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[AK4YA]

I have poorly though out the cable entry from outside into my shack room.  Its only a single small pvc conduit barely large enough for the ladderline.  Its roughly a foot long and the pvc on the outside of the house terminates into one of these:  https://www.dxengineering.com/parts/dxe-ue-2p

Now I need to put a ground braid through there and I also want to do at least 1 RX-only antenna.

How much interference will putting a ground braid and an RG8 cable along with the ladderline for that 1 foot run cause to that ladderline?  Hopefully this will not be too bad?

And, if doing that run is a problem, I possibly have another option; my balanced tuner does have options for either coax or ladderline for antenna connection, and it also has a built in 1:1 current balun on the transceiver side coax connection.  So would my option there be to just terminate the ladderline directly onto a coax pl219 and then put some choke rf suppression on it?  Or would I need an additional 1:1 current balun, so that I have a 1:1 current balun on each side of my balanced tuner?  Or would all this RubeGoldberg-esque scheme be even worse than that 1 foot colocated run?

[NA4IT]

You might try this for your LL feed...
https://www.m0mcx.co.uk/how-to-use-dual-coax-feeders-as-ladder-line/

[W1VT]

Steve K6OIK describes software sufficiently advanced to model your situation.
HOBBIES Software for Computational Electromagnetics [5.6 MB]

QEX Magazine
Nov/Dec 2020
Steve Stearns, K6OIK
[uploaded 10/26/2020]

ABSTRACT: HOBBIES (acronym for “Higher Order Basis Based Integral Equation Solver”) is software for computational electromagnetic analysis. It is a great tool for modeling antennas, arrays of antennas, coupled transmit and receive antennas, and scattering problems. HOBBIES E&M algorithms are similar to those in the professional program WIPL-D. Due to efficient software architecture and numerical algorithms, HOBBIES can handle very large and complex models on a desktop or laptop computer, for which other software programs would require a supercomputer. The best part is that HOBBIES is inexpensive.[$200 for  book and educational license]
https://www.fars.k6ya.org/docs/k6oik

[K9AO]

So why not fix the through-wall run?

The electromagnetic field of open wire line extends at least to twice the spacing of the cable. So your run with the open wire line alone will have an effect on it. Likely not very much and it should be balanced at least. Running coax and a ground braid inside that run is going to be a problem. I'd be as worried about RF from the open wire line getting onto the coax shield and the ground.

Trying to use baluns to do transforms on complex impedances is not a good idea either.

I'd suggest putting in some larger PVC through wall fittings. One for the coax and ground and another pair side by side for the open wire line with ceramic insulators on each end of the parallel through wall pipes for the open wire line. There are enough instances of fires from open wire line coming in contact with PVC or wood t high voltage points when running high power. You can drill glass though. I did that one time for a run literally through a window.

The parallel coax idea mentioned down the thread at least in the long line run that was described would be very lossy. And, the shields do need to be paralleled and grounded to keep RF off of the outside of the coax shield. Normally you would use metal enclosures at each end of a parallel coax run like this with connectors on the cable that maintained shield integrity between the inner and outer surface of the coax shield.

The separate through wall feed is a better solution.

[WB6BYU]

If you are running the ladderline to a tuner, then
adding a ground strap and another coax shouldn’t
be a major problem, especially if you can keep them
against the side of the tube equidistant from the two
wires of the twinlead.  Yes, there will be a small change
in the line characteristics, but the tuner will take
care of it.

That’s not to say that it is the ideal solution, but you
should be able to get it to work.

If the twinlead is truly balanced (not always the case
with the baluns provided in many tuners) and the added
wires are properly positioned with respect to it inside
the tube, there will be little induced current on the added
wires.  In practice there may be some.  If this is a
problem, then adding a choke/balun in the coax may help.
Details will depend on the specifics, and the purpose of
the ground wire.

[K6BRN]

Running parallel coaxes and a ground wire together through a relatively narrow PVC conduit into a home should not cause issues, though the coax SHOULD have a shield ground/lightning arrestor before the entry point

However ladder line will interact with any metallic objects very close by, which is by definition what happens when multiple lines are run through a narrow plastic conduit.

I would suggest either putting in a 2nd isolated PVC conduit entry point away from any house wiring and plumbing for the ladder line or switching to a coax run just prior to the entry point - you will need a balun for this and will also need to consider antenna mismatch and TX power when choosing a suitable balun.

This is one of the downsides of ladder line.

I run multiple coaxes plus ground through a single PVC entrance conduit at multiple stations without issues, evenwhen running QRO.  But none of them uses ladder line.

Brian - K6BRN

[W1VT]

In theory, if you could perfectly decouple the ends of the two coax shields, you could use the two coax shields as your 1 foot of ladder line!

[K4FMH]

Steve K6OIK describes software sufficiently advanced to model your situation.
HOBBIES Software for Computational Electromagnetics [5.6 MB]

QEX Magazine
Nov/Dec 2020
Steve Stearns, K6OIK
[uploaded 10/26/2020]

ABSTRACT: HOBBIES (acronym for “Higher Order Basis Based Integral Equation Solver”) is software for computational electromagnetic analysis. It is a great tool for modeling antennas, arrays of antennas, coupled transmit and receive antennas, and scattering problems. HOBBIES E&M algorithms are similar to those in the professional program WIPL-D. Due to efficient software architecture and numerical algorithms, HOBBIES can handle very large and complex models on a desktop or laptop computer, for which other software programs would require a supercomputer. The best part is that HOBBIES is inexpensive.[$200 for  book and educational license]
https://www.fars.k6ya.org/docs/k6oik

I looked at HOBBIES when the QEX article was published. The book is now $250 which includes the "restricted size of model" academic license. While a version of the NEC software is now free, it does place hobbyists in a different framework bc of limited support now. I'm looking at AN-SOF which is priced similar to HOBBIES but has superb capabilities and graphics output. Just my two cents here..

Frank
K4FMH

[AK4YA]

ok thanks all..  my cable entry box there even had 2 holes in it for wall entry, I have no idea why I didnt do both when I was getting this house built.  Or why I didnt use the larger PVC for the one I did do.  So  Ive talked to some people they are going to help me drill through this brick to make a 2nd hole in my box.  Ive already checked theres not a stud that will block me

[K4FMH]

Hi Richard,

One observation on my use of ladder line for a horizontal loop. I had to run the LL near an attic HVAC unit to get to my antenna switch feed. No problems until a new AC compressor was installed in that unit. Then, considerable RFI pickup was noticed when the compressor was on. Due to the proximity issues, there was little re-routing of the LL that I could do.

So I measured the "bare wire" feedpoint for the impedance on the fundamental 80M frequency (actually 160-10 but 80M was the design). I then bought a balun to reduce the loop's impedance down to about 50 ohms and then a coax to my switch. RFI problem disappeared.

LL is a good thing but it is RFI prone from a variety of sources. I hope this helps you think through your installation issues. I don't have as large of a PVC pipe for my cable feeds, either, LOL.

73,

Frank
K4FMH

[W1VT]

HOBBIES should be able to calculate the loss of an open wire run being placed inside brick or some other lossy dielectric.  Or if you wanted to bury a short length of open wire underground.

[WA3SKN]

Probably nothing.
However, why not describe the power planned and the antenna(s) planned?
Will you be trying to listen on the recv only antenna while transmitting on the ladder line antenna?
AND... braid is no longer recommended for outside grounding... you may want to look closer at this.
Can you bring the ground and/or recv antenna into the house via another box located a foot or more away from the ladder line entrance?  I usually have one box for ground and coax runs and use a separate box just for the ladder line run... 2 in. grey EL boxes work well as entrance points.

-Mike.

[AK4YA]

Just 100w on an 88ft doublet.  Rx antenna a short active whip to go on the other side of the house.  I would like to observe my TX signal so yes on the FDX.

I do have a 25ft roll of some 1" georiga copper but its just about too wide for my hole with the ladderline.  Now that I plan on a new hole I can use it.

[KH6AQ]

I would try all three lines through the conduit and see how it goes. The antenna tuner should have no problem with it. Where a problem could show up is the RX antenna coax having outer shield current induced by the ladder line. If this seems to be a problem a high-Z CM choke before and after the short conduit length of coax may fix things. G3TXQ designed several coaxial cable chokes you can select from. Eight turns of RG-58 on FT240-31 cores will cover the 80-10 meter bands. 

G3TXQ Chokes  http://www.karinya.net/g3txq/chokes/

[K4SAV]

Ladderline is nice in that it is very low loss, but it's extremely complicated to protect that system from lightning because there is no way to conduct the lightning safely to ground.  You may want to give that some thought. 

I have a lot of lightning, a lot more than I ever expected, living in north Alabama.  I see you live in Prattville.  As much as I would like to use ladderline for some things, I can't do it because I would have major damage within a month due to the frequency of lightning strikes.  I lost count of the number of strikes on my 70 ft (to the top of the mast) of my tower, after about 20 direct strikes.  I have a good grounding system and have had no damage so far.

Congratulations on the new house.

Jerry, K4SAV