GoodSoundClub - Romy the Cat's Audio Site - The 75 feet

| Search | Login/Register

Home » Off Air Audio» Help with Math needed. (8 posts, 1 page)

Print Thread |

1st Post |

Page 1 of 1 (8 items)

Select Pages:

	Target	Threads for related reading	Most recent post in related threads	Forum	Replies	Views	Started
»	New	Antenna diversity system system for FM? Why not?..	Trickle Down?...	Off Air Audio Forum	1	28563	06-07-2009
»	New	Antenna attenuator – you got to be kidding?..	Antenna attenuator – you got to be kidding?...	Off Air Audio Forum	0	17617	07-11-2008
»	New	Antenna solutions for FM..	Hurricane Irene ibn Oz in Boston...	Off Air Audio Forum	27	202431	02-21-2008

07-12-2010

Post does not mapped to Knowledge Tree

Romy the Cat

Boston, MA
Posts 10,159
Joined on 05-28-2004

Post #:	1
Post ID:	13979
Reply to:	13979

Help with Math needed.

Guys, I need somebody help me with middle grad school math – I truly can’t do it. I need to calculate if my antenna in the line of sight with my WCRB and if not then what kind elevation I shall have in order to get the line of sight.

The image below is well depicts the situation. My antenna is at 160 feet toll over the sea level and 12 miles away there is 949 feet toll transmitter antenna. 2000 feet away there is a 240 feet tall heal the might or might not cover the line of sight. Who know how to figure it out? I do not remember geometry anymore…

Rgs, The caT

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-12-2010

Post does not mapped to Knowledge Tree

oxric
Posts 194
Joined on 02-12-2010

Post #:	2
Post ID:	13980
Reply to:	13979

Bad news I am afraid!

Well Romy:

A quick calculation shows that the angle of elevation is 1.24310 degrees (i.e tan inv of (949-160)/36360).

At a horizontal distance of 2000ft from the antenna, this angle of elevation results in an overall height above sea level of 203ft (i.e tan of elevation x 2000= 43 + 160 = 203ft). The 240ft tall heal will therefore be in the way of your line of sight... as you said it may or may not adversely affect your reception.

You could always set fire to it...

All the best
Rakesh

07-12-2010

Post does not mapped to Knowledge Tree

Romy the Cat

Boston, MA
Posts 10,159
Joined on 05-28-2004

Post #:	3
Post ID:	13981
Reply to:	13980

Thank you, one more.

Oxric, thank you very very much. Would you be kind to help me to find out what shall be the elevation of my antenna in order to reach the line of sight clarence over that hill?

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-12-2010

Post does not mapped to Knowledge Tree

oxric
Posts 194
Joined on 02-12-2010

Post #:	4
Post ID:	13982
Reply to:	13980

Or you could raise your antenna by 38.731ft

Romy:

My pleasure.

The actual angle of elevation required to clear the summit of the heal is 1.182 degrees (i.e tan inv 709(949-240)/34360(36360-2000)). Using similar triangles (h/2000=709/34360) or simple trig gives an overall antenna height of 198.731ft, so that you need to raise your antenna at least an additional 38.731ft to just clear the heal.

Rakesh

P.S You could move the antenna back if you wanted to maintain a height of 160ft but you would need to move 3877ft from the heal that is a further 1877ft back from the present position of the antenna, not a viable proposition at all I am sure.

07-13-2010

Post does not mapped to Knowledge Tree

oxric
Posts 194
Joined on 02-12-2010

Post #:	5
Post ID:	13983
Reply to:	13982

By the way, what is a heal?

Romy:

I just suddenly realised that by 'heal' you probably meant 'hill'. For a moment I thought it was some strange geographical feature that I had not come across.

Regards
Rakesh

07-13-2010

Post does not mapped to Knowledge Tree

Romy the Cat

Boston, MA
Posts 10,159
Joined on 05-28-2004

Post #:	6
Post ID:	13984
Reply to:	13983

The 75 feet - this is over the "heal"....

Oops, I am sorry. Of cause it was hill, I need to add it to my dictionary

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=3823

The 40 extra feet in addition to my current 35? This would make 75 feet mast. Hm, this is complicate as it will be make the tallest structure in my neighborhood and it will make it very vulnerable to lighting…

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-15-2010

Post does not mapped to Knowledge Tree

Romy the Cat

Boston, MA
Posts 10,159
Joined on 05-28-2004

Post #:	7
Post ID:	13995
Reply to:	13984

10 Feet up– 8dB gain.

I raised the antenna on 10 feet. Got extra 8dB of signal, not a lot itself but it a lot from a point of view of signal to noise ratio and I now can get a the specific station that I want with an acceptable level of noise. Oxric, thanks for your help. If you play 24 bit files then I might send you my tomorrow’s recording and it might be something that you might like.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-18-2010

Post does not mapped to Knowledge Tree

oxric
Posts 194
Joined on 02-12-2010

Post #:	8
Post ID:	14022
Reply to:	13995

You are welcome

Hi Romy:

Please don't mention it.

Yes I can play 24 bit files and yes I don't mind trying your recording.

All the best
Rakesh

Page 1 of 1 (8 items)

Select Pages:

	Target	Threads for related reading	Most recent post in related threads	Forum	Replies	Views	Started
»	New	Antenna diversity system system for FM? Why not?..	Trickle Down?...	Off Air Audio Forum	1	28563	06-07-2009
»	New	Antenna attenuator – you got to be kidding?..	Antenna attenuator – you got to be kidding?...	Off Air Audio Forum	0	17617	07-11-2008
»	New	Antenna solutions for FM..	Hurricane Irene ibn Oz in Boston...	Off Air Audio Forum	27	202431	02-21-2008