Where are the electrons going?

[Zipperhead]

I'm very confused by some behaviour that I noticed at the weekend.

We have a roof aerial (I must admit I haven't checked to see that it's still on the roof after the storms!) which is maybe 5 miles uninterrupted line of sight from Crystal Palace transmitter. With the old television & dvr I used to have a 6db attenuator downstairs otherwise the signal was too strong, but since analogue transmissions stopped I've removed that.

I bought a new television & dvd player just after Christmas and a new DVR about a month ago.

The aerial goes into the back of the dvr, then the dvr feeds into the aeriel input of the television. The dvd player and dvr both feed the television via HDMI.

Now, the weird behaviour was this - the other day the television said there was either no signal or it was too weak. This was happening on BBC1 & 2 (non-HD) and on the 4 HD channels. If I switched the DVR on, leaving the television input on the aerial then that fixed things. Then I noticed that the DVD player was switched on. So, I switched the DVR off, the television complained again, then I switched the DVD player off and the 6 missing channels returned. Switch the DVD player back on (not playing, just switch on) while the television is feeding from the aerial and six channels disappeared.

How? There's only an HDMI cable from the DVD player to the television. I'm very, very confused by this behaviour.

[Kim]

Ground loop or noisy power supply interfering with the signal, I expect.  I'm mildly impressed that the pass-through works with the DVR switched off.

[rafletcher]

I'd guess the DVR would be on standby rathe than switched off, for the pass-thru to work? (I haven't tried with mine as the standby power is small but I'd expect it to work like that - and the DVR is always "on" as it needs to be to do the scheduled recording).

Re DVD - we have Samsung DVD and TV. If we switch on the DVD (ie take it out of standby by insertimng a disc) it overrides the aerial input from the *(Humax) DVR. So the DVR will still record, but we can't watch TV wilst the DVD is "on" - which kind of makes sense!

[Russell]

Our Humax PVR has a setting for power saving in standby which turns off the aerial loop through in standby and saves 2w.  It means turning on the box just to watch TV but 2w saved 22h a day is better than using 10w extra for 2h a day.