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

Mark Hatch
 

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 

 

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 

Mark Hatch
 

Raj,

Thank you very much!

However, I am worried that the inductors I have are not the exact same ones you used. I got them from another HAM that ordered them thru the same supplier that you used, but EBAY suppliers have been know to substitute.

Mine are orange/yellow and are marked "A" and "T" and R68K 1145. However, in your post#60946 you said that they were Marked "S+M". I assume the 68k means 680nh? Perhaps the A+T vs S+M is a country/manufacturing plant?

Thoughts?



I suspect that the apparent power loss on 80/40 is not true. I measured harmonics/spurs 4x. For the Primary:

Band                    1st                     2nd                      3rd                         4th (after l5/l7 replaced)
80                       -65                       -64                      -57                        -65
40                       -67                       -67                      -65                        -70

80M looks like man outlier. And i really don't knew what i am doing with the SDRPLAY spectrum scope software, so mistakes could creep in.


40M does look lower after inductors. I am going to re-measure later today.

73
Mark
AJ6CU


Mark Hatch
 

I am all set. All bands legal (USA) for CW except for 10m where the secondary harmonic is only -30 down. 

73
Mark
AJ6CU

 

Mark I have both S+M and A T, both are working fine on my many test boards.
Every board is very individual in behaviour. I have some which put out lots of power
and some low power out. I have not figured out why as yet.

Some boards I changed only L5 and that was enough. Any RF pickup by L7 is removed by
the filter Y1 during TX.

Raj


At 24-06-19, you wrote:
Raj,

Thank you very much!

However, I am worried that the inductors I have are not the exact same ones you used. I got them from another HAM that ordered them thru the same supplier that you used, but EBAY suppliers have been know to substitute.

Mine are orange/yellow and are marked "A" and "T" and R68K 1145. However, in your post#60946 you said that they were Marked "S+M". I assume the 68k means 680nh? Perhaps the A+T vs S+M is a country/manufacturing plant?

Thoughts?



I suspect that the apparent power loss on 80/40 is not true. I measured harmonics/spurs 4x. For the Primary:

Band                    1st                     2nd                      3rd                         4th (after l5/l7 replaced)
80                       -65                       -64                      -57                        -65
40                       -67                       -67                      -65                        -70

80M looks like man outlier. And i really don't knew what i am doing with the SDRPLAY spectrum scope software, so mistakes could creep in.


40M does look lower after inductors. I am going to re-measure later today.

73
Mark
AJ6CU

Mark Hatch
 

Raj,

I am sure you hear this a lot, but a big thanks for working on the purity issues with the uBitx. Myself, and many others would have been lost without your (and of course others) hard work here. Thank you!

73
Mark
Aj6Cu