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Mini-Circuits ADTT1-1
The next 1:1 transformer tested is the ADTT1-1. The following table lists the results:
| FSA3157 + ADTT1-1 + 74AC04 |
Vdd = 7.0V, Vbias = 1.8V |
Best bias |
| Band |
BPF |
mixer |
MDS -dBm |
IF rej |
spur |
mixer IIP3 (dBm) @ 20KHz spacing |
Bias |
IIP3 |
| IL |
CL |
- |
+ |
|
avg |
-6 |
-3 |
0 |
+3 |
+5 |
|
0 |
| -dB |
-dB |
BPF |
BPF |
-dB |
dB |
dBm |
dBm |
dBm |
dBm |
dBm |
V |
dBm |
| 160 |
3,3 |
5,44 |
133 |
129 |
60,4 |
|
|
|
42,4 |
|
|
3,0 |
44,7 |
| 80 |
1,4 |
5,36 |
133 |
131 |
62,4 |
|
45,5 |
47,0 |
48,0 |
49,7 |
50,5 |
1,9 |
48,0 |
| 40 |
2,3 |
5,36 |
133 |
130 |
63,6 |
|
|
|
48,2 |
|
|
1,2 |
50,2 |
| 30 |
3,4 |
5,32 |
133 |
129 |
62,0 |
|
|
|
46,3 |
|
|
1,2 |
47,5 |
| 20 |
3,4 |
5,36 |
133 |
129 |
60,4 |
|
|
|
45,2 |
|
|
1,2 |
46,7 |
| 17 |
3,0 |
5,44 |
133 |
129 |
66,8 |
|
|
|
43,8 |
|
|
1,2 |
45,3 |
| 15 |
3,9 |
5,52 |
133 |
128 |
64,4 |
-9,3 |
|
|
43,1 |
|
|
1,8 |
43,1 |
| 12 |
3,7 |
5,56 |
133 |
128 |
46,4 |
|
|
|
41,3 |
|
|
1,8 |
41,3 |
| 10 |
2,3 |
5,72 |
133 |
130 |
40,4 |
|
|
|
41,8 |
|
|
1,8 |
41,8 |
| 6 |
|
5,88 |
132 |
|
52,0 |
|
|
|
39,7 |
|
|
1,8 |
39,7 |
| 4 |
|
6,20 |
132 |
|
26,4 |
|
|
|
38,6 |
|
|
1,4 |
39,1 |
Conversion loss is on average 0,4dB worse than with other transformers, somewhere in between TT4-1A and T4-1 and worsening on higher frequencies, much like with the T1-1T.
Average spur level with the ADTT1-1 is really excellent at -9,3dB (!). Note that this applies to a mixer adjusted for best RF-IF isolation, so nothing special was done to minimize the spur level. Also note the excellent MDS levels on 6M and 4M indicating that the spur level is also very low on the VHF bands!
RF-IF isolation is really excellent, better than -60dB, if band specific adjustments are made. The levels in the table are for the best isolation on 15M.
The ADTT1-1 combination has the best average bias point at 1.8V. Noticeable improvement can be made with band specific adjustment of the bias point, but within a band the bias point behaved rather docile. No extreme steep dips on any band.
Except for a slightly higher conversion loss, the ADTT1-1 configuration has it all: IP3 well above +40dBm on all HF bands and almost on 6M. Excellent RF-IF isolation combined with truly excellent spur reduction up to 4M. And last but not least a fairly docile character with respect to the bias point.
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