Thanks its an Sdr V3 dongle and yes the freqs are in the 800mghz range so i will try to add another dongleYou don't mention what type of dongle, so we'll assume a standard RTL dongle. If the site's frequencies span more than 2.4 MHz, you won't be able to track all voice channels with a single dongle. 2.4 MHz is generally the maximum usable bandwidth. If your control channel is in the 769-770 range, and there voice channels in the 773-774, it will not be able to tune to those voice channels.
Add another dongle.
Oh wow that frequency spread is brutal..I hate to be the bearer of bad news, but you're going to need at least 4 dongles to cover that entire site, possibly 5 depending on how busy the site actually is. If it's not a very busy site, you may be able to get away with 3 dongles, allowing two of them to retune as necessary. But if it is a busy site, to cover every frequency, you'll need 4-5 dongles.