I've used a multitude of tracking devices over the past 15 year's or so & to be honest I don't think any of them are very effective in woodland,I'm in the UK & currently use the Astro & Alpha version's, Sportdog Tek was poor & very inaccurate I found even out in the open,the best by far in dense cover/woodland/forestry at least here in the UK is the Dogtrace X20 & I'd assume the newer X30 may even be better still.
Try the longer after market antennas.
I've used a multitude of tracking devices over the past 15 year's or so & to be honest I don't think any of them are very effective in woodland,I'm in the UK & currently use the Astro & Alpha version's, Sportdog Tek was poor & very inaccurate I found even out in the open,the best by far in dense cover/woodland/forestry at least here in the UK is the Dogtrace X20 & I'd assume the newer X30 may even be better still.