EMRFD Message Archive 7649

Message Date From Subject
7649 2012-08-01 07:27:31 wa9cgz DBM max audio drive

What is the max audio drive to the LO port(diodes) assuming
a +7 for RF drive? I have a exciter for a SDR type transmitter
similar but not the same as shown on figure 9.19 I would like to know
what output level to expect with low intermod products. For those
interested its the uhf sdr designed by Dave wb6dhw look at
his site for more info.

Thanks Joe wa9cgz
7652 2012-08-01 15:31:18 kb1gmx Re: DBM max audio drive
7653 2012-08-02 00:51:59 Ashhar Farhan Re: DBM max audio drive
In order to keep the imd down, the audio drive must be low level and
low, preferably 50 ohms impedance. Less than 100mV in case of 1N4148s.
The output should preferably terminate in an attenuator pad. The audio
should be low-passed to prevent higher frequencies from intermoding to
produce responses within the passband.
Look at Rick's T2Pro (did I get the name right?) transmitter. The
modulator is slightly elaborate, the output is amazingly clear.
- Farhan