Satellite 2-23-70 Crossboom separation?

[VK4GHZ]

Hi all

Just wondering what others suggest for separation of horizontally polarised 2m, 23cm and 70cm yagis mounted on a non-conductive crossboom?

I will initially re-purpose my existing terrestrial antennas, all M2 (2M12, 432EME12 and a 23CM35) for satellite use and preset them to a fixed elevation ~20° above my existing G-800DXA AZ rotator and manually rotate it.
If the bug bites, I will implement proper AZ-EL computer control, and with CP antennas.

My proposed layout looks like this:

M2 do produce a LEO Pack for 2m & 70cm which suggests (from supplied crossboom length limitations) a separation of ~2.6m between 2m and 70cm yagis.

So, two questions;
1) Separation between 2m & 23cm yagis should be?
2) Separation between 23cm and 70cm yagis should be?

Also, any suggestions on crossboom material?
ie; lacquered timber, fibreglass of adequate diameter, maybe re-purposed from something else?

[VK3ST]

Mine are M2 and were originally the full cross circular polarization set complete with reversal of polarization kits but have now just left them as horizontal.
Was pulling them down to put in the switching for straight vertical, straight horizontal, right hand circular and left hand circular but then due to lack of ongoing time availability, I have them up as horizontal only.
10 feet is the M2 recommendation and I had quizzed them several times on this matter.
Have measured interaction and at this distance skewing and cross loading is minimal.
Not shown in the pic is that I have a 23 cm yagi mounted on the short mast that holds the duo band vertical.
My horizontal spar is the m2 fibreglass and it is good and solid.
On a smaller satellite setup, I used a metal spar as the yagis were relatively short so I could mount them on the end behind the reflector and as an offset, I did use a small counterweight in the other direction to minimise loading on the elevation rotator. In this set up I had only 2 metres between the two and there was interaction given that the element ends were too close to each other but I just put up with the loading and skewing which was only minor but was there just the same.
Ian - VK3ST

[VK4GHZ]

Thanks for that Ian.

Next trick is to find suitable length(s) of fibreglass tube.

I was looking at re-purposing my extendable paint roller pole, but only the outer tube is fibreglass, with the inner being aluminium.

[VK4GHZ]

FYI, regarding separation I contacted m2, and this was the response;

Hello Adam,

Recommended spacing for 2/70CM is 11’ on a non-conductive cross boom, https://www.m2inc.com/FGCB60 unless you mount them vertically polarized.

You will to change the feed so that the cables exit to the rear and support the feedlines with something like our L-brace kit, https://www.m2inc.com/FGLBKAM , again unless they are vertically polarized.

There should be no metal parallel to the elements.

23CM should go on the 2M side of the cross boom, but it needs to go on a vertical riser at least 1/2 of the stacking distance above any metal. The 23CM35 cannot have a mast extending through the elements.

Alternatively, it could mount vertically polarized, outside of the 2M antenna. Spacing equals the sum of 1/2 of the stacking distance for each band.

Regards,
Robert Brown, KR7O
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