In this case it's much more likely to be a mismatch causing a high
voltage arc.
Did something similar to my ATU last week drawing a 2 inch arc, no marks
on the switch however - it was a real ceramic switch not the Mickey
Mouse (sorry Mickey) types fitted to some amateur equipment.
Paul
In message <030801c0758e$5d146f40$6401a8c0@neptune>, Michael Tope
<W4EF@dellroy.com> writes
>
>I have an old Ten-Tec 4229 tuner that is on its second ceramic wafer switch
>(this is
>the switch used to change the L-network configuration from Hi-Z step down to
>Lo-
>Z
>step up). I destroyed the original switch using an SB-220 and a center-fed
>zepp
>that
>must have had a particulary high input impedance. The SB-220 suffered no
>damage,
>so it is my belief that the damage was caused by arcing of the switch contacts
>that
>resulted from the excessive RF voltage associated with the Hi-Z of the
>antenna.
>
>That is not to say that parasitics aren't in the realm of possibilities. Based
>upon my
>limited experience, I don't know enough about the impedance characteristics of
>HF tank components in the VHF range to really say with any certainty. What is
>clear
>to me, is that load mismatches (wrong antenna, improper tuning, etc) can
>generate
>RF voltages at the operating frequency which are well in excess of nominal
>operating
>levels. This seems to me to be a more likely explanation for switch failure.
>
>73 de Mike, W4EF..............
>
>----- Original Message -----
>From: "measures" <2@vc.net>
>To: <Wt8r@aol.com>; "Tom Rauch" <W8JI@contesting.com>; "AMPS"
><Amps@contesting.com>
>Sent: Monday, January 01, 2001 9:14 AM
>Subject: Re: [AMPS] Alpha
>
>
>>
>> >
>> >In a message dated 12/29/00 12:37:26 PM Eastern Standard Time,
>> >w8ji@contesting.com writes:
>> >
>> >> Hi Bob,
>> >>
>> >> > I don't intend to start a war, however based on my observations over
>> >> the
>> >> > last 2 decades (at least) in going to rallies (what Americans call
>> >> > hamfests) and my observations of some of the questions which crop up on
>> >> > the ham radio newsgroups the average ham is too lazy to do anything.
>> >>
>> >> I don't intend to start a fight, but from my viewpoint the average
>> >> ham is too quick to condemn everyone else.
>> >>
>> >> > Some of the comments which appear on Rich Measures web site about
>> >> > commercial equipment are well justified, rigs with so called fast
>> >> break
>> >in
>> >> > using standard power relays to switch linears, no soft start for power
>> >> > supplies, short circuiting HT lines as a safety measure, band switches
>> >> > that arc because there is inherent in the design of an amplifier a
>> >> cause
>> >> > for VHF parasitic.
>> >>
>> >> I hate to tell you this, but if you think a VHF parasitic can arc a
>> >> bandswitch you need a course in electronics 101.
>> >>
>> >> Perhaps you should look at the voltages and currents required to
>> >> do that, instead of being critical of other for not knowing what is
>> >> going on.
>> >>
>> >> Obviously you haven't researched the problem.
>> >>
>> >> 73, Tom W8JI
>> >> w8ji@contesting.com
>> >> ========================================================
>> >
>> >Tom,
>> >
>> >Since you are not the average ham, what, in your humble opinion, is the
>> >cause of bandswitch arcing ????????
>> >
>> >You seem to have eliminated all the things that DON'T cause arcs, what is
>> >the real cause?
>> >
>> ? according to Mr. Rauch, he has not completed Electronics 101.
>> >
>> cheers, Dave.
>>
>> - Rich..., 805.386.3734, www.vcnet.com/measures.
>> end
>>
>>
>> --
>> FAQ on WWW: http://www.contesting.com/FAQ/amps
>> Submissions: amps@contesting.com
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>> Problems: owner-amps@contesting.com
>>
>>
>
>
>
>--
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>
>
--
To try and not succeed is better than not to try at all (Anon)
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