First a quick description of my setup...
A clear view of Mt Campbell transmitter across the width of Tasman Bay
- via UHF signal to
Phased array UHF antenna (https://www.jaycar.co.nz/heavy-duty-uhf-phased-array-tv-antenna/p/LT3154) with 24dB Masthead Amplifier (https://www.jaycar.co.nz/24db-masthead-amplifier-optimised-for-digital-tv/p/LT3254)
- connected with RG6 coax to
Panasonic DMR-XW380 DVD Recorder (twin tuner & HDD)
- connected from antenna passthru with generic coax cable to
Panasonic TH-L42E6Z LCD TV
I noticed that my antenna was mounted with Horizontal polarity, but Mt Campbell is Vertical (https://freeviewforum.co.nz/tip/rf). So I checked the signal levels on the TV, and all channels were Quality 10 Strength 10 except CH27 (mostly local Mainland TV programs), which was Q5 S10.
I rotated the antenna to Vertical, which improved CH27 to Q7 S10.
ISSUE: Sometime later I noticed ALL channels on the DVD Recorder had gone to Q0 S10 - No Signal! Running the auto-tune didn't detect any stations. But reception on the TV itself was still just fine.
It took me a while to make the connection, but when I returned the antenna to Horizontal, I could auto-tune the DVR, and all was well. I've repeated the antenna rotation a couple of times to confirm results.
The reason for correcting the polarity was an attempt to improve CH27 Mainland TV reception - in spite of good signal metrics, there is still quite frequent pixellation.
Can anyone offer a clue to what's going on?