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>Message-ID: <3311A1FC.62FC@stc.net>
To: <amps@contesting.com>
>Date: Mon, 24 Feb 1997 14:13:16 +0000
>From: Ron Hooper <ab4ru@stc.net>
>Reply-To: AB4RU@stc.net
>Organization: Is there life after Contesting?
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>To: IT9GSF - Fabio <fgrisafi@mbox.vol.it>
>CC: amps@contesting.com
>Subject: Re: [AMPS] QBL 5-3500 by Philips
>References: <3.0.32.19970224032851.00693ec0@mbox.vol.it>
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>
>IT9GSF - Fabio wrote:
>>
>> Hello !
>> I'm interested in finding infos about the QBL 5-3500 by Philips.
>> Is it possible to find it in the market ? It's an external anode
>> tube capable of 3000 W plate dissipation used in the past in FM
>> and band I TV transmitters.
>> Is there any design for using it on HF ?
>>
>> It is a tetrode.....and needs 800 V for the VG2...how to obtain
>> this voltage directly from the anode ? With a resistor ?
>>
>> 73
>>
>> 73 de IT9GSF !
>>
>> Fabio Grisafi
>> via Ferrari Orsi 85
>> 90123 PALERMO - ITALY
>>
>> "One of the Lampedusa Island Marconi Contest Club Gang".
>> -- FAQ on WWW: http://www.contesting.com/ampfaq.html Submissions:
>> amps@contesting.com Administrative requests:
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>
>I dont know that one but can tell you on the supply voltage for the
>grid, it needs to be regulated in order to maintain a linear
>amplification. Using a plate voltage dropping resister and 800v's of
>regulators will do the job but be prepared for a lot of heat from the
>resistor. One advantage from this design is that if you loose plate
>voltage it automatically drops off the grid volage and protects the tube
>from damage. If you build a seperate supply for the grid make sure this
>feature is built in with an interlock to make sure the plate voltage is
>applied before drive. With a loose of plate voltage the grid will look
>like a plate anode and take all the current when the drive is applied. I
>can guarantee instant tube failure under that condition. The Phillips
>company's home office is in the Netherlands, I would check to see if
>they have a home page. One of my guest operators works for the same
>company here in the states. If you cant get the address I will enlist
>his help.
>Ron W4WA
>
>
>
>
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