[TowerTalk] Summary of Analyzers DE K0FF

[K0FF]

The new 269 allow setting any feedline impedance from 10-600. The next
nearest thing is the VA-1 Autek analyzer with 10 discreet steps, 25-450
Ohms.. Problem with the Autec is the digital display and slow refresh times.
Not what you want for making adjustments. OK for taking a measurement on
something, but the MFJ's analog meters allow smooth adjustments to be made,
while dips and peaks are easy to spot.

Either of these instruments also allow you to measure inductance and
capacitance at the operating frequency. I found this to be especially
important with toroid inductors. A reading taken with a bench instrument
that has only a 1 KHz or 100 kHz signal source will inaccurately read the
true inductance.

Both of these will read R and Z. Only the Autec VA1 will give you the sign
of X ( as far as I know).

The MFJ can also be used as a frequency counter, and is perfectly adequate
for a simple test bench, thereby saving a separate piece of gear. As well it
can be pressed into service as a signal generator, especially is used with
an external low power attenuator.

The MFJ's frequency coverage starts at 1.8 MHz but with my mod can go below
500 kHz in two more steps. Top end is 170 and the 269 adds the 415-470 range
as well, but discontinuous from 170-4115.

Autek's RF-1 has limited features and starts at  1.2 MHz (not modifiable) to
35.
The VA-1 has many more features but still only covers .5 - 32 MHz. One handy
mode will even tell you the offsetting capacitance  (or inductance) needed
to equalize the X factor.

On my own test bench I have not found a single instrument that will measure
everything I want to look at. Looking at an actual antenna is the least used
function here, rather I'm always testing a transformer, filter or other
device. Therefore I find the MFJ (mine is an older 259a model modified for
low freq) to be the most useful, backed up by the Autek RF-1, and finally
the HP 250A RX meter . These have supplanted the various resistive and
capacitive bridges we used 8ibn the past.
If starting from scratch now, it would be first the MFJ 269, then the Autek
VA-1.


Happy Building, Geo>KØFF
http://homepages.dstream.net/K0FF



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