I'm thinking of installing an extra 18 inch dish for the satellite at 61.5 degrees or for the one at 129 degrees.
My question is: Is an 18 inch dish proper for receiving signals from these satellites?
( I live in Canada, Ottawa, 45deg North latitude 75 degrees West longitude ).
Yes, you can use a seperate Dish to receive either of those orbital slots, now with that said you will NOT be able to receive a signal from 129 as you are outside of the footprint for that particular satellite. All the HD programing is on either or orbital slot. I use 61.5 for my HD programing (I live in Western NY).
All locations East and North of Pennsylvania are outside that satellites' footprint at 129, as it was NOT designed for that particular orbital slot.
If you want 61.5, 119 and 110, then you could use a Legacy Switch SW64 with Three legacy DUAL LNBF's with Two Cables from each LNBF to the Switch, or you could use all Dish Pro LNBF's with a Dish Pro Switch.
If you go the Dish Pro way then you only need to install one cable for each orbital slot to the Switch. One Cable each from Two Seperate Dish Pro Single or Dual LNBFs on the Dish 500, and one Dish Pro Single. If you wish to use a Dish Pro TWIN on the Dish 500 that would work just fine as well, with the last or third feed coming from the 61.5 to the Dish Pro 34 switch.
The only reason for using Dish Pro LNBF's and switches instead of legacy LNBF's and Legacy switches would be to help you eliminate the extra three Coax Cable Feeds needed from the Dish's to the Switch.