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btt

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1. If I understand what you wrote correctly, having to choose between the 780 MHz band OR the 850 MHz band is a non-starter for me. I have systems in both bands near me.
2. The audio out impedance must work with a PC audio in jack, not just for driving earbuds/speaker or again a non-starter for me.
3. Battery is of no use to me. I don't use as a portable.

Looking forward to more details on this design.
Thank you for the feedback. You did read that correctly. The filters allow blocking of cell tower downlinks. The idea is to create an affordable device that monitors a system with subscriber-like RF performance. If enough people see this as a negative, I will change the design. I may offer an option for battery/no battery. Keep an eye on it. You might change your mind after more details emerge.
 

dustinsterk

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From my understanding, Microsoft never did get that driver to work correctly since the standard was released. This is hard to believe since they had the most input to the standard and it is by far the most simple implementation possible. I can confirm that Windows 10 does not work out of the box. There are documented big-endian/little-endian issues with their implementation. The Linux driver has worked for me since 2011/12 when I first implemented the device-side driver on a project. I tried Mac, but I didn't get it to work. I think it did add a network interface, but there was an issue with the IP adress or routing. I will try that again and see if I missed something.

This maybe why, this guy did some sniffing with wireshark and found some errors with the MS implementation: Difference between USB CDC EEM protocol implementations in Win10 (usbnet.sys) and Linux kernel (cdc_eem.c)
 
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epersson

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Good morning, My use case is very limited.
1) Running the Broascastify feed, but if I change the systems monitored that may require both 700 and 800 as different parts of the Broward systems run one or the other.
2) Bluetooth is important for me as I sometimes take it mobile and want to connect to a remote speaker or the cars system and not have more wires.

All that being said, honestly the two P25rx I have are suiting my needs perfectly. So the option of a new one has to be WOW factor to convince my other half I really need another toy.. :)

But regardless, all that have been done to date and sounds like future, fantastic in all respects.
 
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FreqNout

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All that being said, honestly the two P25rx I have are suiting my needs perfectly. So the option of a new one has to be WOW factor
To me it sounds like Todd is looking to bring a 'low cost' p25 rig to market.

If a 'WOW factor' is desired in a new low cost version of the p25rx what is that WOW factor you would like to see keeping in mind the low cost goal?

Post your ideas.
 
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kb8q

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In Michigan, the Michigan Public Safety Communications System (MPSCS) is undergoing a significant expansion of additional frequencies using the 700 MHz band. A mix of both 700 and 800 MHz bands is now becoming the norm. All 83 Michigan counties use MPSCS for public safety and partner communications. State, federal and tribal departments use MPSCS in all 83 counties. All but 7 of the 83 counties use MPSCS for local public safety and government. More than half of the counties not using MPSCS for local communications are now in transition to MPSCS including the county where I live (Oakland). Oakland County is retiring an OpenSky system that's over 15 years old. The Oakland Co simulcast will be the first phase 2 system on MPSCS.

Michigan has 208 sites on MPSCS and rapidly adding a mix of 700/800 frequencies to the sites. I would be very unlikely to use a single band receiver here.

I'm currently using 3 P25RX-II receivers 24/7/365 and I have 2 original P25RX receivers sidelined until the software catches up.

These are my primary base receivers.

James
 
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epersson

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To me it sounds like Todd is looking to bring a 'low cost' p25 rig to market.

If a 'WOW factor' is desired in a new low cost version of the p25rx what is that WOW factor you would like to see keeping in mind the low cost goal?

Post your ideas.
I get the low cost and am all for it, I don't know what the WOW would be. Better scanning capability maybe, but I have a sds100 so that suits my needs on that as well.. But to me having 2 that suit my needs is enough and I think they are great...
 

FreqNout

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Right now, every p25rx model has one receiver.

A new single band low cost version could allow for a second rx to be added to current models.. with the right software and connections.

The 2nd rx could open up diversity and other features. My point is, a single band version could enhance your current model.

Edit: Stack 2 or 3 single band versions all working in combo with software would also open up diversity rx and other features.
 
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btt

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I've received a couple of email regarding the 700/800 filters as well. I hear you guys. The ultra-selective front-end band pass filtering isn't going to work for many users. I will have an option for bypassing the front-end filtering. The reason I'm going down this path of something different from the P25RX-II is to reduce cost and also to add alternative features. I still have parts to build a few more P25RX-II units. This new development is something different. There is a Wow factor that I haven't mentioned yet. I'm saving that for later. There is one feature I meant to add to the earlier list, but forgot. It will have a micro SD card slot available. It should be useful for logging, recording audio, recording diagnostic network information, etc.
 

btt

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Right now, every p25rx model has one receiver.

A new single band low cost version could allow for a second rx to be added to current models.. with the right software and connections.

The 2nd rx could open up diversity and other features. My point is, a single band version could enhance your current model.

Edit: Stack 2 or 3 single band versions all working in combo with software would also open up diversity rx and other features.
Yes, I believe the network interface / throughput will open up the possibility for some interesting multi-receiver applications.
 

kb8q

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A battery powered receiver with a micro SD card option would make a great P25 receiver for portable use. I'd add one of those in 2 minutes if it had both 700/800. :)

An iPhone app (with subscription) to control the receiver would be a 30 sec purchase decision LOL

James
 
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rr60

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Todd…as a result of frequency congestion here in the NY NJ metropolitan areas, often 700 & 800 MHZ frequencies are both used within the same P25 PII system. This trend will likely continue and even expand as older 800 MHZ systems are retired. Did I understand you to say one or the other bands but not both?

“Options for a single P25 band with a very good front-end pre-selection option before the LNA. The first run will support either the 780 MHz or the 850 MHz band. I will share frequency response of the band pass filters later. They are very good and will eliminate cell phone downlinks from reaching the front-end. I plan on having other options for 450-470 MHz and VHF option at a later date. I may also offer an option for a filter bypass so you can tune the entire range with your own external filters.”
 
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FreqNout

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The reason I'm going down this path of something different from the P25RX-II is to reduce cost and also to add alternative features.
This is the key point. I do not see this new design as replacing the p25rx. It is adding to the current line up.

Yes, I believe the network interface / throughput will open up the possibility for some interesting multi-receiver applications.
Great news here folks. Right now a single rx can only listen to one Freq at a time. It can not listen to a control channel once it moves to a traffic channel.

When on traffic, things are still happening on the control channel you are missing.

With a 2nd rx, you could have one dedicated to control and the other to traffic. Just one example of how a 2nd or 3rd single band rx may enhance your current model with the right software development.

Edit: With one rx, you can also not listen to two or three traffic channels at the same time. (with TDMA you could listen to both slots, but my point remains)
 
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kb8q

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This is the key point. I do not see this new design as replacing the p25rx. It is adding to the current line up.


Great news here folks. Right now a single rx can only listen to one Freq at a time. It can not listen to a control channel once it moves to a traffic channel.

When on traffic, things are still happening on the control channel you are missing.

With a 2nd rx, you could have one dedicated to control and the other to traffic. Just one example of how a 2nd or 3rd single band rx may enhance your current model with the right software development.

Edit: With one rx, you can also not listen to two or three traffic channels at the same time. (with TDMA you could listen to both slots, but my point remains)

Good point you're making. What you're describing is related to my use of 3 receivers tracking multiple simulcast sites and different talk groups. When the crap hits the fan, I can usually see it in the TG Log scroll and use a dedicated receiver to monitor the action. If I miss something, I can go back to the TG audio and listen.
 
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FreqNout

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Good point you're making. What you're describing is related to my use of 3 receivers tracking multiple simulcast sites and different talk groups.
Thank you. I am trying to bring some positive points and think out of the box.

In my opinion, networking or combining 2 or 3 of this new design single rx would allow for better performance features by having multiple rx working together as a system. That is the difference between having 2 single p25rx models and this multiple rx design concept I am getting at here.
 

btt

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Todd…as a result of frequency congestion here in the NY NJ metropolitan areas, often 700 & 800 MHZ frequencies are both used within the same P25 PII system. This trend will likely continue and even expand as older 800 MHZ systems are retired. Did I understand you to say one or the other bands but not both?

“Options for a single P25 band with a very good front-end pre-selection option before the LNA. The first run will support either the 780 MHz or the 850 MHz band. I will share frequency response of the band pass filters later. They are very good and will eliminate cell phone downlinks from reaching the front-end. I plan on having other options for 450-470 MHz and VHF option at a later date. I may also offer an option for a filter bypass so you can tune the entire range with your own external filters.”
Yes, you understand correctly. As I mentioned a couple of posts back, I will add an option to purchase with the filter bypassed. (allow external filtering to be used).
 

dustinsterk

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@btt sorry for my limited knowledge/vocab, does "filter bypassing" mean that this new device is hardware capable to do everything the P25RX-II units can do with old analogue systems and new digital trunked systems but you will make this a software "pay for feature" to unlock?
 

btt

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@btt sorry for my limited knowledge/vocab, does "filter bypassing" mean that this new device is hardware capable to do everything the P25RX-II units can do with old analogue systems and new digital trunked systems but you will make this a software "pay for feature" to unlock?
My thought was to present a new device (based on the only MCU still available) that has the feature of a highly selective front-end option to match the highly selective final IF filter. A "professional P25 receiver". A low-cost P25 device that provides the performance of a subscriber unit. You guys want to know the "Wow" factor? Ok, I give. The size of the device without the battery option would be approximately 2.5 x 0.75 x 0.5 inches. The battery option would add the size of a rechargeable AA sized lithium-ion battery. I was targeting somewhere between $199 and $250 for retail. There is no room for more hardware options in order to achieve what I was going for. I probably need to reevaluate if this is the wrong idea. It may be that I should rethink the P25RX design and fit the new MCU in there instead. Either way I end up going with this, the time spent working on getting the new MCU up and running shouldn't end up being a waste of time.
 
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