Hi Chris, Could u tell me the appx range of this tx rx pair ... Thanks Riaz > > Maxon makes a radio module that I have used to great success. It is basicly a uhf portable radio that has not been completely stuffed of all parts. The transmitter is a complete transceiver minus all receive parts, the receive is just the oposite. Crystal controlled, up to 5 watts out, FM. Turn the power down a bit and run continuous. I used a set of these to send audio from an announcers console at a race track to a FM broadcast transmitter. It has been used for up to 1 week of continous operation. Cost is low. At the least, take a couple of cheap vhf or uhf walkie talkies, any brand and get out the cutters and screwdrivers. You can even get a license for a legal freq to operate on with type accepted equipment. > > From: Chris Carr > > Date: 2001/08/01 Wed PM 04:34:14 EDT > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [EE]: VHF and UHF mini modules > > > > The requirements were for an audio link not data and available in the UK. > > He also only wants transmitters > > and reading between the lines wants Watts of power not milliwatts. And > > wants a quick cheap solution. > > > > Otherwise I would have suggested modifying ex-pmr equipment. > > > > He specifically excluded off the shelf data modules. > > > > Regards > > > > Chris Carr > > > > > > ----- Original Message ----- > > From: "Sean Breheny" > > To: > > Sent: Wednesday, August 01, 2001 4:10 PM > > Subject: Re: [EE]: VHF and UHF mini modules > > > > > > > Hi Scott, > > > > > > On Wed, 1 Aug 2001, Scott F. Touchton wrote: > > > > > > > > > > > I've used the Lynx modules with good success (433 and 915 Mhz). Also, > > RF > > > > Monolithics has some nice small single chip solutions for both a > > > > transmitter and receiver. I've lost track of this thread, and not sure > > of > > > > > > I just used the Linx SC series (916 MHz)in a project and I can second the > > > notion that they work well. > > > > > > > your range requirements. These two solutions are typically about 0dBm > > > > output... and only will get about 300' of range or so. I did get close > > to > > > > 1000' at 915Mhz, but that was open line of sight and the BER was getting > > > > intolerable. Of course, these products are typically 50 ohm output. So > > it > > > > does help to design a matching network to line up with your antenna. I > > was > > > > using quaterwave monopoles on ground plane.. about 75ohm impedance. A > > > > simple LC section did the impedance transformation. Doing this added > > 25% > > > > to the range. > > > > > > I think you went the wrong way, a simple vertical monopole above a ground > > > plane has about 36 ohms impedance (it has the same radiation above the > > > ground plane as a 1/2 wave vertical in free space would, and almost no > > > radiation below the ground plane. This measn that ,overall, for the same > > > antenna current, it transmits half the power, so since power is I^2 *R, > > > this means half the R. R for a 1/2 wave dipole in free space is 72 ohms, > > > so 72/2=36) > > > > > > I'm a bit surprised, though ,that this tiny mismatch made 25% difference. > > > When you say LC section, are you referring to microstrip L and C? It > > > would be difficult to make an LC filter with discretes at 916 MHz. You > > > can just use a 1/4 wave long section of microstrip transmission line as a > > > quarter wave transformer from 50ohm to 36 ohm. > > > > > > > > > > > Also.. since these are 50ohm parts, its very easy to use a MMIC > > amplifier > > > > to get added output power. > > > > > > > > > > Yes, and also to improve their noise figure (if you include n RF sensing > > > TR switch and a second MMIC amp). From their specs it seems as though > > their > > > receivers are > > > quite a bit less than optimal. Too bad the FCC doesn't allow more than > > > 50mV/meter E field strength @ 3feet on this band, otherwise we could use > > > small yagis and get REALLY good range. Come to think of it, we could > > > still use a yagi on the receiver side, provided we had a TR switch, as > > > mentioned before. > > > > > > It's interesting that this thread should come up now as I am almost > > > finished with my online tutorial on wireless communications for > > > microcontrollers. I will be sure to post to the list when it goes up, in > > > a few days. > > > > > > Sean > > > > > > > Scott F. Touchton > > > > 1550 Engineering Manager > > > > JDS Uniphase > > > > > > > > > > > > > > > > Chris Carr > > > > > > > ET.COM> cc: > > > > Sent by: pic Subject: Re: [EE]: VHF and > > UHF mini modules > > > > microcontrolle > > > > r discussion > > > > list > > > > > > > A.MIT.EDU> > > > > > > > > > > > > 08/01/01 08:22 > > > > AM > > > > Please respond > > > > to pic > > > > microcontrolle > > > > r discussion > > > > list > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Maxon SR-214 is a complete handheld transceiver operating tin the 70cm > > > > band > > > > > 10mW output runs off 4 AA batteries. Ideal as the basis for a higher > > > > powered > > > > > unit. > > > > > > > > > > Cost # 29.95 UK. Available from ourselves or Waters & Stanton ( as you > > > > > appear to be in Edinburgh JC, 20 Woodside Way, Glenrothes, Fife KY7 > > 5DF > > > > > 01592 756962 > > > > > > > > > > Otherwise Vectronics have kits to build FM Receivers for 2, 6 and 10 > > > > metre > > > > > bands #35.95 and a 5 watt 2 metre transmitter at #99.95 > > > > > > > > > > Then there are the Ramsey and Ten-Tec Kits it all depends on what you > > > > want > > > > > to do. > > > > > > > > > > Regards > > > > > > > > > > Chris Carr > > > > > > > > > > > > > > > > > > > > > > Thanks for your answer. > > > > I am looking for small synthetized modules that can transmit in VHF or > > UHF. > > > > I do not need tranceivers or a normal LPD already industrial friendly > > > > boxed radio. A PCB (printed circuit board) module is enough for me. Do > > not > > > > need pretty boxes :-). > > > > The final system is going to be a speacial kind of Beacon for RDF. > > > > Thanks > > > > > > > > Sena > > > > > > > > As a quick and easy to implement solution you will have difficulty > > beating > > > > the SR-214. Just key the transmitter and forget about the receiver. Use > > a > > > > PIC to emulate keystrokes. 10mW will get you around a mile with the > > > > attached > > > > antenna. > > > > > > > > Otherwise you are going to have to look at building designs from a > > > > handbook. > > > > > > > > ARRL UHF/Microwave Experimenters Manual > > > > ARRL UHF/Microwave Projects Manual Volumes 1 and 2 > > > > > > > > are a good starting point and should be available at the University > > Library > > > > otherwise they can be purchased from the RSGB > > > > > > > > VHF Communications also supply boards, partial and full kits for the > > > > projects published in their magazine. > > > > > > > > Regards > > > > > > > > Chris Carr > > > > > > > > Please respond via the list and not direct, other people may want to > > > > contribute to the thread. > > > > > > > > -- > > > > http://www.piclist.com hint: The list server can filter out subtopics > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > > > > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics