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H mode mixers at 144 MHz



Hello, All!

Giancarlo did some tests with his H-Mode HF mixer at 144
MHz. 

Here are a couple of emails regarding his results:

Roger, 

following the quick test I did last evening on the 
I7SWX 2 xfrm H-Mode Mixer at 144 MHz, please find here 
below more detailed measures. 

Tests on an I7SWX 3V Two-Transformer H-Mode Mixer with 
a new squarer under study (circuit not yet released), 
driven with LO signal of 0dBm. Transformers are the 
ones used for the HF mixer and cores #41 (mu 850). 

Signal input at 145 MHz -10dBm. The Table reports the 
mixer attenuation at each IF for different Local 
Oscillator frequencies. 

IF frequencies are resulting from RF signal less LO 
and LO less RF signal (I hope it is clear...hi) 

IF= RF- LO ATT LO  RF ATT 
MHz MHz dB MHz dB 

0.455 144.4 -9 145.5 -9 
4 140 -8 149 -8 
9 135 -8 154 -8.5 
10.7 134 -8 156 -9 
21 124 -8 165 -10 
45 100 -8 190 -11 
70 75 -8 215 -12 
100 45 -9 244 -15 

A test done with a lower performance mixer, using 
FST3125 (not yet released), and driven by the 74AC86 
squarer circuit, as in the I7SWX two-transformer 
H-Mode mixer, gave similar attenuation results but the 
LO drive into the 74AC86 had to be +15dBm, from 455kHz 
to 45MHz IF and +25 dBm for 70 and 100 MHz IF. 

These tests demonstrate the H-Mode Mixer could be used 
at 144-148 MHz. Need to do some studies on 
transformers cores (suggested #61 = mu 125) and 
numbers of turns to improve mixer attenuation. 

I hope there are some friends of the Linrad list that 
will tackle trial test at 144 MHz. 
----end of Giancarlo's message

And now to try and find some time to play with these new
mixers ;)




LINRADDARNIL