SWR? My daughter helps me tune my MFJ Ham Stick
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- čas přidán 4. 03. 2022
- Adjusting the stinger on my 40 meter MFJ Hamstick. Can we get a good SWR?
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Here's a bit of a secret.. as soon as you start pushing that rod down inside the coiled fiberglass, it changes the reactants of the antenna and creates an inductive reactants load rather than an inductive load. When you want to shorten your antenna you would be much better off to actually cut the pieces off and avoid allowing it to slide down inside the fiberglass. The whole idea of the whip sliding down inside the fiberglass is actually for storage purposes not for tuning purposes except for fine-tuning where you only allow up to 2 in to fall down inside the fiberglass tube. Source; I am an RF engineer.
You're right! I gave away a 40 meter ham stick, because I could not tune it, and had nothing to cut that stainless steel whip.
As long as the stinger inside the lower half of a Hamstick type antenna is above the upper end of the loading coil windings you should not need to anything off the bottom of the stinger. Cutting length off the stinger may result in it being too short for operation at lower part of a band especially on 75 and 40
meters. I have never had to trim a Hamstick stinger shorter to get the antenna to tune at the high end of the band to prevent the bottom of the stinger from getting to close to the coil.
On the other hand, many brands of Hamsticks have stingers that are too short to permit proper tuning at the low end of the 80’meter band. Extended length stingers can be fabricated from stainless steel rod stock of appropriate diameter. You may be able to find long stainless steel CB whips of the right diameter at truck stops that can be cut to your desired length. Use them extended length stingers only when operating at the low end of a band, the added length will
likely get you in trouble with proximity to the loading coil in the bottom half of the antenna if you try to use it at the top of the band.
73 de Chris AJ1G
Stonington CT
Yes your daughter should get a Ham license
You really don’t need an antenna analyzer to to tune a Hamstick of your transceiver has a built in SWR measurement capability. For
40 meters start out at the high end of the band with the antenna stinger at its longest position in the collet at the top of the lower section. Incrementally shorten the stinger in half inch increments while putting RF into the antenna and monitoring the SWR. If you have a radio that does a frequency sweep SWR plot routine like current Icoms like the 7300 and 7100 , so much the better, use a 10 kHz step for all HF bands. When you are getting close to resonance you will start to see the SWR reading drop. Continue adjusting the antenna until the SWR starts going up, then return to the position that results in the lowest SWR. Measure and record the stinger length in inches from the tip to the top of the collet on the lower part of the stick. If you have properly located and installed and properly
grounded the antenna you should have no problem attaining an SWR minimum of at least 1.5:1. See the details below on how to best locate and install the antenna.
Once you have found the SWR minimum point at the top a a band, shift the transmit frequency down in nominal 10 or 20 kHz increments and incrementally adjust the stinger longer as necessary to hit minimum SWR at each increment, and record the stinger length for each frequency increment. Keep the table for future reference to set up the antenna properly for whatever frequency you wish to operate on. On my 40meter stick minimum SWR at 7140 kHz requires about 2 1/2 inches more stinger length compared to minimum SWR at 7290 kHz. About 3 more inches relative to the stinger length at 7140 kHz is needed at 7030 kHz for CW band operation.
Locate the antenna feedpoint as high as possible on the vehicle body so that no portion of the antenna above the feedpoint is anywhere near parallel vehicle structure such as an SUV lift gate or a truck fender/tailgate - bumper mounting should be avoided at all costs, also avoid mounting the base of an antenna right behind the cab of a truck at the fender line. Always try for a roof mount at the left rear corner of an SUV or station wagon or at the left rear corner of a pickup truck with the antenna base at the top of the fender/tailgate line.
Ensure that the shield side of the feed line is securely bonded to directly to the vehicle body not more than a few inches away from the bottom of the antenna. DO NOT use a mag mount base without providing a bonding jumper to the vehicle structure to the shield side of the feed point at HF. There is insufficient capacity coupling between the mag mount discs and the vehicle at HF, antenna will be very inefficient.
My favorite way to put a Hamstick on a station wagon or SUV is to mount the antenna base either on left rear of a roof rack rail, and run the feedline up along the weatherstripping on the left side of the lift gate frame so it’s hidden with the lift gate shut. Break out the center conductor from the feed line and run it up to the bottom
of the antenna over the weather stripping, add a layer or two of electrical tape over the existing
center conductor insulation to prevent chafing against the lift gate when it is closed. Try to keep the length of the center conductor from the breakout with the shield to the antenna at no more than 6 inches if possible. If it is any longer you may have trouble resonating a stick on higher frequencies such as at 10 and 6 meters. On lower bands a few more inches isn’t significant. At the breakout point of the shield and center conductor at the lift gate opening upper left, bond the shield to the body structure with a ring terminal and starwasher and a stainless steel sheet metal screw into a hole drilled into the lift gate opening structure. Be sure to use a Dremel tool abrasive wheel or equivalent to get down to bare metal around the hole for the width of the ring terminal and washer. The grounding point and feed line will be out of sight with the lift gate shut.
On every Hamstick or for that matter any other short mobile antenna I have used for over 20
years on 40 meters and lower frequencies , shunt reactance must be applied across the feed point to get the SWR minimum below 1.5/1. 500 pf on 40, 500
or 1000 pf on 80, 1500 pf on 160. Many but not all Hamstick type antennas note this in their installation instructions. Don’t neglect this. A shunt inductor may be used instead of a shunt cap, I’m currently using six close spaced turns of No. 16 insulated stranded wound on a prescription pill bottle for matching my 40 meter Hamstick on the roof of our 2017 Volvo XC60, gives a slightly better match than the 500’pf shunt cap. The shunt coil has the added advantage of providing a static drain path to ground for the antenna.
Good luck! And 73 de Chris AJ1G Stonington CT
Yap she very patient and doing great.
I had to run a ground wire from the mount to a place on the chassis to broaden the bandwidth.
Thank you, That's something to look in to. The 20 meter hamstick works great on the same mount and covers the entire general portion at 1.6:1 or less but the lowest part of the dip on 40 meters is about 2.6:1
thanks for watching
73 Wes
I just installed a Diamond 40 meter hamstick on my truck. Finally got it to the point where my FTDX-10 can tune it. Got some POTA contacts today. I hear grounding is important so I will attach a ground strap to the frame.
Sounds great and I'm glad it's working for you. I hope to catch you on the air.
73 Wes AE0OC
Your antenna is closer to the metal vehicle body..
New subscriber here. I am using my nanoVNA tuning my 4 shark sticks. I am having trouble getting them in the SSB portion of any bands (10, 20, 40, 80). Do you use a wider scan than the band of interest? Oh yeah,I am using and tuning with the quick disconnect on the truck. NOTE: I have not bonded the metal of the truck together which may be part of my problem. Any advice for this noobie? All the best 73 de KI5HXM
Yes, I think she should get her ham license.
Break open, Modify - do anything - to to add a thick braid from the base to the closest ground on the truck. Then start over.
Tuning my MFJ 20m stick was not too bad. I got it to 1.18 to 1 with my RigExpert Stick Pro. My 40m stick was a little bit more tricky. The 10m & 17m were pretty easy to tune. I have never trimmed the stinger of the sticks yet. I just got a 12m, 10m & 6m Shark ham sticks and need to tune them. That might happen tomorrow depending on a few things. I could have picked up some Shark quick disconnects while at HRO today. I guess I'd have to retune my sticks if I do.
Awesome work, Wes! 73! Jeff
Thank you Jeff, my 20 meter Ham Stick (generic brand from a hamfest) tuned really easily and even with the shark adaptor it didn't need to be trimmed. One of the guys on the POTA FB page let me know that he is using an MFJ 909 variable capacitor, on 40 & 80 meter Ham Sticks, with really good results. I'm going to look for one at the next local hamfest in a few weeks. On a separate note I finally saved enough to buy a new HF rig for my house and my FT 450D will be my fulltime portable. I think I'm going to get a FTDX10.
73 Wes
@@59RadioUSA The FTDX10 is a great radio! I’m glad I bought that over the 991A. Better receiver (#3 on the market, beating out every Icom radio). 73! Jeff
Did you follow up with your idea about the 40 meter antenna? I have a 20 meter ham stick that I am unable to tune with an analyzer. Did you make a video so that some of us less knowledgeable ham can see how it worked?
Tommy, thank you for watching. I'm a new ham and learning as I go.
Unfortunately I have not revisited the 40 meter ham stick issue yet. I have a 20 meter ham stick that preforms very well on the same mount that I tried the 40 on. It is what I used in all my POTA videos.
Here's a couple of videos I found helpful.
czcams.com/video/3_Z7xEW_d7k/video.html
czcams.com/video/XAs3UTZ_iX4/video.html
73 Wes AE0OC
I’m in the process of trying to tune a 40 meter shark stick with very little luck. The best I have so far is 1.8 at 7.340, anything in the band is 2.0 and up but it’s 1.1 across the entire 10 meter band go figure. How has your effort been ?
I never got it working really good but it will tune with my auto tuner and make some contacts. The 20 M ham stick works great so I've mainly stuck with it.
were you testing your swr with the door open? that can have a big impact
I was and I suppose it could effect it but whatever I do will have to accommodate that because I will have it open when doing POTA activations with it.
Thank you for the advise
73 Wes
Dodge, grab life by the Horns 🤘💯🍻🙋♂
LOL That old Dodge is a little long in the tooth, 516,000 miles.
@@59RadioUSA Awsome 👏👏👏👍
Standing with back to the camera lol
thanks for watching 73 Wes AE0OC
Well it's been a year has your daughter gotten her ham license yet because inquiring-minds-want-to-know?
No she has no interest but my granddaughter (13) spent 2 weeks with me over the summer and studied for/passed her tech KF0NKV