[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[linrad] VHF: mixer question.
I am working on the local oscillator of my home brew Linrad receiver.
I have a crystal controlled source of 116.505 Mhz at +24 dbm.
I also have a PLL source of 25.045 Mhz at +24 dbm.
I would like to mix these two together to provide the needed 141.550 Mhz
local oscillator so I can use a 2.5 Mhz IF for 144.050 Mhz RX.
I plan to drive a pair of TUF-1H mixers. I need two for Xpol operation.
Each TUF-1H requires +17dbm of LO drive. I plan to use a 5 pole helical
filter (2db loss) after the mixer and each TUF-1H should be driven, I think with a
3 db pad to control impedance. Since each mixer will share power, I lose 3db more.
This means I need an output of +25dbm at 141.550 Mhz. That's a quarter of a watt!
I think I can find in my junk box, some VHF transisters that will handle the power
and frequency. I am hoping to combine a pair of them in either series or parallel to
have a power mixer with two inputs. Does anyone have a clever, but simple favorite
circuit to do this?
I am using parts on hand, where possible. The +25dbm comes from the exciter
boards of LOW Band and VHF Motorola Micors.
73, Jim Shaffer, WB9UWA.