[Lowfer] DBM choice

[Stewart Nelson]

Hi Bob,

The mixer should work fine.  Transmit mixers are usually not
critical, especially when both inputs are clean signals.
The sum term and any IM products will be at HF and easy to
filter out.  There may be a little output at harmonics of the
desired Tx frequency, but lowfer finals typically generate
lots of those, anyhow.  They don't normally cause any trouble,
because the resonant antenna attenuates them greatly, and
power is very low.

However, stability is important at LF, and 1 ppm of drift at
3.6 MHz would become 20 ppm at 180 kHz.  Ideally, your 80 meter
rig has a single reference oscillator, and you can use that same
source (via divider, DDS, PLL, etc.) to generate the LO for your
mixer.  That would prevent any drift from being multiplied.

If you plan to transmit using modes that demand really high
stability, you may want to check your transceiver before building
the downconverter.

73,

Stewart KK7KA


> Hi Gang
> 
> Picked up another DBM mixer which has a range from
> 2Khz to 12 Mhz. This is the one I used for the rcv mixer
> 
> it is a WJ-M6H and has a noise figure of 5 Db, a SSB conversion loss of 6
> Db
> the LO drive max is a +7 and the peak input power is a +17. I was able to
> get these
> free so I dont know if they are still made or price but I hope to use it
> in a Tx mixer
> to down convert 80 meter to LF. 
> 
> The rcv mixer works well so I hope it will work OK on Transmit
> 
> any opinions
> 
> Bob  K3DJC