Longwave reception of Flex6400

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  • Updated 2 days ago
Hi,

I found that longwave reception of Flex6400 is only okay with the RF gain at 0. If RF gain is increased sensitivity drops a lot but not linear with the gain. Signal meter reading also drops for example from S9+6dB to S7 , S8, S5 and S5 with RF gain changed from 0 to 32dB. The sensitivity roll off starts at about 350kHz.

73
Thomas
DF1TB
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Thomas Berner

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Posted 2 weeks ago

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Thomas Berner

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Hello,

Maybe someone from Flexradio can give a comment?

Additionally I would be interested in the MDS or similar sensitivity specification for the stated RX frequency range of 30kHz - 54MHz. The Hardware Reference Manual says Nothing about that.

Thank you!

73
Thomas
DF1TB
(Edited)
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HCampbell WB4IVF

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Have you tried a "factory reset" yet?
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Thomas Berner

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This I would only do if some other user tells me that his 6400/6600 is not showing this behaviour. But so far nobody took the effort. 
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N8SDR

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Thomas I'd try and see what happens here, But  I can't I have an AN broadcast station about 700 feet away and it overloads the front end . I wouldn't be able to give you any good info becuase of that.
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Thomas Berner

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Thank you, we no longer have this Problem
 in Germany, all AM broadcasters are gone since several years.
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HCampbell WB4IVF

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Took me a while to find a real signal in all the locally generated noise here.  Finally found a CW signal on 350kHz:

 @ -8dB gain, CW signal strength shows -70dBm  / S9+

@ +32dB gain, noise floor drops and CW signal strength shows -90dBm / S7+

So probably normal Flex preamp behavior at those frequencies.

(Edited)
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Thomas Berner

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Here are screenshots to show my Problem:
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Thomas Berner

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Hello again,

thanks for the help and confirmation of my observation.

For me it is quite clear that the  current Flex Series has a poor performing preamp on longwave. There is even some degradation on AM band of about 3dB at 1.5MHz, 160m seems to be okay.

73
Thomas
DF1TB
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Thomas Berner

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Hello,

I finally found what I was looking for in the ARRL test report on Flex6400M , available in the download area. They measured the noise floor (MDS) with -115dBm at 137kHz (no preamp) and -98dBm (+32dB preamp) and at 475kHz with -117dBm /-115dBm (0/32dB).  The preamps seem to work normal from 3.5MHz up (1.8MHz not tested).
It is a pity that nobody from Flexradio took the small effort to leave a short comment here.
Clarified for me now albeit quite disappointing result.
73
Thomas

DF1TB