[TowerTalk] Traps and Losses

Guy Olinger, K2AV k2av@contesting.com
Tue, 18 Jul 2000 10:28:38 -0400


You remember which trap it was?

- - . . .   . . . - -     .   . . .     - - .   . - . .

73, Guy
k2av@contesting.com
Apex, NC, USA

----- Original Message -----
From: Bill Gode <wiley@interaccess.com>
To: Guy Olinger, K2AV <k2av@contesting.com>
Sent: Tuesday, July 18, 2000 8:03 AM
Subject: Re: [TowerTalk] Traps and Losses


> Hi Guy,
>
> Back in 1966, I replaced my 2el Quad with a Mosley MP-33 (TA-33 driven
> element with TA-33-JR reflector and director).  It's still listed on
the
> Mosley site!
> When I had my MP-33, Mosley didn't specify a reduced power rating of
250
> watts on RTTY.  I homebrewed a pair of 3-500Zs and ran one KW input on
RTTY
> (no wattmeter back then). After a short time on 20M RTTY, the antenna
quit
> working.  When I took it down, I saw that one of the reflector trap
coils
> had melted!  I quickly learned about heating of parasitic elements in
a trap
> antenna. Being in high school at the time, I remember being amazed
that the
> trap melted in an element that wasn't even connected to the
transmitter!
>
> I replaced the tribander with a HyGain 203BA...and promptly melted the
BN-86
> balun!  I replaced the BN-86 with a homemade choke balun and all was
well -
> until the next antenna project came along...
>
> 73,
>
> Bill, W9NHQ
>
> > Why? The answer is in the RTTY (read
> >keydown, constant, no breaks for cooling off) rating of 600 watts.
> >That's 9 dB less than the maximum peak power. It can't possibly be
> >related to arcing as some have surmised. It will not be related to
> >pattern degradation, that's just power radiated in less useful
> >directions. Radiated power doesn't destroy antennas.  All that's left
is
> >heat. The implication is that 1.5 kW is beyond the manufacturer's
rated
> >tolerance for HEAT.
> >
>
>


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