Shortest reasonable time between transmissions when comparing two different antennas

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Joined: 2017/10/13 - 08:45
Shortest reasonable time between transmissions when comparing two different antennas

Hi all WSPRers,

I'm looking for advice on how to best compare two antennas (for transmit) on 20 meters using WSPR. I did a quick transmit test using just one of the antennas, and downloaded the current month's wsprspots csv dump the next day in order to analyze it.

To my surprise, the reported time stamps differ from when I transmitted. I basically did the following:

cat wsprspots-2020-12.csv | grep SM6VNO | (while read a; do B=`echo $a | cut -d , -f 2`; echo -n `date -r $B +"%Y-%m-%d %H:%M:%S"`,; echo $a | cut -d , -f 3-; done) | grep "2020-12-20 "|cut -d , -f 1,5|cut -d . -f 1|uniq -c

which resulted in the following row counts, timestamp, and MHz, for each transmission:

47 2020-12-20 13:16:00,14
1 2020-12-20 13:20:00,14
23 2020-12-20 13:22:00,14
20 2020-12-20 13:28:00,14

The thing is that I only transmitted on 20 meters at 13:16Z, certainly NOT at 13:20Z nor 13:22Z. So it seems that the timestamp in the log is not always that of the transmission, but perhaps sometimes that of when the receiver had time to report it?

(Maybe this is well-established knowledge, and I am simply unaware of how it works.)

I looked at the details in the log to see if it was just some particular program/version that reported 13:20Z or 13:22Z, but there was no obvious pattern.

So, back to what I intend to do and what I would like advice on:

If I transmit at xx:00Z with antenna A, when should I transmit with antenna B to make sure that all "slow" reporting stations have had time to report the SNR for antenna A? After 8 minutes? 10? 20?

(I intend to switch back and forth several times; the entire testing procedure will take a while, so I want to get it right from the start.)

73 de SM6VNO Anders