Cable Penetrations - Corrugated Colorbond Walls

[VK2CSW]

I am looking for ideas for cable penetrations on a corrugated Colorbond shed wall.

What do folks do?

The use of conduit glands is made difficult due to the corrugations.

It needs to be neat and tidy and offer some degree of weather sealing.

It will mostly be 5mm coax. At least three, maybe five cables all up.

[VK5TM]

I can't get on the roof (corrugated iron) to get a photo, but the solar installers used some sort of seal to pass the panel cables through the iron.

Might be worth a bit of searching to see if what they used can be identified and if it is of any use.

A second thought (and one I've used before) - is there any gap between the wall iron and roof at the eaves that will allow feeding cables in?

Edit: Roof Penetration Seals

[VK2CSW]

Hi Terry,

I have looked at some of those types of seals. While effective, they are unsightly and would fail the SWMBO approval process.

I think I may a short piece of some 50mm PVC pipe with a 45° or 90° bend on each end. The opening facing down and once the cables are in place pack it out with, ummm, well something flexible and removable, to stop pests and moisture.

50mm should give me enough room to pass cables with connectors through, as a bonus.

[VK5PJ]

Hello Colin,
if you opt for 75 or 90 mm storm water PVC, there is an abundance of fittings and angle you can use as building blocks.  I have three in the wall here and the outside uses a 45 deg downward bend the middle is a joiner that the outer fitting is connected too via a small bit of 90mm pipe, the inside uses a very neat wall transition I found at the Nuri Mitre 10 (thats why the middle section is a joiner as the transition needs that diameter to work, cannot find it on the Bunno's site for a sample but its worth a browse and let the imagination loose...  I stuff a square of foam mattress material in the hole once the cables are run, its easy to remove and stops the drafts   the key is the imagination LOL

[VK2CSW]

Hey Peter,

I picked up some 50mm bends today at Nuri. Of course, the offcut of 50mm pipe that was under the bench is actually 75mm.

I was looking for mounting ideas while there but came up empty. A small amount of sealant should be enough to affix it all, and allow disassembly if required.

I might stop by BGSFOS (Big Green Shed Full Of Stuff) at Munno Para on my way home tomorrow and get some pipe.

50mm should be enough, plus my hole saws only go to 50mm...

[VK4ADC]

Block out the balance of the 50mm pipe with stainless steel wool - really cheap as per kitchen scourer supplies - just stuff it in. The vermin (/mice/rats/..) won't be able to chew it and won't be able to push it out if you use enough as the blockade.  

The good thing is that it is easy to pull out if you are a human, and won't rust and make more mess.

[VK2CSW]

Cheers Doug.

I shall drop past Cheap as Chips and pick up some scourers.

I dropped in to "Hammer Barn*" and grabbed some 50mm PVC pipe and some silicon sealant.

So now the missing item is now the usual element... Time.

*A pop culture reference to Bunnings. If you know, you know.

[VK2CSW]

Well, some progress.

As I may have said elsewhere, the three supports are up. Three hockey stick eave mounts with a 1m long 40mm PVC pipe cross bar and some custom rigging saddles for the halyards.

This morning I started out getting the "cable duct" done. The penetration ended up being a 50mm PVC pipe section with two 90° bends. A visit to the hardware for a new hole saw and some stainless scourers interrupted play.

Finally the first antenna went aloft. A G5RV Jnr that I found in the same box where I found the old 20m dipole. A fair amount of pruning of trees was needed to get it in clear air, well clearish air.

Got it cabled all the way to the antenna termination plate near the radio. I had just pulled out the nanoVNA to have a look when the full time whistle blew and I was called away to a lunch with friends (that I swear I did not know had been organised).

So the results are not yet in... Nor are any photos yet!

[VK2CSW]

So I dodged some showers and a cold wind this afternoon.

The results on the VNA were disappointing, so more investigation is required.

Below are a few photos of the cable tube, the mounts and the VNA.

   

   

   

   

[VK4ADC]

Colin

There doesn't appear to be much antenna height above the shed roof - or is that an optical illusion ? Close proximity is not going to help your cause.

Secondly, the image of the nanoVNA is too low in resolution for me to see the scales so the frequency and SWR plot (assumed) simply doesn't present useful info. Is it feasible to grab a better image of the nanoVNA screen and re-submit ?

Don't forget that the stainless scourers in the 50mm PVC pipe will also keep out snakes if you stuff the pipe such that they can't push it through/out.

My recollection of a multi-band G5RV-like antenna I used at one time was that there were lots of resonances across HF, and your VNA display doesn't show that. How confident are you that your BALUN is the correct Z-ratio ?  (my memory says that I used a 4:1 but this was some 20 years ago so that might be in error..) Similar resonance responses happened when I tried an OCF dipole for multiband use too, still a 4:1 BALUN. Yours is lacking that effect and the only thing obvious to me is that the impedance transformation ratio could be a long way from optimum.

My multiband wire antennas these days are 'ray dipole' sets, one for 1.8/3.5/7/10/14 MHz and a second one at near right-angles for 3.5/7/10. [ yes, I can fit a full size 160M dipole in my yard..] Somewhat tedious to tune in the beginning but easy-ish once you get the process sorted, and then provides good results without significant tuning interaction.  I used 3mm stainless steel stranded wire (7x7) in lieu of copper so that I would forever lose the moving-frequency effect through wire-stretch.  Set up probably 8 years ago now and never needed to re-adjust dipole lengths...

I know stainless is not recommended by the antenna-bible-bashers (due skin resistance losses at RF) but it is still a good enough option for mechanical reasons.

Keep up the reports Colin, it's always interesting to see how others fare with their antenna experiments/installs.

Doug

[VK2CSW]

Hi Doug,

The wire is about 1.5 metres above the edge of the roof. Not ideal, I agree. I have a cunning plan to raise the centre pole another metre or so but that will be about the limit due to mounts being screwed to the C sections of the shed. I need a chance to get to HammerBarn to get some (more) bibs and bobs.

The G5RV *should* present 50ohms at the feed point at the anointed frequencies, so I have 1:1 choke fitted.

The VNA grab is misleading, due to a PEBKAC error (Problem Exists Between Keyboard And Chair). Apparently the model I have has 101 data points and I swept from 6.9 MHz to 30 MHz. With the narrowness of the bandwidths I suspect it simply bypassed some of the dips.

I will retest using smaller slices around the predicted frequencies.

The other idea is that there is a 4m gap between the two sheds. I will rearrange the antenna so that the "active" leg passes over the gap, with the "counterpoise" leg over the long shed. Will it make any difference? Who knows? It won't take a lot to try...

Time is the killer at the moment. Hopefully at the end of the year I will be able to give full-time work away. (If anyone around VK5 needs a part time Technical Author and Illustrator from next year, don't be afraid to sing out...)

[VK2CSW]

Yesterday and today, between bouts of chainsawing and mulching, I managed to make some, well, progress.

The sweeps of the commercially made G5RV Jnr were all over the place. Nothing where it should be and all very shallow - nothing under 4:1. So the decision was made to replace it with a custom made one. Better, it actually had meaningful dips all half a MHz above where they should be.

So made it half a metre longer on each leg and nothing changed. Mucked around a bit and in the end I decided to leave it for another day.

Next, on the other side of the "yardarm" up went a 20m dipole that I had used in Sydney as a steep inverted V. The sweeps of it were OK with the
lowest VSWR being just below the 20m band. Up, test, down, trim, repeat.

The VNA shows it around 1.3:1 mid band. Good enough for now.

I then pulled down the G5RV from the other side of the yardarm. 20m dipole went to 1.6:1. So more fiddling. Back down to 1.3:1.

So I plugged it into the radio, and dithered around in menus to get it out of digital and into something that would work with SSB. Tuned up OK. Switched to USB on 14MHz and no output. More mucking around (in Sydney I was unable to use voice for several years due to QRM).

Then it hit me.

The microphone wasn't plugged in... There's ya problem.

SB6A in Sweden was calling CQ. So I answered. Straight in. 9&5. Quite pleased...