Bullseye LNB Calibration

I have just purchased a Bullseye LNB for amateur radio use. Whilst the inbuilt TCXO is much better than most LNBs there is still a small frequency error. The published spec says that the frequency is adjustable. Presumably this is done through the red socket by communicating with the frequency setting micro.
Is the necessary adjustment software available anywhere? Or alternatively, is the adjustment protocol documented anywhere?

Colin G4EML

@Syed

Bump to Syed.

@g4eml What is the frequency error? Is it within 10 kHz at 23C?

There is an calibration tool that exists, which requires specialized hardware to control the LNB. As far as I could tell, there was no real interest from Bullseye customers for this additional tool, so it was never produced for sale.

The Freq error on the Bullseye is so small that it will not matter for QO100 etc. just ignore it.

73 Manuel DO5TY

The error on my LNB is 16KHz at around 22 degrees. That is comparing it to a GPS Locked LNB and a GPS Locked signal source.

I am not too concerned about it as such, I have plenty of other equipment that is more accurate.

The LNB is becoming very popular with amateurs and many will have the skills and equipment to adjust it. If the feature is there it would be nice to be able to make use of it.

I appreciate it would need some suitable hardware and it might not be economic to produce that commercially. I would guess that this is probably just a level shifter for a serial interface. With some knowledge of the protocol involved most amateurs would be able to build something themselves.

I agree the error is not that significant for QO100 use where there are constant beacons available for calibration, but the LNB also works well for terrestrial use at 10368 and knowing the frequency is accurate could make all the difference when trying to find a weak station or beacon with a 2.5KHz bandwidth receiver.

Colin.

I’ll look into releasing more details on the protocol.

I am happy to replace your LNB, as it is not functioning as described.

No need for a replacement, this post was never intended as a complaint. It is certainly better ‘out of the box’ than any other LNB and I would certainly recommend it to others.

If you could make the adjustment protocol available it would be appreciated and would add even more to its usability.

Thanks.
Colin.

I will comment on this as there are many factors involved in releasing this information and ill try to explain the reasoning behind them.

The LNB was designed to be as accurate as we could make it at the time of manufacture to the budget we were given. After manufacture each LNB is tested 100% over temperature and then finally setup and referenced to a GPS locked RF test Rack, internal algorithms work continuously to help compensate for long and short term drift but unfortunately like any reference built to a cost, it WILL drift very slowly over time, temperature and use, hence the reason we built in the feature to move the LO on a live basis (or to built a crude GPS Frequency locked loop). It can also store and recall one USER offset in NVM and also retain the factory CAL for backup purposes. All of the LNB’s were built at the same time in 2019

Some of the issues of releasing the protocol and more information on how it all works are IP related, in addition there is a possibility of overwriting the factory calibration if you do manage to work out the sequence to unlock the CAL location so there are some associated risks. Finally there is always a cost associated with design and development of such a product and although Syed footed this for the initial development of the LNB and I can tell you its not cheap or easy to develop such a product. We as the designers/manufacturer also invested time and money to include the ability for the LO to be adjusted live and hoped it would help to recoup money invested developing the LNB. It took ALOT of persuading by Syed for us to develop the product and is a reason why this is such a unique product.

The LNB should, in theory, have the ability to tune in approx 200Hz steps (each unit has a unique profile) @ Ku LO and then remain within the temperature tolerances of the internal TCXO. At the time we did offer to manufacture a programmer and Gui but it required even more investment from Syed but we took the risk and developed a prototype but it was never commercialised. To ask us to release this for free is a difficult decision for us to make, (speaking as the manufacturer and developer), as we have to try to recoup the investment…

It is under discussion as I feel (as the designer) it will show the true potential of the product.

J

1 Like

Good news, we will release the information on the Bullseye. I will work with Syed and Colin to make this available to all

Jon

2 Likes

Many thanks to Jon and Syed for releasing the information.
I have used this to design a simple interface using an Arduino Nano which can be used to adjust the Bullseye LNB Local Oscillator frequency.
Full details including a PCB design are on my github

Colin G4EML

thank you Colin, nice work. Of corse thanks to everyone involved in sharing these info.
Not today but mybe a day it will help me to tune the lnb.
Iw0hjz alberto