Posts by DF1QE

Hey this NXP application-note is high interesting, not only for external XO !

Thanks to Mike !

They say : "The TFF1024 LO needs differential signal as reference, therefore the X-tal driver should have two outputs with 180 deg phase shift."

But I still wonder why ?

In all LNBs MixerICs the Xtal-oscillator-circuit looks very similar to the external oscillator they describe in the app-note.

In every LNB I modified up to now, at the osc. output pin automatically appeared a 180deg signal when I applied RF to the osc in pin.

I think someone really has to compare signal-quality with 2 equal LNBs, one singlepase feeded and one biphase feeded.

I would do this, but sorry, right now no time for it ....

Another interesting subject is, that in the app-note they say, that oscillator lines should not go along with IF lines to avoid spurious IF signals.

They show sideband signals in the diagram.

Hmmmm .... but that's what we do when we use the single coax way to apply the external XO ....

In all LNBs I modified up to now I used the two coax mehode.

73

Armin DF1QE

I do not assume that this methode improves phase noise.

But what may improve it, is the right LO level.

One pin is an output pin and one pin is an input pin.

Ususally between this pins is an c-mos amplifier as oscillator in the IC and further stages are internally connected to the output.

I assume if you connect the "output" side of the coil to ground (via a C for DC-block) you will get the same result.

But anyhow it is a real nice way for de-coupling the 25 MHz.

Good Idea !!!

For me this looks like a bad x-tal or a noisy powersupply.

When I was testing out some TCXOs for LNB-modification I found some close-by effects like wobbeling.

At some TCXOs the received signals (for example the beacon) became "wided up". But I think this occured because of the jitter (and noise) of some TCXOs.

Another effect occured when I used a "dirty" powersupply for powering up the LNB. A test showed that there is also a big drift in frequency when the voltage drifts. This may have the reason in using very simple series regulator ICs in the LNB.

If we are talking about "wobbeling" I assume a "wobbeling frequency".

What frequency are we talking about ? Some Hz ? Some kHz ?

73s

Armin DF1QE

Nearly all components for building this converter, including all semiconductors, are available at : www.reichelt.de

(and at many other distributors)

73s

Armin DF1QE

I developed and build a very simple converter 739 MHz to 145 MHz with just 3 Transistors and one standard XO.

It works excellent for receiving Oscar100 NB transponder with a 2m RX.

I wrote a complete report and building instruction for it.

You can find it at : https://elektronik-muenster.de…-145-mhz-oldschool-style/

Sorry, german language only.

But there are lots of pictures an shematics also for download so everyone should it find interesting.

In other case "deepl" helps

73s

Armin DF1QE

Take a look here :

https://elektronik-muenster.de/viewtopic.php?f=17&t=11

VY73

Armin DF1QE

Meanwhile I modified several Diavolo Twin LNBs for an external LO input.

I found out that there are at least 3 very different versions of this LNB in the market.

After I wrote a report of my modifications V1 several month ago, I wrote a second one called V2 in which I also show the V3.

You can find them at : https://elektronik-muenster.de/viewforum.php?f=17

German language only, sorry.

But there are many photos, so everyone should understand it.

best 73s

Armin DF1QE

Another possibility is, just to remove the antenna-pins from the PCB and mout a coaxcable instead of it and lead it through the waveguide.

73s

Armin DF1QE

The 2 Diavolo Twin LNBs I modified was bought at Reichelt Elektronik Germany for about 12,- Eur.

@Helmut DL8DAK

Where did you buy yours ?

73s

Armin DF1QE

You can check which pin to use with a simple functiongenerator and a scope :

(no need to put it in the dish)

First of all : Make it an antistatic workplace !

All semiconductors in LNBs are very sensitive !

After removing the crystal,

power up the LNB just by giving around 12 V to one of the F-Connectors.

Take a functiongenerator an set it at the crystalfrequency and an output of about 1 Vss sinewave.

Now connect the functiongenerator via a capacitor of about 1nF to one of the ex x-tal pads.

Now check with a scope the unused pad : There should be a signal, similar to the one you supplied.

If not, exchange the pads and check again.

73s

Armin DF1QE

Quote from DE8MSH

Hallo Armin.

Ich danke Dir für das Projekt. Da ich keine externen Taktgeber habe, werde ich wohl auf eine interne TCXO-Lösung setzen (müssen).

73

Marco

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Hallo Marco !

Einen Vorschlag für einen externen TCXO von mir findest Du unter :

https://elektronik-muenster.de/viewtopic.php?f=17&t=12

Der von mir schon genannte Diavolo Twin + dem indoor TCXO läuft super gut und stabil.

Der Conner Winfield TCXO ist an sich ja schon sehr stabil und wenn man den auch noch ins Shack verlagert ist der fast so gut wie GPS stabil.

Und das Signal ist sehr jitterarm. Daraus resultiren sehr saubere und "unverschmierte" CW uns SSB Signale. Wesentlich besser als alles was aus den meissten digital stabilisierten Oszillatoren rauskommt. (bis auf wenige Ausnahmen)

Ich habe hier einen QO100 Dauerempfänger auf der CW-Bake laufen.

Der ist innerhalb 2 Wochen nur um einzelne Hz gewandert.

VY73

Armin DF1QE

Ich empfehle den Diavolo Twin.

Gibt's aktuell z.B. bei Reichelt für 10,95 Eur.

Sehr stabil arbeitende PLL, sehr guter Signal-Rauschabstand, einfach umzubauen.

Umbaubericht von mir unter :

https://elektronik-muenster.de/viewtopic.php?f=17&t=11

VY73

Armin DF1QE

Take a look at :

Umbau OCTAGON OPTIMA LNB auf TCXO

73s

Armin

Hi Frank !

About the different TCXOs you should read my article :

https://elektronik-muenster.de/viewtopic.php?f=17&t=12

Up to now I did not see any TCXO with a frequency at 25.8 MHz.

And variable control-range of VCTCXOs is several PPM only. (so some Hz)

You can never tune a 25,0 MHz VCTCXO to 25,8 MHz.

73s

Armin

Hello Frank !

At the moment not many news.

As I already wrote, I made a new version with Conner Winfield TCXOs and they work excellent.

Meanwhile the TCXO-Board with the golden DIL-case-TCXOs from china came in and I did a quick test. The result was not that nice. This TCXO seems to deliver much jitter. (as other hams also described) I found out that "ghost signals" appear in the receiving window. They appear every 200 kHz.

I assume that inside this TCXOs actually a PLL is running with a loopfreqency of 512 Hz.

73s

Armin

That really sounds intersting !

Hello Sat Fans !

Meanwhile I updeated my Postings about my "simple indoor TCXO for LNBs"

The shematics and layout files for version 1.1 are availabe now.

You can find them at :

https://elektronik-muenster.de/thread/12-25-27-mhz-indoor-lo-f%C3%BCr-lnbs/

(sorry, german language, you can use deepl.com to translate)

I changed from FOX TCXOs to Conner Winfield TCXOs.

The FOX TCXOs are digitally compensate in 1 Hz steps, which leaded to 390 Hz jumps in the received signals.

Not comfortable at CW or SSB.

The well known Conner Winfield TCXOs are analog compensated and very stable.

In my tests the frquency of my indoor LO moved less than 100 Hz in a period of several days.

73s

Armin DF1QE

If it's a standard PLL LNB this schould work.

All new ones are using one of two common PLL / Mixer IC-Familys.

I modified several LNBs for that.

For Dual LNBs you can find Info about that at :

https://elektronik-muenster.de/forum/viewforum.php?f=17

73's

Armin

Taitien VCTCXO in field tested : Works fine ! No Jumps anymore !

Results at : https://elektronik-muenster.de/viewtopic.php?f=17&t=12

I ordered some Conner-Winfield TCXOs and will test them with my constuction.

On success I will do a PCB redesign with them.

73s

Armin DF1QE