Posts by DL5CN

Hallo,
there are two types of LNBs tested here. OCTAGON OTLSO which has two indepedend LOs and Rocket LNBs VENTON and Red Eagle. Both work with 7,5 Volts. The Rockets can be combined now even with a patch or a helix.

Reducing the diameter of the LNB-Waveguide and increasing the copper tube a bit it can be sticked together smoothly. I prefer SMA-Connectors to feed the S-Band-Antennas to avoid mechanical collision with the LNBs and the mounting clamp. That's why the backplane of the helix shows a corner connector. At the front of the tubes is a small ring of brass to fix the lense again.

With the lenses I always expected more gain. It was'nt seen clearly. Looking to a wide spectrum, the difference between transponder noise and background increases. Probably the background noise gathering beside the dish goes dowwn with a smaller radiation pattern?

This is a wide spectrum without the lense.

Here is the same spectrum using the rocket lense. The reduced background noise can be seen in the waterfall also.

Looking to the Datasheet of the TFF1017 the question appeared, woud it be possible to modify the loop filter. The result could be improved phase noise of the LOs.

Of cours it is a very theoretical question and the transponder noise can be seen clearly above the LNBs noise even with a "normal" dish and the lense. SMD components are fare away from easy changing and experiments. But, may be....

73s
Andreas

Hallo,

I don't see the need to feed LNBs with 12V when only one polarisation is used. It can be reduced until the drop voltage of the regulator is reached. This helps to avoid unnecessary dissipation.

73s
Andreas

Hallo,

here are some hints for modification.

My LNB modification nightmare...

73s
Andreas

Hallo,

buying one piece of a 2,4 GHz-circulator in Asia means approx. 70 $ shipping and 25 $ money transfer.
It seems to be not in the amateurs budget. One possible way could be sharing this when ordering more pieces....?

What a pity.
73s
Andreas

Unfortunately at mouser not in stock. Until now there is no response from UIY listed at ALIBABA.
Not sure if they will sell me some parts.

Hallo Heiner,
thanks a lot. Didn't find this although some internet search.
Below one Euro, unbelievable.
I will see what happens.

Thanks again
73s
Andreas

Hallo,

I am looking for a suitable 2,4 GHz circulator. At the output of the amplifier board there is a whole but the Chinese guys didn't place it.

The amplifier works well, I am going to play with more patches and helix antennas and different cables also. Feeling better with an independent load....

Any hints are welcome.
Thanks in advance.
73s
Andreas

DL9SEC
The output of the TCXO is connected to Pin 11 of the TFF1017. Is there any recommendation, 11 or 12? I didn't care, it works.

Interesting, both TCXOs, I assembled in two LNBs give an endfrequency shift of around 3 KHz. Probably it is useful to put an adjusting voltage of 1,5 Volts to AFC-Pin 1 of the TCXO.
My goal was to test the modification of the LNBs. At least, a modified LNB is ok to play around with, doing demonstrations using scanners, little dishes and so on...

Because of the internal 5V, there is no need to operate the LNBs with 12V. If vertical polarisation is ok, reduce supply to avoid dissipation and drift.

73s

Andreas

Hallo,

I just modified two Rocket LNBs. Carefully cut the Silicon to remove the board. The only pin to resolder is the output on the right side. Because of leadfree soldering it is not easy. Don't worry losing the crystal pads. They are not needed furthermore...

Remove the crystal on the backside and place the TCXO 25 MHz. The new Chip is upside down with double sided adhesive tape and connected twice to GND. The output is connectet to one former crystal-via. Remove the capacities from Pins 11 and 12 of the TFF1017 Mixer/PLL. Connect Vcc somewhere to the +5V Bus (Pin 16 of the Mixer). The +5V is generated by the detector chip ZXNB4202. Take care not to squeeze the +5V red wire when closing the case.

Enjoy the better accuracy. Don't mix it with the drift. This is done with SDR Console.

73s

Andreas

Hallo,

to say it more clearly, don't care about the beacons and the user signals to design a receiving system.
Take care about getting the transponder noise above the system noise of the LNB.
This is the only criteria.

By the way, it is important to have the right radiation pattern of the LNB corresponding to the
f/D-ratio of the dish. Commercial LNBs and dishes should work. Adding a patch to a LNB the feed is no longer a horn but an open waveguide. With a rocket-lense to my open tube nothing changed.
This confuses me a bit. Further research has to be done.

73s
Andreas

Guys,

the noise figure of the receiver (system noise) is defined only by the LNB's noise not by the gain. The dish must be large enough to see the noise of the transponder. This can easily be checked by turning the dish to the cold sky. If the noise increases when pointing the dish back to the satellite, all is fine. Reducing the transponder gain requires larger receiving antennas but gives more dynamic range.

@HB9LSV, the signal to noise ratio at the transponder output depends on your uplink power.
It is helpful to operate duplex and watch the output spectrum.

Take care not to overdrive the receiver behind the LNB. Use an attenuator. No matter, where the absolut level of the received signals is. The new S-Meter of the 3.0.13-release of the SDR-Console can show signal to noise ratios which allows useful reports.
73s
Andreas

Hallo,

the text from W1GHZ is interesting. 21,4 dB directivity at 2,4 GHz isn't too much.
I own a chinese directional coupler. But I think, a well designed bridge will perform better. R&S and Wiltron can do. May be a strictly coax design with good grounded semirigid cables and the right balun will give enough performance. The only way to find it out is doing....

73s
Andreas

Hallo,

in combination with a S-Band-dummy load, the return loss at 2,4 GHz is interesting. I am looking for a wide band wheatstone bridge. The usual bridges don't work exactly at 2,4 GHz because of incorrect impedance situations and unsuitable baluns. Commercial bridges don't fit with the amateur budget. A directional coupler gives up to 30 dB dynamic range between open and load, a resistive bridge probably would perform better, I think.
Any ideas ? Thanks in advance.

73s
Andreas

HAMRADIO

Hallo,

thanks to all which were involved in organistion, preparation, presentation and much more details. It was a pleasure to shake hands, and having talks to satellite enhusiasts.

Unfortunately I had another appointment while the dinner took place.
At least, it seems there are many interested Oms and we should think about help them in any way.

Again, many thanks

73s
Andreas

Below the Minimum

more reduction isn't useful.
The CW-Beacon is still there, the LNB is modified with a TXCO to hit the frequency with the scanner easily.

No more than just a joke but it works.
Have save trips to the HAMRADIO.

73s
Andreas

Hallo,
good idea to organize a meeting and events.
Yes, I will be there, not sure if I will take part on meeting and dinner because of some other dates. To shake hands and say hallo at the AMSAT-Desk would be a pleasure of course.
Wish you all save trips.
73s

Andreas

Minimize the Mini-System - Searching the Satellite

Hallo,

another idea to reduce. The combination of LNB with horn and a scanner was used to check a location because of trees and buildings which prevent receiving.

The CW-Beacon helps to find a gap.

73s
Andreas

Hallo,
the modification works.

First grafic shows the 1W PA unmodified and another wide band amp which is ok. S21 is measured against 19 dB attenuators.

The second grafic shows the modified 1W PA. The gain maximum is shifted to S-Band.

Don't be confused about the ripple. It is amateur equipment.

73s
Andreas

Hallo,

very interesting to me also. I own this board and can confirm no gain at 2,4 GHz. Maximum is about 1 GHz. The modification is similar to the datasheet. So, thanks to DK5DN for publishing, I will try it and report. Last question, what is about the feed choke.

I think it is unmodified yet?

73s
Andreas

Hallo,

the problem is fixed with a friends help. Thanks to him.
Pluto works together with a standalone PC without a router.
This is the only change in the config. txt.

[USB_ETHERNET]

ipaddr_eth = 192.168.1.205

netmask_eth = 255.255.255.0

The IP is just an example. Assign a fixed IP in the host with the same subdomain and subnetmask.

Additional type Pluto's IP in the standard gateway mask.

73s
Andreas