Octagon LNB


Brian Flynn GM8BJF
 

Hi Andy,
I spotted that bit a while back and found them quite useful at lower frquencies. I used one to make a GPS locked reference for my aging FT736R which had to be on 20.048 MHz which at first appeared to be awkward but then I remembered about  binary!
They are digital devices and as long as dv by dt is ok they should work. They can't depend on capacitive coupling inside!

73s Brian GM8BJF


Andy G4JNT
 

Ah, didn't read the data sheet properly.    Spotted now that it quotes "For lower frequencies, ensure SR > 130 V/μs."   (SR = slew rate)

For a 0/5V logic input that corresponds to a rise time <38ns which is no big deal using a 74ACxx driver



On Fri, 1 Feb 2019 at 17:05, Andy G4JNT via Groups.Io <andy.g4jnt=gmail.com@groups.io> wrote:
The ADF4113 is specified for Fmin of 200MHz.   How have you made it work with 27MHz input.

I'm guessing by using a square wave and the internal dividers are static logic, so if clocked properly will go down to DC

Even the lowest frequency variant of that family, the ADF4110, only goes down to 800MHz officially.  
May have missed a trick here;  I've quite recently been bemoaning the fact modern synth chips can't go particularly low in frequency



On Fri, 1 Feb 2019 at 16:49, brian.flynn via Groups.Io <brian.flynn=tiscali.co.uk@groups.io> wrote:
Hi Mike,
I have taken the 27 MHz xtal out of my octagon and made an external input using the second F-tyle socke as described by Bernie 'HJW.
I have a waterproof box externally which contains a 27 MHz VCXO based on a varactor tuned Colpitts osc which I have locked to 12.8 MHz ex-cellphone
TCXO.  The PLL uses an ADF4113 with a band width of about 10 Hz. I feed about +10 dbm into the  LNB.  The water proof box with the PLL conrtains a Bias Tee to draw the DC off the LNB feed to power the PLL  I am powering the LNB/dish from a cheapo freesat box which allows Polarisation switching and Hi/Lo band switching.
A byproduct of it is I now get Sat TV as the 60 CM dish I am using is wide enought to pick Astra as well!! The 10706 MHz beacon is about 25 db out of the noise.  There is still a slow drift with temperature but it is only a couple of kHz and I can live with that until I find a better TCXO.

73s
Brian GM8BJF


Andy G4JNT
 

The ADF4113 is specified for Fmin of 200MHz.   How have you made it work with 27MHz input.

I'm guessing by using a square wave and the internal dividers are static logic, so if clocked properly will go down to DC

Even the lowest frequency variant of that family, the ADF4110, only goes down to 800MHz officially.  
May have missed a trick here;  I've quite recently been bemoaning the fact modern synth chips can't go particularly low in frequency



On Fri, 1 Feb 2019 at 16:49, brian.flynn via Groups.Io <brian.flynn=tiscali.co.uk@groups.io> wrote:
Hi Mike,
I have taken the 27 MHz xtal out of my octagon and made an external input using the second F-tyle socke as described by Bernie 'HJW.
I have a waterproof box externally which contains a 27 MHz VCXO based on a varactor tuned Colpitts osc which I have locked to 12.8 MHz ex-cellphone
TCXO.  The PLL uses an ADF4113 with a band width of about 10 Hz. I feed about +10 dbm into the  LNB.  The water proof box with the PLL conrtains a Bias Tee to draw the DC off the LNB feed to power the PLL  I am powering the LNB/dish from a cheapo freesat box which allows Polarisation switching and Hi/Lo band switching.
A byproduct of it is I now get Sat TV as the 60 CM dish I am using is wide enought to pick Astra as well!! The 10706 MHz beacon is about 25 db out of the noise.  There is still a slow drift with temperature but it is only a couple of kHz and I can live with that until I find a better TCXO.

73s
Brian GM8BJF


Brian Flynn GM8BJF
 

Hi Mike,
I have taken the 27 MHz xtal out of my octagon and made an external input using the second F-tyle socke as described by Bernie 'HJW.
I have a waterproof box externally which contains a 27 MHz VCXO based on a varactor tuned Colpitts osc which I have locked to 12.8 MHz ex-cellphone
TCXO.  The PLL uses an ADF4113 with a band width of about 10 Hz. I feed about +10 dbm into the  LNB.  The water proof box with the PLL conrtains a Bias Tee to draw the DC off the LNB feed to power the PLL  I am powering the LNB/dish from a cheapo freesat box which allows Polarisation switching and Hi/Lo band switching.
A byproduct of it is I now get Sat TV as the 60 CM dish I am using is wide enought to pick Astra as well!! The 10706 MHz beacon is about 25 db out of the noise.  There is still a slow drift with temperature but it is only a couple of kHz and I can live with that until I find a better TCXO.

73s
Brian GM8BJF


Mike Willis
 

Not had a lot of success with the TCXO. I do have a PCB for it though. It is accurate but keeps wandering off to either side and coming back.
--
Mike G0MJW


Andy G4JNT
 

I just purchased a dual output one from the German link publicised here a couple of weeks ago.   It's 27MHz, tested by listening on an HF receiver to the IF output.   Interestingly, at 10GHz, one output is within 3kH - spot on for a free runner; the other is a rather excessive 148kHz off,   or 14 PPM.     The difference is audible at the fundamental as an audio tone difference of 400Hz

The postage cost was about the same as the unit itself.

I'm pondering if the 27MHz leakage down the IF could be used to compensate for the frequency offset.



On Thu, 31 Jan 2019 at 15:18, PAUL NICKALLS via Groups.Io <paulnick=btinternet.com@groups.io> wrote:
Hi Martyn,

Most people have the twin output version.  It may be that the identification system does not apply to this.  My 27MHz twin output has 3 marks each side as per Scatterpoint.

73
Paul G8AQA

On 31/01/2019 14:51, Martyn G3UKV wrote:

GA All

Catching up with reading - re Scatterpoint January 19, page 10.

I have the Octagon 'Optima/Oslo' LNB with single output. The Xtal is on 27 MHz (well, 26.9996+).  Markings on the LNB casing include 10 marks each side of a central "V" - which is different to that suggested by Jen (G4HIZ) in her excellent article.

BTW - no need to open up the LNB to find the Xtal frequency - just place LNB close to an HF receiver!  I found the Xtal remarkably stable after leaving on all day, but still purchased a TCXO recommended on the DL-AMSAT pages. [DigiKey part No. CW655CT-ND for 27MHz, CW654CT-ND for 25 MHz]

73 Martyn G3UKV



Virus-free. www.avg.com


Paul G8AQA
 

Hi Martyn,

Most people have the twin output version.  It may be that the identification system does not apply to this.  My 27MHz twin output has 3 marks each side as per Scatterpoint.

73
Paul G8AQA

On 31/01/2019 14:51, Martyn G3UKV wrote:

GA All

Catching up with reading - re Scatterpoint January 19, page 10.

I have the Octagon 'Optima/Oslo' LNB with single output. The Xtal is on 27 MHz (well, 26.9996+).  Markings on the LNB casing include 10 marks each side of a central "V" - which is different to that suggested by Jen (G4HIZ) in her excellent article.

BTW - no need to open up the LNB to find the Xtal frequency - just place LNB close to an HF receiver!  I found the Xtal remarkably stable after leaving on all day, but still purchased a TCXO recommended on the DL-AMSAT pages. [DigiKey part No. CW655CT-ND for 27MHz, CW654CT-ND for 25 MHz]

73 Martyn G3UKV



Virus-free. www.avg.com


Martyn G3UKV
 

GA All

Catching up with reading - re Scatterpoint January 19, page 10.

I have the Octagon 'Optima/Oslo' LNB with single output. The Xtal is on 27 MHz (well, 26.9996+).  Markings on the LNB casing include 10 marks each side of a central "V" - which is different to that suggested by Jen (G4HIZ) in her excellent article.

BTW - no need to open up the LNB to find the Xtal frequency - just place LNB close to an HF receiver!  I found the Xtal remarkably stable after leaving on all day, but still purchased a TCXO recommended on the DL-AMSAT pages. [DigiKey part No. CW655CT-ND for 27MHz, CW654CT-ND for 25 MHz]

73 Martyn G3UKV