Re: [softrock40] RXTX V6.2 20/30M
Sounds like a happy SDR camper to me.
73 Kees K5BCQ
-- "kb2xj" <kb2xj@...> wrote:
Assembly completed early this morning. No issues, works as advertised.
U5, U6 replaced with 74ACT74's and U8 replaced with LTC6231 during
assembly. DX coming through all morning, receiver sensitive enough!
Jim - KB2XJ
- Hi Jim,
Glad to hear the build went well.
>DX coming through all morning,Indeed, still going strong at 5 PM ET on 20m CW.
Just worked OK1TN with 1 watt.
- Hi Jim,
OK on the DX.
BTW, why you used 74ACT74's instead of the specified 74AC74?
The ACT74 may clock higher but it's not an issue at 56 MHz.
What I'm concerned about is that the ACT74 input threshold
is about 1.4 VDC vs about 2.5 VDC for the AC74. The R58/R59
resistor divider was chosen to match the AC74 input threshold.
By leaving the R58/R59 divider the same with the ACT74, the
symmetry is reduced and the negative pulse width is narrowed
which actually aggravate the clocking.
If you change R58/R59 to match the ACT74 threshold, then the
negative input excursion may go below ground which isn't good