Family Historian User Group

DNA tracking.
I am trying to get my head around some of the mechanisms of DNA, and my aging brain is playing tricks on me. I have this scenario to which I am working. Is my logic correct?
My late 93 year old uncle had his autosomal DNA tests done via Ancestry, and I have management rights on the mini tree we built on the Ancestry site. Ancestry has come back and provided me with quite a few 'connections or matches', some of which I can fully agree with and some others where I can see no visible connection to my family.
With that in mind, I have traced my family, and my uncles lines as far back as I can at the moment, and there is one major brick wall where we have no info on my grandmother's father, other than his name, and possible period of between 1894 and 1901 for his death in the London area. He is my Great-grandfather(GGF). In Family Historian, I can Chart my uncle's Ancestors (Charts->Ancestor) and show All his bloodline ancestors. I have exported this Ancestors result into a new project dnamatchtrees, and the individuals are all in Pool 1. Great!
Now Ancestry has an autosomal match with a D.H as 4-6th Cousin <1% shared DNA:47cM across 2 segments, and he has a tree with 907 people. In my FH Project for dnamatchtrees, I am building up the tree supplied by DH on Ancestry, adding him as an Unrelated Individual and working back up his ancestral tree, and all these individuals are going into Pool 2, as I expected. In some of DH's lines, I am researching further back on his tree to confirm that his Ancestry based tree is correct.
My puzzlements are:
1. At some stage I should be able to visibly see the same surnames on the Ancestor Charts, and therefor concentrate on that section of the trees for the match.
2. If I can find no similar surnames between the two trees, particularly my brickwall GGF surname, then DH's connection could be a link to my brick wall, and further research and proof will be needed, OR
3. I may have an error and will have to revisit MY tree, but where, which level of generations?
4. As DH is given as a 4-6th Cousin, how many generations up HIS tree should I expect to see the surname match?
What have I missed? Or am I on the right track to find the links?
Thanks

Regret not a detailed response, and not sure if my situation is relevant. My situation is where there was an unknown father.

I had quite a few known tree DNA matches on my side of an "unknown father", and other DNA matches to same female but with a different "known father". My idea was to get the "known father" descendants (not mine), then check my DNA connections that did not match theirs. There would still have been a lot of possibilities. I did not get anywhere though because I could not get anyone from the known father descendants (not mine) to let me "view" their DNA links/thrulines.

Once you get in the 4th - 6th you are a fair way back so you could need to go back 6 or 7 generations to find a match.

Once useful option if you are "talking" to DH is to cross check shared matches between them and other of your matches.

So for example if they match another 2nd or 3rd cousin there is a reasonable chance they fit on that line some where.

Ideally you would want DH to match with another of your GGF descendants, but not any of your other lines.

If you use GedMatch and uploaded the DNA you can use the tools there to match on specific segments which might throw up some more clues.

Thanks, Jane

Word of warning! There is no guarantee that you will find a common ancestor. I have a very large match with someone on Ancestry, indicating a 2nd-3rd cousin match, yet we are still unable to find a common ancestor. We can’t even find a common surnames as a clue to indicate where the match could be.
We both have extensive trees, yet it hasn’t helped.

We still live in hope

I’d endorse Jane’s suggestion of using gedmatch, as it gives more details of where your match occurs, and by a process of elimination (with other known relatives), you’ll get a better idea of which branch of your tree where the match should occur.