ppFMT #30

[Black Michael]

ppFMT -- pre-practice-Frequency-Measurement-Test

Tuesday 17:45 Central time -- 23:45Z

We will be doing one 30M and two 40M measurements

Join Zoom Meeting

https://us02web.zoom.us/j/86214145228?pwd=T3NJNEVaVnkycEpKWjhpeTQyRCtkQT09

Meeting ID: 862 1414 5228

Passcode: 831620

Join Slack channel

https://vwsandontarionets.slack.com/archives/C01EZ46V3EG

23:45Z Netlogger/Zoom start -- we will be using both communication methods though Zoom seems more popular now

00:00:00 CW ID -- start recording -- will be at 10.134 and shift to new freq for key down.

00:01:00-00:02:00 -- 1 minute 10.134MHz +/- 100Hz -- Recommend set rig to 10.133, reference to 10.1336

00:02:00-00:04:00 -- Idle

00:04:00-00:05:00 -- 1 minute key down again

00:05:01 -- test over -- stop recording

00:10:00 CW ID -- start recording -- will be at 7.064 and shift to new freq for key down.

00:11:00-00:12:00 -- 1 minute 7.064MHz +/- 100Hz -- Recommend set rig to 7.063, reference to 7.0636

00:12:00-00:14:00 -- Idle

00:14:00-00:15:00 -- 1 minute key down again

00:15:01 - test over -- stop recording

00:20:00 CW ID -- start recording -- will be at 7.064 and shift to new freq for key down.

00:21:00-00:22:00 -- 1 minute 7.064MHz +/- 100Hz -- Recommend set rig to 7.063, reference to 7.0636

00:22:00-00:24:00 -- Idle

00:24:00-00:25:00 -- 1 minute key down again

00:25:01 - test over -- stop recording

Note: the two minute idle is meant so you can make and report two measurements for each test.  Ideally you should see a lot of agreement between the two measurements.  If you don't see agreement within 0.5Hz (and usually closer than that) then you probably don't have a Ref signal and your rig is drifting.

It's a touch easier to analyze the CSV file if you stop/start recording in between.

#1 Everybody make sure your computer time is correct.  http://time.is

#2 Rig should be on for at least 30 minutes without transmitting -- and preferably be on overnight...some rigs take hours to warm up.

#3 Turn off your AGC!!!  Changing signal levels during measurement affects the frequency estimation

#4 You need to ensure your RX PPM is correct -- see the WWV codec PPM measurement Section 2.49 in http://www.w1hkj.com/files/fldigi/fldigi_4.1.15-help.pdf

This is necessary to ensure your audio linearity is correct otherwise the offset from carrier can change your frequency estimate.  You can test your linearity with a local AM station.

#5 Tune rig to frequency -- test frequency will be within +/-100Hz of announced frequency

#6 Set your data collection rate to 0.1 seconds in FLDigi -- easier for us to cross-analyze data

#7 Tune your reference to at least 300Hz away from the announced frequency  -- the test frequency will be on a non-100Hz interval to avoid harmonics so you can use a 100Hz increment.

#8 Wait for the start and adjust the Unk offset using the controls to align close to the Unk freq...you just need to see it start tracking and you can stop adjusting.  You really don't need to be close.

#9 DO NOT TOUCH ANYTHING WHILE COLLECTING -- unless you see an obvious error going on.

#10 When done send your results to the net control along with a description of your measurement setup.  We're particularly interested if you have a reference frequency close to the unknown.

#11 After the collection set your Ref offset to the Unk offset and ensure you see the same average error when the Ref was at the lower frequency.  You may see some small difference you can correct for.  For example, the reference may be a little bit high and you can subtract the difference or a little bit low and you can add it.  This is the audio linearity problem that is solved with the PPM correction which I recommend you do.

Here's my transmitting setup -- 10MHz BodnarMiniGPS reference for Apache 100 and BodnarMiniGps for a reference signal on measurement

BodnarMiniGps->Apache 100->Thetis->TX->RM HLA 305 Amplifier>MFJ-998 Tuner->LP-700 Monitor->61ft attic dipole

Here's my measurement setup

BodnarMiniGps->OmniVII(no antenna needed)->RX->FLdigi -- meausre both TX signal and Bodnar reference

Mike W9MDB

[Dana Whitlow]

Didn't we already do ppFMT #30 in early December?  I certainly recorded something

with the right characteristics.

Dana

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[Black Michael]

Oh rats..forgot to record that in my list so yep...this will be #31.

Just gotta' keep you guys on your toes...

Mike

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[Dana Whitlow]

I suppose, although my toes get to hurting a lot from the unusual pose  :-)

Dana

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