Schematic for PARKSIDE/LIDL satellite finder

[RoGeorge]

Recently orbited around RF topics in general, no idea why (not a ham and quite inexperienced with RF).  I was fooling around this week learning and experimenting with directional couplers, bridges and VSWR-meter, and today seen a satellite finder at LIDL for ~$6.  https://www.lidl.de/p/parkside-satellitenfinder-pssfs-3-a2-mit-akustischem-signal/p100344364



Bought one for the box and for the analog uA-meter alone, hoping maybe for some extra RF goodies, too (on the box it says 950-2300MHz).

I can see inside a 324 opamp, some transistors driving 4 LEDs, and some 4 pins RF parts on the Rx/antenna side.  Searched for a schematic but didn't find any.  It's a simple single-sided PCB, so I assume I'm not the first one thinking to repurpose this for ham bands use. 

Bought the thing hoping to maybe turn it into an analog VSWR-meter like this:
https://www.qrp4u.de/docs/en/swr_meter/index.htm
or into an antenna analyzer by adding an AD9850 module I already have (SPI DAC, 10bits, DDS 1-40MHz).

Anybody happens to have the schematic of the PARKSIDE Satellite Finder, please?

[PA0PBZ]

I would be surprised if there's more than a very crude rf detector in there, can you post a picture of the pcb?

[wasedadoc]

Cannot be that difficult to trace out.  Active filter followed by some sort of thresholder to see if the 22kHz is present or not.  That will drive one pair of LEDs. Another thresholder to detect if it is 13 or 18 Volts coming in.  That will drive the other pair of LEDs.  Rest will be the signal strength meter with the pot in that bit somewhere.

[Kleinstein]

For satelite finding it is not a SWR meter, but just a relative simple amplitude detector. This may be as little as a diode and a few capacitors for the RF part. If they have a LM324 in the circuit anyway, than maybe a little DC gain after that.

[RoGeorge]

Not a SWR, indeed, bought it for the uA-meter and for the enclosure, to add 1-2 toroids inside and make a directional coupler, so to turn it from a level detector into a SWR meter for the free bands under 100MHz.

Tested it with an AWG (max 200MHz), the potentiometer adjusts the sensitivity, the 13V and 18V LEDs are switching at ~16V, less than 1MHz input will also turn on the 22kHz LED, and has a funny buzzer, too.    It starts to buzz at indications bigger than 2 on the galvanometer, and the sound pitch goes up with the RF level.

Also has two BFG590/X (NPN transistors 5GHz) at the antenna input. 

Did some pics, one with a phone screen as backlight underneath the PCB.  The microscope can not zoom-out for more PCB area at once, its minimum magnification is 10x.

[PA0PBZ]

Thanks! Indeed no real tuned circuits. I think the circuit in the last picture (amplitude detector) has to do with the leds, I can't really find an RF detector which I expect somewhere between Q1 and the lm324. Maybe they use Q1 for that?

[wasedadoc]

Signals from the LNB on the dish are in the 950MHz to 2450MHz range.

[RoGeorge]

On a second thought, the pic named amplitude detector might be in fact the 22kHz detector (has a LED to signal the presence of a 22kHz carrier on the cable.  I've read the 22kHz is a signal the set-top box can put in the cable, in order to switch a possible antenna multiplexer (usually located somewhere on the roof, when 2 dishes for 2 different bands are connected to the same set-top box), or to switch between low frequency bands (analog, 0Hz) and high frequency bands (digital, 22kHz on), while the 13/18V is to choose vertical/horizontal polarization for the LNB.

Will try to scribble some schematics.

Just for the docs, the specs for the PSSFS 3 A2 model HG06986B satellite finder:
  - Supply current:  approx. 100mA
  - Frequency range:  950 - 2300MHz
  - Input level min:  68dBuV (-40dBm)  <-  should be for 75\$\Omega\$, doesn't specify in the specs
  - Input level max:  98dBuV (-10dBm)
  - LEDs indicators for:  0Hz, 22kHz, 13V, 18V

[wasedadoc]

Originally the 22kHz was simply on or off to switch bands by changing the Local Oscillator in the LNB between 9.75GHz and 10.6GHz.  Later it was extended into a digital signalling system called DiSEqC. See https://en.wikipedia.org/wiki/DiSEqC for what the various versions can control.

(I think the 33kHz in the post above is a typo.)

[RoGeorge]

Sorry for the back-envelopes, initial interest was mostly in the RF section of the schematic.  Eventually raised the complete schematic.  The uA-meter is a 500uA full scale.  Last of the 4 opamps is unused.

Indeed, Q1, one of the two RF transistors, is used as an amplitude detector.

[viktorwolf]

Pozdrav svima,
pisati ću na Hrvatskom jeziku zbog točnosti, stric google je tu pa se lako prevede.
Prvo hvala kolegi na trudu za skinutu shemu
I ja sam došao na istu ideju, kupio tri kom po 4 €, više vrjedi samo instrument.
Za početak probao sam jedan na bandu 2m/70cn, sa predpojačalom napajanim sa 12 V i usmjerenom VHF/UHF MAXON YAGI antenom, i kao S metar je ok, mjeri dobro dolazni signal od repetitora, također kad uključim mali mobil
ljepo očita signal. Sa malim podešavanjima i zavojnicama moga bi se koristiti i kao grip-dip metar.
Moja ideja je ipak dobar SWR metar za VHF/UHF i to na način:
1.-odpojiti L na ulazu i spojiti na njega vanjski 12 V+ masa-,
2.-napraviti dodatnu strip-line pločicu ili feritni trafo ili coax liniju za POWER i SWR signal sa ispravljanjem socky diodama, trimerima za podešavanje
3.-Preklopnik za PWR1, PWR10, PWR50, SWR, S koji bi vodio signal na ulaz djeljitelja C10, ili C11.

Evo teme za razmišljanje, 73 svima

[RoGeorge]

[machine translated]
Hello everyone,

I'll write in Croatian for accuracy, Uncle Google is there so it's easy to translate. First of all, thank you to my colleague for the effort for the downloaded schematic I came up with the same idea, bought three pieces for 4 €, only the instrument is worth more.

For starters, I tried one on a 2m/70cn band, with a preamplifier powered by 12 V and a directional VHF/UHF MAXON YAGI antenna, and as an S meter it's ok, it measures the incoming signal from the repeater well, also when I turn on the small mobile It reads the signal nicely.

With small adjustments and coils, it could also be used as a grip-dip meter.

My idea is a good SWR meter for VHF/UHF in the following way:
1.-disconnect the L at the input and connect the external 12 V+ ground to it-,
2.-make an additional strip-line board or ferrite transformer or coax line for POWER and SWR signal with rectification with socky diodes, trimmers for adjustment
3.-Switch for PWR1, PWR10, PWR50, SWR, S that would lead the signal to the input of the divider C10, or C11.

Here's a topic for thought, 73 to everyone

Welcome on the forum. 

Please write in English, so everybody can read without spending their time with a translator.

[RoGeorge]

Found a mistake in my drawings:  the potentiometer is 30k\$\Omega\$ linear (B30K), not 10k\$\Omega\$.