Post by thread:Spread Spectrum radios

I would be interested, if available for sale in the USA. Thanks Kevin Arrowood Peter Grey wrote: {Quote hidden}> There has been a few threads on these type of radios and I wanted to > let the > list know that in a few weeks there will be some relatively cheap > systems > available which will have very high jamming margins. This will be both > > frequency hopping and also direct sequence. > > If of interest please let me know. > > Thanks, > > Peter Grey > Neosystems > Australia

I too would be interested. Depending on the cost and the package. Troy Powledge TCo. Systems spam_OUTtpowTakeThisOuTeramp.net Peter Grey wrote: {Quote hidden}> > There has been a few threads on these type of radios and I wanted to let the > list know that in a few weeks there will be some relatively cheap systems > available which will have very high jamming margins. This will be both > frequency hopping and also direct sequence. > > If of interest please let me know. > > Thanks, > > Peter Grey > Neosystems > Australia

part 0 527 bytes thanx adam timmons .....ratacusKILLspam@spam@pixi.com ---------- From: Peter Grey Sent: Tuesday, June 30, 1998 1:56 PM To: PICLISTKILLspamMITVMA.MIT.EDU Subject: Spread Spectrum radios There has been a few threads on these type of radios and I wanted to let the list know that in a few weeks there will be some relatively cheap systems available which will have very high jamming margins. This will be both frequency hopping and also direct sequence. If of interest please let me know. Thanks, Peter Grey Neosystems Australia

It will be difficult to find a system that is both cheap and has a high jamming margin. I don't the details on why you need a high jamming margin, but there are a bunch of vendors selling cheap spread-spectrum LAN cards; you could always just buy a few and see if they work in your application. There are more expensive radios made for the transit (i.e., railroads, metros) market that are more jam-resistant, but also much more expensive. Hope this helps. Brian Robinson .....hbrobinsonKILLspam.....lucent.com ---------- From: PICLIST [SMTP:EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU] Sent: Wednesday, July 01, 1998 9:57 AM To: PICLIST Subject: Spread Spectrum radios There has been a few threads on these type of radios and I wanted to let the list know that in a few weeks there will be some relatively cheap systems available which will have very high jamming margins. This will be both frequency hopping and also direct sequence. If of interest please let me know. Thanks, Peter Grey Neosystems Australia

Remember, anything that is transmitted can be jammed. If a person is close to the reciever or transmitter it can be easily jammed. (I demonstrated this to a salesman at a convention when he said "Our units cannot be jammed" by just placing my handheld tranciever next to his reciver and transmitting. It de-sensed his reciever so much that it could no longer recieve it's data.) Spending huge cash on jam-proofing must have a really good reason, and a business or home security system isn't one. (How many B&E artists have a VanEck or other item with higher technology other than a crow bar.) In fact, the government cant come up with a jam-proof system.. they just transmit at Gagillion watts to overcome the jamming signal. On Wed, 1 Jul 1998, Brian Robinson wrote: {Quote hidden}> It will be difficult to find a system that is both cheap and has a high > jamming margin. I don't the details on why you need a high jamming > margin, but there are a bunch of vendors selling cheap spread-spectrum > LAN cards; you could always just buy a few and see if they work in your > application. > > There are more expensive radios made for the transit (i.e., railroads, > metros) market that are more jam-resistant, but also much more > expensive. > > Hope this helps. > > Brian Robinson > hbrobinsonspam_OUTlucent.com > > ---------- > From: PICLIST [SMTP:@spam@PICLISTKILLspamMITVMA.MIT.EDU] > Sent: Wednesday, July 01, 1998 9:57 AM > To: PICLIST > Subject: Spread Spectrum radios > > There has been a few threads on these type of radios and I wanted to let > the > list know that in a few weeks there will be some relatively cheap systems > available which will have very high jamming margins. This will be both > frequency hopping and also direct sequence. > > If of interest please let me know. > > Thanks, > > Peter Grey > Neosystems > Australia >

I didn't expect to see all this good RF discussion on the PIC list! Just goes to show, the people who work with PIC's are applications-oriented. The government does have some very impressive systems that are very nearly jam resistant, but they are extremely expensive, AND take up hundreds of MHz. of spectrum to operate. Brian Robinson ---------- From: PICLIST [SMTP:KILLspamPICLISTKILLspamMITVMA.MIT.EDU] Sent: Wednesday, July 01, 1998 3:44 PM To: PICLIST Subject: Re: Spread Spectrum radios Remember, anything that is transmitted can be jammed. If a person is close to the reciever or transmitter it can be easily jammed. (I demonstrated this to a salesman at a convention when he said "Our units cannot be jammed" by just placing my handheld tranciever next to his reciver and transmitting. It de-sensed his reciever so much that it could no longer recieve it's data.) Spending huge cash on jam-proofing must have a really good reason, and a business or home security system isn't one. (How many B&E artists have a VanEck or other item with higher technology other than a crow bar.) In fact, the government cant come up with a jam-proof system.. they just transmit at Gagillion watts to overcome the jamming signal. On Wed, 1 Jul 1998, Brian Robinson wrote: > It will be difficult to find a system that is both cheap and has a high > jamming margin. I don't the details on why you need a high jamming > margin, but there are a bunch of vendors selling cheap spread-spectrum > LAN cards; you could always just buy a few and see if they work in your {Quote hidden}> application. > > There are more expensive radios made for the transit (i.e., railroads, > metros) market that are more jam-resistant, but also much more > expensive. > > Hope this helps. > > Brian Robinson > RemoveMEhbrobinsonTakeThisOuTlucent.com > > ---------- > From: PICLIST [SMTP:spamBeGonePICLISTspamBeGoneMITVMA.MIT.EDU] > Sent: Wednesday, July 01, 1998 9:57 AM > To: PICLIST > Subject: Spread Spectrum radios > > There has been a few threads on these type of radios and I wanted to let > the > list know that in a few weeks there will be some relatively cheap systems {Quote hidden}> available which will have very high jamming margins. This will be both > frequency hopping and also direct sequence. > > If of interest please let me know. > > Thanks, > > Peter Grey > Neosystems > Australia >

.............................................................................. . Never trust a man who, when left alone in ....... Pete Lynch . . a room with a tea cosy, doesn't try it on ....... Marlow, England . ..........Billy Connolly. ......................... TakeThisOuTpicEraseMEspam_OUTbeowulf.demon.co.uk .. {Quote hidden}> On Wed, 1 Jul 1998, Brian Robinson wrote: > > > It will be difficult to find a system that is both cheap and has a high > > jamming margin. I don't the details on why you need a high jamming > > margin, but there are a bunch of vendors selling cheap spread-spectrum > > LAN cards; you could always just buy a few and see if they work in > your > > application. > > > > There are more expensive radios made for the transit (i.e., railroads, > > metros) market that are more jam-resistant, but also much more > > expensive. > > > My impression was that using something like direct sequencing spread spectrum in a LAN or for point-to-point data comms like this was not so much to make it difficult to eavesdrop or jam, but was to make it possible to have many two-way dialogs going on the same frequency without interfering with each other. If I remember from about 20 years ago when I was working on these kinds of system, when you add transmissions to the same frequency band, the signal/ noise ratio (read: error rate) gets slighly worse. So you need some kind of error detection/correction to keep the comms links reliable. You could use a PIC (I knew I could work it in somewhere) to do this. Pete

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