Ground mounting an IMAX 2000

[RadioDaze]

Hi all I am considering this as an easy option for the winter time DX sessions as a mobile static base station.
I am calling for information on how to do this successfully and wonder if I can get good low angle DX performance from such a set up and how this can be realized. Interested in the science of how this works for DX as I always thought that you need to get an antenna up above the soil.

I operate at high spots between 200 and 400ft above sea level so have a some decent basic ground height which I understand may not make much difference for DX? Interested in mounting methods/techniques, requirements for radials (if any?)

This would help me out in winter as when it is windy I would not have to concern about long masts and wind and guying it all up and the IMAX is an easy antenna to put together. But I would not want to sacrifice DX performance too much either.

Does ground mounting provide as good DX performance as mounting on poles high up? (i.e. 20-27feet poles) I am concerned I would just make a really good cloud warmer.


Thanks.

 

[222DBFL]

If you tend to setup at the same spot and no one else messes about around there, maybe add a ground rod at the base of the antenna. Use 5/8" 8ft ground rod and some #6awg thhn wire. Make it flush it near flush so no one but you knows that it's there. Might help. As far as performance at 20ft vs 30-40ft, yes this might make some difference but I would think it would be mostly locally. With long haul dx I've seen guys with their antenna literally on the ground and talk 5000 miles. I'm not sure how well the GM plays with being abobe ground level of or AGL. I can't personally say whether being up at 400ft vs the 40ft where my qth is located above sea level has much to do with it. The antenna sees AGL, so I would go off that first. Not to say being an extra 400ft in elevation isn't good, but it isn't the main factor you need to worry about. JMO. If you can bury a piece of pipe down deep enough that you can just drop your mast pipe in that would save some time. Also setup some guy wire tie downs at places where you might or would use them. Then maybe try a 36ft push up mast. Drop it a few ft down into your mast pipe already in place and then guied it off with some good Dacron rope. Even 550 paracord works well. Maybe it's too much, I've never run a static mobile, but I would think that if I were to go to a certain spot a lot for static dx, and not many people are around. Pound or dig a pipe just larger than your mast pipe down to 4-6ft. 3ft works but I like a bit of depth. Then add a ground rod. Drill your mast pipe and then add the wire to the mast. Then just leave enough of the ground rod mount up to get the piece of wire down into the hole and tightened. If you are using the fence post setup I would def. ads some ground rods to the setup and tie them all together and take one run to where the mast mounts and leave it with a proper crimped on lug and some no-ox. Tape and un-tape as needed to attach ground lug to mast. Also, add a small piece of pipe about 2ft already attached to your GM. Then just slide it over your current pipe and be done. Add a self tapping screw or bolt. This should make the antenna setup easier to put together. Don't know if any of the things I've listed will help, but maybe they will give you some things to ponder on. Good luck and hope to speak with you soon. 73 and God Bless from 2OR222 Daytona Bch., FL. operator Sean.

 

[RadioDaze]

Thanks Sean, Sage advice.. my issue is QTH changes fairly often and banging 8ft ground spikes in is not practical or permissible at some of the QTHs.

England is small and there is rarely anywhere, unless you go to real wilderness (national parks) where there are no people about. It is very densely populated and people are literally everywhere, even when you least expect them. Mainly because everyone is searching for quiet peaceful places and you meet those people there. : )

You make a lot of good points in your post so it was not in vane I will read through that and absorb it.

I would not use the Gain Master at ground level given the 5/8 wave di-pole design. I suspect the ground losses and interactions would make that a very ill performing antenna for DX when ground mounted. This is relative to an IMAX. I think given the requirement for many ground radials the idea of ground mounting is fairly impractical in my situation. Ok, it is easy to mount it low but all the radials that are required to counter the ground losses seem as painful as putting it on a pole.

 

[222DBFL]

I'm sorry. ID10T alert LOL! Didn't read the heading of the post. Too early I suspect!! At any rate. The IMAX 2000 from what I have seen likes to be up at least 20ft, if you can get more then have at it. You might want to look into the tripod mounts. They aren't too expensive and I believe they make a 30ft one. Will have to check out the EBay. Like I said I've never done static mobile with an external antenna, but I understand the reasoning. Space is becoming an issue in a lot of places!!! What were you planing to use?? There are some nice looking fiberglass tripod mounts on eBay for about $200 USD. Don't know how well they are constructed. But they are 29ft. Which would be well high enough for the IMAX 2000 to work I would think. Even at 20-25ft you will do okay. A local here has one on a fence post mounted about 20ft off the ground and he gets out just fine. Locally I know he can talk 50-100 miles depending on the conditions, and he gets his named called when he shoots dx. So something is working. I would think getting the abtenna as far away from the vehicle and any other obstructions that may affect the antenna from below or even at or near the antenna. A nice open field if possible, or an area about 50-75ft square. Not sure how limited your space is and I could be way off base, but with a base station antenna, or any antenna for that matter the less obstructions under the antenna the better. May not apply to vehicles totally but most of it does. People getting near your vehicle or opening a door while you are talking can definitely make a change. And from what I have seen base antennas seem to work the best with nothing around them or even in proximity to them. Metal porch roof, metal on top of chimney, trees within 10ft. Things like this seem to affect the base antennas the most other than getting them up as high as possible. Again, not sure how high you're planning on using it at, but 20ft would be my minimum height if possible. Closer to 36ft the better. If your budget allows, check into the tripod type mounts like the military uses. Might cost a bit, but I would think they set up rather quickly. Again, hope something out of the text wall helps, and have a good day man.

 

[222DBFL]

Here are a couple photos of one of the fiberglass tripod mounts on eBay. About $200 shipped stateside. Might have to search around over in your neck of the woods for something like this. Or if you can build it, that would work!!

 

[space cowboy]

just try it. my bigstick was an excellent performer with the feed point about 4 inches (10cm) above earth. made many contacts on your side of the pond that way.

 

[RadioDaze]

Hi yes I do have ali poles so when I operate I try and do minimum 20ft with the Gain Master. The tripods look good and I have a small one which I used when I started back up in March.

On this topic I was really just wondering if ground mounting is a viable DX strategy as some have said 5/8 waves etc. can work as well on the ground as they do up in the air, in terms of take off angles.

I am dubious as to whether they can personally.I think you need many radials for this to work well which in itself seems to be quite a lot of work.

 

[The DB]

The higher you mount he antenna the lower the angle of radiation will be. There is no way around that.


The DB

 

[RadioDaze]

That is good to know The DB. Now it all depends on which can produce the best dispersion of angles for long DX and the lowest between the Solarcon MAX2000 and the Gain Master.

Maybe what I am experiencing on my very long haul DX 8,000 to 10,000 miles is relatively weak skip and blaming radiation angles.

I suppose it is hard to know which of your lobes actually got to it's destination and on how many hops compared with others local that made it through. (if you have split lobes as opposed to one nice big one from very low to mid range angles)

With the Sirio Gain Maser I think I know where I stand from a common mode issue, as the built in coaxial choke kills that off as far as I am aware.

With the Solarcon MAX2000 being an end fed 5/8 that could be more cantankerous and unpredictable due to any common mode being relative to coaxial lead lengths and absence of ground plane radials (in my existing set up)

I do have a ferrite based MJF 1:1 isolator I can employ under the IMAX. (Though oddly enough that says it should be put inline at the radio end)

I will have to try the MAX2000 out a few times to see how that shapes up in comparison. I imagine that would need to be built up experience as to rule out merely some days being better conditions than others.

 

[M0GVZ]

Get a copy of EZNEC or other antenna modelling software and model it at different heights and add say 8 radials for ground level mounting. That'll give you a reasonably accurate idea of gain at low angles for different antenna heights.

 

[RadioDaze]

Get a copy of EZNEC or other antenna modelling software and model it at different heights and add say 8 radials for ground level mounting. That'll give you a reasonably accurate idea of gain at low angles for different antenna heights.

Yes I checked it out but it looks rather complex to operate it. The idea behind the ground mounting was ease of setup in part but I wonder if putting a load of ground radials down is actually more work that popping it up on a pole.

In addition it would need a longer feeder to get it away from obstacles and my vehicle. I would not want to skew the radiation pattern with a big lump of metal at the same height. An operational consideration when mobile static is you have a big lump of metal with you that you are sitting in. I think I would need to set up it 15M + away to avoid such problems.


I read that you need to put a hell of a lot of radials down (40 I think I saw) before you start getting it working efficient close to the ground. Though it seemed they need not be resonant. things that may initially seem convenient can turn out more complex than initially meets the eye.

 

[Marcius E. Chester]

I live in a hoa development facility surrounded by mountains to the west and see them east/south of me at a distance. I have a Antron 99 that's sitting in my closet I want to use. My question is will it work mounted on my balcony 10 feet off the ground attached to a 6 feet fiberglass mast pipe using 100 feet of coaxial cable with the braid grounded along with a Ft-240-43 ferrite toroid core attached to the fed point for rfi/tvi/cmn suppression. Any help would be greatly appreciated.

 

[Hurricane145]

Will it work? Yes it probably will. The big question is how WELL will it work for what you want to do and your expectations!
There is no way to know until you put it up and try it out for a while. That is pretty much true for any antenna installation. Put it up and see how it goes. You already have the antenna anyway. Make changes later on if needed to see if there is any improvement.
If it is on your balcony, why is there a 100ft run of coax?

 

[RC4]

When I was younger I used a super big stick and had it in a 120 foot tree and I was on a hill about 500 feet here in Oregon. I could talk skip like no other! Now I know it always depends on conditions but I had nothing but good luck with that setup.

 

[Hurricane145]

The higher you mount he antenna the lower the angle of radiation will be. There is no way around that.


The DB

Not only that but you will be able to hear far better if it is up high as possible or practical.
If you can't hear it you can't work it no matter the angle of radiation or power level you use.
From a more practical sense, you put up the best antenna you can and live with it sometimes. You may never know how poorly it actually works if you never have anything better to use.
Try hard to find a way to get it up there a ways!!