Minimum antenna installation above roofline

[volosguard]

Hello everyone.
I am a new ham radio amateur. I have already installed a Diamond X50 2,5m above the roofline and thinking of installing an X300 at 3m above the roofline. Many told me that I should install the X300, not below 4m above the roofline. However, there are strong winds in my area. Is there a minimum height installation of X50 and X300 especially? Will I see any real improvement installing X300??

Thanks in advance

 

[vagrant]

Here is a useful tool for you. A line of sight calculator. Line Of Sight Calculator

Above the roofline is fine. I have a neighbor with a two story home, so my antenna is instead above her roofline. If you are able to use the repeaters you want using the X50, there may not be a reason to spend extra money on the X300. It does offer some claimed 2dB gain, but that X50 is probably fine plus it has less wind load.

As to 4 meters above the roofline minimum to use the X300 does not make sense to me, unless you have nearby terrain/structure you need to get above. If you want to make sure your system is doing well, ensure you’re using at least LMR-400 or LMR-400UF coaxial cable from your radio to the antenna before you consider a slightly improved antenna.

Also, congratulations on your license and welcome. It is obvious you are ahead of others by coming here and asking questions. You will find that some people will tell you things that are not true, or are true to them. RF is interesting, so keep asking questions like many others should. I still do.

By the way, whomever is telling you 4 meters minimum ask them why. If they get flustered, or are unable to easily explain, make a note about that person. Too many people fall back on, “That’s just the way it is” which is definitely not true for all.

 

[trentbob]

Go as high as you think you should given the advice you have already. Look forward to some very expert and familiar posts you will receive tonight. Good luck, that's my two cents.

 

[trentbob]

Here is a useful tool for you. A line of sight calculator. Line Of Sight Calculator

Above the roofline is fine. I have a neighbor with a two story home, so my antenna is instead above her roofline. If you are able to use the repeaters you want using the X50, there may not be a reason to spend extra money on the X300. It does offer some claimed 2dB gain, but that X50 is probably fine plus it has less wind load.

As to 4 meters above the roofline minimum to use the X300 does not make sense to me, unless you have nearby terrain/structure you need to get above. If you want to make sure your system is doing well, ensure you’re using at least LMR-400 or LMR-400UF coaxial cable from your radio to the antenna before you consider a slightly improved antenna.

Also, congratulations on your license and welcome. It is obvious you are ahead of others by coming here and asking questions. You will find that some people will tell you things that are not true, or are true to them. RF is interesting, so keep asking questions like many others should. I still do.

There you go, as I said.

 

[GlobalNorth]

Welcome aboard and welcome to an expensive hobby.

 

[volosguard]

Thank you so much for your answers. I really appreciate the fact that so many people in this hobby, help the newcomers.
As for my setup, I have a Yaesu FTM-300 and an Icom 2200. The Icom has the X50 and I will use the X300 for the Yaesu. I also use Hyperflex 10 and I am very satisfied comparing it with the RG-213 I had initially used.
As for the minimum height of X300, I was told that the antenna has to be able to "see its idol" at least (excuse me if I don't explain this using the appropriate terminology). So if the antenna is 3 m long it has to be at least 3m above the roofline.
As for the "expensive hobby," I certainly agree and see this at my first steps. However, I am very excited about it.
Thank you again!

 

[Ubbe]

As for the minimum height of X300, I was told that the antenna has to be able to "see its idol" at least

In some sense that might be true for a 1/4 wave antenna, but neither the X50 or X300 are that. It's a wavelength related thing so 1/2 meter above roof would be enough for the longest wavelength of the 2m band. But the higher above ground for an antenna the better it will be, but perhaps not for shortwave wire antennas.

/Ubbe

 

[vagrant]

Ensure those antennas have plenty of vertical and or horizontal separation. You would obviously suffer desense when you TX, but close proximity can be unhealthy for the radios. The power output used along with your antenna gain are factors to consider. I suggest reading up on antenna vertical and horizontal separation. As you have dual band antennas, you would focus on the VHF range (lowest frequency) as that is the larger wavelength.
Horizontal isolation - https://extapps.commscope.com/calculators/qhisolation.aspx
Vertical isolation - https://extapps.commscope.com/calculators/qvisolation.aspx
Handy ERP calculator - https://extapps.commscope.com/calculators/qerp.aspx

While higher is better for Line Of Sight communications, as the calculator I previously linked to conveys, moving from 2.5 to 4 meters is a slight gain, but the cost/effort is probably not worth it. A bigger concern to overcome is physical things in the way like a home, shed, building, etc. Still, much depends on your location and how far you want to TX/RX. I have no problem using a Diamond X50 one meter AGL ( Above Ground Level ) to hit a variety of repeaters, but that is my specific location. Yes, that is one meter above the ground with buildings in the way.

That M&P coaxial cable is pretty good. A friend told me about it a few years ago, but I only recently did some research on it.

The Icom has the X50 and I will use the X300 for the Yaesu.

 

[alcahuete]

The minimum height is the height that works for you at your location. When I lived in a HOA for a few years, I had my Diamond X-510 on 10' of mast, with about 2' in the ground. It was in the middle of trees, nowhere close to any of sticking over the rooftop, etc. I even used 50' of RG58. It worked great! I could hit every repeater, and simplex worked great too.

Was it as good as having it up on a 50' tower? Of course not, but it worked for me with what I had available at the time.

 

[vagrant]

That's a great point. I used a discone as my first TX/RX antenna because that's what I had at the time being into RX when I got licensed. Fortunately, I was using LMR-400UF and it was only a 15 meter run.

Was it as good as having it up on a 50' tower? Of course not, but it worked for me with what I had available at the time.