PicoTuner v3 help please - signal input

[g1tzc]

New to this so here goes.

I appear to have the PicoTuner v3 working.
Voltages on test points are correct (after having a dry joint).
Both the Ryde and Portsdown builds on (different) SD card.
Light blinking on the Pico.
I am accessing the Portsdown via the web interface via 192.168.200.208, which is displaying as expected and works correctly.
Boots fine.

Talking about the ports down;

I have gone in to receive with no LNB connected there is RF Input Level -95db and MER 0.0
I have gone in to receive with LNB connected, rotated through 90 degrees there is RF Input Level -68db (to -70db) and MER 0.0. This does not seem to change at all even if I am pointing totally away from the satellite.

I'm using the external bias T as I read mention that you can cause problems to the 4334 if you are not careful, so decided 12v and rotate was safer. LNB voltage on the unit is turned off.

I think that is all I can give for now.

Neil - G1TZC

[g0mjw]

Let's assume for the moment you are using the correct input socket on the tuner and have the frequency and symbol rate set up correctly. You didn't say what you are trying to receive. Assume the beacon?

What version LNB? Has to be a PLL one. Not a Sky Wideband, old DRO type etc. You will only see a signal if you are pointing at the satellite. Is there a large dish involved? They are very narrow. The level you are seeing is very low, like the noise from an LNB.

I don't know where you read that about the 4334, if you are using the LNB supply it has protection, it is when you try to use bias without protection that the little choke can fail if there is a short on the LNB. With the LNB supply chip it should be fine. As you are using external bias, I assume there is no jumper fitted at JP2 and JP3. Don't ever connect 12V to the tuner f-socket via the bias-t if the jumpers are fitted, it won't end well.

My best guess is either you have the wrong frequency and SR settings in the Portsdown, or you have connected to the wrong socket, or you are not aiming at the satellite. Also I suppose the 12V bias might not be working.

Mike

[g1tzc]

Hi Mike,

Thanks for taking the time to reply.

Let me see if I can do better this time;

Let's assume for the moment you are using the correct input socket on the tuner and have the frequency and symbol rate set up correctly. You didn't say what you are trying to receive. Assume the beacon?

The Portsdown is set to QO-100(a), SR1500, 10491.5 and I was using the Beacon MER option.
For now J2 and J3 are disconnected and LNB voltage is set to Off.
In the config I am using input A, and as this gives -68dB and input B gives -95 I am confident this is correct. I am taking A to be the top one.

What version LNB?

Maclean MCTV-252 Premium Twin LNB SAT Converter Digital Waterproof 3D Full HD 0.3dB (Twin)

You will only see a signal if you are pointing at the satellite. Is there a large dish involved?

I was able to see the Beacon MER screen (handy tool) live on my phone. I was using the existing 80cm dish direction / satellite finder software. I could (if proof is needed) connect my spare DX Partol LNB, absolutely check with narrow band, lock the dish and put the TV LNB back on the dish.

I don't know where you read that about the 4334

To be honest, I can't either.

Also I suppose the 12V bias might not be working.

12v DC was seen at the dish end of the coax using the 12V bias

I am very sorry for not giving enough information previously. Hopefully v2 is a little better.

Neil - G1TZC

[g0mjw]

I thought I would add why back feeding the LNB supply is not a good idea. Theoretically, at first glance it should not matter. That's true, mostly.

Screenshot 2024-12-13 153721.png (16.11 KiB) Viewed 824 times

Imagine if the LNB supply is off and a voltage is fed into the LNB, through the jumper and as V_LNB. It will effectively bias TP1 to whatever voltage is fed in.

D7 is reverse biased, so no problem there, unless the input is more than 50V. We won't feed into anything past D7, protecting the LNB chip.

D6 is a Zener suppression diode. It is there in case of surge voltages. It is designed to break down at about 20V. At that point a significant current will flow, so if you connected say a 24V supply, or a negative supply, it would probably burn out the RFC in the tuner, but if the applied voltage is between zero and +20V nothing will happen. So, this all appears safe, as long as we can be absolutely sure the voltage doesn't get over 20V.

The problem from the protection side is we don't know anything about that external bias supply, what the ground reference is etc. It will certainly attempt to be the same ground once they are connected by the coax screen. When you first make the connection, with an F type the centre pin may engage first and at that point, if the PSUs have different ground potentials there is a potential for the voltage difference to be beyond the limits, which D6 will attempt to suppress. D6 has about 50 ohms impedance, so the current could be high while the grounds try to equalise. If there is more than a few 100mA it is likely that the little RFC inside the tuner will burn out.

Mike

[g0mjw]

What version LNB?

Maclean MCTV-252 Premium Twin LNB SAT Converter Digital Waterproof 3D Full HD 0.3dB (Twin)

OK. The problem is you are not using the correct type of LNB. Assuming Google is right, that LNB is not a PLL type. The chances are the frequency will be off quite a bit and also the phase noise too high for the narrower signals. But then you said you had it working on the narrow band?

What you need is something like the Bullseye PL LNB. Is that what the DX patrol is? If so, a simple solution is to use it for both narrow and wide band. Just switch the LNB volage, or rotate it but you will soon get sick of doing that, especially when it is raining.

[g1tzc]

Hi Mike,

Thank you for your continued support.

I have ordered a Bullseye to resolve the issue of having the wrong LNB type. I really appreciate you pointing that out.

Ultimately I am having two dishes, because I have the space on the top of the workshop to do so.

The DX patrol LNB uses two ports. One is the signal from the LNB and the other is a local oscillator from the ground station, fed in to the LNB. They use a crystal oven inside the ground station.

As I said at the beginning, I am new to this and trying to find my way through it all, so any help from anyone is appreciated.

Neil - G1TZC

[g0mjw]

Hi Neil

A better set up, assuming the dishes are the same size, would be to split the signal from the DX patrol LNB and use it for DATV, you can adjust the LNB voltage on the Picotumer, that's how I have it set up. My picotuner provides the LNB volage for both NB and WB. I simply command it to 12V or 18V. As I use a Pluto for SSB and DATV, I have the LNB connected via a splitter and to the Pluto and the Picotuner. The bias gets fed in via a bias-T, with DC isolation so I am not feeding DC into the splitter. The LNB gain is more than enough for the splitter loss to not matter.

Then your second dish can be TX only. That means you no longer need a dual band feed. With a small dish, that will be better from the receive side because dual band feeds are almost always a compromise and with a small dish, you need all the efficiency you can get.

If you do keep them as separate systems, you can always make the DATV side RX only and have the narrowband dish as the DATV TX and Narrow band TX/RX.

I forgot to add, if it is the DX Patrol with the 70cm IF, you can just connect the Picotuner to that IF for RX. All you need to do is rotate the LNB (or find a way to get 18V/12V selection)

Mike

[Basil]

For what it's worth, and I too am newish at this, I have a quad output LNB which I modified to take a GPS locked LO on one its four F type sockets, but GPS locking is neither here nor there. Multiple outputs is the key. With this I can TX on the wideband and at the same time RX on EITHER or BOTH the narrowband and the wideband, with one dish. The LNB is receiving on both vertical and horizontal polarities at the same time, all the time.

So I can be transmitting DATV and watching my own and another wideband signal, as well as receiving narrowband CW or SSB. But you can't do that with, for example, the single output Bullseye LNB (excellent though they are). RX software is Open Tuner, and my Minitiouner has dual FTDI chips installed to allow two DATV signals to be decoded simultaneously. Narrowband software is SDR Console. (Although I like HDSDR and I am pretty sure it could be made to work similarly).

BTW, did I read recently that a Bullseye can be modded to take a GPS locked LO signal?

[g0mjw]

I used to have a similar system until the LNB stopped working. Power (12v) into one socket, reference into another and H and V. The Bullseye has really good phase noise, quite often I found the locked LNBs. locked to LEO Bodnar GPS disciplined reference were losing a dB in comparison due to the phase noise. A change of reference frequency of 1 Hz made a difference, so it was the reference.

So, while you may be able to lock the Bullseye to something, it will probably not benefit a DATV setup. Once you calibrate them, they stay on frequency quite well on their own. There is a 25 MHz reference signal on one of the ports you could use in a correction loop.

Mike

[Basil]

Hi Mike, thanks. I have a Bullseye and it did work very well indeed, I even made the board to "trim" it, which worked as well, but I do like the simplicity of having H & V available all the time with no messing around. My inability to receive many or most very low Ks signals could be down to phase noise.

I remember Chris ON1RC saying it was possibly my problem. If I had more time I'd swap in the Bullseye and see what happens. But time is sparse right now. Happy Christmas!