[Lowfer] [Hifer] Sunday morning in ME

[pat bunn]

The Epsom chip is sensitive to both Vcc and to temperature and they I 
believe that the two interact.

I shift the frequency on USC by changing the Vcc using a LM317L. When 
the Epson chip failed on USC a few weeks ago, my backup chip was not 
exactly on the original USC frequency so I pulled it into the window 
with adjusting Vcc. ( I have to pots on the board - one for shift and 
one for Vcc) The Chip  seems to be much more sensitive tio frequency 
change now that the original chip which was running at 5 volts with a 
slight change to make the shift happen.

I have two new Epson chips from DigiKey that arrived last week. 
Hopefully these are in the window at 5 V and I can get USC back to the 
original design and more temperature stable. Not sure why the original 
chip failed, but I suspect lightning as I lost my Clifton Labs probe 
about the same time.


Pat
N4LTA




On 5/12/2013 3:37 PM, John Andrews wrote:
> Mitch,
>
> You're well in the clear, now, just above 400. . You could probably split the difference  and land back on 390.
>
> JA
>
>
>
> On May 12, 2013, at 2:37 PM, Mitch Powell <mitch.powell at sympatico.ca> wrote:
>
>> Hi John:
>> Glad that you are seeing the epson chip at work.
>> Using a 78L05 for VCC - and the frequency hasn't been changed for years.
>> However, took a look at Lyle's notes - and see that a slight variation is
>> available - so have changed VCC to 4.5 volts.    DC input is ~50 milliwatts down from 70 mW.
>> That's right on the chip - there is no amplifier stage - so the rf output will be down.
>> I will let it sit there for a day or so and see if there is any change in frequency relative
>> to USC.
>> Thanks for the comments.
>> Mitch.
>> On 2013-05-12, at 10:23 AM, John Andrews wrote:
>>
>>> Listening/watching the Hifer watering hole this morning in Maine. Seeing NC, EH (weakly), the SIW's, MP and USC. The last two are in a death match for control of 13555.38. I remember Mitch as being about 10 Hz higher in the past. Screen shot:
>>>
>>> http://www.w1tag.com/files/HF12MAY2013.jpg
>>>
>>> John, W1TAG
>>> FN43sv
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