My set-up is as follows:
Single medium gain UHF aerial with F type connector approx 12 months old running through three metres of RG6 duo-shield to a Kingray MHW34FS fully screened F type masthead amp running off a DC power supply. (I have no VHF aerial) The masthead amp is also about 12 months old. From the masthead amp there is a 25 meter run of brand new Belden quad-shield RG6 to a four way fully screened F-type splitter. One of the splitter outputs is not used and is terminated with a 75ohm F type resistor. One output runs to my video recorder and loops out to the TV. All of this cable is new RG6 quad-shield too. The other two outputs from the splitter run to my Home Theatre PC which has dual DVB-T tuners in it (brand new). I use this for Freeview viewing and recording. All connectors are crimp on F type other than the ones into the video and TV which are soldered on Belling-Lee type. There are no tight bends or kinks in the coax.
I need the masthead amp to get a good clear picture on Prime analogue. Without it, the loss caused by the long cable run and splitter results in a noisy picture. The amp has variable gain and I have it on minimum (approx 19dB) On this setting I get excellent Prime analogue reception and no rain fade or signal loss on DVB-T. The amp also has VHF gain, this is on minimum with no connection to the VHF input. It also has a built in FM and pager -25dB band stop filter for 158Mhz which is enabled.
Some of the things I've tried:
· Raising the aerial a further two meters above the roof (our house is reasonably low lying) It's now about 3 meters above the roof line
· Varying masthead amp gain between min and max
· Taking the video recorder out of circuit
· Taking the splitter out of circuit
· Taking the masthead amp out of circuit (signal then too weak for DVB-T lock)
· Varying aerial direction (main direction set using compass and bearing to Waiatarua using Google maps)
· Changed masthead amp power pack from AC unit to DC unit
· Borrowed a DSE Freeview certified set-top box and got the same break up issues with this while my HTPC was turned off. Signal strength showed at around 50% on all 3 transponders. (I don’t have a signal strength indication on my HTPC)
· Turned off everything electrical in the house (including hot water, WiFi, cordless phone, cell phone and fridge) other than TV and receiver
· Tried switching on and off some appliances and lights to reproduce the interference. I couldn’t find anything that would reproduce it.
· Independent earth rod and earth cable to earth tag of splitter
So far nothing has fixed my issue (or made it any worse) I contacted Radio Spectrum Management on the suspicion that I have some localised interference and they came out and took field strength measurements (but didn't really seem up to speed on Digital at all) Accoring to them my issue is that my signal is too weak to overcome backgroung interference. On digital I've got around 49 dBuv and Prime analogue is around 70. (I'm not sure why the analogue is so much better)
So I'm thinking my next step is a better aerial. I'm not sure though whether I should be looking at a 90+ element Yagi or a Hunter Phased array. I have no clear line of sight to Waiatarua from my roof.
Any help appreciated.
P.S. I've tried the Skytower too on V pol but not enough signal strength for a digital lock.