> On Thu, 18 Sep 2008 16:31:43 +0000, David Lesher wrote:
>

>> B J Foster yahoo.com> writes:
>>

>>>>> The VOR band is 108MHz to 118Mhz (VHF). The lowest mobile band (UHF)
>>>>> is 900Mhz. If the VOR system has such a poor filter then it is going
>>>>> to be affected by *every* *other* system between VOR and GSM.

>>>> You don't seem to understand RF very well. Lots of weird things happen,
>>>> when you mix multiple emitters and Murphy.

>>> Sure. Such as?

>> Well, when you mix 2 signals, you get 4: the two originals, the sum and
>> the difference. So, for example, mix a 800 and 915 mhz signal, and guess
>> what, you get 800, 915, 1715 and... 115 Mhz crap. ("Hetrodyning")

>
> Yep, all sorts of nW1+/-mW2 stuff. And these days you can not assume that
> the circuit designer actualy knows the craft (i.e. the practical stuff).

>
> I remember the going to a demo of a new in-house product to locate
> PMG cables running across the bay so they could lift them up tp
> repair them when damaged. Lasted a who one minuteas the boxen
> supposed to inject the harmonic intothe cableto be picked up by the
> transducer in the boat let out the majic smoke. Oh dear, they had
> forgotten to ensure they had adequae thickness of copper on the pcb
> to carry the current they were pushing around.
>
> More on topic, given the push the reduce space, a new designer
> might deice that it is really cool simple solution to their layout problem
> to mix the signal on one side of pcb face and locate the filter to
> remove all those nasty harmonics on the other side (same face) side of
> the board, thus inadevertently having a nice aerial to push allthose
> harmoncs out into the ether.
>