UHF switch box

[ed731pdh]

Model is a Triax Unix 52 LTE 800. It cerainly appears to be able to cope with mobile phone interference.

[ed731pdh]

Specs.

Freq (MHZ); 470 - 790
Channels; 21-60
Band; BIV/V
Elements; 52
Gain (db); 11 - 14.5
LTE Rejection (db) 821Mhz - 8, 832Mhz - 10, 862Mhz - 15
Front to back ratio(db); 25
Beamwidth (degree); 15
Windload (N); 96
weight (kg); 1.36
Length; 1392
Connector; F female

[ed731pdh]

Well this explains why the signal is sometimes iffy.

[ed731pdh]

Static testing of the switch box this morning. One of the major worries was if the box on chaning inputs grounded out or put a momentary short on the line. This would have been a bit of a ball breaker bearing in mind that 12 volts goes the other way to power either the masthead amp on the new aerial, or the built in amp on the old log periodic. Thankfully, it's a clean disconnect switch with no shorting, so I can now progress to live testing.

[Terry]

Ah! I thought the masthead amp was for the log!

Being so close to the transmitter, have you tried the aerial without the amp in case it is being overloaded? You might be benefiting from refraction over that high ground. Also, your aerial could be higher AGL than the 10m default.

The closest I could emulate your signal profile is this:


But raising the aerial gives this improvement:


So it might not be as bad as you think.

As for the switch, I would expect it to terminate the unused feed in 75 ohms but the selected feed to be connected straight through, as you have found.

[ppppenguin]

More generally, amplifiers can be worse than useless for digital tv unless they are used correctly. Correct uses are at the masthead to overcome losses in a long feeder and as part of a properly designed distribution system. When used wrongly they can give worse results due to intermodulation. Either between the multiple carriers within a multiplex, between multiplexes or with unwanted signals such as police radio.

[ed731pdh]

Tried it without a masthead amp, signal quality was next to useless.  By my calculation a pole twice as high should bring in a better signal.

[ppppenguin]

Strength or quality? Most tv's will give an indication of both. If strength is ok then an amp will be harmful. If quality is ok but strength is low then an amp might help.

It's not like analogue where a glance at the picture usually tells you what you need to know.

[pwdrive]

We're a fair distance from the transmitter and there's a big hill in the way, the "installation" below worked for several years giving perfect reception of digital on all channels, in the end I had to move it to avoid it getting damaged by doing various DIY jobs around the site, at the moment it's propped up against the house with the antenna pointing below the horizontal straight into the roof.....

   



Lawrence.

[ppppenguin]

At the other extreme I recently fitted an aerial for a friend in Balham. Pretty close to CP. Even in their ground floor flat a finger in the aerial socket worked. Despite a tall building directly between them and C P. I chose a tiny log periodic from Screwfix and fitted it to the wall just outside the window. Perfect results. Reckon I could split it 4 ways without an amp.