Not sure of the application, judging from another thread you maybe looking to modify an existing dongle, in which case this probably wouldn’t work without getting creative. .59db insertion (@1090Mhz) & 1.09 VSWR along with a relatively sharp rollout makes these great contenders. EDIT: Just noticed that you maybe looking strictly for SAW - in which case this wouldn’t fit the bill.
To keep the cost of ProStick reasonably low, the Chinese SAW filter is most practical solution. This filter is not as good as mini-circuit’s filter, but its price is substantially lower than mini-circuit filter’s price. I purchased a lot of 5 TA1090EC filters for $13 ($2.60 per piece) in retail from Ali Express, and awaiting delivery. It seems the wind is not favorable, that is why Chinese sail boat is taking too long to arrive.
Those Chinese SAW filters come with a pretty picture – I’d like to see what one actually looks like on a network analyzer, and also do a unit-to-unit comparison to see how close the different peas from the pod are.
I bought 4 of these when PeterH did a bulk buy last year. I messed about trying to solder one but failed miserably. This thread prompted me to have another go.
I’ve now got 5 of the 6 legs soldered but I can’t see which is Pin1 anymore Does it just not work if connected wrongly or will it be damaged?
I’ll post pictures once I get pin 6 attached.
[Edit] forgot to say I’m mounting it “dead bug” style.
Several things you need before starting this challenge:
at least 5 hands to hold all the pieces
2 of the hands should be quite small and belong to a surgeon
the eyes of an eagle to see the contact patches
the patience of a saint
I have none of these so don’t critisize my soldering
@abcd567 - by the time there is solder on the “bug”, it is impossible to see which is pin no 1.
I have put it on test with rtl_panorama. It doesn’t seem to matter which way round it is connected. Maybe this is because I’ve fried the internals with the solder? It certainly removes frequencies at 850Mhz and 950Mhz but also at 1090Mhz
Whether the insertion loss is worth it will depend on the RF environment near you. If you are getting strong local off-band signals that are interfering with ads-b reception then the insertion loss should be a small consideration in return for improving the signal to noise ratio on 1090MHz. If you are seeing a loss in performance with the filter in line, then it’s probably not worth it however. A filter is only any use if there is actually something that needs filtering.
You can run rtl_power to get an indication of what signals the filter is affecting. I get much worse performance without a filter, be it the flightaware one or a satellite diplexer acting as a high pass filter. Both give similar performance, so they are obviously both removing whatever is overloading the dongle effectively.
You still need good hands and good eyes, but an illuminated magnifier helps
A temperature controlled soldering iron with a good, clean, small tip is a must
30 gauge solid wire (such as wire-wrap wire), available pre-stripped
a small sharp blade such a hobby knife (I use a #11 scalpel, replaceable blades)
double-sided tape and a scrap of pcb material
The input and output connections are seemingly the hardest, but there’s a trick to make it easier (well, a little easier)
Secure the SAW upside down to the pcb material using double-sided tape
take a 1 - 2 inch piece of bare 30 gauge wire and solder it across the input and output pins, leaving at least half an inch hanging off the side of the chip.
A way to make this easier, and to insure you work quickly is to use about a 3 inch piece of wire. Hold it down to the pcb in place across the SAW with two fingers of one hand, say your index and middle fingers. Place a small amount of solder on the soldering iron tip and tack the wire to the SAW. It won’t hurt that much.
When both input and output are soldered (work quickly, please), use the hobby knife to cut the part of the wire shorting input and output
Do the same thing to solder a piece of bare wire across the ground pins on either side of the input and output wires
Now that you’ve got your wires attached to the SAW, you can use the tip of the hobby knife to peel it from the pcb, and then place it on your target board.
Solder the ground wires first. Keep the length of the wire between the chip and the board short, but don’t get overly concerned about a fraction of a mm.
Solder the input and output wires last, putting the edge of the hobby knife across the wire at the SAW to keep it in place in case the solder decides to flow.
Thanks Bob, some useful hints for when I do my next one.
Does the SAW filter work both ways round? I’ve tried it with the antenna connected to both the input and the output but can’t see any difference in signal. As I explained above, I have no idea which is pin1 so don’t know the orientation of the chip.
Bob’s directions are the most sane. Really, without a rework station and fine tip adjustable iron, working with these components is very difficult if not nearly impossible to do successfully.
I would add at minimum a set of Helping Hands of your choice, these seem OK amzn.com/B008VO7H9E
Unfortunately, working with SMD components for a one-off project is not very cost effective in this case unless you plan to do mass production of filter mods.
That said, once you get the hang of it, using Bob’s method, you could probably knock out several of these once you get the hang of it, especially if you can figure out how to make a sort of jig to hold the thing in place for the initial tacking.
It looks like those notches might be your friends if you are creative with tweezers and the Helping Hands.
Second day of testing so far so good.
This filter worked for me.
I also used the “dead bug” design.
With some(little) experience it is easy enough to solder all these pins.
The RF environment is more or less quiet in my location but I wanted to get rid of my own HAM radio transmission RFI as it dropped significantly message rate.
Now I should say filter did the trick - no message drop when my station is on air.
The filter did introduce some insertion losses, so I had to increase gain to max (-10 vs 49).
But I have a home made SPF5043Z LNA in the attic around 13db gain (ANT is 1/4 wave spider).
So, filter is behind the LNA…
I think without LNA the insertion losses effects would have been more noticeable though.
Does it just not work if connected wrongly or will it be damaged?
