Hello again all.........
Based on my experiences and considerable "prior-to-design-research", I found
the following to be great considerations when using the MiniCircuits SBL-1 and
TUF-1 mixers in receiver designs, particularly receiver front end mixer
designs:
1. Rather than installing preamplification before SBL-1 mixer, add
amplification after SBL-1 mixer (a practice of Motorola and other major
knowledgable RF commercial designers as well as our elite and well known Ham
designers.).
2. Consider SBL-1 etc. Ports to be 50 ohms. For best - and most widley
proven - output matching,and filtering, refer to articles by W7ZOI
(Progressive Communication Receiver, QST and ARRL Handbooks) and W7EL in his
famous transceiver of 1980 which is still the design basis of many of today's
SBL-1 designs.
3. If you get AM signals on your receiver, don't jump to the conclusions that
it's the fault of the front end or mixer!!!!! All too often it is a problem
(bad solder joint, open part in the RF signal chain, etc) between antenna and
the volume control of the AF amp. Use the Finger Touch and Probe Method (12
VOLT RIGS ONLY!!!!!!!!!) and seek out the offending section. For example,
touch the wiper solder tab of the volume control. If AM signal volume
increases, the problem is probably between the vol control and the antenna.
If no AM signal increase is noted, check around the vol control for bad
joints, broken wires, etc.
4. Learn what your problem is or at least where it is. Then you can ask
questions...however, if you get that far, I'll bet you can answer your own
questions, trouble shoot the problem, fix it, and give us all glowing reports
of your success!!!
Good Luck and successful designing and troubleshooting to you all
Bill, K5BDZ
[
QRP-L Archive |
]
[
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000
]