Richard Clark wrote:
If, by this description, you mean that there are four wires, two for
20M and 2 for 40M; then that is all good and well.

Yes, there are four wires. Ok. Now I understand, it is called a Fan
Dipole. Thanks.

Okay. I did afew simple tests this morning. With output power at the
lowest level (L - on IC-706, I guess this may output 5 W probably), I
measured the SWR at various points at 14 and 7 Mhz. For 7 Mhz, I had to
increase the power, as the SWR meter needle couldn't achieve full swing
when measuring FWD power. I used CW as input. The SWR seem to be around
1.25 to 1.5 for higher frequencies (for almost all of 14 mhz), but
touches very high values 4 and above on 7 Mhz. I used around 20W for 7
Mhz to achieve the needle full swing. By the time, I finished the 7 mhz
tests, the radio got heated up. I suspect, that there can be an open
circuit at the balun-antenna connection for 40m dipole wires(?). I am
not sure.. Anyway, I am going to rework the entire antenna installation
this weekend or next. Too bad, I cannot do it before. :-(

I take this whole issue of SWR mismatch as a blessing in disguise, as
it prompted me to read a lot on dipoles, transmision lines, baluns and
general antenna installation decisions.

73
Ramakrishnan, vu3rdd

On 24 May 2005 21:47:45 -0700, "
wrote:

For 7 Mhz, I had to
increase the power, as the SWR meter needle couldn't achieve full swing
when measuring FWD power. I used CW as input. The SWR seem to be around
1.25 to 1.5 for higher frequencies (for almost all of 14 mhz), but
touches very high values 4 and above on 7 Mhz. I used around 20W for 7
Mhz to achieve the needle full swing.

Hi Ramakrishnan,

Sounds like 40M needs work. The SWR values for 20M were spot on.
Well, when you get to it this weekend, you should be aware that for a
fan dipole, you should adjust the lower frequency band first. This is
because its tune will cast an effect into the higher frequency dipole
(because of near proximity - otherwise known as coupling and their
harmonic relationship). Undoubtedly this tuning of 40M is going to
upset what appears to be a well tuned 20M dipole. Such is life.

Likewise, tuning the 20M side will cast an effect into the lower
frequency dipole, but to a lesser degree. Several back-and-forths and
the job should be done.

Again, the lesson of flexibility and anticipating these ups and downs
can reduce the pain of repetition.

By keeping the two dipoles' ends further separated, you can reduce
this coupling. However, I am sure this is dictated by the anchor
points that support your antennas. You can allow the 20M to droop
further away from the higher span of the 40M to accomplish this -
several feet is a useful guide suggested here, although others might
suggest less.

By the time, I finished the 7 mhz
tests, the radio got heated up. I suspect, that there can be an open
circuit at the balun-antenna connection for 40m dipole wires(?).

No, this "heating up" was a product of what I described earlier. If
your balun-antenna connection works so well for 20M, it isn't going to
limp along for 40M. A 1:1 W2DU style BalUn is very robust over the
majority of HF, and certainly for these bands.

73's
Richard Clark, KB7QHC