100w PA bias current when SDR-1000 power switch is OFF
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100w PA bias current when SDR-1000 power... Expand / Collapse
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Posted Wednesday, January 20, 2010 6:03 AM
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I have some problem with my SDR-1000 (included 100w pa & ATU). When my power supply (13,8v/25a) is ON and SDR-1000 power switch is OFF I observed: radio gets current about 0,6A. When power switch is ON radio gets nearly 0,8A. In this moment when I switch MOX in powersdr current is 1,4A. What do you think about? Its normal situation? the radio gets current 0,6A when power switch SDR-1000 is in OFF position. I checked it.... this curent 0,6A its from bias of fianal PA. When power switch is OFF bias polarization voltage is active. When I switch power ON switch in SDR-1000 bias current is going down 0mA (bias polarization voltage is not active). In this moment when I switch MOX in powersdr (mode USB) bias current is OK (600ma and polarization voltage is active). Anabody have some experience with it? Please helpe mne if it possibly. Another problem: I observed then may PA sometimes oscilate on 28mhz and 18mhz. When i work in USB mode some times going to oscilating. I have good antenas and good ground system. Pa oscilate also when i connecting sdr-1000 to 50ohm dummy load.

Rafal SP9VFD

SDR-1000 (100W & ATU) + FA-66 Firewire
Post #2188
Posted Wednesday, January 20, 2010 10:58 AM
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The power switch in the SDR-1000 does not switch the power to the 100W PA module.. The switch is not rated for the 20 amps the PA requires to operate. So PA idle current with the Power supply on but the SDR-1000 power switch off is, unfortunately, normal. With the power supply on but the switch off, the bias control logic is unpowered and can no longer hold the PA idling current off. Best practice is the turn off the power supply when you are not using the SDR-1000.
I don't know if your radio has the 'ATU RFI shield' installed but I have found that the shield is helpful at reducing PA oscillations even on SDR-1000's without and ATU.
See http://kc.flex-radio.com/KnowledgebaseArticle50284.aspx?Keywords=ATU+shield




AL, K0VM
SDR-1000, Flex5000, Flex user since 2006
Post #2189
Posted Thursday, January 21, 2010 8:44 AM
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Many tnx Al for your post and quickly information. Of course my SDR-1000 has the 'ATU RFI shield' installed but....... I dont know why, but It was instaled copper side up, not such us recommended in flexradio website FAQ. Today I was changed it to properly instalation (copper side down) and I forgot about Pa oscilation. Many tnx Al and 73s....you have nice shack (sdr-1000 + flex-5000.....very nice )

Rafal SP9VFD

SDR-1000 (100W & ATU) + FA-66 Firewire
Post #2190
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