>Subject: coils for direct conversion receiever using NE602
>Date: Fri, 23 Aug 1996 11:28:09 +1100>I am interested to know if anybody is
building or has built reveivers using the>ne602 device.>I am particularly
interested in the design of rf and oscilator >coils for such>devices and am
interested in any >design specifications any >one can submit.>EG preselector
coils homebrew if coils home brew socilator >coils home brew. I would like to
put together a database of designs that >could be shared
The NE602 (and it's derivitives; SA602, NE612, A, AN etc.) has been around for
about six years . Although not a particularly "strong" mixer, the easy
implementation, coupled with low power supply requirement has made it a
deservedly popular chip. It can provide "adequate" signal handling
characteristics in receiver applications in all but the most hostile
environments (see below).
It would be difficult to derive a table or quick reference for the many coil
combinations that are possible. However, much valuable information on the '602
may be found in;
"NE602 Primer"- Carr, Elektor Electronics Jan. '92 (has formulas for
calculating oscillator coil values etc.).
"Simple Receivers from Complex I.C.'s"- Parrott, Ham Radio (USA) Dec. '88.
"Using the NE602"- Zavrel, Technical Correspondence, QST May '90.
"Using the NE602 in Ham Circuits"- Carr's Corner, 73 Amateur Radio Feb. '93.
"Single-chip Frequency Converter"- Covington, Radio-Electronics Apr. '90.
Two things not specifically mentioned in any of the above; when using the '602
in direct conversion receivers (particularly where an RF amp. is used); much
improved performance will be had if the internal oscillator is not used, but
rather, use a separate metal- boxed VFO (when using the internal osc. it is
difficult to keep the osc. signal from entering the input of the RF amp.,
causing "tunable hum" and other unwanted effects), and, contrary to some
reports that the '602 is rather too weak as a mixer, if the builder uses a
separate osc., and applies the input signal (at pins 1 and 2) in "balanced
mode" i.e. true push-pull, without grounding pin 1 or 2 for RF, and
extracts the wanted product also in balanced mode, the strong signal
handling of the chip will be significantly improved.
73, Kind Regards, Drew, VK3XU. Telstra Research Laboratories.