Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: elmers, what is the front end of a radio?  (Read 651 times)
KC5UUS
Member

Posts: 103




Ignore
« on: April 23, 2009, 07:26:31 PM »

i know another elementary question. hi hi, but i hear the term front end a lot . u know over load the front end. or what have ya. so what does the front end actually consist of? thank u. u elmers are much appreciated around this shack . 73s
Logged
AD7WN
Member

Posts: 113




Ignore
« Reply #1 on: April 23, 2009, 07:53:09 PM »

As it is typically used in ham radio, the front end is the first stage of a receiver or the first stage of the receiving part of a transceiver.

Thus, a receiver with an RF amplifier that is being overloaded generates distrotion.  If it is being overloaded by a very strong off-frequency signal, it may desensitize the receiver to the point that the desired signal cannot be received, or may be received poorly.

Hope this helps, 73 de John/AD7WN
Logged
VE3EFJ
Member

Posts: 89




Ignore
« Reply #2 on: April 23, 2009, 08:08:47 PM »

My understanding of the term is -

Everything in the signal path from the antenna to the first mixer, including the first mixer.

This would include such things as

- bandpass filters
- band switching
- attenuator
- RF amplifier
- mixer
- post mixer attenuator (if included)

Some would also include the oscillator that drives the mixer.


Wayne
Logged
WB2WIK
Member

Posts: 20599




Ignore
« Reply #3 on: April 23, 2009, 09:02:24 PM »

I'd say it's the first active stage the incoming  signal hits in a receiver.

If a receiver has a passive preselector, I would not include that as part of the "front end."

In most cases, the "front end" is the receiving first preamplification stage, closest to the antenna.

Some receivers have no RF preamplification stage and the incoming signal directly drives a mixer, in which case that  would be the "front end."

WB2WIK/6
Logged
TANAKASAN
Member

Posts: 933




Ignore
« Reply #4 on: April 24, 2009, 12:03:50 AM »

As somebody who conducts research on HF Front Ends I agree with VE3EFJ  100%, everything in the receiver chain from the antenna connector to the first mixer. There are various ways of tackling this and my favorite method is a front end with no AGC and 0dB gain/loss, this means that the second I.F. has to supply the gain and the front end has to be bomb proof.

If you want some ideas grab brochures for the FT-9000, IC-7800 and PT-8000 then look at the block diagrams.

Tanakasan
Logged
AA4PB
Member

Posts: 12854




Ignore
« Reply #5 on: April 24, 2009, 06:03:40 AM »

Here's a definition: http://en.wikipedia.org/wiki/RF_front_end

I think most would agree that its typically everything in the signal path from the antenna connection to the first IF amplifier.
Logged
N9DG
Member

Posts: 315




Ignore
« Reply #6 on: April 24, 2009, 06:47:11 AM »

So what if there isn't a first mixer at all but there's just an A to D instead?

Kinda muddles the traditional definition for what a front end is doesn't it?
Logged
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #7 on: April 24, 2009, 06:50:55 AM »

"So what if there isn't a first mixer at all but there's just an A to D instead? "

I'd probablyu still call everything before the A/D the front end, myself.

Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #8 on: April 24, 2009, 06:52:04 AM »

er, up to and including the A/D I mean....
Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AA4PB
Member

Posts: 12854




Ignore
« Reply #9 on: April 24, 2009, 06:57:59 AM »

Anybody building a receiver where the whole HF spectrum (2-30MHz) goes staight to an A/D?
Logged
N9DG
Member

Posts: 315




Ignore
« Reply #10 on: April 24, 2009, 07:11:38 AM »

"Anybody building a receiver where the whole HF spectrum (2-30MHz) goes staight to an A/D?"

A few in Amatuer circles that I can think of:

http://www.rfspace.com/Home.html

http://hpsdr.org/

http://www.philcovington.com/QuickSilver/

http://www.microtelecom.it/perseus/

http://www.adat.ch/index_e.html

Each of these are direct sampling RX's. Some may, or optionally include a pre A to D gain stage and/or bandpass filtering, but they do not have any pre A to D mixers.
Logged
KA2UUP
Member

Posts: 388




Ignore
« Reply #11 on: April 24, 2009, 07:14:38 AM »

In simple terms:  The front end is the one with the knobs.  The back end is the one where you hook things up!!!!!

Aside from that, the explanations above are very good!!!!
Logged
WA3SKN
Member

Posts: 5484




Ignore
« Reply #12 on: April 24, 2009, 07:20:49 AM »

The "front end" is the part of the receiver between the signal input (antenna jack) and either the detector (or in a superhetrodyne) the first IF stage... and yes, it includes the mixer.
It determines both the sensitivity and signal-to-noise ratio of the receiver.  The filters after the mixer determine selectivity.
But the bandwidth available in today's radios can let strong signals get through to the mixer diodes.  This causes the "intermod" problems that are so talked about.
73s.

-Mike.
Logged
KG6WLS
Member

Posts: 507




Ignore
« Reply #13 on: April 24, 2009, 08:26:04 AM »

RE: elmers, what is the front end of a radio?  Reply  
by KA2UUP on April 24, 2009  Mail this to a friend!  
In simple terms: The front end is the one with the knobs. The back end is the one where you hook things up!!!!!  



Smiley
Logged
W9OY
Member

Posts: 1305


WWW

Ignore
« Reply #14 on: April 25, 2009, 06:11:30 PM »

In the SDR realm, If there's only an A/D converter then that's the front end.  The back end is all in software in the computer.  

I view my Flex radios as 2 conversions.  Everything before the computer (that is what ever is in the flex box) is the first conversion and every thing done in the computer is the second conversion.  I view everything from the antenna jack to the QSD or Tayloe detector as the "front end".

73  W9OY

 
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!