Just a thought - rather than buying another antenna, if I could support it adequately is there any reason why I couldn’t use my Slim G antenna horizontally polarised for 2m SSB?
Simplistically speaking it will work but not as well as an antenna designed for horizontal polarisation. Approx. 40% of your radiated power will warm the clouds and be wasted. Approx 40% will hit the ground and be absorbed or bounce up and interfere with the horizontal component. About 20% gets radiated towards the horizon if it doesn’t get too badly screwed with by the ground reflections.
Make (not buy) a horizontal dipole out of a bit of plastic and 2 telescopic antennas.
It won’t work very well at all, because it is designed to be used over a ground plane.
For 2m SSB you could either make a dipole as Andy suggests or, if you want something with a bit of directivity and gain then you could try building a Moxon rectangle, Google “moxon rectangle 2m” for info and construction ideas.
As the others have said, better to build a dipole and it’s quite simple. Or, just use it as a vertical and live with the cross-polarization loss. I have used a vertical for 2M SSB and while a weaker signal it does get out better than turning a vertical on end. An old set of TV rabbit ears can easily be cut to length for 2 meters and can probably be found real cheap.
This is the first I’ve heard of the Slim-G, but it appears to be a variant of the J-pole, from what I can find on the web. A J-pole is an end-fed half-wave which doesn’t need a ground plane.
I don’t see any recommendations for a ground plane from the manufacturer of the Slim-G, so it could work just fine horizontally. I expect it would be somewhat directional sideways to the wire, just like a center-fed dipole.
If you need horizontal polarisation I recommend the HB9CV The aerial manufacturers supply 2 m and 70cm versions. This beam has 2 active elements and delivers about 6dBd forward gain. For transportation strap it to your rucksack, you can dry your socks on the upper elements and the weight penalty is small for a fit lad. It is usually supplied with a small variable capacitor at the feed point to tune out the inductance of the feed arrangement. This needs to be adjusted for best SWR. The 3dB beam width is about 40degrees so easy to use. Buy or make according to your taste, feed with RG58 and sit it on a 10ft pole, let the magic begin.
I use a Slim Jim from 300 ribbon and another from 450 ribbon. They work much better than the rubber duck thing on the HH. I often pull it over a bit to help with H polarised signals. It makes a difference doing that even if you only get it to 45 degress. If you can make the contact who really cares about the theory? I have qualified a summit with aircraft enhancement on 2m with the Slim Jim.
I also have an Arrow 2/70 yagi if I want to get serious on 2 and 70.
any reason why I couldn’t use my Slim G antenna horizontally polarised for 2m SSB?
At least better than trying to make SSB-contacts with a vertically polarised antenna.
The Slim-JIM and other J-poles are dipoles fed from the high-Z end. If the transformer section is working as it should the radiation pattern is that of a dipole. What Andy says about the radiation pattern applies equally to a dipole. No ground plane is required.
For vertical use it makes a lot of sense to feed from the bottom, being more convenient than trying to bring the feeder out perpendicular to the feed point at the dipole centre. It will work fine on its side, but then it doesn’t really offer any advantage. A horizontal dipole is nicely balanced (in a mechanical sense I mean), so you’re probably better off building a good, solid dipole to use this way round. I have used my 70-cm Slim-JIM tied to PVC pipe on its side quite effectively though.
If tempted by the HB9CV you might also like to consider a Moxon: