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Thoughts on U2 temperature stabilisation

"peter_helm@..."
 

A temperature controlled heater placed inside the U2 case set for say ten degrees above the highest expected ambient temperature. To warm just the air inside the box, rather than heat individual components.
E.g crystals.

73's Peter G8AEN
Andy Cutland
 

Hi Peter,

That's the what I've gone with this. Am testing on 28mhz but am still getting intermessage drift. May need to go warmer?
And maybe further reduce heat ingress from the pa section. Its not easy!

73's
De Andy

------------------------------

On Thu, Aug 1, 2013 10:41 PM PDT peter_helm@... wrote:

A temperature controlled heater placed inside the U2 case set for say ten degrees above the highest expected ambient temperature. To warm just the air inside the box, rather than heat individual components.
E.g crystals.

73's Peter G8AEN

Tony Volpe
 

Before I got my GPS working (firmware update v2.03) I ran my U2 very successfully on twenty meters housed in a polystyrene box. After careful adjustment to the value of the SYSTEM CLOCK parameter and adjusting the transmit frequency to the middle of the band I found that it would run very happily for well over a week and not gain or lose time more than was required for WSPR and that its transmit frequency might wander only 20htz in a day. It never went outside that limit and ran for weeks like that until I got the GPS working. On the original version of the UQRSS last year, I did employ a crystal heater because when ever there was a change of transmit frequency it affected the width of the FSK modulation which for WSPR did create a problem. The frequency never went that far out, but on the first kit, it would move enough to make the fsk jump too wide or too narrow for detection. The new kit doesn't do that. It is a FAR better product and is an incredible item for the money. I'm loving it and getting over a thousand spots a day on twenty.
"andyfoad@..."
 

Not sure if this data might be useful to others...

My current U2 is housed in a metal box.

The DDS can has stick on heatsink.

The internal PSU regulators generate a fair bit of heat and so does
the PA, so the internals of the box do get quite warm.

I experience no ill effects, and the PA at 9v and no heatsinks just
keeps on running at 100% duty cycle on QRSS.

From switch on (NO GPS) I might experience about a 1Hz drift as
observed on WSPR.

Within 20 mins everything is perfectly stable and doesn't wander
in the slightest. It's better than my FT817 or IC706's ;-)

My experience in the past though with excessive drift was caused
by even the *slightest* temeprature movement on the DDS can.

Exactly as per the instructions from Hans mentioned when the U2
was released.

Hope this helps.

73 de Andy
"andyfoad@..."
 

Andy, my own thoughts are that it should not be about stopping heat
reaching anywhere, but getting the U2 up to whatever temperature
it is going to be run at and then keeping the temperature STABLE.

Once it's reached operating temperature which could be anything really,and then kept STABLE then you should not have any problems.

This has always been my philosphy since the day I started radio,
and it's never failed me.

Good luck.

73 de Andy

--- In QRPLabs@..., Andy Cutland <gj7rwt@...> wrote:

And maybe further reduce heat ingress from the pa section.
Its not easy!

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