A High-Level Accessory Front End for the HF Amateur Bands
by Sergio Cartoceti, IK4AUY (QEX march- april 2003, pages 45 to 56)


Until now I have found only one mistake in QEX March-April 2003 page 52, Fig. 6, schematic of the PIN-diode attenuator circuit in which the by-pass relay must be as follow (our pc board template is OK): RF In goes to the common and RF Out goes to the other common.

100nF input capacitor goes to K11A terminal, the output 100 nF capacitor goes to K11B terminal. Of course the relay position indicated is at normaly close OFF position (NOT exited), so RF is bypassed by the short and the attenuator circuit is kept outside the RF path.

One more odd thing:

I have discovered a very powerful tool to play with receiver gain, noise, IP3, MDS, per stage and cumulatives data to simulate with a complete receiver system without getting tired about long calculations.

Try this professional-nice and available for free software by AGILENT: Version 2.5.1  AppCAD

Download file name: setup251.exe

Download file size: 12.2 MB


 Choose the menu function "Noise Calc". And  enjoy it.

I  have some more info, and dBm to dBmicroV  easy conversion relations,  in my  web site at
http://www.webalice.it/romano.cartoceti/article_5.htm (under Measures & simulations an article in Italian which is under future publication in our ARI magazine, but the relations are easy to read).


My  push-pull  preamplifier schematic  alone has been included 
by  John Delvoldere, ON4UN
in Low - Band DXing    (Fourth Edition)  by ARRL

ISBN: 0-87259-914-0
ERRATA CORRIGE: in this schematic there is a printing error
the emitter resistor to ground in each 2N5109 should be 100 Ohm
(not the wrong value shown of 560 Ohm)
My QEX article is correct.
The text article in the book at page 7-98 and 7-99 is indeed 100%
correct so with 100 Ohm emitter resistor  each transistor is biased
for about 50 to 60 mA  (so for 2 X 2N5109  a total current of
around 100 mA at 12V DC or about  115mA at 13.8VDC.



Best Regards.         Sergio Cartoceti, IK4AUY

page updated: March 12, 2008