1. Chinese version by TAI-SAW Technology Co. - Price at Ali Express on-line Marketplace = $13 for a lot of 5 pieces ($2.60 each)
  2. USA version by TriQuint Semiconductor - Price at at TriQuint on-line Store = $32 each piece

Specifications (pdf)

  1. Chinese (TAI-SAW) Filter:

  2. USA (TriQuint) Filter:

Insertion Loss
Chinese TAI-SAW 1075 to 1105 Mhz = 2.3 dB typical, 3.0 dB max
USA TriQuint 1085 to 1095 Mhz = 2.6 dB typical, 4 dB max





This filter(TA1090EC), or something very similar, is used in the miniADSB and the Mode S Beast (and possibly the radarcape). … PIDX=59245

Have seen these by chance?

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.

The criteria is not SAW, it is COST.

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. :slight_smile:

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.

bob k6rtm

Unfortunately, the only piece of test equipment I have is this one

The other piece of equipment which I purchased last year was a noise generator, but it fried itself due to overheating within a week of purchase. :frowning:

But I have firm plans to purchase Keysight’s PNA/VNA when I win a lottery :slight_smile:
$ 70,750

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 :open_mouth: 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.

Good luck Dave!

May be these diagrams will help. Terminal B is input, E is output. Terminals A, C, D & F are ground.

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 :wink:

@abcd567 - by the time there is solder on the “bug”, it is impossible to see which is pin no 1.

A photo from my camera of the final piece.

The SAW filter naked.

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 :open_mouth:

I’ll put it in the live system tomorrow.

{Edit} added the photos from my camera

After reading your story :open_mouth: , I am considering to sell the 5 pieces of TAI-SAW filter when I receive these.

If the insertion loss of the SAW filter is 2 to 3db, what does it bring to the party?

My message rate drops from 1650/sec to 1500/sec and aircraft tracked from 200 to 180 when it is inserted into the feed line.

Should I be looking for a reduction in noise?

Admittedly I’ve only had it in line for less than an hour.

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.

Some measurements. Look at the db scale on the left. The FA filter removes stuff around 820Mhz but the SAW filter removes both 820Mhz and 950Mhz

  1. No filters

  2. With FA filter

  3. with SAW filter

Some hints on how to make the job easier–

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.

bob k6rtm

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.

The drawings and diagrams show that the input side is the middle pad on the side with the long ground pad.

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

and a head magnifier like this

Then you’re gonna need one of these

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.

I’ve made a second one of these following Bob’s instructions. Much easier the second time, thanks Bob :smiley:

I use as a spectrum analyser. The filter takes out 850Mhz and 930Mhz as above. This one does pass 1090Mhz unlike the first one I made. I use

Putting the filter in line, the messages/sec and aircraft numbers drop by 20 - 30%.

Anyone else put one of these in their system?

[Edit] Is it necessary to connect all 4 Grounds? Would make life easier to just do one.

Connect all the grounds, and connect them with short wires! The RF performance relies on all the ground pins being ground.

From your description, you popped your first SAW, and the second one is performing nominally.

These SAWs have an insertion loss of around 2.4 - 2.8 dB, which can be quite noticeable. If you don’t have your SDR gain maxed out, crank it up a bit!

bob k6rtm

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.

73 Igor AK4T