I'm going to experiment with a semi-stealthy vertical wire antenna here soon.

I have a tall pine in the backyard that is ~45ft tall, and I was wanting to experiment with a ~53ft wire.

I am thinking of getting a push up pole, not just for antenna experiments like this, but, for other things as well, and I was considering a 40-50ft fiberglass push up pole.

I'm pretty sure, that I'm going to have a few feet more of wire than i do push pole, so, my question is this...

Is it better to have the extra length at the top fold over horizontal, or, let the wire slightly coil around the pole to where the end of the wire is at the top of the mast?

I haven't quite yet mastered EZNEC to see what it will do;  but, I am working on it so I won't have to ask all these questions (as often)...

I decided that while I had the nice weather outside this afternoon, and that I already had the wire cut, I'd string a 20M droopy loop on the roof to see what the difference would be.  I fed the loop with ladder line, inside to a 4:1 balun, then through the wall to 3' of coax, then to a tuner.

Oddly enough, on 20M and up, I have absolutely no RF in the house, even at 100watts tx.  No rf in the radio, no HVAC issues, no wife coming upstairs telling me the blender is freaking out...

This is a MUCH better improvement so far.  I'll continue to play with the loops.

I'm pretty limited on where I can put an antenna at the new QTH, as the house takes up quite a bit of the lot.

Last night, I finally got some time to put up a simple 20M dipole over the roof, just to see how things would go.

My shack is on the 2nd floor, which was an attic converted to some extra bedrooms and a bath, and the space I've claimed as my ham shack.  The dipole was directly over the shack, and laying on the composite shingles.  Yes, I expected some RF, but, I got more than I anticipated.  At about 20 watts and above, the RF turns on the inducer fan for my HVAC unit upstairs, which is in the mechanical closet next to my shack.  I also noticed that it was turning on some lights downstairs with the touch-on controls.

My initial thought was to make a cobweb antenna, and place it just above the roof on the 2nd floor (mainly because of it being the highest point on the lot), but, does it look like that I'm going to be running into the same RF problems by having an antenna directly over the roof?

If I put the cobweb antenna further down the roof line, it will get it further away from the HVAC and shack, but, it's still going to be directly over some kind of electronic equipment and/or bedrooms.

My only other option is going to be putting it directly over the roof of the storage room, but, it's only about 15ft above ground, and will be set lower than half the house.

Any magical distance above the roof that will cut out the RF into the house?

Makes sense.  Think I'll forgo wasting coax, and try to some other options.

Thanks for the response, and 73's!

I'm trying to make a semi-stealthy dipole for a rooftop, and after knowing that you can use 2 runs of coax together as semi-ladder line, it got me to thinking.

What characteristics would an antenna have, if made from coax, and the shield was separated in the middle, and tied to a run of "coax ladder line" back to a tuner?

The coax would be on top of the roof pitch, and would blend in, with the pitch being about 35ft off ground.

I don't have any antenna modeling software, and I though I'd run this by you guys first before I started waiting good coax.

Thanks in advance!

Sorry; yes, for most practical purposes, I'm interested in 80m-10m.

The deck is wood, and the house is rock face.

I do have an ATAS-120a, which for "now" purposes, I could mount on the deck, and have a counterpoise going down the deck supports towards the ground.  I do have a dog in the back yard, but, I'd make sure to keep it out of nose range.

The house was built in 1935, and even though it's been updated quite a bit, it still needs some work.  Enough that it's probably going to take away from most of my wire antenna building time.  I'm not against building my own, and I do enjoy building my own things.  But, for now, if it's anything more than a simple dipole, it's going to have to be put on hold.

Would the ATAS work with the vertical counterpoise?  Well, for as good as an ATAS can work?

We've just moved to a new (well, new to us) house, and I have a lot more room to play with antennas.  Although, not a HUGE amount, but far more and different options than my last QTH.

I will be setting up my office/ham shack on the 2nd story.  Right next to the office, is a door leading to small deck that overlooks the back yard.

One of my main questions is, does radio height above ground affect the performance of an antenna?  The reason I ask, is because I may be able to put up a vertical in the backyard with a good radial system, but, the radio being on the 2nd story, will be at least halfway up over ground as a vertical antenna would be.

My other option would be to put a dipole over the tree tops in the backyard, but, the coax would be coming off horizontally to the dipole as opposed to going vertical to the ground first. what characteristics would this antenna have?

I have also thought about putting a vertical on the deck railing, which would put the radio elevation-wise at the same height as the feed point.  But, I wouldn't have an option for a radial field.  How well would a counterpoise work, going down to the ground from the feed point, essentially creating a vertical dipole?

Last night, I changed up my antennas a little.  Since I really only have 2 trees to play with, I did the best I could.

I know have a 43ft vertical wire, fed by the UnUn, and still using the fence as a counterpoise.  I lost 160M, but, the BCB is now gone.

Oddly enough, with just the limited amount of playing I did last night after the fact, I don't think I lost much receive (that I can tell), and from looking at my trends on WSPR, it appears I'm a bit more omnidirectional with both my tx and rx.  I know it's a very un-scientific way of looking at things, but, it seems to be working just as well as the inverted L did, if not better pattern-wise.

I also believe I've lost a lot of local noise from neighbors TVs, wireless routers, etc.  Just seemed quieter on the bands with the 43ft vertical, which could also be attributed to the fact that there's now less than 1/2 of the wire in the air as there was...

I guess I can live with the loss of 160M; it's coming up that time of year where it starts to get too noisy around here anyways, and I can only remember having 2 QSOs ever on that band.

I do know that my IC-7000 is now able to function on 40M and below....  Still bakes my noodle as to why the BCB was there on 7.300, but, disappears on 7.301....

I have a ~130ft inverted L with a 4:1 UnUn.

The feedpoint is on top of a 6ft metal (not chainlink, but metal) fence, and the metal fence is connected as the ground plane.  Not optimal, but, I do not have the ability to lay radials on the ground.

It's fed with about 40ft of 213u, and before the coax enters the house, I have about 20 turns on a piece of 4" pvc.

I've been pretty happy with the performance on this setup on all my rigs so far, which include(d) a Yaesu FT-450, Kenwood TS480HX, and a Yaesu FT-817nd.

My problem has appeared when I bought an Icom IC-7000.  On 40M and below, I get horrible AM broadcast interference from a local station.

The interference is awful on the IC-7000, BUT, you really have to listen close on the other radios to hear the AM station.  In fact, the interference is so slight on the other radios, that I never noticed it until I went looking for it after I heard it on the IC-7000.  When the IC-7000 is on 40M, it goes so deaf that you can forget about hearing much at all 40M and below.

It's not a fault of the radio; this is the 2nd IC-7000 I've tried, so, I've eliminated that issue.  The local station is 1 1/2 miles away on 1450, and running 1kw.

I'm guessing the antenna is far too sensitive to be that close to the AM station?

I can remove the 4:1 UnUn, and go directly to the wire and ground plane, and the interference goes away on ALL radios, including the IC-7000.  The problem is, I believe I have a far worse match to the tuner, and, I loose the 160M band.

Is there another direction I need to be heading with my antenna setup?

Would shortening the wire portion of the antenna deafen it enough to bring back 40M on the Icom?

Kinda at a loss here...

I played around some more with it today.  Here's what I found.

The IC-7000's issues go away when the coax has no Balun or UnUn, and is connected directly to the antenna.

Once I introduce a 4:1 Balun or 4:1 UnUn, the interference flows in.  I put a 1:1 Balun inline, and no interference.

I'm bumfuzzled...

Just to update some things here, and hopefully clear up some details...

After some more experimenting with different configurations, it ultimately boils down to this...

The IC-7000 has cross modulation from an AM station that is 1.3 miles from my house, broadcasting at only 1kw (all info from FCC)

The cross modulation occurs ONLY on the IC-7000, and not on any of my other rigs.

It ONLY occurs when the UnUn's ground is attached to the metal fence.  It all goes away when as little as one counterpoise/radial  is attached.  It actually is absent with NO counterpoise/radials attached.

I need to also recant one thing...  I said that I hooked the coax directly to the radio with the metal fence hooked to the UnUn and the interference went away.  It does not.  SO, to clarify, the interference DOES occur when the coax is directly connected to the radio with the UnUn connected to the fence; in fact, again, it happens any way when the UnUn is connected to the fence.

Thanks again for the help!

I could see how a chain link fence would do that.  But, this one is a metal framed fence with sheet metal panels as fence panels; it looks much better than it sounds.

Well, I don't quite know why it is, but, I do know now, how to keep it from reappearing.

My antenna is an inverted L.  The feed point sits on top of a 6ft tall solid metal fence that divides my neighbors and my house, and runs the entire back length of my yard and his yard.  It's all welded together.  The feed point is a 4:1 Unun, in which the ground plane is the metal fence itself; I have the balun's ground lug connected to the fence via copper strap.

I plugged a miracle whip antenna on to the ant 2 connection of my LDG-600pro tuner.  When I had the radio on the ant 2 option, I had NO interference.  I also had very poor reception, even with the MW antenna tuned for 40M.

As soon as I would switch to the ant 1, it was back to the interference.

I decided to take the tuner completely out of the equation.  I hooks the coax directly from the antenna, into the radio, and NO inteferrence.

For whatever reason, I decided to take the copper straps off the fence, and replace them with a few elevated radials, just for testing sake...

What I discovered is, that when you have the antenna grounded at the feed point, you will get a LOT of AM interference.
When you have the Unun with even just one radom length radial, voila, the problems immediately go away...  I DO however loose 160M capability on the antenna.

What am I missing here?  Can you have TOO much ground plane for an antenna?

I picked up a fairly new, but used IC-7000 this week.  It was used as a demo for a local communications company, and to my knowledge, and for what it looks, it wasn't abused.

But, I noticed that when I hooked it up to the same antenna that I have my Kenwood TS-480, I have horrible crossmodulation from a local AM broadcast station in which I've never heard before on any other transceivers I've had before.

You can hear it on LSB, and it will actually cover up weaker signals, making it nearly unusable on 40M and below.  My TS-480 doesn't hear the AM station, and hears the weaker signals just fine.

If I change the mode to AM on the IC-7000, I could hear the local station even better.

Is this something that is plagueing the IC-7000's?  I haven't seen much said about it, and everything on the radio seems to be in fine working order.  In fact, I really like the filters a bit better than the Kenwood's (although the difference isn't what I would call "staggering", but, noticeable).

Is there a setting that I'm forgetting somewhere?  It is a new radio to me, and I haven't figured out all the "ins and outs" of it yet...

I took a video of it last night to give a better idea of what I'm hearing.

http://youtu.be/P0T8MZa-1I4

tx inhibit isn't on, otherwise I wouldn't be able to hit the local repeaters.

What other options would there be?  I can't find anything else that would cause it?