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"wacky"? SWR readings on tuning antennae.. Help??

Dec 2nd 2018, 18:36

KM6SQB

Joined: May 4th 2018, 11:28
Total Topics: 0
Total Posts: 0
Hi All, just got general license few months ago, and antennae tuning has me going in circles.

Brierfly, have Yaesu 450 D and purchased 2- 20 meter hamsticks PLUS dipole assembly from MFJ. Tuned both sticks separately to about 1.2, when attached both to dipole mount, the SWR reading went up and resonant frequency decreased! SWR readings are different when comparing readings from 6 ft RG8X coax connected to ant analyzer, to reading with the 50 ft run from antennae to actual radio, Funny thing too, if I leave out the whip on one hamstick, and insert whip in other(depth in fiberglass base about 1.5 inches), SWR reads about 6 @ 13.7 Mhz, and SOMETIMES the int tuner can tune in the 20 meter band(lowest point, of course).When I insert whip further into the fiberglass base, SWR jumps to 7 around 14.7 Mhz, just moving whip a few mm)!! I cannot fathom what is going on. Tried isolator/ 1:1 balun, and results no better. Any wisdom from your greater wisdom/knowledge than me in this situation would be much obliged!!!

Sometimes wondering about getting mobile mag mount, obtaining as big a metal cookie sheet as possible(using as ground/radial??? and seeing how that goes. Saw Youtube video on a ham who did this, but he also put out 4 radials from the mount base, but don't know how he calculated the radial length.

thanks in advance!!
Harry KM6 SQB
Dec 3rd 2018, 14:01

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Have you tried tuning up the dipole using two hamsticks as a dipole, adjusting both whips so that they are equal?

When you tune a hamstick as a vertical the ground or counterpoise affects tuning.

Zak W1VT
ARRL Senior Lab Engineer
Dec 3rd 2018, 19:55

WA0CBW

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I have found that if you are using a metal mast it needs to be insulated from the dipole mount. I have used a 3 foot piece of fiberglas or plastic pipe. Also make sure the whip isn't inserted so far it engages the top coil of the mast.
Bill

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