The one I had used triple conversion superhet. Mircoprocessor
controlled.
The first IF was like 336Mhz to 10.7Mhz to 455Khz. There was no front
end. just direct conversion to the IF. So all the micro had to do was
control the oscillator from 336Mhz to 900Mhz using up conversion on
the low bands and down conversion on the higher bands. Cell phone band
was locked out. Guess what you can pick cell phone band on the image
frequency back in the day.
========
Are analog cellphones still used in the USA ?
I thought by now it is all digital sigs which can not be received with a
'normal' receiver , so what's the reason to 'lock out' the cellphone
frequencies ?

Frank GM0CSZ / KN6WH

wrote in message
...
Guess what you can pick cell phone band on the image
frequency back in the day.

Given how much time was spent discussing the need for image rejection and the
sometimes-elaborate techniques for achieving it, I suspect a lot of my college
professors would be incredulous to learn that many receivers do just fine
without it.

I've noticed that many Yaesu radios lock out the images of the old AMPS band,
which sucks because the image is where there are also 100%-legal-to-receive
paging bands. Yaesu lost a sale to Icom over this.

Hopefully the stupid law will be dropped one of these days -- it's not like
any large percentage of all cell phone conversations are carried out on an
AMPS anymore, and most of the cell phone carriers are quietly shutting down
their old AMPS equipment altogether.

---Joel

On Mon, 07 Jul 2008 06:08:21 +0100, Highland Ham wrote:

The one I had used triple conversion superhet. Mircoprocessor
controlled.
The first IF was like 336Mhz to 10.7Mhz to 455Khz. There was no front
end. just direct conversion to the IF. So all the micro had to do was
control the oscillator from 336Mhz to 900Mhz using up conversion on
the low bands and down conversion on the higher bands. Cell phone band
was locked out. Guess what you can pick cell phone band on the image
frequency back in the day.
========
Are analog cellphones still used in the USA ?
I thought by now it is all digital sigs which can not be received with a
'normal' receiver , so what's the reason to 'lock out' the cellphone
frequencies ?

Frank GM0CSZ / KN6WH

The same government logic that made TV broadcast standards
backwards-compatible for over 50 years.

__
Gregg