the amp indicates that there is an update needed (resistors
changed) to fix this problem on this band.  So most likely the amp will
be moving to the Jeep in the future and I don't have a 160m antenna I
may not worry about figuring out the update.  I will call SGC just to be
sure I know what it will take.

What have I learned.

With low power 100W a lot of poor installation techniques work and you
have no idea that you have a problem  With an amp things have to be
correct to work.  I had lots of poor techniques.

Proper grounding is important, if you don't use a single point ground
you can expect to have ground loops.  There are many references on the
Internet that show grounding schemes that will create ground loops, so a
single point ground is important.   You also have to have sufficient
copper on the ground as small diameter wire does not cut it.    I do not
know if braid would have been better than the 10ga but I did not have
braid at this time.

Proper choking of all leads that connect to each device in the shack.
In now have a minimum of 7 turns of cable for each device with a #31
choke clamped on to each one.

When you bury cable you must make sure that you purchase cable that is
rated for direct bury if you don't you have problems.  Cable rated for
direct bury is marked on the coax, my first cable was not rated this
way.

What is left to do.

I do not have a proper choke at the antenna so I need to make one in the
next couple of weeks.   I have a bunch of clamp on ferrites but it is
not sufficient for 160m, which will be required if I try to run the amp
assuming I make the update.  I do it for the sake of the K3 cause I can
run barefoot.

Next weekend if I have time I will again connect the loop antenna and
try that again.   However, this time I suspect that I will have a better
chance to make it work based on what I now know and what I have done to
the shack.

Bottom line this is why its called amateur radio.

Thanks for all the help and information that folks sent to me, as I am
now on the air again and safer.


~73
Don
KD8NNU

Unfortunately I fear you are correct on my blender approach.  I have just put in a new coax run for the 100 feet and the problem is exactly the same.   I really thought that would be it but I was wrong, now I am not sure what to do next.  Right now the fun is gone.

Don KD8NNU

Purchased coax is what has gone bad.  The amp goes offline to protect itself, that was one of the other symptoms.

The RF is feedback into the transmitter and amp.

With this RF the amp kicks out and the alc on the K3 trys to back everything down even when there is no carrier on SSB as not talking.

It appears to be mostly the coax as I believe I have a shield problem because if I move it around the problem can go away and if I move it again it comes back this is with the PC turned off.

New coax is ordered and will be installed next week and a new update will be added to the posting based on the results.

KD8NNU

Look me up on qrz and send me an email and I can help you with pics of my mount.  KD8NNU

Jeeps can be a real hassle I have been thru the ordeal with mine and I have the exact system you have so I can help you a lot.  If you email me I will share my phone number and we can talk directly.

Please explain your static drain solution to one who is not knowledgeable.

kd8nnu

First, let me say thank you to everyone on the list who has replied via the list or directly.   The help has been fantastic and has increased my general knowledge as well as helping me with the problem.

Although I have pointed to the start of the problem with the installation of the propane tank and possible crushed coax, I now believe that I have always had some RF issues but it was brought to my attention by the Loop being real bad and then I was highly sensitive to the whole system.

First I had made a significant error in the basic grounding of my shack. This error I will call the green wire mistake.  What I had done was add the chassis ground of all my 12v devices  and tuner to the green wire ground of the house electrical system.  This is in fact a significant error and has been corrected.  What I have learned that there is a difference for a saftey ground for lightening protection and so on and it has nothing to do with an RF ground.  So green wire error fixed, long term a total revamp of the system for a safety ground.

Second I did a lot of checking of the coax yesterday.  Checked it with nothing attached, checked it with a dummy load, used functions of my MFJ 259b that I did not even know existed.  Basically the coax checks out fine, but I still have RF.   The coax at this point in time is no longer buried, I completely unearthed it.

At this point in time I put a choke at the antenna feed up in the air with 31 mix ferrites and no improvement.  So if the problem is at the antenna feed this should have fixed it.  I remove my lightening arrestor from the system just to check it out no change.  So I pull the choke down.

Next I put a choke right at the antenna out the same choke that I had put on the antenna feed point.  Wow big improvement plus I added more snap on 31 ferrite s directly on the coax.   So I have a choke in the shack and now I can go full power.   So having the choke at the feed into the antenna tuner has a dramatic effect.

Now I am thinking ok I will bury the coax again, easy to do in the soft grass plus I want to see if the problem turns on again as I have changed the system with the coax laying on the ground and the outside is dry not directly coupled to the set ground.  After the bury RF is bad real bad. So coax is now on laying on the ground again unearthed and the system again functions, points again to bad coax.

I am now convinced that this is it so I turn on the shack PC to get some more information and so on.  Plus I am talking to some other hams on what I have found.  As the PC boots up the RF is back and it is strong. Holy Sxxt Batman, now what.   So I ponder this for a moment, since I removed my green wire error the PC is no longer connected to the K3 than thru the rs232 so I am assuming Pin1 problem.  I make a ground wire from the chassis of the PC to the center of the grounding point (grounding star as it is referred to) and fixed.  So I take a critical look at the PC installation and the coax runs right next to the PC.  So I disconnect everything and move the PC to the other side of the desk to get it as far away from the coax as I can plus this eleminates short jumper cables for the mouse and so on.  So other than a brief instant when the PC boots up and it is a very specfic part of the boot cycle there is no RF.

So in a nutshell

1) fixed green wire problem
2) unearthed coax and it is laying on the ground on the top of the grass
3) build choke with 31 mix at antenna out on the tuner
4) moved PC

I am on the air.

To do when the order shows up from UPS.

Install new coax, I assume the one I have is not happy anymore and test the system to see if I can remove the choke at the tuner.

From my perspective I am on the air, but I do not have a robust installation being on the 2nd floor.  I probably can survive this winter this way with the simple antenna shield grounding outside as I did last winter as there is no lightning normally.  However, I have to determine the best way to redo the installation and am considering moving the shack to the basement where then it will be signficantly eaiser to have the shack properly grounded for safety and then bonded.

Again thanks for the help, as I am on the air but not convinced that I have it fully cured.  So there may be more questions in the future when I find stuff starts to not work again.

The statement regarding you may see it on some frequencies but not others does match with the problem.  Which is why I was not sure of the coax being a problem or not.   However, if I think about wavelength in the coax and the crush distance it could make a big difference.

I agree with your statement that I will replace it and I can put new ends on it for other installations. 

I have found a simple statement on the web that basically says the impedance changes and RF is reflected back.  Maybe it is just that simple.

Thanks
KD8NNU

I am getting large amounts of RF in my shack.  Everything was working ok up until last weekend and now I have RF issues on TX. 

I was blaming my new loop antenna however, after I removed it I was still getting intermittent issues.  After much research, I realize that I have a lot of ground for both DC and RF work to do with a shack on the second floor.

However with the above being stated, I started to think about what changed and it was a new propane tank installation.  The installer needed to drive the truck on my lawn which means he also drove over my burred coax.  I did have boards down to minimize lawn damage and never gave a second thought about the coax until I started to get the RF in the shack.  I pulled up the coax and found that there is deformation or permanent bends where the edges of the boards were.  So i am thinking that there is a crush in the coax.

I am wondering if this will increase reflected RF as power goes up.  Below 40 watts no problem at 100 watts is starts to show up and turn on the amp once you start a qso in SSB there is a carrier even if you stop talking. 

Does it make sense that it could be the coax.   I can easily afford to replace the coax but I need to try and understand how to diagnose how crushed coax might be the cause.  I would like to understand than just replacing stuff.

Thanks in advance for your help.

KD8NNU
Don

My K3 already has the mic modification from the factory. I have checked this today. 

I also have learned that a 1:1 current balun is what I should be using not a 4:1.

The real issue is that I am in the center of the loop and there may not be anything I can do to rectify the situation short of moving the antenna to another section of property and using masts instead of trees to hold up the wire.

Thanks
Don
KD8NNU

Yep, it is how the trees are set up.   


I have removed the ladderline from the shack and will just use the dipole.   

From some discussions with some hams online, they suggest a 4 to 1 current balun on the outside of the house and only bring COAX into the shack and make sure that all the COAX shields are grounded. 

So short term this experiment is on hold.