Cushcraft R6000 over a 10-80M multi-wire dipole

[Moleculo]

Just thought I'd throw this out here:

I had an I-10K over the top of a 10-80m multiwire dipole. This weekend i attempted to replace the I-10K with a cuschcraft R6000, which is a 6-20m antenna. The antenna was tuned up perfectly on a fence post before i put it on the roof.

When I put it on the roof, I couldn't get it to match on any band. Now, I think I know what the problem was after thinking about it. I think the mast on the roof (which is smaller diameter than the fence post) was exending too far up inside the antenna and hitting and making the mast part of the antenna, which won't work at all with this one. I'm going to alter the base of the antenna a little and try to put it back up this weekend.

Now, here's the part I hadn't really thought about until today: What are the chances that my inverted V 10-80 dipole is going to interact adversely with the 6-20m vertical above it? The distance between the two feedpoints is about 18". I never had any problems on 10m with the 11m antenna above it, so I assumed it would be the same on lower bands. Any thoughts?

 

[W5LZ]

Mole',
I had a similar problem with an 'R-7', tuned fine on a fence post, worked really terrible on top of the house. Found that tuning the thing on the post means that you are taking the relationship with the ground/dirt into consideration. That state of 'tune' isn't going to be the same when the antenna was moved to the roof... dirt not quite as close, right? finally just remounted it on the post.
As far as the other antenna being close to the 'R6000', that might be 'good', acting sort of like a substitute for the dirt? Good luck.
- 'Doc

 

[Moleculo]

I actually thought of that, also. That's also NOT what I wanted to hear :x That was my first concern since the ground plane radials are so short.

If this antenna won't work, I'll be looking for a new 6/10-20 or similar vertical to put up there. And I'll be taking suggestions....

 

[W5LZ]

Mole',
Don't give up on it too quickly! The reason I didn't re-tune the 'R-7' for the top of the house was it consisted mainly of adjusting section lengths, and you'd have to see my roof! It would have meant trying to keep the instructions from blowing away while holding everything else to keep it from sliding off the house. Think I maybe would have gained 20 feet in height with the move. Just didn't figure it'd be worth it, I don't like heights, except in an airplane.
Then again, if your antenna doesn't work out, I've these parts left over from that 'R-7'... I might make a trade for it??
- 'Doc

 

[SR385]

From what I understand, with HF verticals you don't gain much with elevation other than some ground wave coverage enhancement.

I mounted my GAP Titan on a ground mounted post just high enough to mow under it after reading many accounts of really no noticeable improvement from elevating them. It's a whole lot easier to tune it and otherwise maintain it with a ground mount too.

40m and up I've been happy with the Titan so far. It's not an ideal antenna but for my type of operating (casual) it works out well. 80m is pretty much a lost cause with it, though it tunes to spec. Then again, that is what I expected from it.

My GAP is a balanced antenna though, not sure about the Cushcraft design.

 

[Moleculo]

The main reason I want to get it up that high on the roof is because on my block the homes all stair-step down the hill. If I don't get it up at least 20', I'm shooting RF straight into my neighbor's living room TV. Besides, I like being the tallest thing on the block....

 

[rfoverlord]

:?: Well i have a titan dx now, my problem is where to mount it in my yard whiched is fenced in I have a 35ft tower up and a cobra ultralite sr. up so now where do i put this with out too much interference from everything else? the yard is 100 x 50 the tower is dead center 20 ft. from the house (off the deck) one corner has the last utility pole in the neighborhood outside of the fence. Anyone have any ideas or experience? I was thinking of one side that the neighbor will allow me to run 2 of 4 the guy wires that will support it but then it will close to the one leg of the ultralite and 5 ft over the fence.

 

[Master Chief]

Yep, ground coupling when mounted on a fence post.

Unlike the I-10K, which takes it's ground plane up the pole with it, the R-6K is NOT a ground plane antenna! Its a vertical antenna requiring a ground plane (which is accomplished when mounted close to the ground and using radial wires). Those short radials are more of a decoupling ring and nothing more. The I-10K has a full size (1/2 wave) ground plane right near the feedpoint.

The 10-80 dipole below the antenna will not affect the vertical much on any frequency except for the resonant length of the dipole, and even there, it would be minor due to the way the wires move away from the base of the antenna. You can test this by using a coax switch that grounds the dipole when not in use.

I have one of these......
http://www.cometantenna.com/pdf_review/Comet-CHA250B-Review.pdf

I installed it for a customer and after 5 days he had me remove it. I ended up taking it back as he decided to go with my original suggestion of a skyloop antenna. If you want to try it out for free, let me know. If you like it, its $300.00 (only up for 5-days). If you don't like it, give it back. Let me know and I'll bring it to you.

Vertical antennas radiate equally POOR in ALL DIRECTIONS! In order to to get them to play well, you need to mount them low to the ground (affects talk-off angle) and have a substantial ground plane!

The best reading on vertical antennas can be found at the Force 12 website and from the members of "Team Vertical"......
http://www.k2kw.com/verticals/verticalinfo.htm
http://force12inc.com/brvinfo.htm

I have the Force 12, Sigma-11......
http://www.worldwidedx.com/gallery/Force_12_Sigma_11

I have yet to do any serious tests with this antenna, but someday!

 

[rfoverlord]

:shock: You actually recommened that comet dummy load to some one!!! Wow . I would stick with the titan which i know is near the bottom of the list as far as verticals go, but it still beats the coment and a few others.

 

[Master Chief]

Shhh...I'm trying to unload it! :twisted:

Actually, it does have it's place and works without ground radials. Yes, there are better vertical antennas!

 

[rfoverlord]

I got the titan as part of the deal for another univeral 15-40 tower and a yaesu 450G rotor with extra control box(new) for a very good price now the question is do i really want to put it up.
Especially up here in the frozen tundra.

 

[Master Chief]

I got the titan as part of the deal for another univeral 15-40 tower and a yaesu 450G rotor with extra control box(new) for a very good price now the question is do i really want to put it up.
Especially up here in the frozen tundra.

I'll buy the 450G with the extra box!

 

[Moleculo]

I finally got the antenna up and working this weekend. There were many lessons learned, mostly caused by working with a second-hand antenna. When I have more time, I'll write up a little debrief of the experience. Anyway, it's interesting to be able to switch back and forth between the inverted V and the vertical, both which have the feedpoint at nearly the same height. I didn't have much time to do extensive playing yesterday, but I will soon, hopefully.

 

[Highlander_821]

I finally got the antenna up and working this weekend. There were many lessons learned, mostly caused by working with a second-hand antenna. When I have more time, I'll write up a little debrief of the experience. Anyway, it's interesting to be able to switch back and forth between the inverted V and the vertical, both which have the feedpoint at nearly the same height. I didn't have much time to do extensive playing yesterday, but I will soon, hopefully.

Have you been able to play with the antennas yet?

 

[Moleculo]

Update here:


http://www.worldwidedx.com/showthread.php?t=28376