Re: HP 5086-7906 YTO
¿ªÔÆÌåÓý? Hi Aldri, ? ? For your second converter, when you do debugging it's easy to make a mistake, there is so much manipulation. You have to keep the positive side, this part is set and you have a second spare converter. ? For the YTF, it's not easy, centering the spheres is not enough, don't forget that it's a bandpass filter. So you have to align the filter for a certain reference frequency, but which one, we could assume that it's in the center, but not necessarily, it could be at the beginning for example (lowest frequency). The filter will deform according to the frequency, it's about finding a happy medium. The YTF calibration will find the coefficients of a polynomial trying to have the best for all frequencies. The level differences will be compensated during the frequency flatness calibration. However, don't forget that if you have too much loss to compensate, the DANL test could become out of spec. ? The fact that you use a precise external power supply is not a problem for the alignment of your YTF. The important parameter of this power supply is its stability. ? I had sent you a picture of my 8595E, here it is again, it represents a cumulative test of the frequencies: yellow curve -> test at 3GHz cyan curve -> test at 5GHz magenta curve -> test at 6.5GHz We can see that on the left, there could have been an improvement by re-adjusting one of the spheres, but nothing is certain. The insertion loss varied from 2 to 3 dB between the minimum and the maximum of these 3 frequencies. You have similar results, I think your YTF has good results...nothing is perfect :) ? You say that you have problems in the high band, what are the frequencies in play. from 2.9GHz to 6.5GHz? (highband). For the second converter, the path loss for the highband is -1.8dB. After this point two bands go through the same path, so if the YTF is correct, either there is a problem with the YTF control source, the first converter or the second converter (highband section). You should be able to easily find where the excess loss is. ? You are at the end of your troubles, don't give up, you will find it. ? ? --------------------? Here is the verification of this second converter after reassembly. The flatness is good, only 0.03dB for 5MHz width at output IF 321.4MHz (lowBand). Multiplier x6 for 3600 MHz, adjusted for best match (lower loss at 321.4MHz), very sensitive adjustments. Path for 321.4MHz highBand was verified too. ? One sweep with 50 MHz span, another with 2950MHz span¡to see the stop band. The loss for IF highband include loss of filter and RF switch, around -1.8dB. ? Yves De?: [email protected] <[email protected]> De la part de alfa beta ? Yves, thanks for the info about the 2nd converter? After having installed the one bought on the bay?I checked?the original one?on the bench and it?seems to work normally ? I'm starting to suspect the blindness on the LOW BAND was due to a bad connection I did when the repair was suspended years ago ¡ ouch ! ? Meanwhile I'm investigating?a certain deafness on the HIGH BAND (from 2.4 to 11 dB) ? I measured the insertion loss of the SYTF I had realigned and found figures?from 5.2??to? 8.5 dB on the range? 3 to 6 GHz ? These figures?seem not too bad?and?the AMP CAL routine should be able to recover them ...unless there is some hardware problem in the generation of the tuning current (I performed the insertion loss measurements by manually tuning? with an external precision power supply) Will see ... Adri ? ? ? ?
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