On 9/5/2011 6:47 PM, Owen Duffy wrote:
Jeff wrote in
:

What bugs me is that the diodes are blowing up despite this rather low
resistance to ground. Either hams are finding some rather high power
ESD sources with which to blow up their analyzers, or some other
failure mechanism is involved.

But the reality is that people do damage these things... and so the
method you suggested earlier is not likely to be sufficient to protect
them.

I am careful to avoid connecting an instrument of this type to an
antenna system unless I have drained any static charge first, and avoid
other transmitters on air nearby.

I think you are correct. I do think that more care needs to be taken
with these devices than with a lot of other electronic items Hams use.
I liken them to RF attenuator blocks. You see a lot of them in company
repair shops, because people are often trying to put too much power
through them.

After getting the new replacement analyzer, and using the dummy load,
and I do the static drain too, plus I keep it away from other people,
it's lasted FB.

- 73 de Mike N3LI -

On Mon, 05 Sep 2011 19:46:16 -0400, Mike Coslo wrote:

I liken them to RF attenuator blocks. ... people are often trying to put too much power
through them.

This leaves me wondering about intentions:

"Must - get - more - power - out - of this attenuator!"

73's
Richard Clark, KB7QHC

Mike Coslo wrote in news:j43n06$ds52$1
@tr22n12.aset.psu.edu:

;... plus I keep it away from other people,
it's lasted FB.

That is probably key, don't trust other people... and be pretty wary of
one's self!

It is interesting you mention the Other Persons thing... I am in the
process of drafting a web article commenting on the advice that is so
common these days on online fora, "can you borrow an analyser?..."

This is almost always offered to some newbie who is having trouble
"tuning up his antenna".

Most don't understand complex numbers, impedance, transmission lines,
etc etc and someone tells them get an analyser and tune for resonance. I
can only guess that the advisers are equally lacking in knowledge and
experience, but I will concede that the analyser dumbed down to a VSWR
meter with self contained RF source than can be tuned outside band
limits, can be a pretty handy thing.

But despite the fact that adjusting many, if not most antennas for
minimum VSWR is the sensible objective, the resonance brigade chimes in
with make X zero looking into some arbitrary length of feed line, a
condition which isn't always associated with minimum VSWR and may
actually not be achievable. Some newbies have clipped their mobile whip
away to make that discovery, but perhaps without understanding that it
was a likely outcome from that strategy.

So Mike, it is likely that someone borowing an analyser to fix a problem
wont obtain real benefit, but may damage it in the process.

Owen

On 9/6/2011 12:58 AM, Owen Duffy wrote:

That is probably key, don't trust other people... and be pretty wary of
one's self!

It is interesting you mention the Other Persons thing... I am in the
process of drafting a web article commenting on the advice that is so
common these days on online fora, "can you borrow an analyser?..."

It is a good lesson, (be wary) and I think that MFJ makes another
"analyzer", the 207, which will suit the average user just fine, as long
as they are not needing V/UHF. It's cheap, simple, small, and I used one
before I got into HF mobile. It doesn't show anything but SWR. Given
that that is what most people are interested in, it suits well.

Then after a bit of reading, and talking they might start to look for
the interesting details, and the instruments to measure those details.

- 73 de Mike N3LI -

Mike Coslo wrote in :


Then after a bit of reading, and talking they might start to look for
the interesting details, and the instruments to measure those details.

Absolutely, if acquiring an MFJ259B or the like is a stimulus to learn more
of impedance, transmission lines and antennas, that is great.

Owen