Noisey VHS recordings from DTV

[Retro in RI]

So I've been trying to record my favorite METV shows on VHS using an RCA antenna into an Insignia converter. The converter is wired to my VCR with a coax cable with another coax going out from the VCR to my little 12 inch Zenith knob tuned set. Problem is, when ever I make a recording, it comes out very quite upon playback (regardless of which VCR/TV I use it on), and when I raise the volume to comfotably audible levels (my hearing is fine so it's not "cranked"), the sound is really "hissy", if that makes sense. My mom says she's experienced the same at her house. Here's what I've tried so far:

1) A different VCR to record with

2) Different coax cables

3)Verifying converter box sound output is set to "mono" (recommended when using coax)

4)Jacking the sound on the converter box

5) Running A/V cables from box to VCR, while keeping coax from VCR to tv (wouldn't work at all in this configuration)

It's not bad to listen to at first but it does get annoying after a while and some of the commercials have a really loud hum. If it helps at all, I am recording in SLP mode to get 6hrs of programming onto each tape.

I tried calling Insignia and the outsourced representative didn't understand my complaint as her suggestion was "....just wire the converter box to the tv and skip the VCR"

So, has anyone heard of this, is there a noise filter they sell?

Btw, the sound is otherwise fine on this tv,converter vcr set up, only the recorded sound isn't good.

Thanks.

Al