Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: UHF band for hand held radio application
Posted: Sun Mar 09, 2008 6:43 am
Joined: Fri Dec 14, 2007 11:23 am
may i know why we used UHF band for walkie-talkie or also known as hand-held radio?
Posted: Mon Mar 10, 2008 5:01 am
Joined: Fri Feb 17, 2006 12:07 pm
Location: London UK
Basically a trade-off was decided between available spectrum vs technology cost 20 years ago, plus the cross-over point between antenna size and losses like building wall materials, wet leaves on trees etc.
Also 10-20 years ago the band-width per channel needed only to support a single 2-way voice call, so little spectrum was needed per call.
UHF offered a good compromise between the conflicting factors. Antenna size can be small, losses through building materials is only around 10 dB or so, and pipework within buildings ensured re-radiation was possible within a building in UHF. Adequate transmitter power and low receiver noise factors could be achieved at low cost and high repeatability in MMICs at UHF. All this implied a good economic cell radius per base station, so UHF represented the cross-over spectrum where all the conflicting factors for mobile telephones met.
Today there is inevitably a shift towards higher frequencies (L and C band) as technology costs fall, MMICs improve and band-width demand rises.