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50 ohm pads
Posted: Sun Nov 18, 2007 11:14 am
by arlojanis
I want two 50 ohm pads for use during duplexer alignment. What is a good brand and part number. What should be the dB? I am thinking used condition.
Re: 50 ohm pads
Posted: Sun Nov 18, 2007 2:57 pm
by Doug
Almost everything that I've read says use a 3db pad, it seems that it's used more for creating a balanced 50 ohm match than anything else. I have a set of 3db's from Elcom systems (AT-51)..... I've got no complaints.
Doug
Re: 50 ohm pads
Posted: Sun Nov 18, 2007 5:37 pm
by Al
Author Harold Kinley, in the several books he has written on radio communications testing, recommends using 6 dB pads on your test equipment input and output. The return loss on a 6 dB pad is twice the attenuation value or 12 dB. 12 dB return loss(1.6:1 VSWR) provides better isolation than lower valued pads while still allowing use of nearly the maximum dynamic range of your signal/tracking generator and spectrum analyzer/service monitor.
Re: 50 ohm pads
Posted: Mon Nov 19, 2007 3:02 am
by Einstein
If you use a Wiltron or Eagle bridge you will have your 50 ohm pad and it will be accurate.
Re: 50 ohm pads
Posted: Tue Nov 20, 2007 6:05 pm
by AEC
I personally use an Eagle return loss bridge when I tune cans, then I sweep the individual cans and tune for the best match and once you widen the display after the initial tune, you can really get down to the nitty gritty and deep tune the notches so even a super powered system will not show any desense in the RX cans whatsoever.
It does take time, but it can be done, and when it is, you will be amazed.
Re: 50 ohm pads
Posted: Wed Nov 21, 2007 10:32 am
by BIGSTICK
What is deep tune ? and super powered?
Re: 50 ohm pads
Posted: Wed Nov 21, 2007 10:29 pm
by AEC
Deep tuned is getting the notch depth deeper than 'normal' sweep tuning, and super power is running 250 + watts(my opinion).
When you can hear a -120 signal with the transmitter keyed at 250 watts....THAT'S a deep tune!