OT: Frequency probe

[Greg Derda-2]

I've searched and Googled all over for this, but can find nothing.  I
have both a benchtop frequency counter (from a Hamfest w/ no probe),
and the NorCal FCC-1, and I need a frequency probe for both of them.  I
have some RG-174 and BNC connectors.

For the benchtop counter, I presume I connect the center conductor and
shield to the BNC connector in the usual way.

For the FCC-1, there are two holes on the board for the conductor and
ground.

Question is, what do I do on the other end?  Do I need a capacitor like
the K2's internal probe has?  Do I need to ground the shield to the
circuit under test (with a clip)?  Is there more than one kind of probe
depending on the type of measurement?

One goal of mine is to use the FCC-1 with the AMQRP Tenna Dipper (which
has one hole for frequency measurement).  So, in addition to learning
how to build a generic probe, I am also hoping to learn enough (from
you all) to let me know whether I need to ground the shield to the
Tenna Dipper, in addition to connecting the center conductor to that
hole.

Any and all comments will be greatly appreciated!

Thank you & 73,
Greg
ki4mmm
k2 #6100

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[Curt Milton]

Greg

FB on your improvision here.  

The reason for the capacitor is to provide a DC block,
so if there is DC on the circuit being measured, it
won't get into the counter.  

A counter probe is a bit more forgiving than trying to
measure a signal level - you merely need to get enough
RF energy to counter to measure, without loading the
circuit being measured.  

To see some probe designs, look in a ARRL handbook and
also visit the N5ESE website.  For your application,
nothing complicated is required - use your coax,
provide a short probe tip at the end, and a DC block
either as part of the counter or the probe. Do
consider the max power that your counters can handle,
and whether you need some form of limiting to protect
your counter.  

73, curt

--- Greg Derda <[hidden email]> wrote:

> I've searched and Googled all over for this, but can
> find nothing.  I
> have both a benchtop frequency counter (from a
> Hamfest w/ no probe),
> and the NorCal FCC-1, and I need a frequency probe
> for both of them.  I
> have some RG-174 and BNC connectors.
>
> For the benchtop counter, I presume I connect the
> center conductor and
> shield to the BNC connector in the usual way.
>
> For the FCC-1, there are two holes on the board for
> the conductor and
> ground.
>
> Question is, what do I do on the other end?  Do I
> need a capacitor like
> the K2's internal probe has?  Do I need to ground
> the shield to the
> circuit under test (with a clip)?  Is there more
> than one kind of probe
> depending on the type of measurement?
>
> One goal of mine is to use the FCC-1 with the AMQRP
> Tenna Dipper (which
> has one hole for frequency measurement).  So, in
> addition to learning
> how to build a generic probe, I am also hoping to
> learn enough (from
> you all) to let me know whether I need to ground the
> shield to the
> Tenna Dipper, in addition to connecting the center
> conductor to that
> hole.
>
> Any and all comments will be greatly appreciated!
>
> Thank you & 73,
> Greg
> ki4mmm
> k2 #6100
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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