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Comparison of the K4 to the T41 on frequency stability

 

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Have a look at these two notes.? An easy comparison of the K4 at $7K vs the T41¡­ not completely 1:1 but close enough¡­.

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From Al¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­.

I just tried my rig with the Ver53.12 I sent you for frequency accuracy. I am using the TXCO and waited about 30 minutes to let everything warm up.

  • First checked the T41frequency calibration with my Rubidium 10MHz source, WWV@10MHz, and my Siglent SDG2122X Sig Gen at 10MHz. All three indicated a T41 frequency error of about -0.4Hz, using the T41 SAM AM detection method.
  • Then transmitted into a 50 ohm DL at 7.200000MHz and measured the frequency on my HP 53131A counter and SA. The counter result was 7.200000.8 MHz, a 0.8Hz difference and less than 1Hz with the SA. The Siglent 3021X SA was set to 7.200000MHz center freq with a span of 1KHz and BW of 1 Hz.
  • The Rubidium source showed 10.000000.85 on the counter. Looks like my counter needs to be recalibrated slightly. On the Siglent 3021X SA, set to 10.00MHz with a span of 1KHz and BW of 1 Hz, the reading was 10.000000. Hz, so I am pretty certain of my sources and the frequency readouts.
  • The T41 CW transmit frequency was within 1 HZ out of 7.200000MHz.

I would suggest you check the calibration of your T41 with WWV, if you can, using the SAM AM detection mode.

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And this for the K4 from Jim N8OQ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­.

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From: [email protected] <[email protected]> On Behalf Of James DeYoung - N8OQ via groups.io
Sent: Tuesday, February 11, 2025 6:45 PM
To: [email protected]
Subject: Re: [Elecraft-K4] K4 On FMT

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This afternoon while it snowed I did 2 minute sampling of each of the Bodnar GPSDO carrier located at 7.05000 MHz, CHU 7.850000 and CHU 3.330000 MHz.

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The K4 frequency on the display was positioned to put the each carrier at +2 KHz near the middle of the receive passband.? WSJT-X FreqCal was used to make the measurements for two minutes sampling (Measured - K4 Tuned display) to the nearest 0.001 Hz.? The summary stats follow.

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The spec for the K4 is 0.1 PPM using just the internal TCXO.? So all three of these checks show better than the spec.? There are still small state changes in the data but within the K4 spec. My K4 was actively using the 10-MHz input, Menu: Ext Ref. Lock.? ?Somewhere I read, but couldn't find the note today, was that a 10-MHz external input was not expected to bring huge improvements in frequency accuracy/stabiliity over the internal TCXO.

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Jim (N8OQ)
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