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SqEyez12

Multiple Wisi Antenna Array Possible?

34 posts in this topic

13 hours ago, alanh said:

Obviously the pair of signal are not in phase due to the reduced level of signal increase and the reflections causing the increase in errors. Whilst the ideal is to have equal lengths, the reality is that not all cables have the same delay characteristics.

Alanh

Dear Reader

For the purposes of phase matching at UHF television frequencies, you can trust that two equal lengths of RG-6 will have the same delay. This is not some ideal world goal that the poster above is suggesting, just proven practical advice.

James

 

 

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12 hours ago, CMatten said:

Where in Springfield are you located? Did you try getting a signal from Sydney?

 

Hello CMatten

I don't know where Adrian is however when I checked the path profile from a central Springfield location to the three local transmitters and Sydney they are all woefully terrain obstructed.

Adrian really has a challenge.

James

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1 hour ago, James T Kirk said:

For the purposes of phase matching at UHF television frequencies, you can trust that two equal lengths of RG-6 will have the same delay. This is not some ideal world goal that the poster above is suggesting, just proven practical advice.

He might be worth listening too if he was clearly talking about PE vs foam. VF 0.66 v 0.83 is enough to be a problem. But he hasnt said that and yeah for equal lengths of the same basic type youre right.

Hell I've bench tested 9290 9913 9292 & 300 ohm twin against each other. All have close to the same VF. You could use equal lengths of foam core RG6 on one leg and ribbon cable on the other wirh no probs due to VF.

Edited by Pesto Lovin' Man
stupid calculation

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3 hours ago, James T Kirk said:

Hello CMatten

I don't know where Adrian is however when I checked the path profile from a central Springfield location to the three local transmitters and Sydney they are all woefully terrain obstructed.

Adrian really has a challenge.

James

Hi James

Check these plots out I did back in 2009.  You'll be able to see why it all depends on the location in Springfield as to what is the best option.

Bouddi (West part of Springfield is in the shadow of Mt Kincumber)
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426165.jpeg

Forresters (May be possible on the eastern side and the higher western parts.
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426206.jpeg

Rumbalara (Most of Springfield is in a shadow)
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426265.jpeg

Regards

Colin

Edited by CMatten

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21 hours ago, CMatten said:

Hi James

Check these plots out I did back in 2009.  You'll be able to see why it all depends on the location in Springfield as to what is the best option.

Bouddi (West part of Springfield is in the shadow of Mt Kincumber)
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426165.jpeg

Forresters (May be possible on the eastern side and the higher western parts.
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426206.jpeg

Rumbalara (Most of Springfield is in a shadow)
http://www.dtvforum.info/uploads/monthly_10_2009/post-88880-1256426265.jpeg

Regards

Colin

Hi Colin

Yes indeed.

One of the things we use is coverage overlap map showing the combination of the three local transmitters plus Sydney. It clearly shows residences in the same street can have field strength differences more than 24dB, Waratah St being a fine example, I think your attachments will certainly help Adrian sort his options.

James

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4 hours ago, James T Kirk said:

Hi Colin

Yes indeed.

One of the things we use is coverage overlap map showing the combination of the three local transmitters plus Sydney. It clearly shows residences in the same street can have field strength differences more than 24dB, Waratah St being a fine example, I think your attachments will certainly help Adrian sort his options.

James

I wouldn't rely on the level in these maps as it was a hack I did. Also, they are based on omni directional pattern which isn't the pattern at each transmitter.

Since i last looked, the ABC have updated their reception maps. http://reception.abc.net.au/Reception.aspx

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3 hours ago, CMatten said:

I wouldn't rely on the level in these maps as it was a hack I did. Also, they are based on omni directional pattern which isn't the pattern at each transmitter.

Since i last looked, the ABC have updated their reception maps. http://reception.abc.net.au/Reception.aspx

Hi Colin

Genuinely I understand however I would not be too concerned about your "hacks" the HRP's for these sites on the Springfield bearing.

Although they certainly are not omni-directional, in the direction of Springfield are:

Bouddi (V) is -3dB ERPmax (640W)

Rumbalara (H) is on ERPmax (300W)

Forresters  (V) is -8dB ERPmax (200W)

James

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Installed my last 9 metre mast over 15 years ago. Couldn't do it by myself now as my shoulders are shot.

I wouldn't even bother now that VAST is here, I'm thinking the cost of labour, masting, antennas, amplifiers, planning approval etc. would outweigh a dish & a couple of decoders.

I've tried stacking phased arrays(or using pre-built arrays) in areas of diffuse horizontally polarised signal before & found the performance is not necessarily better than a single unit, or a long yagi, even though horizontal stacking of the phased array should sharpen the directivity in the horizontal plane, & reduce some of the garbage that can be captured.

Edited by I am not a duck
Reason: Just curious.

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1 hour ago, I am not a duck said:

I wouldn't even bother now that VAST is here, I'm thinking the cost of labour, masting, antennas, amplifiers, planning approval etc. would outweigh a dish & a couple of decoders.

 

Agree, sometimes using VAST is the cheaper / more reliable solution. Only problem is the ads are for sheep dip in Mt Isa ;-)

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