Looking forward to the filter! Thanks for making this available at such a reasonable price!
While the Amazon page has some response plots, I don’t like them. The -3dB point should be measured from the bandpass filter center. This is about -1.5dB, the insertion loss. The bandpass corners are -3dB from that point, the insertion loss, or around -4.5dB, not the -3dB points chosen and shown.
A simple thought experiment – if the filter had an insertion loss of 8dB, would you look for points that were at -3dB? Nope, because you wouldn’t find any, at leas not near the bandpass center. You’d look for the -11dB points, 3dB down from the (insertion loss) center frequency.
In remarks to Peter, I posited that a bandpass filter for ADS-B use doesn’t need as steep a low-pass skirt above 1100 MHz, as there isn’t much commercial stuff (now at least) until we get to around 1800 MHz. I’ve got a book around here somewhere (in storage in the garage?) that talks about bandpass filters with asymmetrical response. Yeah, ask most folks to design such a beast and they will probably throw things at you until you go away. You can do it as the convolution of separate high pass and low pass sections. The relaxed low-pass skirt should result in a lower insertion loss (my gut is telling me – although it just might want lunch, and it was a while since I did that stuff in detail)…
HABamp put’s the filter after the LNA - perhaps try both before and after - see what works best.
Before if your cell tower would saturate the LNA
After if you do have a cell tower problem, it doesm’t saturate the LNA and you don’t want to reduce the signal into the LNA by putting the filter first.
Most PiAware users are not radio amateurs, the whole set up runs using a cheap computer, a cheap dongle (which has a 75 Ohm input), uses a 75 Ohm downlead and possibly 75 Ohm satellite amplifier and a 75 Ohm power injector all connected with ‘F’ connectors.
Maybe there should a second item on the filter sales site that includes SMA - ‘F’ adaptors. (M - F and F - M)
I ordered two filters on Monday morning (in stock status at that time) with 2-day Prime shipping. The order still has not shipped yet. However, the order is still showing a delivery of Friday, which was the original delivery day shown on Monday.
Ordered on Monday using Amazon Prime says delivery will be on Friday ??? Checked just now 12:34pm on Thursday Item has not shipped yet … Claimed receive date is Friday 8/20/2015 …
the item was in Stock when I ordered it… I am going away on vacation Saturday what is going on ???
Me: Strange order status. Ordered on Monday…not shipped? What’s happening to Amazon?
Vignesh: Hello, my name is Vignesh. I’m here to help you today.
I’m really sorry about that.
May I have the order number please?
Me: Order #
xxx=xxxxxxxxxxxxx
Vignesh: Thansk for the order number.
Let me check that for you.
Thanks for waiting.
I’ve checked the availability for “Temporarily out of stock”, and can confirm that it’s now back-ordered on our website. I’m sorry about this delay–we certainly didn’t expect this would happen
I want to make sure your order gets to you faster once we have stock. To help make up for the delay, I’ve upgraded the shipping method to one day at no additional cost.
Me: I ordered it the same day it was made available on the site.
I was charged for it.
Vignesh: I do understand your concern.
Me: This makes me nervous. Several damaged shipments, now this.
Vignesh: I’m sorry the order will be charged only when the items ships.
I see that as soon as the item is available the package will be delivered to you.
Me: ok.
Not good. Will escalate.
Strange. In stock here out of stock there. I probably ordered one of the first 10 or 15 when available.
EDIT: Just to be clear, I don’t care if it gets here tomorrow or Saturday. I’ve never seen this strange Amazon shipping thing going on. No rap on FA - all good.
Well, it’s Friday and my Amazon filter order still has not shipped, but the order is still showing it will be delivered by end of today. Maybe it is coming via same-day Drone delivery?
Just in from amazon. These must be a scalding hot commodity!
Hello SCOTT x. xxx xxxxxxxx,
We’re sorry to inform you that there is a delay in shipping your order. The new delivery date is indicated below. We’ll send a confirmation when your item ships. We apologize for the inconvenience.
Details
Order #xxx-xxxxxxx-xxxxx
Placed on Monday, August 17, 2015
New estimated delivery date:
Wednesday, August 26, 2015
Ship to:
Scott xxx xxxxxxxx
x xxxxx Ave…
ADS-B 1090MHz Band-pass SMA Filter
Sold by FlightAware
If your shipment arrives too late, you may refuse delivery or return it for a refund.
Ordered w/in an hour of dbaker’s posting on Monday. 2 day shipping morphed to today (8/21) Today just morphed to 8/26.
DBaker, you might want to asked them why the orders got ‘Amazonized’. They don’t seem to explain it from this end. Thanks for putting them out there, whenever they arrive
Update: Called AZon. They said there was a problem processing the xact thru ‘your bank’. I advised them that was odd, since this was the only of several this week to have the problem - that it was paid via AMEX (so much for their script). They upgraded the shipping to 1 day for $7.98 which they said they will credit to my account when it ships for deliver 8/24. We shall see. shock:
Amazon screws up all the time. Once, they sent me a used/returned item. Inside the box, had the personal information of the person that returned it. Every couple months, they mess up. You can often get a discount on your next order, or get free overnight shipping.
They upgraded the shipping to one day for this item. They must have 98% discount pricing at UPS. Imagine the volume of stuff that goes through there. Any complaint at all will get you a replacement shipped next day (almost).
With the bad press re: Bezos and the beatings, etc. I imagine they are looking to gloss it over and move on.
