Re: SAW Filter limitations

Steve Stroh N8GNJ <steve.n8gnj@...>

This view is probably heretical, but here goes.

The US band plan is largely an accident of a lot of spectrum chasing a small use base, adopted in a very different time, assuming very different technology. Thus, allocation of multiple 6 MHz channels that go unused in most of the US.

And, of course, Line A, which I seem to be forever cursed to live North of... in my latest location, less than a few miles, which rules out 420-430 in parts of the US.

And in a few really rare locations like San Diego and Atlanta, interference from our US Government spectrum landlords.

So, maximum spectrum flexibility within 420 - 450 would be best.

My point is to assume very little about historical uses of 420-450 MHz, especially given that 100 KHz channels will be used - I think it's safe to assume that there will be demand in much of the US (South of Line A) that will want to be using 420-430 MHz, so plan on that variant of the UDRX.



On Mon, Mar 17, 2014 at 8:50 AM, <bhhoyer@...> wrote:

The UDR has a SAW Filter in both the transmit and receive paths. We are currently using a 440MHz filter with a 19MHz BW, meaning we are 3db down at 430.5MHz and 449.5MHz.

I have been searching for 20MHz filters and have found no reasonable cost solutions. I will be traveling to China later this year to look into the cost (MOQ really) of having SAW filters made to our specification.

Looking at the ARRL BandPlan for 70cm, ATV is up to 432 and the top of the band is for Voice repeaters. Many countries only go up to 440.

The question for the group is, how does this affect your planned deployment? Is it a real issue for production.

Bryan K7UDR

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