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

[BriansBrain]

2Bay or not 2Bay ?

This is my Question

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

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

[BriansBrain]

This is what I have available

Am I going to have a tuning or SWR problem ?

All to Scale

[NOYB]

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

[BriansBrain]

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

It will be 6dB Gain ... going from 150W > 300W

And Like you say... I'd like to minimise the local downward radiation

[Banus_radio]

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

[sinus trouble]

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

Some may disagree?

[Albert H]

Delete this one please.

[Albert H]

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!

[BriansBrain]

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

[BriansBrain]

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' .......
I've always wanted a bigger pole ever since I was a teenager

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

[BriansBrain]

OK...

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

For 'Brian' @ 96.8MHz this Antenna would have to be nearly 3.7M tall

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.

[Albert H]

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.

[BriansBrain]

Thanks for the suggestions Mr H

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

[teckniqs]

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

[Albert H]

Teckniqs suggestion of giving it a try is probably best! You MUST get the lower antenna as high as possible above the building roof, or you'll get a poor match and waste energy into the brickwork!

Another aerial with a helpful radiation pattern for you (with your low site) would be a Slim Jim.

[BriansBrain]

Thanks Teckniqs & Mr H

After doing some more research I find that my Actual Elevation above sea level is only +/- 17M
So add my 8.2M pole and my Antenna is only 12M above sea level

I can't get my lower antenna in a 2Bay to high above the building roof because of keeping inconspicuous.

I might look into this - from eBay

[thewisepranker]

Build one, they're easy to build from standard parts from a plumbing shop, easy to tune and you'll get some satisfaction out of it. You'll have to tune the eBay one anyway. I'm not keen on those eBay ones - your coax will fill with water.

[BriansBrain]

OK..........

I'm forgetting the idea........ for now anyway

We are moving house, up the local hill, which happens to be at 200M Altitude

Therefore my Dipole will be at a total Altitude of 212M
Antenna Height Above Average Terrain (HAAT) = 125M

I will keep you informed

Terrain Profile