Re: trick to soldering in L5 and L7 or why did spurs on 80/40 get worse and 20/10 get better...

 

For 40/80 spurs you need to change the 3 filter relays to AXICOM.

L7/5 improves the higher bands in my experiments.

L5/7 should have equal effect on all bands as it is an IF stage and all bands will be same unless you are over driving
the PA.

Power loss noted by me is minimal with yellow inductors, with other SMD inductors there was severe opwer loss.

Raj


At 24-06-19, you wrote:
Hi all, could use some pointers here on replacing L5/L7 on a V4 board. Not having a real spectrum scope, i am using the sdrplay with their spectrum scope software... Was using a RF sampler + 110db attn (HP 355d)

I got the following results...

                     Spur                Spur                                      Fundamental
Band .          Before             After replacement l5/l7 .        Before              After
80 .               -34db             -28db                                      -57db             -65db
40                 -19db             -13.5db                                   -65db             -70db
20                 -28db             -33db                                      -60db            -61db
10                 -32db             -40db                                      -65db             -63db

Looks like the main culprit is a decrease in output of the fundamental on 80 and 40 of 8db and 6db respectively.

So I am wondering...
1. Measurement error? (does the transceiver need to warm up for 30 minutes or more?)
2. Wrong part for L5/L7? Mine are orange, with markings of "A" and "T" and R68K 1145
3. One of the solder joints is poor
4. Inductor damaged during solderin g

?

Does the fact that 80/40 output reduced point the finger at either L5 or L7? 

How did you bridge that gap, especially for L7. That seems to be a likely target for a cold solder joint.

Appreciate any thoughts and experiences here!

73
Mark
AJ6CU 

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