Building a K6STI small 5 elts Yagi

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Patrick73
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Building a K6STI small 5 elts Yagi

Post by Patrick73 » 13 Aug 2015 18:41

Hello,

Where could I find a clear and simple sketch showing how to build K6STI 'small 5 lets Yagi' ?
Of course, I had a look at his home page but there are so many figures, charts, diagrams ... I only need a basic drawing with spacings, lengths and so on.

Help would be much appreciated.
Patrick
Main interests : NDB, MW & FM DX'ing
REU Editor http://www.classaxe.com/dx/ndb/reu

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Julian Hardstone
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Re: Building a K6STI small 5 elts Yagi

Post by Julian Hardstone » 13 Aug 2015 21:53

Patrick - The drawing on the K6STI page does not show dimensions, but the dimensions are lower down, in the "Antenna Files" for the European version. From these we can say:
The reflector half-length is 823.0353mm, but I think ±1mm is accurate enough :-) - so:
Refl. 823mm
Driven ele 753
Director 1 665
D2 641
D3 583
The distance along the boom is given from the refector:
DE (feedpoint) 448
D1 578
D2 898
D3 1598
See Brian's construction notes below the Antenna Files

I was thinking about making one, but the big problem is supporting the driven element at 20° and making a waterproof connection. It has to be strong enough not to move in strong winds. One way would be to use a conventional dipole insulator and bend the tube 20° where it joins the insulator, and change the spacing of the reflector to keep the ends 154mm from the reflector. which would probably make very little difference to the analysis (remember, he is working with dimensions specified to 0.1 micron :)

Brian may even see this and post some suggestions, so I hope he will forgive me for taking liberties with his dimensions!

daveB
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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 14 Aug 2015 00:10

As the proud owner of a home-built K6STI I can offer some pointers. First off to say that the finished aerial gives me some 20-23dB f/b ratio right across the band as crudely measured using the dB reading on a sony SB920 . I know it is not that accurate but when a Triax FM3 gives 7dB at the low end up to 15dB at the high end and both agree with the polar plots in 4NEC2 it's good enough. The main proof is I can virtually kill off the London stations when beaming directly away from them.

To the key question - how to mount the driven element. I used Stauff insulators throughout and the insulators were mounted on the lid of a small ABS box. If I remember correctly I used a 150 mm x 100 mm box (it's 6 m in the air so I can't measure it now). I think a 135mm x 75 mm box was too small. The lid of the box was bolted to the boom and then the box it self went over the top after making the coax connection to weather proof it. I cut slots in the box to clear the elements/coax. So the box is not waterproof but weather-proof (so far so good after 20 months) with a couple of small drain holes drilled in the lid. Boom size is 25 mm x 25 mm

You need to make an accurate paper template using a protractor to measure the angle correctly and I've attached a not to scale diagram of how it goes together. I suggest you buy the stauff insulators first play about with the template and confirm what size ABS box you need. Drill the holes with a hand drill to avoid them being sloppy - and use 1-2mm drill to carefully make a pilot hole first. Even so there is just enough movement to allow the elements to be aligned the correct distance from the reflector before finally tightening everything down.

You will find that the driven element will be about 2mm above the plane of the other elements due to the thickness of the ABS box - which is actually less than the difference when buying a commercial dipole centre and element clamps from the same supplier.

If you look through all the pictures on Brian's web-site my one is in there right at the bottom.

Now I am a fumble-fingered 'klutz' and I always measure three times, agonise over it, and then drill /cut. I made sure I used a drill stand / workbench when drilling the boom - and all turned out well with no mistakes made.

All the best - hope you go ahead and build one as it's a really good aerial. F/B ratio isn't as good as Korner but it has a lot lower wind resistance. I used two great big clamp-on ferrite chokes to act as a balun.

Just to add: the aerial is rock solid with no sign of movement of the elements after it was installed in /November 2013. It has been up and down a couple times prior to storms and there is no sign of deterioration in performance even after today's torrential downpours.

Rgds

David
Attachments
K6STI Yagi dipole box.jpg
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 14 Aug 2015 00:27

I'll see if I can find my original notes and bill of materials (if I made one!) to find the ABS box size.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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Re: Building a K6STI small 5 elts Yagi

Post by Julian Hardstone » 14 Aug 2015 02:17

Yes of course David - I see now that Brian has added you to his page.
A bit of that f/b ratio would be welcome here, I ought to be making one now!

daveB
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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 14 Aug 2015 09:46

Hi Julian,
I found my notebook and a prototype template. The ABS box size needs to be something like 115 x 75 x 35 to accommodate the clamps. Here is a link to the Stauff catalogue that contains all the dimensions of the clamps http://www.uk.stauff.com/fileadmin/Down ... s-2014.pdf You can find ABS boxes on e-bay - a company called Discount Devices does a range. I must have used a 135 x 75 x 35 box. They do a more expensive 115 x 90 x 55 box with a deeper lid which might be more suitable from the pov of the amount of box you need to cut away to drop over the elements.

The boom length is 1700 mm as I allowed around 30 mm at each end before the first fixing hole is drilled. Bolts for the clamps should be M6 x 60 mm except for the driven element clamps and the two to attach the box to the mast which should be 40 mm

I should add that my version used half-inch tubing for everything except the driven element as I found that I could only get 16 gauge 3/8th tubing which was quite a bit more than the 18 gauge half-inch stuff. As I've managed to use 4nec2 for basic modelling I could check the effect and adjust dimensions accordingly - I lopped a couple of mm of the element lengths. The reason I stuck with 3/8 for the driven elements was that it resulted in a perfect alignment of all elements in the horizontal plane allowng for the thickness of the ABS box. Probably totally un-necessary to do.

Rgds

DAvid
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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Patrick73
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Re: Building a K6STI small 5 elts Yagi

Post by Patrick73 » 14 Aug 2015 10:53

Thanks Julian and Dave for the precious tips. However, it looks like properly bulding this unit requires some "handyman skills" ;-) (which I don't have).
Patrick
Main interests : NDB, MW & FM DX'ing
REU Editor http://www.classaxe.com/dx/ndb/reu

k6sti
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Re: Building a K6STI small 5 elts Yagi

Post by k6sti » 16 Oct 2015 15:29

I hardly ever visit this forum these days and only happened across this thread by chance. Thanks to Julian and Dave for helping Patrick. I'd like to recommend a commercial version of the Körner 9.2 to Patrick if he doesn't want to construct his own antenna. It works much better than the five-element Yagi and can be purchased from Germany at a reasonable price here:

http://www.antennenland.net/UKW-FM

For those who do want to build their own small FM antenna, this five-element log-Yagi has about the same gain as the five-element Yagi but a much better pattern:

http://ham-radio.com/k6sti/ly5.htm

It is more difficult to construct, but I think the improved performance is worth the trouble. Gain and F/R curves comparing the two antennas and a couple others are near the top here:

http://ham-radio.com/k6sti/five.htm

Brian

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Re: Building a K6STI small 5 elts Yagi

Post by Julian Hardstone » 16 Oct 2015 19:39

Exciting news about the new compact K6STI design, Brian.
As ever, the F/B ratio is most impressive; in a location like mine, that parameter is the most important by far.

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Re: Building a K6STI small 5 elts Yagi - photos

Post by daveB » 25 Oct 2015 11:20

I've just taken down the K6STI small yagi for a pre-winter maintenence check - after 23 months in service.

I've attached photos of the driven element support so a) you can see how I did it and b) that after 23 months there is no sign of corrosion - even though as one photo shows the box is not waterproof. [My original intention was that if there were to be signs of corrosion I would buy a new box and re-mount the dipole differently].

The main thing IMO is to protect the connections from the rain, not to waterproof it - it's the coax that needs to be protected from water ingress- obviously the way I crudely hacked holes in the side of the box wouldn't do for vertical mounting!
Dipole connections.JPG
The brass mounting pillars came off a commercial dipole centre which was surplus to requirements. The eagle eyed will spot that I have drilled two small drainage holes to prevent moisture build up.
Dipole Mount Top.JPG
Spot where the spider has been!
Dipole Box.JPG
A crude hacksaw job to give clearance to the dipole elements.

I hope this will encourage others to try and build this aerial - which I think will be easier than the latest design using phasing lines. The box size is 100 mm x 75 mm x 40 mm. The cheapest you can buy one of similar size on ebay is £3.90 inc from electromartuk2000

BTW - I was looking for dipole centre supports - three years ago the ones for half-inch elements cost around £4.50 - ebay is now selling than for around £15!

Regards

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

mnicolau
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Re: Building a K6STI small 5 elts Yagi

Post by mnicolau » 13 Feb 2017 14:00

Hi,
Could you upload the photos again?
Could you post the photos again?
Thank you


Miquel

mnicolau
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Re: Building a K6STI small 5 elts Yagi

Post by mnicolau » 13 Feb 2017 16:03

Hello!
I'd try to building a K6STI small 5 elements Yagi and I have a lot of questions.
Look at the image in the next url and tell me if I understand it. All are in mm.
https://drive.google.com/open?id=0B-4Sh ... WFaN1g2enM
Do you see any mistake?

And in the second image in https://drive.google.com/open?id=0B-4Sh ... 2sxb3ZaR2M . What is OK? 752 mm or 742 mm?

If I can building the small 5 elements yagi. The next building perhaps will be the Körner 19.3 :x
Thank you

Miquel

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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 13 Feb 2017 21:34

Hi Miquel,

The dipole dimension is 752,8 - but 753 mm if cutting by hand. All the other dimensions are correct according to the K6STI web-page - for 10 mm elements.

Here is a picture of how I used Stauff clamps and a small ABS box to mount the dipole.
Dipole Mount Top.JPG
The picture was taken after the aerial had been in use for 2 years. The next picture shows the bad job I made of cutting the top of the box to make space for the elements - but as the first picture shows - it provided good protection as there are no signs of water ingress. But only good for horizontal polarisation.
Dipole Box.JPG
Draw out the angle and placement of the element clamps on a piece of paper and use that as a template for drilling the holes.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

mnicolau
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Re: Building a K6STI small 5 elts Yagi

Post by mnicolau » 16 Feb 2017 16:31

I live in Majorca Island (Spain)
I tried to buy a Körner 9.2 last year in http://www.antennenland.net . But Antenneland.net told me "We do not ship to the Balearic or Canary Islands. (+99999.00 €)"
I just have tried to buy aluminum 6063 but in stores they do not know what is "aluminium 6063". They only sell "standard" aluminum
The minimum size I can buy round tubes in Mallorca is 20 mm of "Standard" aluminium.
The shops on-line in Spain do not sell to islands.
What happen if I build the antenna with standard aluminium?
Thank you David and all the people for your time.

daveB
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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 16 Feb 2017 23:32

I have checked the performance of the compact yagi using 20 mm diameter elements using the 4nec2 program. It appears to work quite well up to 106 MHz - but I would not recommend spending lots of money to build one - it may not actually work the way the computer program says. The problem is DHL and others will not ship 200 cm long packages. From UK to Balearic islands they want 85 euros to ship a 2 kg parcel 120 cm long - more than the cost of an aerial.

Can you purchase any Band 2 FM aerials on Mallorca - a standard 3, 4 or 5 element? If so it might be cheaper to buy a couple and use the elements as parts.
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

daveB
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Re: Building a K6STI small 5 elts Yagi

Post by daveB » 20 Feb 2017 21:38

Here is a copy of an e-mail I just got from Garry Smith of HS Publications who can make a 5 element compact yagi.
No problem in sending the antennas abroad, quite a few of the large Band I arrays have been sent to all corners of the globe.

Tracked airmail delivery is currently coming up at £33 (Balearics) but I could do with his address to double check. If he is still interested probably it is best he contacts me with his full details so I can confirm the current price just in case it alters.

The other option is if the guy is able to obtain the alloy locally then I am happy to supply all the other fittings (junction box drilled, saddles, bolts, other hardware, etc). This would work out considerably cheaper in postage as it would only be small parcel.
The e-mail address is GarrySmith@dx-tv.fsnet.co.uk

I hope you can sort something out.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

mnicolau
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Joined: 08 Jan 2016 01:58

Re: Building a K6STI small 5 elts Yagi

Post by mnicolau » 22 Feb 2017 16:56

Hello!
Thank you but it's a little late!
Thank you for help me.
I bought an Antiference FM1085T antenna last week on https://www.amazon.co.uk and today I received it. (Very fast delivery)
The antena has a little problem:
https://drive.google.com/open?id=1IgKvm ... LP2GsQjrng
https://drive.google.com/open?id=1ADj5A ... rQaFPHtCDg
https://drive.google.com/open?id=19pOYz ... tFMHxftWJg
https://drive.google.com/open?id=1B5Mtp ... UrfSOtkpQA

I can only buy an omni directional FM antenna in Spain.
I can not buy in Spain a standard 2, 3, 4 or 5 elements FM aerial.
I bought an Antiference FM1085T because I thought it was the only antenna directive I could buy.
I din't know last week I can buy in HS Publications.
I found the website https://mastil-boom.es last Saturday where I can buy aluminum tubes 6063 in Spain.
They can send to Mallorca a lot of tubes up to (untill) 2.5 meters for 50 euros of shipping costs.

I would like to replace my old FM antennas with new and good aerials.
I currently have a Televés 1029 antenna in vertical polarization but it has a problem https://drive.google.com/open?id=1VzEz4 ... zXjHNFSIzg
I can not touch anything because if I touch it it will break.
I hope the antenna Televes will hold out until next winter.

I want to try to build FM antennas with good forward gain and good F/R.

If I can not buy a good aerial I 'd try to build them.

I'm afraid the K6STI five elements antenna could be worse than the Televés 1029. But the Televes 1029 is old and with problem.
Some technical specifications of five element antennas:

Televes 1029. G: 9 dB F/R: 22 dB
Antiference 1085. G: 6.9 F/R: 16
K6STI 5 elements:. G: 6 F/R: 20

What do you think about these technical specifications?
I have always thought that Televes "lies" in its Technical specifications

I will build the K6STI the next winter and I will compare the Televés, the five K6STI elements and Antiference 1085T.
Building 5 elements K6STI will be a test (new experience for me)

My aerials at home https://drive.google.com/open?id=18NilX ... K49V_6gUpg
I also have a Fanfare APS-9 and 10 elements RKB but I can not use at home.

I wrote a very long message yesterday but I was wrong and everything was lost

Sorry for my bad English.

Miquel (A crazy FMDXer guy in Majorca)

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Julian Hardstone
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Re: Building a K6STI small 5 elts Yagi

Post by Julian Hardstone » 22 Feb 2017 23:13

What exactly is wrong with your new Antiference antenna? Some of the elements look slightly bent, but you can easily straighten them.
I hope you will find that it works ok

Regarding the 'optimistic' gain figure for the Televes, there are two ways to quote 'gain'. If you quote the gain compared with a hypothetical omnidirectional antenna you will get a gain figure 2.2dB higher than if you quote the gain compared to a dipole. Brian always specifies gain by reference to a dipole. Also, it is always possible to get a high gain figure at the optimum frequency, but Brian designs for the flattest gain across the full band, and quotes the gain at the band edges as well as mid-band.

Remember that gain is not so important in a busy broadcast band as it is in a quiet Amateur band. You don't need much gain to hear the 10kW tx at 100km distance, but you need the best possible directivity to hear the 1kW tx at 200km distance on the same frequency!

mnicolau
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Re: Building a K6STI small 5 elts Yagi

Post by mnicolau » 20 Oct 2017 11:54

Hi,
What is the best size for the boom? 20 x 20 mm or 25 mm x 25 mm?
Is it necessary 6063 aluminium for the boom?

Thank you

73

Miquel

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