Wikipedia has an article on the technology:
http://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum

after some google, it seems that some people built theirs like a Yagi(well a bastard child of a yagi and the circular wave guide), but most seem to be circular wave guides.

on that note I found:

a handy yagi calculator:
http://www.saunalahti.fi/elepal/antenna2calc.php

a circular wave guide calculator:
http://www.saunalahti.fi/elepal/antenna2.html

and then there’s my personal favorite, the cubic quad:
http://www.softcom.net/users/kd6dks/quad.html

I actually hit a repeater about 30 miles away a cubic quad driven with my 1.5 watt ht.

To answer some questions:
1. The transmitter power is 15dBm which is comparable to off the shelf WiFi components so the range is very comparible. I’ve seen broadband amplifiers at Digikey for a few dollars that can do up to the limit of 1Watt but they are all very tiny SMT components and I am not advanced enough in my soldering skills for that.

2. The DP1205 is a dropin module for the XE1205. At the time I built this this was a regular stocked item at Digikey. Apparently, the sales volume has been low so now it is only a backorder item and minimums apply.

The documentation for the module is here:
http://www.semtech.com/pc/downloadDocument.do?id=1796

The documentation for the XE1205 chipset is here:
http://www.semtech.com/products/xe1205/

I’ll add more links to the website. As I say on the website, the modules do not contain a protocol layer. That is all done in C on the PIC.

Can anyone find the RF module he is using? he says its a “Semtec DP1205 RF module” that uses a Semtec XE1205 transceiver, but i can only find info on the XE1205 chip, not the DP1205 module.

So once you put that cb antenna on there you would have a horrible swr because a cb antenna is tuned for around 30 mhz and thus would be 93.6 inches long while this project works on the 900 mhz band which wants an antenna at 3.12 inches. As you can see, that antenna would be considerably too long, and you would run the risk of burning out your transmitter.

A better method would be to build a directional antenna such as a yagi (like your tv antenna on your roof) or cubic quad. Although, if I remember correctly, the FCC doesn’t actually care about the transmitter power, but more the effective radiated power, so if you have a 1 watt transmitter, and an antenna with 12db gain (remember: power doubles every 3 db) so thus you would have:

1 watt * (2)^(12/3) = 16 watts

so basically, you would be out of compliance with the FCC.

well, just my 2 cents.

73′s
KE5GQS

thanks hack-a-day (and mainly to whomever came up with this excellent writeup)