Collinear v Yagi (without rotator) for DX

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Collinear v Yagi (without rotator) for DX

Postby ACL » Mon Dec 14, 2015 5:53 pm

I'm interested to hear people's opinions on this. In the next couple of months I plan on putting an aerial for 2m/70cm FM vertical on my roof. I live in a built up housing estate with the only clear opening being north easterly. The idea was to place the aerial facing in this direction in order to hit the continent. I know that for direction and weak signals Yagis win hands down but as there is no rotator involved in this installation would I be better off with a collinear? If I use a yagi to beam in this direction I will be aiming at North Holland and potentially Germany exclusively and would have to rely on French and Belgian contacts coming off the back or side of the yagi.
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Re: Collinear v Yagi (without rotator) for DX

Postby m0lsx » Mon Dec 14, 2015 6:45 pm

What are you wanting to work?? Yagi's are in general horizontal, but will work well vertically polarised. While in general a base fed antenna is a vertical only on VHF & UHF.
Also the chances of working DX to the north is very slim, even in flat conditions several hundred Km are possible on 2 meters SSB.
If you are looking at a beam for SSB use, how about a Halo, a clover leaf or a big wheel?? The halo would give you close to 300 degrees of coverage & probably closer to a full circle. You should get a full 360 coverage on the clover leaf & a full 360 degrees of coverage plus some gain on the big wheel.
A vertical in general makes a poor VHF DX antenna. But for 6 meters due to the nature of propagation, polarisation is less important. As like HF, polarisation on 6 meters does change & often several times during a single over.
I saw someone running two antennas (dual polarisation) on 6 into two radios & it was interesting to see the signal fluctuating between radios. It was not I know scientific & yes I know there are different types of propagation on 6 meters, but it does help to show that rigid vertical, horizontal polarisation is less important on the lower VHF bands.
A three band 6/2/70 would give you much more chance of DX. I have worked all over on 6 meters, often using QRP & normally from a vertical in a less than ideal location. I have worked Poland on 1 watt mobile to mobile. The other station running less power than me. I could make the journey on 0.5 watts, but my audio was not as readable.
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Re: Collinear v Yagi (without rotator) for DX

Postby G4RMT » Mon Dec 14, 2015 7:27 pm

Just a thought - you say North Holland and Germany - so that alignment puts you in the Wash upwards?? That's a fair distance, and Germany seems pretty unlikely - I doubt you will get very much off the side of the beam - the polar performance drops off very quickly when you go above 6 elements. Even a few degrees on a rotator make a big difference, so the advice to perhaps look at something else makes a lot of sense.
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Re: Collinear v Yagi (without rotator) for DX

Postby ACL » Mon Dec 14, 2015 8:06 pm

Thanks Alan, this setup would be for FM on 2m and 70cm. I know we have discussed that working distant FM repeaters is not viewed favourably within amateur circles so it would be for simplex communications. In terms of dxing the countries mentioned, I know this would only be possible during tropo lifts and occasionally SpE when the MUF reaches as high as 2m. The ssb setup will have to wait until I have more money and time to invest in the hobby.

G4RMT, I'm based in North West Norwich so I know under flat conditions using FM dxing will be impossible but with tropo I'm hopeful of something. I can receive Dutch and German repeaters when there's stable high pressure and on occasions Danish FM radio.
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Re: Collinear v Yagi (without rotator) for DX

Postby m0lsx » Mon Dec 14, 2015 8:47 pm

If you go for a beam with only say 3 elements, it will not be too narrow. So should work in one direction & give a fair spread of workable direction. As G4RMT says, the more elements the narrower the beam.
Another option is put it on a mast you can move slightly by hand.
My first beam was back in the early 80's, it was a botched up 3 element amateur radio 40 meter beam set up for Echo Charlie (6.6 Mhz) But I did also at one time mod it for the 41 meter free radio broadcast band. My rotator was a TV ariel mast inside a scaffold pole with two lengths of rope used to hold the beam on target.
Rotating the beam was not advisable in anything beyond a breeze & took time to achieve. But a rotator does not HAVE to be electric or simple. If the antenna moves & is acceptable to you then it is fine.
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Re: Collinear v Yagi (without rotator) for DX

Postby ACL » Mon Dec 14, 2015 9:11 pm

Thanks to you both for your advice. I will go for a dual band 3 element beam then. In terms of mounting I may consider a mast where I can reach and manually turn but doing that I would potentially loose valuable height.
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Re: Collinear v Yagi (without rotator) for DX

Postby G4RMT » Tue Dec 15, 2015 12:08 am

A dual band beam? I'm not sure that a 3 element beam is going to be that useful, to be honest - what will you get? 3 or 4dB gain over a dipole. For DX that's going to be less than ideal. Is there any way you can get something longer up there? A 9 element for VHF and maybe something similar in length for 70? Makes a big difference.
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Re: Collinear v Yagi (without rotator) for DX

Postby ACL » Tue Dec 15, 2015 1:57 pm

G4RMT wrote:A dual band beam? I'm not sure that a 3 element beam is going to be that useful, to be honest - what will you get? 3 or 4dB gain over a dipole. For DX that's going to be less than ideal. Is there any way you can get something longer up there? A 9 element for VHF and maybe something similar in length for 70? Makes a big difference.

Unfortunately due to money and space I can only mount one beam. If a dual band is not suitable maybe I will just get a 2m. I guess I could always use it on 70cm as well even though it wouldn't be ideal for any dxing. The problem with getting a 9 element is that it may be too narrow for anything other than the direction it is facing. I'm really not sure. Is a dual band Collinear completely unsuitable for dxing? I'm leaning towards the beam but it is not as straight forward as I had previously assumed.
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Re: Collinear v Yagi (without rotator) for DX

Postby G4RMT » Tue Dec 15, 2015 3:25 pm

Vertical aerials, as Alan mentioned are really designed for local use - with repeaters, hand held users and of course mobile - all which have their aerials working in the vertical plane. DX is totally different. It isn't just getting a weak signal up out of the noise, it's getting rid of the others that pop up when conditions are in the 'special' state. Almost all the station you are wanting to talk to will have their aerials pointed at you, and horizontal. Rotating a vertical beam to horizontal usually guarantees that with everything apart from strong local stations will just vanish. As frequencies get lower, then the polarisation shifts over distance - so something that started vertical rotates with reflections and can be heard on a receive aerial in another plane.

You have a difficult choice. A vertical and depending on where you live, have a service area of maybe 20-50 miles, pretty well all the time, and DX as a rarity, and probably a fluke.

When a lift starts, everyone starts calling - so an omni, or hardly directional aerial system makes for chaos. A 5 degree nudge on a rotator can help you hone in on who you want. You just cannot hope for DX when you don't have the right equipment. Vertical aerials are for chat, horizontal ones for distance. A small beam is going to limit you. On a cliff next to the sea, facing Holland, with a sea path, and you will get some Dutch activity, but into Germany may simply not be possible. If everyone else in between stopped transmitting, then maybe with a good lift, it would work - because as has been said, power is not everything if the path works. Trouble is you are never on your own. Somebody up the road with a 16 element beam and 100W will hear you working into Europe and you will vanish into the noise at the other side.

There's very little point in expecting DX without the correct equipment, especially if you are inland here and want to work Europe.
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Re: Collinear v Yagi (without rotator) for DX

Postby ACL » Tue Dec 15, 2015 4:22 pm

Thanks, yes, I take your point. I need to get it right and invest in the right equipment and use it properly. I think I was being naive in what I was proposing. I hadn't taken into account nulling unwanted signals.
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