Open LRS

[ORCA]

Just a heads up to this latest offering from Flytron

http://store.flytron.com/16-openlrs

May be of interest to those who are happy to experiment and dont need plug and play.
Please remember the legalities surrounding the use of this system.

[Swissnic]

OMG - thats an awesome site!  If only I'd paid more attention in the electronics class at Uni!!!

:+

[Devonian]

Ooops, seem to have hit the buy it now button.

A very quick look at the code and it seems that it can be configured for 459MHz without too much trouble?

We'll see what it's like in the next week or so...

Nigel.

[Swissnic]

Hey Nigel,

I downloaded and checked the code - yep, it does seem to specify the current system to 435mhz.  This is specified in two places for each the Tx and Rx.

I am SOOOOOO temped to order one for a play, but I already have more Control frequencies than I have models - and as you can see below - I have quite a few of them!

Let me know how it goes though!

Cheers, Nic.

[Devonian]

Nic,

Found this for calculating registers (right click and 'save as')

http://www.hoperf.com/upfile/rf22%20register%20settings_revv-v23.xls

Some more resource and tools (near top right) of this link
http://www.hoperf.com/rf_fsk/rfm22b.htm

I lost my last posting as the server won't take any more attachments :(

Nigel.

[ORCA]

Just a thought, would not some of the RF circuitry and SM component values need revision for use on 459mHz?

[Devonian]

No other curcuitry is required, but I think that the 433 chip will be at it's limit at 459MHz and maybe requires the 470MHz chip to work efficiently at 459MHz.

Check out the spec:
http://www.hoperf.com/upfile/RFM22B.pdf

Nigel.

[ORCA]

Had a quick scan of the 70 pages. Looks like spec limit is 453mHz for the item on offer, may/may not go the rest of the way. Wait and see results of his tests next week.
Off topic; Been scanning the 70cm band in my area for the last week and its all but dead. I'm 250ft up a hill with unrestricted view for 10's of miles over populated areas. Using Yaesu FT-60 transceiver and Yupiteru MVT-7000 scanner. Is it just my location or perhaps the norm?

[Devonian]

I have my OpenLRS Tx and Rx now and will try to get some testing done over the coming days.

Found a few niggles with it 'as is' but nothing that can't be overcome.

I think it will ultimatley need the fitted 433 module modifying to match the PA matching requirements to run at 459MHz.

I have asked Melih (Flytron) to consider getting some HopeRF 470MHz modules, which are better suited to 459MHz.

Nigel.

[Swissnic]

Hi Nigel,

I have been in contract wtih Hope, and they have confirmed that the RFM22B 470Mhz module is a slot-in replacement for the OpenLRS module.  Unfortunately, the 430Mhz module won't reach 459...

I also have a company that can supply these modules - but min order is 50...

I'm getting a quote anyway to see what the price is...  will post when I get further info.

Cheers, Nic.

[Devonian]

Hi Nic,

Yep, I saw from the spec of the 2 modules that each is tuned for a certain bandwidth.
The small train of impedance matching components can be changed to suit any frequency on the HopeRF module, but they are pretty small and I have to source the ones I need to get to 459MHz by swapping them out on the 433 module.

I asked Melih to get some 470 modules when he next places his batch order with HopeRF, which he agreed to do, so we'll wait and see...

Nigel.

[Swissnic]

Hey Nigel,

Swapping the module is one thing - but swapping components on the module...  I bow to you sir!  :laugh:

Looks like you have it all in hand!!!

Looking forward to hearing about your results - please take loads of photos as well!

Cheers, Nic.

[Swissnic]

Nigel - I just checked the updated doc's on Hopes website, and it looks like they've dropped the 470mhz module...  Not sure if your mate can still get stock, but I thought I'd let you know...

Cheers, Nic.

[Devonian]

I asked MelihK the producer of OpenLRS to get the 470 modules.
Maybe I really do have to go down the component swap route.

Have a read of pdf file 'AN435' - PA matching, near the bottom here:
http://www.silabs.com/support/pages/support.aspx?ProductFamily=EZRadioPRO
Table 2 on page 3 makes a good read (or not).

Only 10 'ickle SMD components need changing - on each board!

Nigel.

[Devonian]

Quick update... (click the images for a larger view - you might need it !!)

Traced out the PA matching network on the HopeRF module (sorry it's my hand sketched layout)





An extract from the AN435 pdf file, shows





Here's the bits that need changing (highlighted in the green boxes on the green PCB module)






So, ordered some new 0402 size components (0402 = 1mm x 0.5mm component size) and will endevour to swap out the various ones to get to 459MHz PA matching.

Nigel.