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MFJ-949E Tuner with Comet SBB-5

Nov 6th 2014, 17:29

AF9U

Joined: Nov 5th 2014, 18:48
Total Topics: 0
Total Posts: 0
Hello,

I'm brand new to antenna tuners. But I'd like to test this new tuner against a somewhat known result. Right now when I key up on a quiet 2 meter frequency I getting a really high SWR, much higher than I would expect. So I think I have something set wrong and I'm hoping for some help doing this for the first time.

So here is what I have:

Radio - Yaesu 857-D, I have RF power dialed down to 5 watts for now so I don't blow anything up.

Antenna - Comet SBB-5 (mag mount) - antenna is stuck to a metal pan so that it works (it works great when connected directly to the radio)

Tuner - MFJ-949E

Here is how I have everything connected:

Antenna is plugged into Coax 1 on back of antenna tuner.
Tuner "transmitter" port is connected to my 2 meter antenna connection on the radio with a short coax antenna tuner cable.

On the Antenna Tuner I have:
Antenna Selector set to TUNED - COAX 1


Transmitter - variable (I have been try to adjust these to a low SWR)
Inductor - Set to I
Antenna - variable

Meter is set to the 300W setting (button pushed in)
And Peak/AVG is set to Peak (button pushed in)


Given all that, shouldn't I expect my forward needle to be somewhere close to 5 and my reflected needle to be somewhere between 1 and 1.1?

What I am seeing is my power (when Inductor is set to I) is about 5, but my reflected is like 1.4 or 1.5.

If I set my meter to 30W my reflected needle is up by infinity.

Thoughts?

I appreciate any help I can get.

73,
Drennen
AF9U




Nov 7th 2014, 13:44

WB1GCM

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

Check the specification of the MFJ-949E. You will see the tuner is designed to operate between 1.8 and 30 MHz. It will not work on 2 meters.

A good rule of thumb is to use a resonant antenna, when possible, so no antenna tuner is needed. There is no need to add a tuner if your mag mount antenna works well without one.

I used to use the same type of antenna when I lived in an apartment back in the 80's. I had a Larsen mag mount on top of a well seasoned baking pan. The outfit was placed on a flat roof, about 10 feet away from my shack window. It worked great.

Have fun,

73,

Bob Allison
WB1GCM
ARRL Senior Test Engineer
Nov 11th 2014, 15:43

AF9U

Joined: Nov 5th 2014, 18:48
Total Topics: 0
Total Posts: 0
Thank you Bob, I appreciate the information. I thought I had read it would tune almost any antenna, but I obviously misunderstood.

Thank you for clearing this up for me.

Take care,

73,
Drennen

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