2Bay or not 2Bay ? - - - that is the Question

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BriansBrain
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2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Sun Jul 14, 2019 3:41 pm

2Bay or not 2Bay ?

This is my Question :roll:

This is what I have now with my height limitations to go 2Bay :cry:

Antenna is 4M above building and a total of 8.2M from Ground Level

This is my Question... do I have enough height to go 2Bay without problems :?
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Tue Jul 16, 2019 12:51 pm

This is what I have available

Am I going to have a tuning or SWR problem ?

All to Scale :shock:
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by NOYB » Tue Jul 16, 2019 4:13 pm

Just wondering why the bother for just 3dB gain - are you trying to minimise downward radiation locally?

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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Tue Jul 16, 2019 7:15 pm

NOYB wrote:
Tue Jul 16, 2019 4:13 pm
Just wondering why the bother for just 3dB gain - are you trying to minimise downward radiation locally?
It will be 6dB Gain :whistle ... going from 150W > 300W :tup

And Like you say... I'd like to minimise the local downward radiation :roll:
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by Banus_radio » Tue Jul 16, 2019 9:22 pm

Take my word and use a Super J-Pole. Similar gain and nice doughnut shape radiation.

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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by sinus trouble » Tue Jul 16, 2019 9:58 pm

Just to add, Your mast should be a quarter wave above your boom (Level with top element) to be theoretically balanced!

Some may disagree?
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by Albert H » Wed Jul 17, 2019 2:45 am

Delete this one please.
Last edited by Albert H on Wed Jul 17, 2019 2:47 am, edited 1 time in total.
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by Albert H » Wed Jul 17, 2019 2:46 am

With a twin, the lower dipole needs to be at least a wavelength away from the building structure - you're going to need a bigger pole!

The "Super-J" would probably suit your site better, and would give you significant gain (if properly matched). It also has very little downward radiation, so there's little risk of local interference or overloading problems.

The big trick - whatever antenna you use - is to get the damn thing as high and as far as possible from the structure of the building!
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Wed Jul 17, 2019 10:42 am

sinus trouble wrote:
Tue Jul 16, 2019 9:58 pm
Just to add, Your mast should be a quarter wave above your boom (Level with top element) to be theoretically balanced!

Some may disagree?
Now...... I did not know that....... thanks :tup
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Wed Jul 17, 2019 10:55 am

Albert H wrote:
Wed Jul 17, 2019 2:46 am
With a twin, the lower dipole needs to be at least a wavelength away from the building structure - you're going to need a bigger pole!

The "Super-J" would probably suit your site better, and would give you significant gain (if properly matched). It also has very little downward radiation, so there's little risk of local interference or overloading problems.

The big trick - whatever antenna you use - is to get the damn thing as high and as far as possible from the structure of the building!
Thanks Mr 'H' ....... :smoke
I've always wanted a bigger pole ever since I was a teenager :lol:

Anyway..... I'm trying stay as Inconspicuous as possible, but I also thought I need to go higher...

How about like this... giving me an extra 1.3M
2 Bay Dipole-3 + Extra 1.3M.jpg
The "Super-J" you mean this one ? .... or another ?
on eBay >>> FM band 88 to 108 mhz jpole antenna
JPole.jpg
:whistle
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Wed Jul 17, 2019 12:16 pm

OK... :whistle

I have looked up the Super J-Pole Antenna
Here is a Calculator :smoke
http://www.hamuniverse.com/superjpolecal.html

For 'Brian' @ 96.8MHz this Antenna would have to be nearly 3.7M tall :roll:
Super J-Pole Antenna - in M-s.jpg
I have also looked here...
https://www.hamradio.me/antennas/improv ... per-j.html

Where is stated...
Some web sites suggest the Super-J has a full 3 dB gain over the plain J-Pole which is a pretentious claim obvious to anyone with a copy of the ARRL Antenna Book and other references. Indeed, the Super-J will never approach the gain advantage of a properly separated two element collinear antenna, but we can get closer to this goal.
:?
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by Albert H » Thu Jul 18, 2019 1:48 pm

Getting your twin stack that bit higher will help, but a good vertical colinear would be even better.....

The Super-J is a reasonably easy aerial to build, but the centre matching section always weakens the aerial, which might pose a problem out at sea as you are.

You could consider a ⅝-wave or a ⅞-wave according to high up your site is. These can be made to look (almost) like base-loaded CB aerials, so they're really good for keeping a low profile. Look at the radiation angle you want, and decide on the antenna.

Each will require ¼-wave ground planes (minimum 3, 4 is better, but 6 is great!) angled downwards (the angle affects the match somewhat). This type of aerial also gives you other advantages - low radiation downwards into the building, low field strength in the immediate vicinity (confuses people trying to track it down) and it is an unbalanced aerial, so no balun is required. There are plenty of on-line calculators that will work out the dimensions for you and the number of turns on the matching coil.

These groundplane types are commonly used for amateur repeaters and commercial PMR base stations, where the operators want fully omnidirectional coverage, useful antenna gain, and a robust, easily constructed, aerial.
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by BriansBrain » Sat Jul 20, 2019 11:46 am

Thanks for the suggestions Mr H :tup

But....
2Bay or not 2Bay ? - - - that is the Question

Geographic coordinates of Maspalomas, Spain
Latitude: 27°45′38″ N
Longitude: 15°35′09″ W
Elevation above sea level: 32 m = 104 ft

This is one of my biggest problems :(
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Re: 2Bay or not 2Bay ? - - - that is the Question

Post by teckniqs » Sun Jul 21, 2019 2:57 pm

I think the best thing to do is just try adding the other bay and find out. :tup

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