Hi Maarten:
Thanks for the information. More and more it is looking like a
hardware problem, but hopefully it will be easy to solve. Tomorrow I
will attempt to measure the 200 MHz. oscillator frequency. Got to be
getting pretty close to the culprit that is causing the short term drift.
Brian K7RE
Maarten N1DZ wrote:
> The same drift you described I encountered once in my 2m transverter.
> I had stabilized the transverter with a thermistor soldered to the
> crystal.
> Everytime I transmitted the voltage would sag a little causing a
> temparature change that caused the oscilator to drift a little.
> It would only occur in high duty modes. Ultimately I gave the
> thermistor its own power supply. After that the problem was solved.
> Good luck and let us know if you are able to solve it.
> 73 Maarten N1DZ
>
> On Sun, 31 Dec 2006 17:00:57 -0500, Brian Kassel
> <[EMAIL PROTECTED]> wrote:
>
>> Hi Jim:
>>
>> Thanks for the note. Let's see if I can describe to you what I
>> see. After even a short transmission of, say, 5 seconds, running
>> something like 5W, the frequency of the received PSK-31 signal slowly
>> moves to the left on the waterfall display of my MixW program traveling
>> about the width of a typical PSK-31 signal in about 2-3 seconds. There
>> seems to be no greater frequency shift running 50W for periods up to 1
>> minute duration. I am not sure if my TX frequency is varying. I can't
>> tell by ear at this point on another receiver. I have a frequency
>> counter, and can measure the TX frequency on CW if that will provide any
>> insight. The PS should have no voltage sag at this low power level. I
>> use it for other projects. It is a commercial switching supply SEC
>> 1223. Since I didn't really suspect the PS, I haven't as yet done any
>> measurements. on it. I certainly appreciate any assistance you can
>> provide.
>>
>> Brian K7RE
>> Jim Lux wrote:
>>
>>> At 12:22 PM 12/31/2006, Brian Kassel wrote:
>>>
>>>> Hi Ross:
>>>>
>>>> As I had mentioned in 2 messages to Tim:
>>>>
>>>> "I also got a reply from Ken, N9VV. He basically agrees with you,
>>>> and
>>>> I gladly accept the turn on drift, no problem. I stand informed and
>>>> educated by you both, thanks!
>>>>
>>>> What does bother me though is the drift that occurs for about 2
>>>> seconds after going from TX to RX. This same amount of drift
>>>> happens no
>>>> matter what power level is run, and no matter for what time period
>>>> the
>>>> transmission occurs. Makes for tough operating in a digital mode
>>>> contest, which is my main operation here. I have never seen this
>>>> mentioned on the Flex reflector. Owing to the fact that the drift
>>>> amount and time to stabilize remains the same, it doesn't seem like
>>>> any
>>>> temperature related phenomena. If this is inherent to normal
>>>> operation
>>>> of the SDR-1000, then it would appear that either the K2WS mod, or the
>>>> GPS mod may be in order. I really want to be sure though before I
>>>> spend
>>>> the big bucks, that there is no other alternative. "
>>>>
>>>> " I should have mentioned before that I did indeed test with the
>>>> AFC on
>>>> and off in both sound card programs (MixW and Digipan), no
>>>> difference in
>>>> the drift was seen in any case, still a few tens of Hz. "
>>>>
>>>> So even accepting the short initial turn on, I am still saddled with
>>>> the TX-RX drift. Also, I am not totally sure that going with the K2WS
>>>> or GPS mod, the TX-RX drift will be cured. Still open for any
>>>> ideas!
>>>
>>>
>>>
>>>
>>> Something weird is going on. There shouldn't be that much change in
>>> the frequency just changing from Tx to Rx and back. Is your power
>>> supply voltage varying (although, I think the XO runs off a regulated
>>> 5V)? Is the frequency change a "step" change or a slow drift to a new
>>> steady state (where slow is a couple seconds)..
>>>
>>> My SDR1000s (old ones, no thermistors) drift on initial power up, but
>>> are rock steady shifting between Tx and Rx.
>>>
>>>
>>>
>>>
>>> James Lux, P.E.
>>> Spacecraft Radio Frequency Subsystems Group
>>> Flight Communications Systems Section
>>> Jet Propulsion Laboratory, Mail Stop 161-213
>>> 4800 Oak Grove Drive
>>> Pasadena CA 91109
>>> tel: (818)354-2075
>>> fax: (818)393-6875
>>>
>>>
>>>
>>
>>
>>
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