Title: TX Intermod Meausements
Post by: oz4hz on 07. November 2022, 09:58:55
I have made a lot of TX IMD measurements both with the original
PIN diode ant. switch and the relay modification.
See pics below
First picture is with the original PIN diode switch
and the second with the relay modification.
There is quite a difference in IMD
Vy 73 OZ4HZ, Hans
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Title: Re:TX Intermod Meausements
Post by: oz4hz on 07. November 2022, 10:00:29
Title: Re:TX Intermod Meausements
Post by: oz4hz on 07. November 2022, 10:01:11
| IMD with relay modification |
Title: Re:TX Intermod Meausements
Post by: DF8OE on 07. November 2022, 12:10:55
That's the reason I implemented relay switching few years ago...
vy 73
Andreas |
Title: Re:TX Intermod Meausements
Post by: SP9BSL on 08. November 2022, 11:08:20
Totally agree to remove the PIN diodes.
I have some remarks to your measurement, be careful with measurements of such high signals because:
- you have performed different measurements because of TOI your SA, look at first measurement - you have 30dB attenuator set and signal level is over 3dBm at input mixer. SA itself may produce false intermodulation. With the second measurement, mixer signal is 10dB lower becuse you have 40dB attenuation. It is good to measure or find in manual IMD of SA mixer first to be sure the limits and reliable measurement. Believe me, R&S ESR (very expensive) has significant IMD3 rise at the level of -15dBm at input! Even worse with cheap Siglent or Rigol...
- if you do not have proper external attenuator you may destroy the SA input mixer/attenuator with 2W power |
Title: Re:TX Intermod Meausements
Post by: oz4hz on 08. November 2022, 16:03:29
You are absolutely right, but there is also an external power attenuator of 30dB - so in the first picture the signal is -29dBm at the mixer input. In the pictures you can't see that there is a reference offset of 30dB from the external power attenuator-
.
Vy 73 OZ4HZ
(also eine alte Hase) |
Title: Re:TX Intermod Meausements
Post by: SP9BSL on 08. November 2022, 18:28:07
| Thank you for clarification - now everything is ok :) |
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