[Collins] RF Choke ID

[Phil M.]

Aha....according to my KWS-1 manual, L403, the plate
choke for the 4X250B's is listed as Collins part no.
540 7979 00

73, Phil
W5BVB


----- Original Message ----- 
From: "Phil M." <pmills7 at comcast.net>
To: <collins at mailman.qth.net>
Sent: Monday, April 28, 2008 4:57 PM
Subject: Re: [Collins] RF Choke ID


> Any chance this is the choke used in the KWS-1 or
> possibly the ART-13?
>
> 73, Phil
> W5BVB
>
>
> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
> To: <collins at mailman.qth.net>
> Sent: Monday, April 28, 2008 4:34 PM
> Subject: Re: [Collins] RF Choke ID
>
>
>> On Mon, 2008-04-28 at 12:54 -0400, bill riches wrote:
>>> I found a NOS Collins  Ceramic Plate RF choke that I am trying to 
>>> identify:
>>>
>>> Total Height 5 9/16
>>>
>>> ¾ diameter
>>>
>>> 1 7/16 x ½ mounting flange with 2  6-32 mounting holes drilled from the
>>> bottom of the flange.
>>>
>>> Coil wire has green insulation and measures 37.5 uH. The number 540-7979 
>>> was
>>> written in pencil on the bottom.
>>>
>> That would be a Collins fab part number. Google turned up a reference to
>> a federal stock number 5950-00-772-8399 but the only hit for either
>> http://www.tpub.com/content/logistics/59/50/282/00-772-8399.htm didn't
>> really describe the part or show usage. Its too tall for a 32S or KWM-2.
>> Maybe it would fit a 30S-1, though my schematic doesn't show the
>> inductance of its plate feed choke and my 30L-1 schematic shows its was
>> 44 uh.
>>
>> Its ID is complicated by the fact that every PA needs one. Its reactance
>> is about 400 ohms at 1.8 MHz which looks low for 160 meters. Or a PA
>> that goes down to 2 MHz. 850 ohms at 3.5 MHz might work in a PA with a
>> low plate load Z. But the RF choke will run hot.
>>
>> The apparent inductance will be affected by the frequency of measurement
>> because of the distributed capacitance of the winding. Without an RX
>> meter to measure its parallel properties, it can be checked with a grid
>> dip meter. Resonances found with the terminals open are high impedance,
>> good frequencies for use. Resonances found with the terminals shorted
>> are series resonances and frequencies where it should not be used.
>>
>> It sounds as if it has considerable insulation between the mounting
>> flange and the lower terminal so can operate at a few KV plate voltage.
>> You can check the wire size and probably figure at least 500 circular
>> mils per amp of plate current (high current density for a multilayer
>> winding, dependent on cooling of a single layer winding).
>>>
>>> Any info on this choke would be appreciated.
>>
>> If there are no series resonances between 3 and 30 MHz, I'd guess its
>> for a Collins 1 or 2 KW linear covering that range, else if there series
>> resonances outside ham bands (excluding WARC bands), I'd guess 30S-1.
>> There is some chance it was used in several power amplifiers, maybe even
>> for a grid choke in a higher power PA.
>>>
>> I don't know of Collins supplying plate RF chokes as a commodity item
>> though they did that for toroids.
>>>
>>> 73,
>>>
>>> Bill Riches, WA2DVU
>>>
>>> Cape May, NJ
>>>
>>
>> -- 
>> 73, Jerry, K0CQ, Technical Advisor to the CRA
>> All content copyright Dr. Gerald N. Johnson, electrical engineer
>>
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>