Help with balun - K6STI 5-ele Yagi (HS Pubs)

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Alex Cator
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Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by Alex Cator » 04 Oct 2016 21:40

I am about to get the K6STI 5-el from HS Publications, which has "space for an optional balun" but doesn't come with a balun. My dad emailed Garry about this and Garry recommended the idea of a homemade halfwave coaxial balun, but would it be possible to get a balun from Maplin (http://www.maplin.co.uk/p/balun-30075andohm-fd78k) and somehow put it in the connection box?
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daveB
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Re: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by daveB » 04 Oct 2016 22:43

You need a 75 ohm to 75 ohm balun - the Maplin one is 300 ohm to 75 ohm and totally unsuitable.

What I did with my installation was to clip two large ferrite beads on the coax as close to the connection box as was practical and then wrapped insulating tape around them to secure them to the boom. You need chokes that will take 7 mm diameter cable - easily purchased off ebay a lot cheaper than Maplin do them. Type TDK-CLIP-ON-FERRITE-BEADS into the search box. I need to get some more myself. For USB cables you need 3.5 mm.

If you to K6STI's page you'll see various pictures to give you an idea clip on ferrite beads are discussed and detailed instructions of how to construct a coiled coax balun - which appears to be a case of coiling up a couple of feet of the coax as close as possible to the dipole connection. Precise detail is given but as a split ferrite bead is a case of 'click' to fit, I went the easy route.

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


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: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by k6sti » 05 Oct 2016 12:20

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Julian Hardstone
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Re: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by Julian Hardstone » 05 Oct 2016 15:42

k6sti wrote:When you receive the antenna... make sure they are conductive
As in 'connected to the boom' Brian?

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Re: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by k6sti » 05 Oct 2016 16:46

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Re: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by daveB » 05 Oct 2016 17:07

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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: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by Julian Hardstone » 05 Oct 2016 17:56

Thanks for the clarification Brian. On your own original design, I wonder if you have any requirement for the parasitic elements to be connected to the boom. I note that the implementation of the design by VHF Teknik AB uses insulating element mounts.

I have always felt sceptical that insulation vs. contact can make any difference to performance, but many published designs are quite specific about this matter

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Re: Help with balun - K6STI 5-ele Yagi (HS Pubs)

Post by daveB » 05 Oct 2016 19:56

Slightly off-topic but I just saw on the Antenneland web-site that they say the supplier of their small parts has closed down - and the message suggests you won't see any more Korner 9.2's from them.

Home construction or getting someone to do it for you seems to be the only choice - and the compact 5 ele design on Brian's web-site seems to be the most straightforward to reproduce. Once you've made it and found how well it works one could then progress on to make your own Korner 9.2 (unless, like me, you are so constrained that even that is too big a wind load).
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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