Hi Stan, see below.

El 29/03/16 a las 21:37, Stan escribió:

Hello.

I don't have the QYT KT8900 radio with 220Mhz yet, but I'm planning on getting one soon. This may help you a little, from my research the QYT KT8900 radio with 220Mhz is model QYT KT8900_R_ (note the "R" on the end). Also the Zastone MP-320 appears to be the exact same radio. These claim that they have a range of 240-260MHz, therefore they do NOT cover the US band of 222-225MHz.

Yes, all data I got points that the QYT KT8900 is an ancestor of the actual BTECH 2501+220, and the QYT KT8900_R_can be a specimen in the middle of both.

I have yet to see an schematic of this radios (any of the big family that is forming) to form an better opinion, but as this units are based on a SDR chip like the Baofeng UV-5R and schematics of this are on the public now /_I can speculate_/ about some facts:

- It's a common practice to have /_just_/ a Low Pass Filter in the output stage, so if the radio is for a slightly higher freq (260 vs 230) it will not do any harm on if you managed to get it TX low in the band. - Almost all Chinese SDR radios do only low pass filtering or a roughly band pass filtering with quite lower Q in the RX path (My UV-5R has just a capacitor in the UHF "supposed high pass + band pass filter") so I think band pass filtering will be enough to pass way beyond the lower and upper edges of the designed bands; as to alow reception on the 220-240 Mhz with decent reception. /(all this is just speculation as I mentioned.)

/Does any have a schematics for this new Chinese radios? I'm eager to see one. / / The big issue remains to be the lowering of the band limits of the 240-260 Mhz, but don't despair, the current development of the btech driver in chirp with support for the QYT KT8900 and others have revealed some clues that *maybe* this is possible.

All that is needed to start is the cooperation of the users to bring support for the radio to Chirp, then a brave user that want to risk his radio to test with us a way to lower the radio to the USA ham radio.

I have found this, too, but haven't tried it yet: "Changing the 'PASSWORD' on these is supposed to change the range of the associated band coverage. I have been told to 'hold F and power on, get PASSWORD' and then you could use this to change the 'PASSWORD' which supposedly _actually changes the Rx/Tx range_." So that procedure could be used to change the "222MHz" range from 240-260 to 222-225MHz, /_*IF* it actually works that way!_//_ _/The filters in the QYT KT8900R may not be able to cover 222 though, they may be designed to just cover 240-260. Again, I have not tried this, I just found it on the internet.

Only practice will reveal truth. Keep us posted about the results.

I have the BTECH MINI UV-2501+220 (haven't tried it yet) and it appears to be the same thing also, except it comes already set up for 210-230MHz instead of 240-260. Maybe the filters are tuned a little differently?? Maybe something else is different also??

I must not make an statement here before knowing all the elements at play, but seems to me like the BTECH family is the less bugged and most up to date evolution of this radios. (as per the review on public availability info everywhere on the net, as I don't own any of this radios)

I just pushed a fix for the BTECH 2501+220 on the devel queue that solve a problem with uploading to the radio.

A tip: Some of the magic word to open the radios into clone mode has some bytes that appears to be dates and you can build a line in the development that follows the date of the availability of the different models, so far we have...

First the Waccom Mini 8900 & QYT KT-UV980, then QYT KT8900, then BTECHs 2501 & 5001, then BTECH 2501+220, then ?

73 CO7WT, one of the Chirp's developer working on the btech driver.

PS: we still need the serial log capture from a QYT KT8900R !