In Case of Trouble Matching
DEFINITION OF "TROUBLE MATCHING"
The obvious situation is when you are unable to find a decent match on one or more bands.
You don't have to have 1.0:1 but normally you should be able to match all bands to within 2:1 or better. If not, you may have trouble with your transceiver folding back power. Read on below...
The not so obvious, especially if you follow good operating procedures and alway tune your matchbox with low power (10 to 20 watts), you may find a good match on all bands (i.e. good SWR on all bands) but find when you increase the power level on one or more bands, you hear arcing inside of the matchbox. I have often experienced that I could only run 70 or 80 watts on 40m before arcing occurred. To cure this problem, read on below...
ADJUSTING FEEDLINE LENGTH
As stated under "Matching Solutions", it is very important that you use the right kind of antenna matchbox for matching openwire fed antennas.
On my web page showing "Charts of Lengths", you see that for each different length of antenna, there are several lengths of feedline that will work and several lengths that will not work. Obviously we should choose a length that will work.
Sometimes we have difficulty matching one or two bands, even though we think we have chosen a good feeline length.
The solution is simple, add more feedline.
The Rule of Thumb is 1/8 wavelength, but in practice, often just 1/16 wavelength is long enough to move the impedance far enough to obtain a match. You will just have to try it. Calculate roughly 1/16 wl and start there.
BEFORE YOU GO TO THE FIELD . . .
You may wish to prepare yourself 4 lengths of feedline as pictured above.
Use your 4 lengths to try different extension lengths.
The chart above shows (in feet) how to use just 4 pieces of coax to enable creation of 14 different feedline extensions. Simply solder 2 female banana jacks to one end of each segment and 2 male banana jacks to the otheer end. Instead of banana, you might use Anderson Power Poles.
I have often experienced the need to add more feedline, especially on 40m, but I have never had to add more than 13 or 14 ft. to enable my matchbox to find a match on all bands.
If you have difficulties on 80m, this may not be enough. In that case, cut one more piece of feedline 15' long. This will enable you to create feedlines up to 29 ft. long in 1 ft. increments.
Note: the broader the matching range of your antenna matchbox,
the less often you will find yourself adding feedline in the field.
ME and MURPHY
Sometimes I think Murphy is my best buddy.
Seems he's always there when I don't need him.
My favorite band is 40m. For some reason, that seems to be the band I always have trouble with, even though I am often starting with a brand new 100 ft. piece of openwire and cutting to length required at the destination.
Since 13 ft. seemed to always work for me, I just started carrying a 13 ft. piece openwire with me every time I went to Field Day.