G5RV & 40 meters

[KC0ZXZ]

I have a MFJ-1778 (G5RV) and I can't get it to tune on 40 meters? The peak of the antenna is about 25-27ft and the ends are about 12ft. I'm using a MFJ-941D tuner into a Icom 735. Any ideas of things I could try? Thanks for any and all help!

Mick-KC0ZXZ

[AG3Y]

You need to supply us with more information. Where do you see the best match, at the high or low end of the band? What kind of match do you get on all the other frequencies you try?

Will the tuner match other antennas on 40 , and just not this one?

MFJ has had a record of poor quality control. Is this tuner new, or picked up at a hamfest or off of EBay ? If you are not afraid of voiding a warranty, I would suggest opening the tuner up and seeing if there are any poorly or unsoldered connections to the components. Stranger things have been known to happen with MFJ products!

Good luck, and be sure to give us a few more facts.

73, Jim

[WB7DMX]

get out your OHM meter and measure to connector from the center pin to the outside shield, it should be open, no measureable resistance at all, if you do measure anything you may need to find out where its shorted at.

[AG3Y]

DMX is referring to the Antenna, of course !

[KC0ZXZ]

AG3Y
I can get 1.2 or better on the other bands. I never got below 2.7 on 40? I usually try to tune around 7.200. I have tried a Hy-Gain AV-18VS vertical also. It would not tune either, but it don't have any ground radials right now? If I install some radials do you think it would help?

Thank You!
Mick - KC0ZXZ

[AG3Y]

Certainly installing radials under a vertical is going to help, even in those installations that say "no ground radials necessary" . One of the prime indications of a vertical that is not working efficiently is that the SWR reading will be possibly a bit high, but relatively flat over a wide frequency range. For instance, a 75 meter vertical that also covers the 80 meter ( lower half ) portion of the band with a relatively flat SWR curve is probably losing half or more of the energy in the lossy ground surrounding the antenna!

Please let us know what kind of readings you are getting on each band without the tuner being in the line. And check out the tuner's "innards" too! You need to know if the problem is due to the tuner, or your antennas, or a combination of both!

73, Jim

[K3STX]

Make sure you are putting at least 10 watts into the tuner, they don't work well at very low power. You should be able to get a match easily. Is the SWR on the G5RV with NO TUNER below 3:1, it should be. Maybe the G5RV is not right.

People love to malign tuners, but there's not much in there that can go wrong. It usally either WORKS or it DOESN'T, not much in between.

Can you get a match on 30 meters? That should be the hardest band to get a match, if you get a match on 30 but not 40 something is wrong.



paul