Element mounting ideas/methods

[VK2FAK]

Hi All..

I wonder what methods that last over at least a couple years, for mounting antenna elements have been used..

I know as far as cost goes, it may not be cheaper to do it yourself than buy fittings from O/S.

I try to stay away from drilling holes in square tubing...I don't have a drill press and from my experience its a pain to get the elements straight ..without one.

While doing something else, I had a look at 10mm tubing with 2 pieces of that Heat shrink tubing that has glue inside, as it is fairly thick stuff, wrap one layer of plumbers tape, the Teflon stuff to give the shrink some cheap and replaceable U/V protection......and then use a saddle clamp to hold it in place. I found some Nylon coated clamps that fit nice and tight over the shrink tubing with no slip and no wobble........weather would be the questionable consideration..
I have used this shrink tube on a balun with some teflon tape wrapped around it,,and its been in the weather a year or so now with no issues...

At the end of the day it would still look ok....

http://g7rau.demon.co.uk/sm5bsz/antenna ... ses413.htm

John

[VK7DX]

Hi John,

I use Pirtec hydraulic pipe fittings,they are available with various hole sizes to suit your element diameter.
Then use steel roofing screws to direct mount to a square boom,very easy and strong.

cheers
Frank
VK7DX

[VK4FP]

I use Stauff clamps..The green ones..Very cheap the 2 shells are to buy..
Get them from your local agent .
Can buy all the mounting hardware as well if required.

http://au.stauff.com/index.php?id=1431

Think it's on their Web site or try phone book to find locally.
Cheers ,Lloyd VK4FP.

[VK3DXE]

Stauff clamps are great, but make sure you do them up tight enough (but not too tight, or you'll squash them), otherwise every time a bird lands on your antenna, the elements get knocked out of alignment. I've finally got mine right now.

Have a look at some of the LFA yagi designs for pics of them.

[VK7DX]

About the only difference between stauff and pirtec clamps is the colour,pirtec is blue,stauff is green.
Use a large flat washer to get them tighter without sqashing.
Pirtec usually sell both brands

cheers
Frank

[VK2GOM]

The last clamps I used were polyamide ones sourced from Nuxcom.de - they are superb. These will take 10mm elements and include the seating to ensure the elements sit squarely on the boom. One but and bolt does it all. Just be sure to use the exact same boom size quoted for the clamps. Some lazy Australian aluminium suppliers quote the size you need, but only after you buy it do you realise it's a 'close(ish) imperial equivalent'. Been there, done that, wasted my money...

They do them for round and square boom of various sizes, and are all on this page:

https://shop.nuxcom.de/index.php?cPath=113_15

Nuxcom do a whole host of antenna building parts, so if you haven't heard of them before, they are a revelation

Thanks to a ZL ham for supplying me with them, although they were a gift, I don't think he has hundreds of them

73 - Rob VK2GOM / GW0MOH

[YU7EF]

Over past 25 years used many different methods and most of them worked fine

However, lately I am using only heat shrink tubing over the element center and fix it in position with hot melting glue
and it proved to be very easy and reliable - my current EF0213M was built 3 years a go and still did not show any sign
of problems, working just as it was on day one. Additional benefit I discovered is that hot melting glue is absorbing
element vibrations so antenna is behaving even better at windy conditions

Attached are pictures showing how I did it

GL, Pop, YU7EF

[VK5APN]

John

I can vouch for the heatshrink tubing over the centre part of the element. I use Silicon sealant.

See my webpage for a how to do, with pics, just like Pops way.

http://people.aapt.net.au/~pearsons/Yagi.html

Regards

Wayne

[VK2FAK]

Hi all....

Thanks to all for the info and suggestions..

I really do have to buy myself a hot glue gun.......have heard it being used before on antenna...but never convinced....but seems plenty have done it....and I always go with experience..

one of the guys in my reading here last evening said he tested it in the microwave and the glue did not heat at all..

John

[VK5ACY]

Hello Pop and others...

I used the heatshrink and hot glue method on a DL6WU-tyle 12el 144MHz Yagi to good effect on Kangaroo Island.

The only problem was that the white cockatoos - for some weird reason - felt the need to pull all the
glue away from the joint. This made for loose elements, so I applied a blob of RTV (Silicone Sealant) as used by
VK5APN in his post above. The cockies still had to play with it but it survived longer.

This is a good method for making experimental beams as the bits and pieces can be cleaned up and reused.

Bill VK5ACY (proud owner of a YU7EF EF0213M "built by VK5PJ" on Pop's website here:- http://www.yu7ef.com/ef0213m.htm)
PF95sb

[VK2FAK]

Hi all....

Just so I have this clear, if I mount on top of the Boom and insulate the element.....what if any adjustments do I need to make to element Free space lengths...?

John

[ZL1RS]

Hi all....

Just so I have this clear, if I mount on top of the Boom and insulate the element.....what if any adjustments do I need to make to element Free space lengths...?

John

It depends on the distance the insulator holds the element away from the metal boom and also what material the "insulator" is made from. Some are loaded with carbon black for uV stability and colour, but this has a measurable effect on the element/Yagi "tuning" at VHF/UHF ... however this will probably not be noticeable on designs with a VERY wide SWR bandwidth (which is usually the only parameter most amateurs check).

The green Stuff clamps hold the elements far enough off the boom that the correction factor required is negligible. I seem to remember G0KCS's web site mentioning +2mm at 2m ??? This will only shift a 2m Yagi by 280kHz and probably not be noticeable amongst the other construction tolerances.

Some commercial Yagi insulators like Nuxcom, Interlanco and Matriplas (I suspect all made by Matriplas?) are loaded with carbon black and only hold the element about 2mm off the metal boom. Both these characteristics have a measurable effect on the elements. Actual experiments here with a VERY narrow SWR bandwidth 2m Yagi design showed a correction factor of +8mm was required for the particular insulators I had from Interlanco (no longer available). This +8mm is actually MORE than the through-boom correction factor(!) and largely due to the carbon black content in the "insulator". Parameters checked were SWR and radiation pattern, both were corrected after applying the +8mm factor determined from the SWR frequency change. Note that this was a VERY narrow SWR bandwidth Yagi of my own design and specifically designed/made to check the particular insulators used because I had been warned of the issue. The next 2m Yagi built was a GoKSC 9 element OWL with the +8mm "insulator correction factor" applied for THOSE PARTICULAR insulators. The resulting SWR curve and radiation pattern were almost exactly as the computer modeling on Justin's web site predicted for that OWL Yagi.

As mentioned above ... although the radiation pattern, SWR and gain curves may be shifted from those indicated in computer modeling, this may not be particularly noticeable or a problem at 2m. I've even built Yagis with insulated through-boom elements (method exactly as shown by YU7EF and VK5APN) and forgot to add the +3.5mm correction factor. The SWR dip was a little high in the band as expected, but I still went on to work dozens and dozens of 2m EME QSOs with the two Yagis and low power (150W) so no real drama. At 2m a 3.5mm error will shift the Yagi by 500kHz ... so if the SWR dip is at 144.6 instead of 144.1 and the SWR curve is wide (as most modern 2m Yagi designs are), then who cares? Regardless of the SWR curve, the Yagi gain curve is usually VERY wide and a shift of 600kHz at 2m will only make a difference of around 0.1 to 0.2 dB ... and no one will notice that in reality. The radiation pattern (including f/b ratio) may still be OK ... again, most modern design Yagis have a reasonably wide f/b ratio bandwidth.

The pedantic should also note: putting plastic caps on the ends of tubes in VHF and UHF Yagis will shift the frequency downwards, and screws through the center of the element into the boom made from magnetic material also have an effect (non-magnetic stainless steel has less effect). There is even a measurable effect between using solid rod and tubes for elements ... if you have a precision laboratory able to measure it!

The real "antenna killer" is using an element diameter that is different from the original design. This can have a profound effect on the frequency of the Yagi.

73, Bob ZL1RS

[VK2FAK]

Hi All...

I had made a 70cm beam using the DK7ZB 16 element version..

It seems to work ok...

This is the simple element mounting I used and I thought I would ask the question, does anyone see any issues before I make a second one..

Its simple, the elements can be removed, repaired if needed and maintenance done on the insulation when needed...
Its been in the weather now for a couple of months with no signs of weathering and having Magpies jumping all over it...
An issue I thought may be a problem but I could not see one, was the clamp holding the element down, it is iron I think, and has a nylon covering.....but testing....I removed the clamp on the 1st Director thinking maybe it they were an issue it would show up there, but nothing was noticeable..

The element has 2 layers of heatshrink with a layer of plumbers tape.....this I know can take the weather as I have the same covering a ferrite balun for my MagLoop. which has been there for 2yrs now with no problems..and the element is sitting on a piece of Poly breadboard, everything can be replaced with no problems if needed..

John

[VK5PO]

the metal over the element (saddle) would have an effect on efficiency of the yagi.

the element lengths would not be correct.

especially at uhf frequencies.

What Diameter are your elements?


Cheers.
John, VK5PO

[VK5BC]

Hi All...

An issue I thought may be a problem but I could not see one, was the clamp holding the element down, it is iron I think, and has a nylon covering.....but testing....I removed the clamp on the 1st Director thinking maybe it they were an issue it would show up there, but nothing was noticeable..

vk2fak 028.jpg

The element has 2 layers of heatshrink with a layer of plumbers tape.....this I know can take the weather as I have the same covering a ferrite balun for my MagLoop. which has been there for 2yrs now with no problems..and the element is sitting on a piece of Poly breadboard, everything can be replaced with no problems if needed..

John

I built a 6el YU7EF design 6m yagi and used white bread board strips across the boom to mount the elements on, the elements were then held to the bread board with black irrigation type clamps. The yagi was up for over 2 years and performed well with no degradation in performace & 1:1SWR.

I would be very hesitant to use metals clamps and in fact tested the bread board & clamps in the microwave prior to using them where there was no heating effect .

73's Brian
VK5BC

[VK2FAK]

Hi all....

The element length issue was the reason I removed it from the 1st director as this would show a sign of some detuning but I found no change...

As I tested it on a Satellite and could still get good copy on a 200mW CW beacon as the bird was crossing into the antarctic at LOS maximum range.....so has reasonable gain.

But I do see the point, and thats the reason I have held off on making a second one just yet....a bit more playing to do......

10mm dia elements..

John

[VK5PO]

10mm elements.
great..

No Glue, No heatshrink tubing, nor silicone, metal saddles, tape .....etc etc...

email me at: vk5po@wia.org

I will send you a picture of a perfect fix.

Cheers.
John