In an avionics book i read that the IF of a reiceiver is 29.05 Mhz. How does that figure come out? Does it come out by the difference between the incoming radio signal and the Local oscillator frequency? Am i saying it correctly?
IF frequency
Jan 28, 2006
16 Replies
You are about to answer it yourself. ;-)
Yes
Yes
Just curious, where did you see that I.F. frequency mentioned?
I think I would put it another way around: The designer of the radio chose to use 29.05 MHz as the IF, and designed the IF amplifiers to pass that frequency. The frequency that the receiver will receive is that IF frequency plus (or minus) the local oscillator frequency.
Peter Bennett, VE7CEI
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"Peter Bennett"
** Much clearer.** Err - not usually.
Since the local oscillator is normally at a *higher* frequency than the IF frequency - the received frequency is the LO frequency plus or minus the IF frequency (single conversion assumed).
....... Phil
In article , snipped-for-privacy@hotmail.com (known to some as thejim) scribed...
Yes to both questions.
I would offer a minor spelling correction ('receiver' as opposed to 'reiceiver'), and I would also say that 29.05 is only one example of an IF. It is by no means standard across all receivers.
Example: Motorola has used IF's of 45MHz, 10.7MHz, and 17.9MHz in various land/mobile 2-way radio products. GE/Ericsson has used 10.7, and many others.
There are still other receivers that use more than one IF (dual- conversion or triple-conversion).
Happy reading.
Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
http://www.bluefeathertech.com -- kyrrin a/t bluefeathertech d-o=t calm
"Salvadore Dali\'s computer has surreal ports..."
I think he stated it rather succinctly since the IF _is_ the
difference between the carrier and the LO, regardless of the
location, spectrally, of either the carrier or the LO.
"John Fields" Peter Bennett
** That excludes those receivers where the IF is the sum of the received carrier and the LO......... Phil
Not so.
Notice that he asked:
"Does it come out by the difference between the incoming radio
signal and the Local oscillator frequency?"
If we choose an arbitry IF, say 10MHz, and we have a carrier of
100MHz, then the LO can be either 110 MHz, whereupon the IF will be
the difference between the 110MHz LO and the 100MHz carrier, or
90MHz, where the LO will be the difference between the 100MHz
carrier and the 90MHz LO.
"John Fields" 'Phil Allison"
( snip bunch of irrelevant stuff )
** Try reading my post again.More carefully this time.
....... Phil
To what end?
It\'s obvious that you didn\'t understand the OP\'s post in the first
place, obviously don\'t understand heterodyning, and are trying to
become argumentative for the purpose of changing the direction of
the discussion away from could only end in your having to admit your
ignorance of the subject.
I\'ll have none of it.
He seems to think that it's common, or done at all, for the LO to be _added_ to the received frequency, resulting in an "IF" that's the _sum_ of the frequencies.
But, it is Phil Allison, after all.
Thanks, RIch
On Mon, 30 Jan 2006 23:20:51 GMT in sci.electronics.basics, Rich Grise wrote,
I gather this system is used in premium wideband scanner designs so that image frequencies are far away and easily filtered out of the very high freq 1st IF.
"John Fields" "Phil Allison"
** So you might discover your error.If that is not it too *horrible* an experience.
** No is isn't........ Phil
"David Harmon"
** It is also done in some HF ( ie "communications" ) receivers for the same reason - where the first IF may be as high as 50 MHz......... Phil
Joining late:
summing is also common in swept receivers (aka Spectrum Analyzers).
Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA
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