Thanks!

The spring adds physical length. Thus lowering the resonant freq. Also, the stinger should never extend down into the coil area.

I use a tri mag mount and Ham Sticks from MFJ (600watts) on my Ram and used a Nano VNA and I was able to tune them to 1.1. 40M, 20M, 10M Ham Sticks

What if by adding the spring to the base of the antenna you've actually added physical and electrical length to the antenna? You were resonating high in frequency which is indicative of an antenna which is too short for the desired resonant frequency. But when you added the spring you added both mechanical and electrical length to the antenna making the antenna longer which lowers the resonant frequency of the antenna. What is inside that spring to connect the antennas radiating element to the center conductor of the coax? My guess is bare copper wire. The couple inches of copper wire added to the electrical length of the antenna is certainly long enough to lower the resonant frequency of the antenna. Most certainly the metal within the roof rack has some influence on the antenna as it is less than 1/4 wave away from the antenna. While there is a null immediately below the vertical dipole, the metal frame of the roof rack is 90 degrees from the feed point of the antenna. I imagine that the lobe of the vertical antenna is quite wide at the feed point, perhaps wide enough to be influenced by the roof rack.

Interesting experiment! One variable not discussed but is an elephant in the room is that the mag mount capacitively couples the ground plane. It would be interesting to note how a solid electromechanical connection via a mount drilled into the roof would affect resonance. Another thing to consider is... since there is no good electromechanical connection to the ground plane, the coax is also acting as a non resonant counterpoise, and it ALSO is capacitively coupled to the body of the car as you move the target around on the roof. This experiment DOES prove how dubious the ground plane is when capacitively coupled via a magnetic mount and when there is not solid connection of the antenna to the ground plane. You may wish to further test your conclusions with these additional considerations. Best 73's Dan. K1YPB - On the air since 1962.

Excellent hamvestigation! That's my new word now!

I've wondered about this as I prepare to do a mobile install of hamsticks on my Forester with the same rails and a sun-roof. Now I no longer need to wonder. Thanks for your work and thanks for your channel. I know it's a lot of work -- but trust me, a lot of us really love your content. I hope that's a motivator to continue producing content. 73, de KØADL

I use hamsticks for my POTA activations. I started with a 2014 Dodge Caravan, and a 5" mag-mount, and the hamsticks I have cover 10m through 75m. This set up was used for 3 years and 390 successful POTA activations. Last August I traded in the van and bought a 2022 Nissan Frontier. I was worried that the much smaller roof of the truck would detune the hamsticks. What I discovered is that nothing changed, the hamsticks still tune the way they did on the old vehicle, and I'm now up to 465 successful activations. I operate exclusively SSB or CW QRP. Thanks for the interesting video and lots of food for thought.

I drive an Outback and I use the Shark HF sticks. I had the exact same problem you are experiencing. But I don't think its the roof rack as much as it is the poor capacitive coupling of the magnet base. They way I solved the problem was to add 25 feet of coax to my mag mount. I believe this creates a counterpoise of sorts as the resonant point of the antenna drops right into the band. I've done this on vehicles both with and without roof racks with similar results.

You make a great engineer. Thanks for work.

Makes sense of a situation I had. Old SUV was a solid roof, new SUV, has a huge sun roof. SWR was fine on old SUV but same issue you're having with yours with my new SUV.

I remember adding coax segments on the 20-40M Hamsticks when installing on my 2023 Silverado 2500HD to bring down the SWR from 2.5 to 1.5:1 for my POTA Activations. I attributed it to only using a 5" magnet instead of the powerful 3-magnet versions. That was just a guess, but it appeared the longer coax made a better counterpoise. I regretted dropping my magnet in Colorado, every tiny piece of gravel with magnetite magnetic characteristics was almost impossible to remove without a lot of patience & perseverance, lol. Cheers, Davey --KU9L

When I first started messing with whip antennas on top of cars using my MFJ whip on a magnetic mount, I noticed that by moving my coax around I would get unpredictable results. I wrapped my coax around a toroid as many turns as I could fit (they certainly give you enough coax for mobile use) as close to the antenna as I could. This eliminated common mode currents and interaction with the car body. I haven't had a problem tuning my antenna since making the modification. KE8RWW, 73.

Nice analysis and insight. Thanks.

I used to use Hamsticks on an F-150. I cut a 20m and 40m radial and ran them to the back of the truck and just threw them into the back of the truck. A few months ago we went down to Arkansas and I put a tri-mag mount on top of the wife's Outback. There is no sun roof. I always add ground radials connected to the mount. The radials were roughly cut for 20m and run down each side and into the car and stuffed under the back seat. I did not put my meter on the Hamsticks due to lack of time before we left. The KX2 tuned it just fine and I worked many POTA stations on the trip. Try it with ground radials Tracy.

Thank you for this. Looking at what you've found, I think I'll use my Wolf River Coils Mimi antenna not only as a base but also as a way to tune my hamsticks more precisely Only for my 75 meter stick.i can use the WRC mini as a stand alone for the other bands

Hi there. i have on occasions experienced similar unexplained problems. There is a likelihood that your VSWR readings are being affected by common mode currents. Try installing a ferrite core choke near the base feed point of the antenna. Sometimes a choke at feed point to the transceiver will also correct this problem. Give it a try. 73 Peter G3OJV

It’s more of a unicorn mount than a rhinoceros. 😂

Hi, Just wondered if you thought of using a piece of faraday cloth and laying it on the vehicle roof under the mag mount? It's very pliable and would not scratch paint finish. It seems to be an effective ground plane and is becoming popular with hams operating portable, replacing radials and metal screens. Good luck . VE3WNS

I've never had much use for Hamsticks. They are under performers. I prefer Hustler mobile antennas. Your problem is more likely lack of bonding to the body. The magnet mount does not give enough coupling. It is almost always necessary to add a physical bond with a wire to the car body. In some cases without a solid bond, you can get an RF tickle from your mic while transmitting if it has any metal in it. That's been my experience.

Good experiment Tracy! Very interesting outcome! Hamsticks seem to be notorious for difficulty in tuning on anything anywhere. Some have had success cutting the whips down a few inches. I used a 10,20, and 40m MFJ Hamstick on the top center of my extended cargo van. No rack rails and no sunroof. Right out of the package they all 3 were resonant somewhere within the band they were intended for. I put the same Hamsticks on top of my KIA Soul with no racks or sunroof and couldn’t get them to tune anywhere near their intended band. After hours of trying I gave up. I might try cutting the whips down and see if that helps. 🤔

I have heard that the sticks expect to use the top of the vehicle as a counterpoise, thus not performing as well if they aren't directly connected to it on the shielding side near the base of the antenna. I have not done enough experimentation to confirm this one way or another. Just passing along what I've heard. Cheers.

the problem is probably the magnetic base, try using a different one for subsequent measurements

DX commander showed that sometimes you should ground the roof as those can be isolated from the car. Also Ham Radio Tube was experimenting with ham sticks and discovered that 40m one is really hard to adjust. He used few ferrites to make it work. Just go to their channels and look for it. I managed to make those work but I don’t use mag mounts with my car. 73!

It might not matter, but isn't the roof of those aluminum? Looked pretty stable in the rhino position, so maybe not. But possibly not coupling efficiently with the chassis due to lack of inductive coupling (if that's true). Just a thought. One of the guys in our local club runs a Subaru and can't do mag mounts. I run ham sticks on an MFJ triple mag mount (80-20, mostly 80) set on the back third, right behind a 3' sunroof, that's never been an issue, but I have a steel roof (older X3 BMW). I normally do run 2 other antennas at the same time (ATAS & 60" 2M), but that doesn't seem to affect it much. Thanks for posting, always good to see hams getting out of the shack! 73

Try a triple mag mount

Tracy you need to put a feed line choke between the rig expert and the antenna . Secondly the adapter has raised the base of the antenna off the magnet mount and the magnet needs to be a minimum of 5" diameter for best results .

I've played around with mag-mounts and ham sticks and 17 foot telescoping whips. My 17 foot whips always has a higher resonant frequency when on a mag-mount on vehicle. Ground mounted with radials, the resonant frequency is lower and where I would expect it. I believe this is due to losses created by the mag-mount and how it capacitively couples with the body of the vehicle. Just like you did with the spring, I use a coil to make my antenna a little longer and the problem is solved. The mag mount is probably coupling better at different points on your car due to the vehicle construction and better still on Mike's car.

Was wondering if you bonded all of the body panels in your Subaru. It sounds like you have a ground plane problem, other than just positioning. I have a truck with removable hamstick mount and permanent ATAS 120. I kept adding bonding straps and the swr's got lower. Ended up with 25, bonding straps, bonding the hood, doors, pickup bed , tail gate, and muffler all to each other and to the frame. With a mag mount you need to bond it directly to the ground plane you create, also. It's a LOT of work, especially for a low clearance vehicle. I get very good signal reports and a lot of contacts are impressed, especially coming from a mobile.

I using a telescoping whip as the stinger for my ham sticks this allows me to use one stinger for all two (but soon to be more, hopefully) of my ham sticks. I also mark in the fiber glass rod what length the whip needs to be depending on car and if I am going digital or voice. I just made a recent short on my channel as a quick demo

We were experimenting with an Outback with roof rack and sunroof and found on a couple hamsticks that opening the hatch helped with the tuning. I don’t remember the exact numbers, it wasn’t my Outback or radios, but we did get all the sticks we tried to tune to usable. Since that time they have swapped to the triple magnet and spring with reports of much better tuning but each still needs a different roof location for tuning.

I use the bigger metal triple mount behind the cab of my F150 on a steel toolbox. Not ideal behind the cab, but everything from 20-10m tunes almost flat. My sticks are screwed directly into the threaded mount, no extra hardwares, no adapters or springs. I can pretty easily tune my 10m stick down into 11m if I want. Interesting to see your tests and results. Keep on!

Interesting🤔!

My Nissan Rogue has a big sunroof and racks. I put the triple mag mount on the rear driver or passenger side and get a good match.

MAYBE TRY SOME FARADAY CLOTH UNDER THE MAG MOUNT

Hi Thanks for the info. Question- if you were not planning to drive with the magmount - wouldn't you be able to place the mount on the car hood. I assume this would allow it to be more resonant ?

I have ham sticks on roof of my Ford Expedition with a mag mount. And a roof rack and get perfect swr. And I have two sunroof’s. But what I also did was run a ground wire from the ground of the antenna along the coax and then bonded the other end of the wire to the car body. Swr problems solved.

The coil is lengthening the antenna, not just raising it. I experienced some issues when operating mobile with a mag mount and Hamsticks. Down to 20M, they worked pretty well, but on 40M, not so much. Going from a single magnet mount to a triple magnet mount helped, probably because of the additional capacitance to the car. I finally screw a tab into my car body and used copper braid to the antenna ground on the mag mount and that fixed the problem. Of course, at the time, I was just using an SWR meter, not an antenna analyzer, 40 years ago. Still your results are interesting.

Tracy do you run your coax around the car? My coax is long enough to go right around the car and back to the take off point. This gives a good ground coupling and my SWR is always at its best. The coax is best placed outside the line of the car slightly not under the body. try it if you haven't already.

That's no rhinoceros--it's a narwhal, LOL. Nice hamvestigation!

Wondering how it would work on the front hood? I have an outback and was thinking about the mag mount + ham stick for pota

try making sure the metal on the roof racks are grounded

Yeah, roof area matters. Another local ham to me tried to duplicate what I've done on my Honda Element with a trim-mag mount and some ham sticks (same as I use). On the roof of their pick-up truck, they couldn't get the ham sticks to get a good SWR... Vehicle roofs matter so much. Good info to know. 73!

Would be nice to know and I have seen a significant between a regular mag mount and a tri-mag mount, usually is there is a difference it gets higher the lower in frequency you go. Would have nice to see what clipping a few bundles of radials did to it. KF0LZX

Your biggest problem is the Comet mag mount, which I also own. The thick rubber pad on the bottom inhibits proper capacitive coupling. Try either removing the pad or use one of those three magnet mounts.

Before antenna analyzers, we commonly added a capacitor/inductance coil at the base of the antenna to get better matching.

Did adjusting the stinger change anything or make it worse? I found that hamsticks can be pretty finicky to make them resonant. 73 de K2CJB

Get a different mag mount with a 3/8-24 to directly mount your ham stick. I also drive a subaru outback and do not have any such problems when in the field. Also, get the adapter to run 2 of them as a horizontal dipole. I mount mine on 4 - 5 foot tv mast sections as a (hand) rotatable dipole. The 40 meter ones are too short to work well, less than 1/3 of full size. Yes, they do tune a bit differently that way. Counterpoise resonance issue. Oh, no. The roof rack dont matter. Put your mag mount in the center of the roof. Jerry wa2omu

I think that with the sunroof, you might be coupling to the edges of the sunroof itself and that it is acting like a slot antenna. Regarding the spring, is it acting like a spacer, changing the capacitance coupling, or is it acting like an inductor? It might be interesting to stick some thin plastic between the coils of the spring to see what changes. Who knows? You might even be able to bring the antenna to resonance with this makeshift "variable" inductor! 😂Love to see a follow-up video. All the Best! 73 DE W8LV BILL (W8LV/VE3 pre pandemic)

My mercedes is aluminum and mag mounts won't work, plus my roof is glass

In general HF mobile antennas require direct bonding to the body using a wire or strap. One sometimes can get enough capacitance by using a mag mount with three magnets or attaching a long wire strap to the base and taping the strap to the body. The Idea in to increase the surface area of capacitive contact between the antenna base and the body. Your observations have been known for decades. Direct bonding works better.

That spring will help the fiberglass live longer too because eventually all the hamsticks break in the fiberglass and become no good. Tuning is just a part of mobile installs. The ultimate antenna rule: What WORKS works.

coil or spring ??

Thanks!

Thanks!