DVB-T Comparison Phased Array VS Yagi in fringe area reception

Forums › Freeview (DVB-T/DVB-S) › DVB-T Comparison Phased Array VS Yagi in fringe area reception

1 | 2 | 3

2388 posts

Uber Geek

#783488 18-Mar-2013 14:52

The masthead amp in pic one is not shown in the optimum position. Try reducing the cable length and mounting it on the back. The cable to the balun to the MH can be reduced to about 2 or 3 inches.

Masthead amps should be as near to the balun as possable to cut signal loss.

ageorge

626 posts

Ultimate Geek

#783510 18-Mar-2013 15:52

Apsattv: The masthead amp in pic one is not shown in the optimum position. Try reducing the cable length and mounting it on the back. The cable to the balun to the MH can be reduced to about 2 or 3 inches.
Masthead amps should be as near to the balun as possable to cut signal loss.

I read you the first time, but there is an issue with doing this; it can cause instability; the recommended length of feed cable by some authority is no closer than 1m. I am actually around 500mm which is as below:

Faults in UHF LNA: Mounting in close proximity to, or on, the antenna. Locate the amplifier away from the antenna (at least 500 mm) and not between antennas.

Assuming that the balun and coax are matching the attenuation of a piece of high quality UHF coax at 500mm is very little although I share your thoughts with close proximity, provided the amp has lower gain. When its around 14Db (which most are or more) that can easily lead to instability. For example, if I was using a MAR-6 with 5v feed then I'd probably mount that right on the aerial, but the commercial amp I'm using has got much more gain than this.

sliding

2 posts

Wannabe Geek

#789668 30-Mar-2013 16:55

What is the brand and part number of the amplifier you are using? I only use kingray MDA20U in fringe reception areas as these are shielded and block out all unwanted VHF and Fm signals

ageorge

626 posts

Ultimate Geek

#790717 2-Apr-2013 14:27

sliding: What is the brand and part number of the amplifier you are using? I only use kingray MDA20U in fringe reception areas as these are shielded and block out all unwanted VHF and Fm signals

Its called Metroamp distributed by Matchmaster. But the amp is not the problem. An amp is no use if you have little or no signal.

Etacovda

31 posts

Geek

#793606 4-Apr-2013 23:18

Considered WISI's? two stacked should work well.

Apsattv

2388 posts

Uber Geek

#793630 5-Apr-2013 00:06

I still think you should try to move the masthead as suggested.

chris48

10 posts

Wannabe Geek

#805698 26-Apr-2013 07:58

Hi

I have similar issues working from waiatarua at Ruakaka about 120 km from the transmitter. A few points that might help..
1. When you are receiving UHF by diffraction, which is probably your case, the signal can be very localised. A quarter wave can make all the difference. Try your earlier location again. Higher is not always better. I have found best signal points as low as a metre from the ground.
2. Commercial aerials are optimised for gain at the top end of the band. Freeview HD is at the low to mid channels. This can make a few dB difference, enough to fall over the precipice. Try making your own, or search for one optimised for band 4 only.
3. Because of point 1, a phased array is often better as it has more resilience to the variation over short distances vertically.
4. It is important to have a very low noise preamplifier. Many are poor in that respect. Check the specs and get one with a nf less than 2db. If necessary, source from the UK. This is the most important part of your setup.
5. Expect variations. Wind churn across ridges between you and the transmitter can drop the signal several dB.
6. Try a stb instead of your inbuilt tuner. Some have much better receivers.

Good luck

Equinox IT

Cloud spending continues to surge globally, but most organisations haven’t made the changes necessary to maximise the value and cost-efficiency benefits of their cloud investments. Download the whitepaper From Overspend to Advantage now.

ageorge

626 posts

Ultimate Geek

#805801 26-Apr-2013 10:03

Thanks for the answer above I have set the thread as answered, as your info is particularly relevant.

ObidiahSlope

260 posts

Ultimate Geek

#812600 7-May-2013 10:31

I have previously posted in this thread because I am in a fringe area and was wanting to know if a phased array would resolve my reception problems.

My problem was while I got a good reception on the whole when a large vehicle went past the roadway outside the picture froze and pixelated. The most obvious cause for this was signal bounce off the vehicles.

I rang Matchmaster aerials in Christchurch to ask if changing from a yagi to phased array type would solve my problem. The person I spoke to expressed doubt whether this aerial type change would make an improvement. He mentioned the possibility that the analogue switch-off may result in an improvement

As I am a South Islander I decided to wait and see if the switch-off would make a difference. I pleased to report that since the switch-off passing vehicles no longer cause picture freeze or pixelation.

Obsequious hypocrite

lchiu7

6476 posts

Uber Geek

Trusted

#813038 7-May-2013 16:52

You would probably have to use Youshop to get one over here but I have heard and read very glowing reviews for this UHF HDTV aerial

http://store.gomohu.com/the-leaf-ultimate-hdtv-antenna.html

It talks about a range of 50 miles or about 80km

Staying in Wellington. Check out my AirBnB in the Wellington CBD. https://www.airbnb.co.nz/h/wellycbd PM me and mention GZ to get a 15% discount and no AirBnB charges.

Skolink

1081 posts

Uber Geek

#813319 7-May-2013 22:06

lchiu7: You would probably have to use Youshop to get one over here but I have heard and read very glowing reviews for this UHF HDTV aerial

http://store.gomohu.com/the-leaf-ultimate-hdtv-antenna.html

It talks about a range of 50 miles or about 80km

I suspect a high gain yagi with a low noise amplifier would do better.

sliding

2 posts

Wannabe Geek

#813537 8-May-2013 10:06

ageorge:
sliding: What is the brand and part number of the amplifier you are using? I only use kingray MDA20U in fringe reception areas as these are shielded and block out all unwanted VHF and Fm signals

Its called Metroamp distributed by Matchmaster. But the amp is not the problem. An amp is no use if you have little or no signal.

I don't use any of the match master products as there failure rate was to high and they introduced to much noise into the system in fringe areas where your signal was marginal anyway. I tried to find the NF spec on the amp your using but was unable to.

The MDA20U has a noise figure of only 1.6
http://www.kingray.net.au/products/distribution-amplifiers/low-gain/MDA20U

In my experience a phased array is good if you have trees and the like to contend with. But you cant normally beat a high gain Yagi that has been optimized with a proper aerial meter for its best location on the property and an MDA20U mast head amp.

If you still cant make it work with that then satellite is your only option in my opinion.

lchiu7

6476 posts

Uber Geek

Trusted

#813542 8-May-2013 10:24

Skolink:
lchiu7: You would probably have to use Youshop to get one over here but I have heard and read very glowing reviews for this UHF HDTV aerial

http://store.gomohu.com/the-leaf-ultimate-hdtv-antenna.html

It talks about a range of 50 miles or about 80km

I suspect a high gain yagi with a low noise amplifier would do better.

No idea but the reviews I read were enthusiastic. One undeniable fact - it would be way less of an eyesore!

Staying in Wellington. Check out my AirBnB in the Wellington CBD. https://www.airbnb.co.nz/h/wellycbd PM me and mention GZ to get a 15% discount and no AirBnB charges.

chris48

10 posts

Wannabe Geek

#813585 8-May-2013 11:24

It is true that Yagis can have a higher gain than phased arrays but most of the commercial ones available hit their high gain figures towards the top of the old UHF band, whereas most of our digital channels are below 670MHz. Their gain can be 5 or 6 db less in the range we need for digital TV. In the UK they provide aerials for band sections - the most useful one for us would be the K band. Some digital sites use a tight range of channels, say 32, 34, 36 - these lend themselves to a narrower band yagi - but you would probably have to make it yourself. Check out Gray-Hoverman on Google for an interesting alternative. Another area I would like to follow up is to make a balanced pre-amp so as to avoid the balun losses. I can't find a commercial one of these.

Chrisso43

6 posts

Wannabe Geek

#813622 8-May-2013 12:17

Chris48 In regards to your statement : Another area I would like to follow up is to make a balanced pre-amp so as to avoid the balun losses. I can't find a commercial one of these.

Have a look at the look at the DAT range of UHF antennas which have inbuilt preamps and full AGC control and see if they will do what you require, link provided: http://matchmaster.co.nz/product/uhf-antennas

Your search may be over :-)

1 | 2 | 3