----------
>Från: "sm5ki" <sm5ki@algonet.se>
>Till: "Terry Gaiser - W6RU" <w6ru@lightspeed.net> , Phil Clements
<philk5pc@tyler.net> , Amps@contesting.com
>Ämne: SV: [AMPS] Chokes
>Datum: mån 13 mar 2000 08.45
>
>Hej:
>
>Let us start a discussion on placing the plate choke instead at the antenna
> end of the pi/L filter to eventually get rid of these series resonance
>problems? It works fine according to what I have seen in, I believe, PAT
>HAWKERs RADIOCOMM column?
>
>Regarding the small plate choke in that HARRIS amp, is that not also the
>case in the ancient SB 220 as well? Are not the small plate choke and its
>red door knob decoupling condenser at the cold end, actually part of the
>ouput circuit on 80 meters? I guess RF current must pass through the choke -
>there is otherwise no reason to use the doorknob at the cold end instead of
>disc capacitors?
>
>Did we have the WARC bands in 1968-9 when the SB 220 came out? If not, then
>it was much easier to design a plate choke. But one has to be VERY careful
>to use an old amp like this on the new WARC bands. The plate choke may be
>very well series resonant and you get easily fire works.
>
>
>PAT HAWKERS monthly column has been collected in several books over the
>years. They contain a gold mine of many interesting ideas including amps.
>Pat collects ideas from other magazines as well he receives many very good
>and interesting ideas from other sources. The latest edition is avaible
>through the RSGB and I believe ARRL? Ask for TECHNICAL TOPICS.
>
>sooner................ de Hans SM5KI
>----------
>>Från: "Terry Gaiser - W6RU" <w6ru@lightspeed.net>
>>Till: "Phil Clements" <philk5pc@tyler.net>, <Amps@contesting.com>
>>Ämne: Re: [AMPS] Chokes
>>Datum: mån 13 mar 2000 00.22
>>
>
>>
>>I agree with Phil on this choke ... as he stated. It has worked very well
>>for me on a couple projects.
>>Terry W6RU
>>
>>----- Original Message -----
>>From: Phil Clements <philk5pc@tyler.net>
>>To: <W8JI@contesting.com>; <Amps@contesting.com>
>>Sent: Sunday, March 12, 2000 9:15 AM
>>Subject: Re: [AMPS] Chokes
>>
>>
>>>
>>> > Stray capacitance at the middle of the choke is the problem at the
>>> > first resonant frequency, so removing turns there and making an air
>>> > gap will shift the first series resonant frequency higher.
>>>
>>> The choke sold by RF Parts Co. and Ameritron has been a "God-send"
>>> to me in the last few amps I have built. I tried several other things
>>over
>>> the years; using two chokes and switching one in and out, (good, but
>>> expensive) mounting two chokes at right angles, (crispy-critter time)
>>> and using B&W 800's and 802's, even though the L was too low for
>>> adequate operation on 160 meters.
>>>
>>> Let's look at the RF parts/Ameritron choke. It is around 210 uh on a
>>> 1" x 5 1/2" ceramic form. The windings are split into three sections;
>>> 5/8" 7/8" and 1 1/2". The distance between windings is 5/8" and
>>> 1 1/4." The 1 1/4" gap in the winding is in the center of the form.
>>> The first resonance is marked on each choke, which is parked
>>> between 11.7 and 12 mhz.
>>>
>>> I think the reason that the "gapped choke" described in the ARRL
>>> handbook does not change much from a standard winding is that
>>> the gaps were too close to their adjacent windingsto make much
>>> difference, as Rich has pointed out and I have confirmed by building
>>> one. I saw no advantage to the ARRL choke at all.
>>>
>>> Here are some proven facts about the RF Parts/Ameritron choke.
>>> 1. It works in a wider variety of layouts than other chokes.
>>> 2. It works from 160-10 meters and runs cold on all bands @ 4 KW.
>>>
>>> The argument can now start on the hows and whys, but I use this
>>> choke exclusively now on all my projects. It saves a lot of time,
>>> money, and chassis space. It does the job on 9 ham bands and
>>> runs cold while doing it. Just what I needed!
>>>
>>> (((73)))
>>> Phil, K5PC
>>>
>>>
>>>
>>>
>>>
>>> --
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>>>
>>>
>>
>>
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>>
>>
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