[Johnson] 250-37 directional coupler
James M. Walker
chejmw at acsu.buffalo.edu
Tue Jun 13 09:25:10 EDT 2006
Some of the meters used were, 0-250uA and 0-1 Ma.
For better sensitivity at low power, a 0 - 100uA meter is
recommended. The directional coupler samples the RF
flowing to and from the antenna circuit, IE into the MB
and reflected back to the transmitter.
There is a dropping resistor in the sample circuit on both
sides, to limit the current to the meter. It uses a matched
pair of rf diodes to rectify the sampled RF.
ARRL handbooks from the middle 1950s to middle
1960s had similar circuits in them.
Do you have the manual pages for the Matchbox, or
would you like them?
Jim
WB2FCN
http://eshop1.chem.buffalo.edu
----- Original Message -----
From: "C E" <catman351 at yahoo.com>
To: "Steve" <steveac at charter.net>; <johnson at mailman.qth.net>
Sent: Tuesday, June 13, 2006 9:10 AM
Subject: Re: [Johnson] 250-37 directional coupler
> Hi Steve:
> I think you can go to the ARRL handbook and find a
> directional coupler that will take the place of the
> '37. The coupler (if what I think is right) rectifies
> and turns the sampled rf into a DC level and sends it
> out to the meter for your SWR or relative power meter
> reading. Cal. N6KYR/8
>
> --- Steve <steveac at charter.net> wrote:
>
>> What is the output of the 250-37 directional
>> coupler?
>>
>> Is it a sample of the RF signal?
>>
>> If so, what is the level of the sample as compared
>> to the main signal?
>>
>> Thanks.
>>
>> Steve K8JQ
>> Johnson mailing list
>> Home:
>> http://mailman.qth.net/mailman/listinfo/johnson
>> Help: http://mailman.qth.net/mmfaq.html
>> Post: mailto:Johnson at mailman.qth.net
>>
>
>
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