Posts by PA3FYM

Training license? So you are now both DD0KP and DN5KAN ?

Unlimited licences?

Heiner, what do I miss? ; -)

IK8XLD Rocco, at least somebody who took the (good?) advice I tried to give/gave last January (when QO-100 wasn't operational yet).

BUC mounted on the arm of the dish, looks perfect !

iz1fks What is your question . . . how to modify it, or how it performs with the crystal alone?

dg0opk Of course it can be corrected with software (computer), but I want to make QSO's without the necessity of a computer. Like the ARRL says concerning the context 'in the middle of nowhere': "A man with his rig" ; -)

Nevertheless, the depicted phase noise plot looks very good! : -)

SV1BDS the 10/2 = 5 MHz x 5 trick is known for a while, see this link.

Almost all people one actually hears making QSO's via the NB TPX made creative contraptions .. to make QSO's .. that why one hears them ; -)

Considering your picture above, are you sure you are using a GPSDO, because the CW beacon is not on .550 ?

Good phase noise!

Concerning stability ... hmmm ; -)

SV1BDS No I haven't because they were discarded in the selection process, in around 2017 or so, due to bad phase noise properties.

E.g. my 25 MHz VC-CXO owns (at least) 15 dB better phase noise @100 Hz compared to the VC-CXO in link2. The link2 VC-CXO has -150 dBc at 5 Mhz whereas my selection owns this figure @10 kHz (according to the datasheet).

SV1BDS IN that case 12 U$ 10 MHz OCXO from Ebay (also has to pass through customs ; -)

OK, I did some research here and discovered I was wrong, sorry. The 27 MHz version is Abracon ASVV (I have two seperate transverters, one for an Octagon (27 MHz ref, Abracon) and one for 'other' (de facto standard now) LNB's with 25 MHz ref, Taitien).

The 25 MHz VC-CXO I use in my 'current' setup is this one. Iirc it has the same (phase noise) characteristics as the ASVV series and is cheap (around 2 euro).

OK, fair deal. 10 MHz Bliley OCXO's are around 12 U$ (10.50 euro) available on Ebay.

I use such an OCXO (see picture somewhere above) in my Lars GPSDO and it works well.

However, I think the Abracon ASVV 25 MHz VC-CXO might be a very good lead to discipline with the Lars contraption.

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My advice (I'm not specifically talking to you):

Some other users at this forum, asking questions for more than six months, and after that time not being able to make QSO's across the NB TPX, time is also a factor.

There are/were early QO-100 adapters which thought about the whole frequency factory very thoroughly, based on years and years of (microwave) experience, hard work, frustration and learned it the hard way (like me).

Trust, copy them and learn, in order to improve 'the science of QO-100' for the benefit of successors (who may improve accordingly).

Yes, I forecast that after one week a new posting will emerge here with a question, 'invention' or 'new idea' to use a TCXO inside a PLL LNB, write their own 'discovery' on their own blogs and soon discover it doesn't work as they expected.

Considering my forecast: I hope I am wrong ; -)

In addition to Davids correct statements (S-band section somewhat over illuminates a f/D = 0.6 dish etc): bear in mind that when you optimise the 10 GHz part with lens and subsequently remove the lens (which is favourable for lower f/D ratios) you have to realign the feed because the phase centers of the dielectric lens and open waveguide differ. With the lens the phase center lies more 'out of the waveguide' compared to an open waveguide.

SV1BDS You mean in my case using it with a 10 MHz OCXO?

If yes, that isn't the case here. 10 Hz up/down would be 3.9 kHz off on 10 GHz.

My Lars has an accuracy/stability between 1E-9 and 1E-10 (after a while) and converges to tc's between 250 - 500 , which is good enough for QO-100.

Indeed phase noise goes with the square, so 20logN (where N is multiplication factor).

I have not tried the TCVCXO in your link, but (like I mentioned several times here, and will repeat it again ; -) I use the Abracon ASVV series locked with an ADF4001 to a 10 MHz (Lars) GPSDO.

But of course, feel free to reinvent the wheel ; -)

I did. Mine had no Vcontrol pin and output amplitude was only 200 mV (iirc), meaning I was not satisfied.

How is Lars?

The length of the waveguide was determined based on several types of dish mounts. But, like Heiner said, can be reduced accordingly.

For a friend I replaced the RP SMA with a normal SMA flange.

I can't figure that '25 Hz' out, but the software is written for a reference with intrinsic short term stability (like an OCXO).

More interesting would be, if you supply this 25 MHz signal to the LNB and listen to the CW beacon. Is it stable (enough) and does it sound clear (so no crispiness/phase noise) ?

What I do/did:

Take h1, let it run for a while and determine average diff_ns.

Do the same with h65535. Take the difference between the two values, the

gain then is 65536/difference. (suppose it's 123)

Give in the terminal window g123 and 'r' (for run) and let it run.

Your DAC values are somewhat high, try to get the VCO voltage so that you are somewhere in the middle (around 32000 or so). Perhaps tune it with a potmeter.

Your filtX10 looks good (approx in the middle of the ADC range).

The only weird thing is your timer1 value, it seems to have a lot of jitter (but that probably is due to the fact you don't have a (very) stable 25 MHz reference yet).

I use a 10 uF elco from RESET to GND. This prevents the Arduino from rebooting after you connect/open a terminal session. Of course the 10 uF needs to be removed when (re)programming the Arduino (I use a jumper for this)

Rasto, where did you buy these? They look so nice : -)