I'm a bit concerned that you know little about scanners, you own only 1 scanner, and you want to provide an audio feed with it. You should not use your only scanner for an audio feed in my opinion. Audio feeds are not supposed to carry 'every channel you can receive' but select frequencies and talkgroups which meet the RR feed requirements and terms of service.
Limiting your HP-1 to only those channels which meet the feed provider terms will be both difficult to set up and severely limiting to you, personally. Your $500+ scanner will be basically doing only what a cheap 4 channel crystal scanner from the 80's would do. You won't be able to meet the T.O.S. with 'everything' enabled nor should you try.
In my opinion, you'd be better off to get a cheap refurbished scanner to provide your audio feed (and obtain the download privileges which come with it) and then use the HP-1 for your personal use. It seems like you're working against yourself here.
As for an antenna, you can likely do it relatively cheaply and provide signal to multiple scanners by using a broad-band discone antenna on the roof and TV splitters, RG-6QS wire and adapters from F to BNC or SMA as required. I think I spent about $150 for everything to provide good solid signals to 3 scanners using this method.
This whole idea of dedicating an HP-1 to be a feed provider just bothers me... Why? There are many cheaper alternatives which will allow the HP-1 to be used for what it was designed for... Listening to 'everything' - something you cannot do on an audio feed you're providing.