Scott wrote:
JIMMIE wrote:
On Jan 23, 6:43 pm, Kenneth Scharf wrote:
JIMMIE wrote:
I was wanting to listen to VHF/UHF SSB. All of my present UHF/VHF
radios are FM. I was thinking of rigging up a simple downconverter
using a mini circuit mixer and my HP signal generator as the local
oscilator that I can connect in front of my HF rig. I have an antenna
mounted pre- amp that I think should suffice for my front end. Any
foreseeable problems short of keying my transmitter while it is
connected.
Jimmie
For best performance these mixers require a constant impedance at all
three ports (usually 50 ohms). The preamp will provide this for the RF
input and the output of your HP signal generator should have a 50 ohm
selectable output. You may need to add an attenuator between the
generator and the mixer if the HP does not provide a 50 ohm termination
using a variable output. You will need to set the oscillator injection
level to the mixers required 7dbm drive level for best conversion
"gain". The output should go through a bandpass filter covering the IF
frequency you are down converting to and provide a 50 ohm impedance.
A duplexer network here is a good idea (provides a 50 ohm termination at
the IF frequency and a low impedance (short) to ground to out of IF
signals).

Any reccomendation on the best mixer to use?
Jimmie

Here's one good to about 600 MHz. Been used a gazillion times in just
about all VHF/UHF transverters at one time or another. If casual
listening is all you need, hook it up just like you said...VHF/UHF
antenna to the RF port, HP signal generator to LO port (set to +7 dBm
output for this mixer and frequency appropriate for your IF frequency
such as 116 MHz for 144 MHz to be 28 MHz out of the mixer) and connect
the mixer IF pin to your HF radio antenna port. Probably a good idea to
use capacitor coupling at each mixer port, something like 1000pF should
work.

http://www.minicircuits.com/pdfs/TUF-1+.pdf

Scott
N0EDV
For what it's worth, that's the same mixer used in the Elecraft K2
receiver section.