900 Mot. PA SGTF1020B
Posted: Sat Jan 05, 2008 9:47 pm
Got one of these in a round about way from the person selling them on Ebay.
Sort of surprized that it works quite well.
Ran basic tests prior to making some modifications suggested on the VHF South Website referenced on Ebay.
I can get near 150w out with 28 vdc, and drive around 4 watts on 927.
Seems to me that 28 v is a bit high for these.
Still get over 100 watts with 24 v with 4 in, and for appx 1 watt drive I get around 30.
The one I have has a single RF board attached to the heatsink, and a small single stage circulator that is also attached to the single RF board.
The one the Ebay seller references on the VHF South website has a "stand alone" circulator fastened to the heatsink connected by coax jumpers.
And that Website states that the circulator won't work at 927.
Seems to me that it also states this model PA won't work at 927, but there was hardly any TX out difference between 902 and 927.
I am pretty sure that the circulator is WAY off its design specs, but the power output, and current draw are in specs, so I am going to use it for a bit and
see how well it works.
The heatsink gets warm after several minutes of Tx at 60 watts out.
But not hot enuf that I have a concern.
So, heres the questions.
Anybody familiar with these?
I have a couple of 28 V nomial supplies, but none that will go as low as 24 (Ferro-resonant) anyone know if these will take 28v?
Anybody have experience removing or bypassing the internal circulator?
I kinda hate to remove it since it is integral to the power control, but I have several dual port isolators for actual protection,
so I could take out the circulator, use an external dual port only, and drive it to only around 60 watts.
Sort of surprized that it works quite well.
Ran basic tests prior to making some modifications suggested on the VHF South Website referenced on Ebay.
I can get near 150w out with 28 vdc, and drive around 4 watts on 927.
Seems to me that 28 v is a bit high for these.
Still get over 100 watts with 24 v with 4 in, and for appx 1 watt drive I get around 30.
The one I have has a single RF board attached to the heatsink, and a small single stage circulator that is also attached to the single RF board.
The one the Ebay seller references on the VHF South website has a "stand alone" circulator fastened to the heatsink connected by coax jumpers.
And that Website states that the circulator won't work at 927.
Seems to me that it also states this model PA won't work at 927, but there was hardly any TX out difference between 902 and 927.
I am pretty sure that the circulator is WAY off its design specs, but the power output, and current draw are in specs, so I am going to use it for a bit and
see how well it works.
The heatsink gets warm after several minutes of Tx at 60 watts out.
But not hot enuf that I have a concern.
So, heres the questions.
Anybody familiar with these?
I have a couple of 28 V nomial supplies, but none that will go as low as 24 (Ferro-resonant) anyone know if these will take 28v?
Anybody have experience removing or bypassing the internal circulator?
I kinda hate to remove it since it is integral to the power control, but I have several dual port isolators for actual protection,
so I could take out the circulator, use an external dual port only, and drive it to only around 60 watts.