Tom,

The pre-scaler is great, but you still need an amplifier or a comparator to=
 reach the safe zone of the pre-scaler, 0dBm +/- 5dB for signals below 200M=
Hz.
This pre-scaler might not work with a signal from -25dBm to -5dBm. it will =
need an amplifier with a gain of ten or better twenty, which can be done wi=
th a single transistor.


Jean-Paul
AC9GH


On May 4, 2014, at 9:13 PM, Thomas Sefranek <wa1rhp@comcast.net> wrote:

> Think pre-scaler=20
>=20
> http://www.onsemi.com/pub_link/Collateral/MC12080-D.PDF
>=20
>=20
>=20
> On May 4, 2014, at 8:41 PM, Martin K wrote:
>=20
>> I want to divide an RF signal down from 100 MHz to something between 1=20
>> and 5 MHz for precise counting.
>> The RF is essentially CW with a bit of frequency modulation. Signal=20
>> power is -5 to -25 dBm which corresponds to a voltage on a 50 ohm load=20
>> of 12.5mV to 125mV.
>>=20
>> My plan is to use a very high speed comparator to capture the (AC=20
>> coupled) zero crossing and put the output (LVPECL) into a couple 1:8=20
>> dividers in series. The signal will probably end up going to an FPGA so=
=20
>> LVDS or LVCMOS is desirable.
>>=20
>> Is there a better way?
>>=20
>> Thanks,
>> Martin
>>=20
>>=20
>> --=20
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>=20
>  *
>  |  __O    Thomas C. Sefranek  wa1rhp@comcast.net
>  |_-\<,_   Amateur Radio Operator: WA1RHP
>  (*)/ (*)  Motorcycle mobile on 145.41 MHz.
>=20
> ARRL Instructor, Technical Specialist, VE Contact.
>=20
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>=20
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