For all that are interested, see: http://user.super.net.uk/~equinox/8877.html
In this article, it tells how to build the SHORTED stub to preclude the need
for a safety RF choke on the output.
(((73)))
Phil, K5PC
>
>This is an excellent idea, but is incomplete in engineering detail.
>
>The "trap" must be tuned to the harmonic. Reactance is generated at the
>fundamental frequency, which must be compensated for using an open
>circuit stub (a piece of coax which is simply clipped off until the SWR
>is as low as possible).
>So a four-way coax split is required.
>
>The trap is tuned at low power by shorting the outer and inner with a
>pin, while watching the attenuation of the harmonic an a receiver. Then
>solder permanently. The stub is then tuned for best SWR and left open.
>Unfortunately there is interaction, so the GDO will not tell the truth;
>tuning is still necessary.
>73,
>Ian ZS6BTE
>
>Phil Clements wrote:
>>
>> If you really want to get fancy, cut a piece of RG-8 coax a bit over 40
>> inches
>> long; grid dip it and prune it to 50.100 mhz. put a suitable coax fitting on
>> one end of the stub, and short the braid to the center conductor on the
>> other. Install the stub with a coax "T" connector at the antenna jack of the
>> amp. This gives you a "big time" connection to DC ground, and puts your
>> second harmonic down about 30 db. You can do the same thing on the
>> inside of the amp if you wish; just use small teflon coax for the stub,
>> solder
>> it in, and coil it up.
>>
>
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>
>
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