[hpsdr] external 10MHz reference input

[H.A.Meijer]

Hi,
thanks for your thoughts about the freq jumps from the 10MHz osc.
You are talking about "just 0,5 Hz' but my Hermes is jumping 30 to 40 Hz 
when on 10/6 mtr and with transverters (MF=28MHz) use.
This is very annoying and for me not the so called "high performance"  
I'm looking for.

I did change the R141 and still see that is has some locking problem to 
my external 10MHz, now and then.
I will do some measurements at that circuit, maybe my 10MHz level is to 
low..

Bert


Op 18-5-2013 1:57, John Marvin schreef:
> Just out of curiosity, what are you doing when you care about those 
> jumps? Yes, the behavior can be annoying, but those jumps are 
> typically less than 1Hz. That's a problem when you are doing things 
> like precise frequency measurement (e.g. FMT) or measuring doppler, 
> etc. But for most use cases no one is going to notice those kinds of 
> jumps (I'm just imagining someone exclaiming "hey your frequency just 
> jumped 0.5 Hz" during an SSB contact :)).
>
> I've done FMT without an external clock using my Hermes, and that is 
> when I care about the TXCO behavior. I've decided for those few cases 
> to just turn it off. The internal VXCO is a lot more inaccurate in an 
> absolute sense, but that can be compensated for (for example PowerSDR 
> retains a calibration feature that can handle this case). Once the 
> case heats up the VXCO is more stable than the TXCO, with smooth 
> changes. I've considered asking the firmware developers if they would 
> consider adding the capability to ignore the TXCO/external clock so 
> that I don't have to open my case to disable the TXCO for the few 
> times I care about this (perhaps overload one of the mercury specific 
> clock config values for this purpose), but I don't think enough people 
> would care about that feature. Perhaps once I learn a little more fpga 
> programming I can develop the code, since I expect the change would be 
> trivial. I may just wind up buying an external reference before I get 
> around to this.
>
> John
> AC0ZG
>
> On 5/17/2013 1:37 PM, H.A.Meijer wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi,
>>
>> Thats the one I was looking for.
>> I want to use my 10MHz gps ref. osc. because my onboard 10mhz osc 
>> starts to jumps in freq.
>>
>> Thanks!,
>> Bert
>>
>> Op 17-5-2013 21:18, Bruce Beford schreef:
>>> ***** High Performance Software Defined Radio Discussion List *****
>>>
>>> Hermes R141 was changed from 100 ohms to 50 ohms. Picture here:
>>> http://home.myfairpoint.net/vze1t5sc/Hermes%20R141.jpg
>>>
>>> 73,
>>> Bruce
>>> N1RX
>>>
>>>
>>>> I know there has been a resistor change at the input circuit but I 
>>>> don't
>>>> know which one and can't find it back.
>>>> Can someone help me out which resistor has changed there?.
>>>
>>>
>>>
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