Thank you. The coupler I have is too high frequency for my current
needs. I am interested in a 1 to 100 MHz bi-directional coupler. However
bi-directional couplers are much less common then uni-directional ones.
There appear to be uni-directional couplers in the HF and VHF range
available.
Are couplers 'reversible, that is can the output be applied to the
input? The purpose if this would be to make a bi-directional coupler
from 2 uni-directional couplers. Is this practical?
Thanks again - Dan
m.ford wrote:
>
> ----- Original Message ----- From: "Dan Sawyer" <dansawyer@earthlink.net>
> To: "amps" <amps@contesting.com>
> Sent: Friday, November 18, 2005 4:10 PM
> Subject: [Amps] bi-directional coupler question
>
>
>> All,
>>
>> This journey started several months ago with the purchase on an 8405a
>> to measure an antenna. One of the items listed at that time was a
>> bi-directional coupler. Finally I have found one and am beginning to
>> experiment. The first readings seem to show that the coupler may be
>> supplying readings that are out of phase? Direct input to the coupler
>> terminated in a 50 ohm dummy load produce readings that appear to be 90
>
>
> Hi Dan,
> A bi-directional coupler has a mainline input and mainline output. The
> other two ports are the coupled ports. One is zero degrees phase shift
> and
> the other is 180 degrees phase shift because it is looking at the
> reflected
> power coming back to the mainline output. It is very useful because you
> can see forward and reflected at the same time using two meters.
>
> If you are seeing 90 degrees phase shift then you may have a
> quadrature
> hybrid which is a four port device that will give you two outputs that
> are
> 90 degrees out of phase when any port is fed and the opposite port is
> terminated.
>
> A 180 degree hybrid is similar however in this case there are two
> ports
> that will be in phase when the opposite is terminated and two that will
> be 180 degrees out. A bi-directional coupler is essentially a special
> type
> of 180 degree hybrid.
>
> Hope that helps, Mike
>
>> degrees out of phase. Is this correct? Is it a coupler design issue?
>> I am a novice in this area so I am not sure what is normal and what
>> is not.
>>
>> Is this one of those cases where the 8505 is biased to read 0 phase
>> angle into a known termination and then read the difference in the
>> circuit under test?
>>
>> Thanks in advance - Dan
>> _______________________________________________
>
>
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