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Frequency Stability
Vernon Matheson
?Hi all, ? I have been trying to reduce the drift on my wspr tx when running 5-6 bands. I seem to be able to get one band with zero drift and the next band in sequence has some drift. See the data for 20m versus 30m below ? I have attached a small heat sink on the 27mhz xtal as suggested but am wondering about park mode. U3S is also in a qrp labs case. ? If I set to mode 2 and say 149.000.000 as suggested it doesn't change much. ? Would I be better to use park mode #1 and then 149.000.000 for a frequency. ? Vernon ?
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Hi Vernon I suggest putting the sequence of the bands the other way around: start with the highest frequency and then step down.? Park Mode 2 is useful in the gaps between transmissions but makes very little difference if the gap is only 8 seconds. So use Park Mode 2 for the long wait at the end of calibration and before the Mode 0] configuration starts. Have it sequence through starting at the highest frequencies then stepping lower.? 73 Hans G0UPL On Thu, Nov 9, 2017 at 5:35 PM, Vernon Matheson <vmath@...> wrote:
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Vernon Matheson
Thanks Hans...would I reduce the 150.000.000 maximum frequency by 28.200.000?? ? On 11/09/17 10:54 AM, "Hans Summers" <hans.summers@...> wrote:
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Hello Vernon The idea of the 150MHz is that it keeps the Si5351A "busy" while not transmitting, which keeps it warm; then when it starts transmitting, it is already warm and there is not much temperature change. Sometimes 150MHz is too high and causes a drift in the other direction, and needs to be reduced for that reason. It takes some experiment to get it right. But I always found best results on a multi-band Ultimate3S by having 10m first, then 15, 20m, 30m etc going down in frequency.? 73 Hans G0UPL On Thu, Nov 9, 2017 at 6:22 PM, Vernon Matheson <vmath@...> wrote:
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Vernon Matheson
¿ªÔÆÌåÓýThanks Hans...I redid the order of tx as you said and used park mode 2 @ 150 Mhz plus the small heat sink and all I see is zeros ( just like my bank account) LOL! So success as it also removed the small curl on the start of each dit and dah in the qrss signal. Many thanks for your help. Vernon Sent?from?my?BlackBerry?10?smartphone?on?the?Rogers?network.
Hello Vernon The idea of the 150MHz is that it keeps the Si5351A "busy" while not transmitting, which keeps it warm; then when it starts transmitting, it is already warm and there is not much temperature change. Sometimes 150MHz is too high and causes a drift in the other direction, and needs to be reduced for that reason. It takes some experiment to get it right. But I always found best results on a multi-band Ultimate3S by having 10m first, then 15, 20m, 30m etc going down in frequency.? 73 Hans G0UPL On Thu, Nov 9, 2017 at 6:22 PM, Vernon Matheson <vmath@...> wrote:
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Excellent, Vernon! Nice to hear some good news! 73 Hans G0UPL On Fri, Nov 10, 2017 at 2:14 PM, Vernon Matheson <vmath@...> wrote:
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