Ping bill

[alan_m]

A log periodic refers to the type of aerial not a add on filter after an aerial.

[alan_m]

Video

[Tim Lamb]

snip

I see out Bill gets an honourable mention on that site:-)

I have tried matching my aerial with on line pictures and failed. It has the big angled grids at the back and a single row of 10 *figure of 8* elements. So perhaps already log periodic.

Ok. There are several local outlets but only Welwyn and Hertford don't have blocking high ground.

I see CP is 160 degrees from (45K distant) here and Sandy is 3 degrees and 36K.

Same as immediate neighbours but further up the hill, some have two.

I think this discussion has covered the issues not met when we discussed installing a freeview dish. Still on my to consider further list:-)

Thanks all.

[Tim Lamb]

That would explain a lot!

>

[Tim Lamb]

So it claims. DVB-T2/T Not actually used so no experience.

[Robin]

Do you have any attenuators* you could stick between aerial and set to see what effect they have on other channels?

*like e.g.

[Paul]

There's two ways to design antennas.

A directional antenna without a ground screen on the back, the 4NEC2 calculation shows gain lobes on both ends of the antenna. This means you can be pointed at compass 30 degrees and be picking up an interfering signal from 210 degrees compass.

A directional antenna with a ground screen on the back, the gain lobe sticks out the front of the antenna. Most of the time :-)

One commercial antenna, the channel 9 gain, pointed backwards into the ground screen, and I think this made the antenna "deaf" to channel 9 VHF. And this is why we do analysis of antennas with 4NEC2, for the gain pattern.

This is an example. One of my faves. The Radio Shack bow tie. The barbecue grill on the back of the antenna, is the ground screen (reflector). If you point that antenna at 30 degrees compass, it only gets signal from 30 degrees, and sees nothing at 210 degrees compass (trying to come in the back side of the antenna).

In this example, the gain pattern is only out the front, and there are no lobes on the back. The picture is one of the output modes of 4NEC2. Antennas have a 3D pattern, so showing a 2D slice is not showing all aspects. Still, a 2D slice is easier to print out on a laser printer.

( )

The 3D pattern is important for home Wifi routers. If you have a basement, a ground floor, a second floor in the house, pointing the 2dBi antenna straight up, only services the main floor well. If you tilt the antenna, you may be able to service the basement, or the second floor, but not both. The 3D pattern helps predict how your house will be served with Wifi. If the Wifi router has multiple antennas, you can leave one straight up, and tilt the other two.

Paul

[charles]

No - a log periodic has nothing at the back in the way of metalwork. It is, however, very good at rejecting signals from the back

[alan_m]

You need a T2 tuner to receive one of the MUXs but if you are getting the HD channels then it is a T2 tuner.

[Tim Lamb]

Yes.

[wrights...]

I've been offline for a few days.

1. C Palace ch35 is just a local mux so will likely be very low power.
2. This time of year tree screening is a big thing. It tends to affect higher channels more than lower ones.
3. If ch35 is low power it is more likely to be affected by co-channel (or other) interference.
4. If the other muxes are OK I shouldn't alter the aerial. Pointless. Bill

[Tim Lamb]

Ok. Bill. Thanks. Pretty much covered by our other residents. The aerial is relatively young, 4 years from installation.

The low output power/distance is clearly the issue but not obvious from amateur investigation:-)

I'll stop fiddling with coax connections!

>

[SH]

regarding Low power muxes, these tend to be local TV channels along with usually 3 or 4 other niche TV channels.

Although they are lower power, they use QPSK modulation instead of QAM which means that you can get away with much lower Tx power and greater errors (QPSK is more robust to QAM against errors) and still be able to recieve it reliably.

In contrast, the QAM256 (the HD muxes!) reqiure higher signal to noise margins and lower error bit rates to recieve reliably.

I did at one time manage to recieve Thats Oxford which was on a QPSK modulated mux from Oxford Tv here in deepest Northampton until it changed frequency and became directional.

[The Natural Philosopher]

Looking at the original post, if we are of the opinion that you are tuned to CP, then the fact that signal strength is good but quality is not, suggest you may have interference rather than low signal as the issue. And interference specific to that MUX frequency.

Which means that a (slight) change of aerial direction, position or aerial type may in fact fix the problem.

[Tim Lamb]

Hmm.. Inviting a rigger to play with TV aerials here is a £200 touch.

Around the freeview satellite dish cost which I can d-i-y

[The Natural Philosopher]

Is the aerial roof/chimney mounted? Do you have a usable loft position? None of us like pratting around on rooves...

[Tim Lamb]

Chimney on a long pole.

>

[SH]

Or a versatower.....

[Tim Lamb]

Not for improved signal quality on a channel I rarely watch:-)

[SH]

So why all this fuss over Ch 35 from CP? :-)