EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: babysitter on February 20, 2014, 09:13:07 pm
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Not too bad for 50$ on eBay auction: #who cares with acceptable shipping to Germany... :-+
Some cleaning with Baby oil, Tuner spray and cotton swab on the outside was necessary.
This device, quite unknown at the omniscient landfill named www, is a 50 Ohm 0-100 dB , 1 dB step attenuator.
Each switch, when pressed, engages a single Pi-shape attenuator with the corresponding value, when not pressed, the signal is routed trough without intended attenuation. The configuration is 1+2+3+4+10+10+10+20+20+20 dB.
Impedance and connection: 50 Ohms N female. Estimated max. input power around 20 dBm. Don't want to cook it for testing.
Bandwith: Depends on your requirements, it seems to be really flat to ~200 MHz but acceptable up to 450 Mhz where it rolls off rather steep. Better measurements will follow here, Baby prevents me from finishing the measurement. :)
Now, lets get some Verzwakker show ! (Sorry people from the nederlands, PA4TIM I am looking at you!)
(http://dg3hda.primeintrag.org/lib/exe/fetch.php?cache=&media=2014-02-19_09-27-30_937.jpg)
The boring outside, hinting on quite a age. All the good stuff is behind the front panel, the back of the housing is only for stand and protection without active parts.
(http://dg3hda.primeintrag.org/lib/exe/fetch.php?cache=&media=2014-02-19_09-30-24_581.jpg)
2 groups of 5 attenuators in sub housings behind the switch rows, cabling between the sub housings and the N connectors in RG-58.
(http://dg3hda.primeintrag.org/lib/exe/fetch.php?cache=&media=2014-02-19_09-34-59_578.jpg)
Pron starts here: the diecast sub housings have 5 chambers, each contains a PCB-based switch and the corresponding pi-constellation attenuator. The additional resistors from ground to somewhere invisible, any idea what they are ?
A bit more description in german at http://dg3hda.primeintrag.org/doku.php?id=daven_650-50 (http://dg3hda.primeintrag.org/doku.php?id=daven_650-50)
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Don't know about that one, but these are nice, I love mine... good to 1 mHz...
http://www.ebay.com/itm/HP-350D-Attenuator-Set-5W-55V-600Ohm-DC-IMC-/300956945533?_trksid=p2054897.l4276#ht_388wt_1121 (http://www.ebay.com/itm/HP-350D-Attenuator-Set-5W-55V-600Ohm-DC-IMC-/300956945533?_trksid=p2054897.l4276#ht_388wt_1121)
But the one you really want if you can live below 560kHz is the 353A Patch Panel very very nice. Looking for another one.
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As promised, the measurement of attenuation over frequency.
Conditions
Made with a Rigol 815-TG, using 2x ~50 cm N(m)-BNC(m) some 7mm type coax cable and 2x BNC(f)-N(m) adapters.
Tracking generator setting at -20 dBm "normalized" to 0 dBm line with a N(f)-N(f) barrel adapter before putting the attenuation network inline. No additional inline attenuators used.
The plot
(http://dg3hda.primeintrag.org/lib/exe/fetch.php?cache=&media=daven_650-50.jpg)
The blah
The Marker shows the 3 dB bandwidth of the low pass characteristic.
The 2 m ham band (EU) is well within the useable range.
At the 70 cm ham band (EU) it is already down at the steep edge of the low pass :(
Note the curious decrease of attenuation above 600 MHz, fun guaranteed when using a power meter and a source with harmonics >:D
Conclusion
I consider that a good result for a "feeling lucky" ebay experiment at that price.