P25RX-II Can one use a P25RX-II as a digital decoder using a 10.7 IF input signal?

wb4sqi

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Many Icom R8600 owners lament the lack of DMR along with other modes that are popular with the AOR receiver crowd.

Can a P25RX be used with the R8600 10.7 IF to decode DMR and NXDN?

Yeah, I know this seems redundant but no more so than using an AOR DV1 bolted to the R8600 IF signal, which some users are doing. Please, no negative comments, those have been covered elsewhere.

If this is possible it offers a lower cost solution to those wanting DMR. Ideally if the P25 offered Tetra decoding the Euro crowd would beat a path to Todd's door.
 

btt

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That is correct. You would need to upconvert the 10.7 MHz (external LO + Mixer) in order to use with the P25RX receivers.
 

wb4sqi

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Slipped my mind about the P25RX frequency coverages. Not being the engineering type, is this a complex procedure?
 

wb4sqi

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Nooelec sells Ham It Up 125 MHz upconverters for less than $60. That gets you to 135.7 MHz.
Just be make sure I understand, I use the 10.7mhz output from my receiver, the upconverter output is 135.7mhz. I would set the P25RX to 135.7, select DMR mode and tune the main receiver to a dmr signal?

If I understand this correctly the Ham It Up Nano looks like a great choice. Now if we had (hint, hint) P25RX software with multiple mode decoding this would be one great new product.
 

FreqNout

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Just be make sure I understand, I use the 10.7mhz output from my receiver, the upconverter output is 135.7mhz. I would set the P25RX to 135.7
From the hardware RF signal point of view, yes. The IF signal is upconverted by 125 MHz. There will be up to 10db signal loss due to the upconverter.

The decoding part is a software question.
 

brndnstffrd

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Not meant to be a snarky comment, but a serious question, Why go through the hassle of using a separate device as a receiver, then add an upconverter to feed the P25RX, when the P25RX is able to receive on its own? I get that the P25RX doesn't have the same frequency coverage, but is anyone even running DMR on a band that it cant receive? I suppose one reason might be that the ICOM might have a more sensitive receiver and can pull in signals a little better, but I would think any gains over the P25RX would be negated by the signal loss from the upconverter. Again, this isn't intended to be a negative comment or derail the thread, just legitimate curiosity.
 

FreqNout

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My reading of the OP appeared to have a desire to decode digital 'HF' signals using the btt hardware. While it could be done with the RF upconversion, the overall performance will depend on factors/hardware beyond btt control. Once the 10.7 MHz IF is at 135.7 MHz, a simple RTL SDR could be used to feed software already in the marketplace to decode the digital signal.

Back to the OP, yes it could be done. How well it would work compared to other solutions, that is the question.
 

wb4sqi

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Go back and read my original post. Heck, I've been around radios since 1959 and I realize this is not the "best" idea to decode digital modes but it may be definitely cheaper than buying an AOR 5700 "do it all" receiver. i have an Icom R8600 and am pretty happy with it's performance, doesn't bother me that it can't decode DMR. Having said that, there are lots of owners who believe Icom is missing a huge market by not offering other modes.

Doing this with an SDR dongle has been done and can be somewhat effective but it has been proven the cheap chinese dongles leave a lot to be desired, thus my idea of using Bluetail receivers. Todd's receivers are far and above the chinese dongles and possibly could be re-purposed for a new function.

Thanks to all for your comments. I can see where my idea is fraught with issues and isn't really the "best" way to achieve the goal of "all-in-one" digital decoding.
 

FreqNout

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Doing this with an SDR dongle has been done and can be somewhat effective but it has been proven the cheap chinese dongles leave a lot to be desired, thus my idea of using Bluetail receivers. Todd's receivers are far and above the chinese dongles and possibly could be re-purposed for a new function.
My comments were not meant to be negative to your idea. Give it a try.

There is no question the btt hardware is far better than any sdr dongle. My point was once the signal gets through the ham it up converter, the btt hardware has to deal with the output of the other low performing hardware.

The software defined radio designs Todd posted in the open source thread offer an opportunity to bring a new high performance all mode radio to the market. Of course, time, money, and supply chain make that difficult.
 

wb4sqi

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The software defined radio designs Todd posted in the open source thread offer an opportunity to bring a new high performance all mode radio to the market. Of course, time, money, and supply chain make that difficult.

There is a small market for competition to the AOR AR5700D receiver. The sell for north of $3k, nearly $5k in the UK. Firmware can only be updated by a trip back to the mother ship in Japan, which is a non-starter for me.

A high performance all mode receiver would be a nice product and clearly would be a game changer in a the market. There are SDR's showing up from India, China and Indonesia but likely not designed with high performance in mind.
 
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