Flex 5000 producing 160 meter Spike - causing problems with SPE 1k-FA amplifier
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Flex 5000 producing 160 meter Spike - causing... Expand / Collapse
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Posted Monday, August 19, 2013 12:48 PM
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I have a more than occasional problem of my new SPE 1K-FA amplifier suddenly switching to 160 meters when operating on 20 meters or 80 meters. Since I have no antenna for 160 meters, the amp stops transmitting. This can happen at the start of a transmission or sometimes within it. It always seems to switch to 160 meters, even when using a dummy load. Sent the unit back to Flex and their techs looked at it and reported they saw a 160 meters spike, but it was down from carrier by 92 dB, which more than meets FCC specifications. They said they took a new one out of the box and saw the same 160 meter R.F. spike likely caused by the DSP processing.

The problem is the SPE 1K-FA amp is seeing this spike and trying to change to 160 meters. This problem does not happen when I drive the amplifier with my FT-950, when the amp is solid as a rock.

I can pull the CAT plug from the amplifier and the SPE's R.F, sensing alone works to change the band, however the problem still exists.

So, what I do now? Has anyone else experienced this particular problem and come up with a solution?

K0DV
Post #6794
Posted Tuesday, September 24, 2013 3:59 PM
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Hi OM,

I never experienced unattended band switching of my SPE 1K-FA in conjunction with my Flex 5K.
But sometimes the amp would go in error mode displaying "POWER MANAGEMENT : V PA < 20 V". It produced this error randomly as well in transmit or receive mode on any band.

I emailed to Italy and got a quick answer advising me to check solder points in the the power supply unit in the amp. (they even sent close up photos of the inner of the 1K-FA to guide my investigation)
Obviously there was no poor solder joint to be incriminated.

Finally I found out that the only way disturbing signals could get into the amplifier to the processor unit, in receive mode was via the CAT cable coming from the computer's serial port.
One single big ferrite bead snapped on the CAT cable near the amp input, cured the problem at once and for ever.

I hope this helps;

If not you could try a Hi-pass filter on the x-mit antenna output of your 5K used for 75 m and up. This could attenuate this spur by some 40 or 50 dB more and prevent the the frequency reading in the Expert to trigger the band switching. When operating top band you should utilize another antenna output from the Flex and connect it to the second input of the Expert linear. (you will have to switch to input 2 on the Expert to go on 160).

Regards, Phil FM5GB
Post #6849
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