Tuning a Kelemen Trap Dipole

[SpaceForceCmdr]

UPDATE: I got a Rig Expert AA-35. Expensive, but neat little device, and seems intuitive to use. It's very helpful being able to see what's going on. My FTDX10 will tune my antenna as is on 30, 20, 15 and 10m, and this seems to make sense based on my readings. My SWR isn't great on any band, but it's 11-12 on 40m, which explains why my radio can't tune it.

Here's some quick measurements I did at certain freqs, and the SWR at those freqs. Also, I attached a couple screenshots with a full sweep. I don't care too much about 15 and 10 meters, but if I could get 40m to fall into line, that'd be great. Also, 20m is very important to me, so if I could tweak that, too, I'd be happy. The biggest problem is my antenna seems to be resonant at 6611 khz, so that needs to be raised by around 600 khz. 20m is most resonant around 14.036, but at least it'll tune with my radio's tuner.

So, to raise the 40m resonance, it sounds like I can shorten the ends of the antenna by folding them back. Not sure if I need to loosen the nut on the egg insulator and move it? Or do I just fold back some of the extra wire that's hanging down beyond the insulator?

Also, to tune a band, I can try squeezing the corresponding trap. However, I'm confused as to which trap is which. I was thinking the traps closest to the center balun would be 10m, then next would be 15m, and the traps near the end of each wire would be 40m. Problem is, the traps have writing on them, and the labeling doesn't seem to match. For example, the traps labeled 40m are actually second from the ends of each wire. Maybe I'm misreading the handwriting, or maybe I'm misunderstanding the design of the antenna.

 

[popnokick]

The subject / topic of this thread has changed completely from looking for an antenna analyzer to tuning a Kelemen Trap Dipole. To draw the right attention and response I suggest you start a new thread in this forum titled something like, "Help Tuning a Keleman Trap Dipole". One of the eHam reviews for the antenna suggests that proximity to large objects can detune the resonant frequency of one or more bands... which is your case in what may be happening to 20M resonance ending up on 6611 kHz. The tuning procedures described in the manual may work but could also end up shifting resonance on the other bands that presently are tuning up for you. You may have to pick and choose what to give up to get 20M. In any case it's a good thing you got an analyzer - it will be very useful when you start the tuning procedures described in the instructions.

 

[prcguy]

Don't squeeze or change the traps. For a trap antenna you tune the highest band first by changing the length of wire before the trap then progress to the lower bands. Once a higher band is tuned changing the lower bands should not affect the higher bands. Since the higher bands sound ok you can just concentrate on the lower bands.

If 40m is the lowest band on that antenna then the end length of wire is for 40m and probably also 15m as a 3rd harmonic. If you need to adjust 20m that would be the next length of wire or the wire on the other side of the trap from the 40m wire and you need to adjust that first. For a 14.036 resonance you would want to shorten that wire to get maybe 14.175 to favor phone or 14.150 to bridge phone and CW. Once 20m is where you want it you can then adjust the 40m wire for maybe 7.150.

You will have to break into the middle wire, cut and reattach for 20m. For 40m you can untie the wire at the insulator and pull it through effectively doubling it back.

 

[SpaceForceCmdr]

Thanks, all! I think I am good The tuning process is a real pain because the antenna is in my attic. Crawling up there, adjusting and coming back down isn't easy. Anyway, things aren't perfect now, but I'm in the ballpark. My radio will tune up at 40m, and the other bands are still fine. There might've been some confusion in my other post, but 40m was always the problem band. The SWR on 20m wasn't great, but it worked.

To improve 40m, I ended up folding back some of the end wires, and zip tying them. This did the trick! Also, I changed the small, 20m loops at the trap to be more of an oval shape, rather than a circle. This raised resonance slightly in the 20m band.

Min. SWR is 1.36 at 7190 khz, and 1.69 at 14.175 khz. I could probably lengthen the antenna just a hair to tweak 40m even more, but I'll probably leave well enough alone for now. I can now transmit on all bands, so I'm happy. Someday, I may be able to put the antenna outside where it belongs.

In the attachment, the green line is after tuning.

 

[popnokick]

Anything under 2 to 1 works well for me. I have bands on both my vertical and off-center dipole that are worse. Sorry for the confusion I introduced in my other reply. Rereading it now I realize 40M is where your biggest problem was (not 20M). Glad it's all working, and very likely the best it can in the attic.

 

[SpaceForceCmdr]

Thanks, man. No worries! Since I'm usually on the radio in the late evening and night, I was most interested in 20m and 40m, and now I'm up and running with those, so I'm a happy camper! Glad I bit the bullet and got the analyzer. It's extremely helpful being able to see what the antenna is doing. Overall, it looks like Kelemen did a nice job with it. Even up in my attic, it only required minor tweaking. When I got done playing last night, it was like 4am, so I just did a quick test on FT8, and my signal made it to New Zealand and Australia from here in OH.

 

[KC5AKB]

Looks like you are on a roll. That’s the cool thing about this site all the folks helping out.

 

[SpaceForceCmdr]

Yes, sir! Glad to have this site and its members as a resource!