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is there any interest in my experiences with GPS locked source
Posted: Tue Apr 15, 2025 11:29 am
by Richard-g8jvm
,
Hi, got the impression very quickly here that my face doesn't fit
I have completed the 27MHz source locked to a SV1AFN GPS locked source at 100MHz, with a AD9850 DDS.
Is it worth writing up as I found a few gotchas ?, but it is very low cost and DDS does produce low phase noise.
Richard G8JVM
Re: is there any interest in my experiences with GPS locked source
Posted: Tue Apr 15, 2025 11:53 am
by G3GJA
I would certainly like to see an article from you about this topic in CQ-TV
Clive G3GJA
Re: is there any interest in my experiences with GPS locked source
Posted: Tue Apr 15, 2025 12:26 pm
by Basil
I don't think a lot of people here, unlike myself, have seen your face Richard
Replies here can be tardy, in my experience. It can be quiet for days, then there's a small rash of posts.
Knowing your expertise with microwaves and electronics in general first hand I for one would be interested in your write up, go for it!
Re: is there any interest in my experiences with GPS locked source
Posted: Tue Apr 15, 2025 1:58 pm
by g0mjw
Richard-g8jvm wrote: ↑Tue Apr 15, 2025 11:29 am
,
Hi, got the impression very quickly here that my face doesn't fit
I have completed the 27MHz source locked to a SV1AFN GPS locked source at 100MHz, with a AD9850 DDS.
Is it worth writing up as I found a few gotchas ?, but it is very low cost and DDS does produce low phase noise.
Richard G8JVM
Hi Richard,
I expect there would be a lot of interest, even more so it it were possible to generate at say 25 MHz which seems to be a common LNB reference these days and 40 MHz where the Pluto likes to have its reference. Now 25 MHz is probably trivial, just divide 100 by 4. 40 MHz a little more work. A typical station would need both 25 MHz and 40 MHz.
The other thing is, while the satellite reference is aiming at 9.75 GHz LO, in practice we would quite like something a bit higher to move the QO100 IF from 739 MHz into the normal 950-2000 MHz range of the LNB. Even better if it could be put somewhere useful like 23cms but that's probably a bit too far.
Mike
Re: is there any interest in my experiences with GPS locked source
Posted: Tue Apr 15, 2025 2:27 pm
by Richard-g8jvm
Ok , I'll write something up on it
It will do 25MHz, and probably 40MHz as , as I'm using a 100MHz clock.
It uses a single pole xtal filter followed by a MMIC and a two section LPF
If used on 25MHz , use the xtal from the LNB
I haven't payed with moving the IF as the HB TRx has 739MHz helical filters on the SAT input.
But it could be useful to nudge it up to around 900MHz as many 2,70 & 23 cms TRx's also cover 900 MHz for the USA market,
usually just remove a diode .
Richard