Hi again all,

the dipole was suspensed on a pole and the MFJ-269 was connected to it,
no body effects here. After adjusting frequency then I move away from
the setup.

I do understand that 65 + j16 is not really a bad match, if I did add a
capacitive reactance, then would I have to place two caps, each of
equal value in series with coax?

If I wanted to do a shunt capacitor, would I find the admittance of the
above and then determine a shunt from the resulting reactance?

de KJ4UO

The Autec Analyser is a better instrument than the MFJ for
suspended-in-mid-air measurements. It is much smaller and is lighter
in weight and has a smaller capacitance.

The Autec case has a self-capacitance of the order of 3 pF
corresponding to a reactance of 1768 ohms at 30 MHz which can be
ignored when measuring 50 ohms with zero lead length.

The Autec's highest frequency is 35 MHz.

The MFJ's highest frequency is at VHF. With a self-capacitance of 7
pF at VHF substantial errors can occur.

To estimate capacitance, the DC capacitance of a sphere is -

pF = 55.55 * Diameter in metres.
----
Reg.

Hi again all,

the dipole was suspensed on a pole and the MFJ-269 was connected to it,
no body effects here. After adjusting frequency then I move away from
the setup.

I do understand that 65 + j16 is not really a bad match, if I did add a
capacitive reactance, then would I have to place two caps, each of
equal value in series with coax?

If I wanted to do a shunt capacitor, would I find the admittance of the
above and then determine a shunt from the resulting reactance?

de KJ4UO

Are these antennas all in parallel for have you posted the identical
request multiple times ?

wrote:
Hi again all,

the dipole was suspensed on a pole and the MFJ-269 was connected to it,
no body effects here. After adjusting frequency then I move away from
the setup.

I do understand that 65 + j16 is not really a bad match, if I did add a
capacitive reactance, then would I have to place two caps, each of
equal value in series with coax?

If I wanted to do a shunt capacitor, would I find the admittance of the
above and then determine a shunt from the resulting reactance?

de KJ4UO

To keep things balanced, it would be best to split the series
capacitance into two parts. They should be -j32 ohms each, as they are
effectively in series: 200pF (or 180 or 220) in each leg. It wouldn't
be the end of your world if you used a single 100pF cap, though.

Yes; convert to admittance and parallel a capacitive suseptance to
cancel the reactive part, about 11pF. Or as I suggested before, put
more capacitance in parallel with the feedpoint and add series
inductance: 38pF shunt and a pair of 47nH inductors, one in series
with each leg between the feedpoint and the feedline, will get you very
close to 50 ohms resistive from the stated 65+j16 at 50-54MHz. (I
assume the antenna doesn't stay at that impedance over the whole band,
though.)

Cheers,
Tom