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SAW Filter limitations
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bhhoyer@...
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. Thanks, Bryan K7UDR
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Andre <pe1rdw@...>
op 17-03-14 16:50, bhhoyer@...
schreef:
All 9k6 AX.25 channels in the Netherlands are between 430.400 and 431.025 and german duplex ax.25 channels have input between 430.400 and 430.5875 and output between 439.800 and 439.9875. So there would be some limitation if the 19 MHz SAW filter is used in this configuration. 73 de Andre PE1RDW
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John Ronan <jpronans@...>
On 17/03/14 16:05, Andre wrote:
It is a similar situation here in Ireland, and I guess throughout all of IARU Region 1. Regards John EI7IG
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bhhoyer@...
We could do a UDRX-430.
there is a 20MHz 431 Filter (421-441). Takes care of the bottom of the US Band as well It's in a different package (of course) so we'd end up building 440s in mass then reworking the filters. Might be a small upcharge of 20-25 USD Bryan K7UDR
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Steve <yahoo-udr@...>
How does this discussion affect digital voice (DV) and digital data (DD) modes in the USA? Do DV repeater operators always enable DD capability? Or, are there separate DD repeaters? Do the repeater operators follow the ARRL or other local band plans?
toggle quoted messageShow quoted text
Steve
---------- Original Message ----------
[ Sent by bhhoyer@... at 03/17/2014 10:27 AM ]
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"John D. Hays" <john@...>
Hi Steve, Currently, the only DD network implementation is 128 kbps on 23 cm from Icom (ID-1 terminals, and RP-2D access point) and is half duplex (no repeaters). The UDRX will change this, as it will permit DD at data rates from 4.8k to the top data rate (estimated to reach 100k+) of the radio using 70cm band(s). In the US we are limited to a 100 kHz channel.
In the Icom architecture DD is always a separate band module. With the UDRX we have the potential to run both DD and DV on the same module (at 4800bps). It may also be possible to build a repeater having 100 kHz channels using the UDRX. (Either bonding 4 adjacent 25 kHz channels at 440 band or using a split in the 430 band.)
DV (which includes a slow data subchannel) is typically simplex, repeated, or simplex access point (hotspot). This is a 6.25 kHz channel (or repeater pair). In the US DV repeaters usually are following the local band plan. Here in Western Washington (State) we use high in/low out for our repeater pairs and the bandplan has 12.5kHz and 25kHz pairs. John D. Hays K7VE PO Box 1223, Edmonds, WA 98020-1223   
On Mon, Mar 17, 2014 at 11:01 AM, Steve <yahoo-udr@...> wrote:
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"Michael E Fox - N6MEF" <n6mef@...>
In Northern California, packet and other data activity is in the 433, 434 and 438 range, with wideband channels in the upper of those two ranges. This is where we would intend to use the device.
http://ncpa.n0ary.org/ncpabandplan.html
Michael N6MEF
From: UniversalDigitalRadio@... [mailto:UniversalDigitalRadio@...] On Behalf Of bhhoyer@...
Sent: Monday, March 17, 2014 10:27 AM To: UniversalDigitalRadio@... Subject: Re: [UniversalDigitalRadio] SAW Filter limitations
We could do a UDRX-430.
there is a 20MHz 431 Filter (421-441). Takes care of the bottom of the US Band as well
It's in a different package (of course) so we'd end up building 440s in mass then reworking the filters.
Might be a small upcharge of 20-25 USD
Bryan K7UDR
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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.
Thanks, Steve
On Mon, Mar 17, 2014 at 8:50 AM, <bhhoyer@...> wrote:
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"Michael E Fox - N6MEF" <n6mef@...>
Also, I’m an “appliance operator” so I don’t understand the purpose of the
filter. But I wonder why the radio would have a limitation that other amateur radios in the 440 band don’t have. Is this limitation necessary? Our existing 440 radios are supplemented with cavity filters at sites where that is needed, just like any radio would be expected to have. One site, in particular, will probably require the two port version so an isolator can also be used, just like any repeater would be expected to use. This is required regardless of how well the radio rejects out-of-band stuff because we must operate near (physically and frequency-wise) other amateur radios. Michael N6MEF In Northern California, packet and other data activity is in the 433, 434 and 438 range, with wideband channels in the upper of those two ranges. This is where we would intend to use the device. http://ncpa.n0ary.org/ncpabandplan.html Michael N6MEF From: UniversalDigitalRadio@... [mailto:UniversalDigitalRadio@...] On Behalf Of bhhoyer@... Sent: Monday, March 17, 2014 10:27 AM To: UniversalDigitalRadio@... Subject: Re: [UniversalDigitalRadio] SAW Filter limitations We could do a UDRX-430. there is a 20MHz 431 Filter (421-441). Takes care of the bottom of the US Band as well It's in a different package (of course) so we'd end up building 440s in mass then reworking the filters. Might be a small upcharge of 20-25 USD Bryan K7UDR
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bhhoyer@...
The filter is required to suppress carrier feedthru on the TX side in the 350-380 range (Fc-IF). On the receive side it's a nice to have.
We are working towards commercial certification, so some of our internal design goals are tighter than what is typically found in Ham gear.
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bhhoyer@...
Thanks to all who contributed.
We have a couple of inquiries in for custom filters, the NRE looks reasonable. In the mean time we'll move forward with the current design and plan on a UDRX-430 for region 1 and 3. Cheer, Bryan K7UDR
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kdcarlso@...
Is it possible to use two narrower filters switched for the high and low end of the band?
Dave KA2OQZ
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marklfriedlander@...
John,
I have a question in connection with your comment, "Currently, the only DD network implementation is 128 kbps on 23 cm from Icom (ID-1 terminals, and RP-2D access point) and is half duplex (no repeaters). The UDRX will change this, as it will permit DD at data rates from 4.8k to the top data rate (estimated to reach 100k+) of the radio using 70cm band(s). In the US we are limited to a 100 kHz channel." Will the DD data rate be user configurable? If so, in what increments? Thanks & 73 Mark KV4I
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