UHF switch box

[Terry]

I'm sure I've mentioned this before but many years ago had to install a Bush TV128 in a house on the southern edge of Crystal Palace park.

405-lines perfect on the existing set top aerial but UHF useless.

Needed a small yagi in the loft angled upwards towards the top of the Crystal Palace mast!

[ed731pdh]

I remember this write up well, not at all surprising considering the close proximity of CP. In Westow Street, you don't even need an aerial.

[ed731pdh]

So, looking at the Philex switchbox product and some testing.

The first thing you notice is weight, it's a chunky, weighty little thing, feels pleasing to the hand in density and form. Two push buttons, marked A and B. On the side, the two outer F connectors marked A and B as expected, the inner middle F connector marked TO TV. Two mounting screws are provided in the box, No.4 x 30mm types to reach through the switchbox casing. Nice heavy chunky black plastic.

Testing. With both aerials connected the first immediate issue is that of switching aerials on the fly. I found that although the box quite happily passed power to the rooftop amp, there was a risk of the power supply shutting down when operating the A/B switches. Maybe it detects the load momentarily coming off and doesn't like it, or there is a momentary short. I tested both switches with a DMM before fitting and there was no evidence of shorting when changing but as we all know, real world testing is always different to the workbench. No major big deal, just pop the power to the amp off at the mains, operate the switch, and pop the power back on. Best this way I suspect.

Input, despite on the box the claim minimum loss of 4db in use, there was no detrimental effect under normal weather conditions to the signal being provided to the televisions running off the system. The least sensitive of the televisions, a kitchen under unit mounted Samsung, registered no issues with the signals provided from Midhurst or Crystal Palace. The second worst, the main bedroom Sony 15", again had no issues but this television will be observed as it's often the first to show issues with the quality of DTV signal, pixellating and when really bad dropping out completely.

We have now been advised that some channels are in the process of being moved or will be moved away from certain areas of the upper part of the DTV spectrum, the ones that have been clashing with mobile phone frequencies have moved down the channel list from the mid 50s to low 40s, this all prior to a big shakeup being planned in June next year when all the channels will apparently get a shakeup and move down the bands. One wonders if the interference is going both ways, the mobile companies getting interference from the DTV as well.

[ed731pdh]

One additional item I found when working out the prime direction in which to aim, Google Earth.

GE has a nice ruler mode, so you find the transmitter you want to tune to, and then draw with the ruler back to your house and the chimney stack you have your aerial mounted to. Then look along the ruler sight for a suitable landmark to initially point at.

Worked with the old log periodic that was pointed towards Palace. Just laissez faire aimed at the middle chimney pot of the local pub and bingo first time.