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




Additional info NOT given in time for press about the preamplifier performance:

IN3LNC, Claudio has performed for us  an accurate set of tests of our preamplifier alone and here are the results that fully confirm our preliminary data:

Gain:     12 dB                                            (12.7 dB at 7 Mhz, 11.3 dB at 30 Mhz,  flat within 2 dB over all 30 Mhz range)
Output third order IP3 (OIP3) =
+ 43 dBm  (with 7L14 by Tektronix and 2x HP8640B, -6 dB hybrid coupler, 10 dB attenuator each leg, the two tones at 20, 50,100 Khz spacing and  for all three offsets that OIP3 data has been confirmed)
Input third order IP3 (IIP3) = (OIP3 - Gain) = + 31 dBm
Output second order  IP2 (OIP2) = + 41 dBm (so ie. with a band pass filter with 60 db of stopband  at the two outside test frequencies (our QRM signals) the total OIP2 will be much much better. IP2 has a 2:1  relation with power input).
        3.9 dB (measured with a calibrated noise source at 30 Mhz)
1dB Compression point: +24.5dBm (input + 11.5dBm)

The output impedance resulted to be lower than 50 Ohm, but in this application this is not a problem, performance are not degraded and maybe useful  ie. when paralleling two 50 Ohm receiver without any 2:1 three way-combiner.

It is interesting to compare this 2x2N5109 push-pull with  a single transistor Norton noiseless feedback circuit:

our friend IN3LNC compared for us our 2x 2N5109 push-pull with one transistor Norton circuit noiseless feedback (transistor type BFG135 or BFR134 or BFG34 with same results) with + 13 Vdc, I= 35 to 40 mA, G=11dB NF=2 dB, OIP3= + 41 dBm, but OIP2 was only +31 dBm (10 dB poorer). He confirmed to us that our pushpull is a better performer. Norton feedback amplifier is also very much load impedence sensitive inverse isolation is low.

Please compare the above data with W8JI, Tom, PREAMPLIFIERS SUMMARY test report <----click here the link.

Useful software tools:

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

APPCAD from here  or from official AVAGO site from here

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

Best Regards.         Sergio Cartoceti, IK4AUY


Last update: Jan 16 - 2014