Transmission1

Hi guys, (and gals)

For those of you that run yagis, can I run a few ideas by you and see what you think..

I am in the process of collecting materials to build a mast, this will be of all metal construction with a proper ground rod network.
The top plate of the mast will be a 5 inch square steel plate to mount rotor assembly, and a Yagi on top of the rotor.

I am planning to build a 3 element Yagi this will be centred at 27.8MHz (27.84125 FM is my 'monitored' freq)
I have done many calculations and 'digital virtual models' etc and am planning on a folded dipole as the driven element.

One thing I can`t pin down yet is...

I intend to orient the folded diplole as: (unbroken) long element positioned vertically above the broken feed side of the loop.

Would it be best located with :-

Option 1: the unbroken (continuous) side of the dipole in line with reflector and director.

Option 2: the broken (feed) side of the dipole in line with reflector and director.

Option 3: the centre point between the continuous and broken sides of the dipole in line with reflector and director.

I look forward to your wisdom on this matter...
73s. EARS-EGPK

Option 1, with the balun hanging down below the boom in space.

Cheers Chris! I am sure there are many long convoluted explanations as to why this is the best way but I thought it would be much quicker to ask and see if my own assumptions regarding best positioning on 'long side' of folded dipole we heading in the right direction.
All the best.
73`s EARS-EGPK 108-PK-303 (waiting for confirmation on 108-TM-303)

EARSEGPK wrote:
I am planning to build a 3 element Yagi this will be centred at 27.8MHz (27.84125 FM is my 'monitored' freq)
I have done many calculations and 'digital virtual models' etc and am planning on a folded dipole as the driven element.

That's quite a weird narrowband arrangement. Wouldn't it be best to make it cover the legal 80 channels in the UK as broadbanded as possible?

Or is the aim to make it a 10m antenna that will cover portions of 11m, notably UK Muppets?

I suspect fixed communications between different towns myself .Though at 27.8 it should have just enough bandwidth to cover the top part of the cept and also the ssb portion of ten metres .useful little article here----http://www.arrl.org/files/file/Product% ... ebik2a.pdf

you don't need to 'hang a balun down' on a beam, you can bolt it to the boom, heck you even buy them this way

building a folded dipole as a radiator should be pretty broadbanded, but it's the beams element spacings that determine the bandwidth..

Skulcracka beams are that narrow banded they lose SWR after about two channels either way..
built and centered on one frequency, i know a guy runs 15kw up one and get 5w YUP..!! FIVE WATT reflected on 27.025
but as soon as he goes a couple of channels up or down his SWR is like 2:1 i have the same curve on a magnetic loop..

build it wide spaced and the bandwidth will suffer, make it narrow spaced and you'll manage 40 or more channels..
then there's the matching, hairpin, gamma ?? i know a folded loop doesn't need any matching nor does it need a balun, but if you change you feed arrangement then there's several ways to match. i'd use a hairpin match,less things to go wrong unlike a gamma..!!

Cheers for the info folks, The 3ele project was going quite well until the wonderful Scottish weather decided to wreck the place.. During storms in Jan-Feb had major storm damage to antennas and shack roof -- The Yagi was working quite well covering part of 10m 11m and a wee bit of 12m (although not all that well) all down to the diameter and spacing of the elements.. but after the storms severely redesigned everything I gave up trying to repair the mangled yagi. Looking at a Cubical Quad next time around.. New mast base-pad and ground network installation almost complete, will be sticking with verticals for now. (BTW. UK 40 up here surprisingly free of muppets, mostly local farmers) :-) 73 de 108TM303