AGC -- Fast vs Slow
Al Klayton
What is the strategy for deciding when to use each?
Thanks,
Al
mbz07
Al Klayton <akla...@pcisys.net> wrote in message
news:t9ecnls...@corp.supernews.com...
You would use slow AGC when listening to SSB or certain DATA modes, try it
and see how much more comfortable SSB is with slow AGC!
mbz
Ron Hardin
A radio with only a slow AGC (yb400 eg.) is very hard to use with a MW loop
because you can't tune the loop. The results are delayed too long. Sometimes
using the local setting on the local/dx switch will disable the AGC and help.
A radio with only a fast AGC (2010, 7600G) is painful to listen to when there
are two MW stations on the same frequency that pump each other. You can back
off the RF gain on the 2010, or switch to local on the 7600G, sometimes, to
disable the AGC.
In both of these cases what's wanted is the opposite sort of AGC.
--
Ron Hardin
rhha...@mindspring.com
On the internet, nobody knows you're a jerk.
Fcathell
steady carrier) thus reducing distortion and a "whooshing" sound on some
receivers. Fast AGC is for AM signals although you won't notice much
difference with slow.
Frank
Michael Dawson
the RF gain set at the critical point where the signal has adequate signal
to noise ratio.
For general searching FAST agc is best. This stops strong signals
desenstising the rx too much as you tune by them.
With a moderately strong SSB signal SLOW agc lowers the background noise
between pauses in speech.
With a moderate to strong AM signal the drill is FAST agc with the RF gain
backed off to to the same S reading as with slow AGC. eg the s meter is on
s9 with slow agc. Switch to fast agc and then back off the RF gain 100%.
Slowly increase the RF gain till the S meter reads S9 or slightly below.
Mikey Dee DXer
"Ron Hardin" <rhha...@mindspring.com> wrote in message
news:3A97AB...@mindspring.com...
Al Klayton
"Michael Dawson" <fre...@connect47.freeserve.co.uk> wrote in message
news:978l5s$iea$1...@newsg2.svr.pol.co.uk...
> The preferred option for AGC with extreme DX signals is of course OFF,
with
> the RF gain set at the critical point where the signal has adequate signal
> to noise ratio.
I'm using a RX-320 with Clifton Turner's excellent control software, but it
doesn't seem to provide AGC OFF as an option ( choices are slow, med and
fast). I guess slow AGC is the closest I can get ( other control software
may offer an AGC OFF option -- don't know).
Thanks to all who responded to my question -- good info!
Al
Volker Tonn [odo]
> A slow AGC is better for listening and worse for tuning.
>
Yep. If you're tuned in on a steady signal take the slowest AGC possible.
On HAM-band SSB-QSOs you might prefer a fast AGC when stations have very different
signal strengths.
>
> using the local setting on the local/dx switch will disable the AGC and help.
>
> A radio with only a fast AGC (2010, 7600G) is painful to listen to
There is a easy fix to the AGC of the 2010 :-)
There is to change only one electrolytic capacitoror, or if you prefer make it
switchable with an additional capacitor.
I've done that mod on the Sony 2001D (same as the 2010) with a very fast and a
very slow AGC switchable and I'm very satisfied with it.
odo
AC6V
Weak signals -- AGC fast or OFF -- when OFF use RF Gain and AF gain for optimum
reception.
For strong SSB stations -- use slow to medium AGC. Thus when the audio pauses,
you won't have the receiver gain open up in between and blast you with noise.
For AM SWL, I use med AGC to alleviate fading
Al Klayton wrote:
--
73 From Rod AC6V In San Diego
700 Ham Topics & 6,000 Links
http://ac6v.com/
I Doubt, Therefore I Might Be!!!
matt weber
wrote:
It's mostly a matter of what you are receiving. For CW, you usually
want fast AGC to avoid being deafened by the dots and dashes, You go
from no signal to possibly big signal in a big hurry.
for SSB you usually want slow, as the intended audio level is pretty
much the same, but the signal level varies considerably because there
is no background carrier. I.E. fast AGC on SSB produces 'interesting'
speech patterns, so slow AGC tends to make SSB volume behave more like
the AM signal it is suppose to sound like...
On a strong AM signal, it doesn't make much difference, in short
order, all AGC's speeds will produce the same result...
who?
matt weber wrote in message ...
>On Fri, 23 Feb 2001 21:04:31 -0700, "Al Klayton" <akla...@pcisys.net>
>wrote:
>
>>Can someone discuss the advantages/disadvantages of fast vs med vs slow AGC?
>>What is the strategy for deciding when to use each?
>>Thanks,
>>Al
>It's mostly a matter of what you are receiving. For CW, you usually
>want fast AGC to avoid being deafened by the dots and dashes, You go
>from no signal to possibly big signal in a big hurry.
<snip>
I've heard this particular bit of advice and do not see how
it can possibly be valid. A CW signal received with slow AGC will have the gain set at a level appropriate to the CW carrier level
at all times, making the CW signal comfortably loud and (for signals that are not weak) the noise between the dits/dahs softer. At
best, a strong CW signal can sound as clean as a code practice oscillator. THIS is why slow AGC is much better for CW than other AGC
options.
CW received with no AGC is the next best choice. The signal will hopefully be stronger than the noise and so can be comfortably
audible. The problem with no AGC is that heavy fading will sometimes result in a signal that is too loud at some times and too soft
at others. The function of AGC is to correct this!
A CW signal received with fast AGC is the worst option. The receiver gain will be reduced during the dits/dahs and increased between
them. The result is that the signal is made softer and the noise between dits/dahs louder. Who in their right mind wants the noise
to be louder?
BTW - I've seen this "fast AGC for CW" advice in a number of receiver instruction manuals. I've tried both fast and slow AGC for CW
on many different receivers over quite a few years and have yet to find one where CW sounds better with fast AGC than with slow. I
can only guess that perhaps the authors of those manuals either are not hams/SWLs and are simply copying someone else's bad advice
or that they have simply not tried both options on a CW signal!
73 de Glenn
Bill Meacham
Depends on the CW signal. Nice, strong, CW above the noise sounds
quite nice with slow AVC. If you're copying high-speed signals
fading into the mud, no AVC is the only way to go cuz dits will be
lost in the attack time of even fast AGC. Fast AGC doesn't seem
to be very useful even between these two extremes. On a decent
receiver with a good CW filter, tuning for weak signals with the
AVC on may result in a "dead" band except for the thumpers.
---
Bill Meacham WX4A
Vieques, PR
Ron Hardin
a stronger one, because the strong one changes the gain on the
weak one via the AGC.
With slow AGC the worst it can do is reduce the gain once but will
not be changing the gain constantly.
That is, the YB400 is better on CW than the 7600G, not that anybody
uses these receivers for CW.
King Pineapple
Here's a good test: find a station a long ways off (I use Radio New Zealand)
and try both fast and slow, and see which sounds best. In my location, RNZI
sounds much better with slow AGC; at fast it fades in and out rapidly.
--
Craig
Meredith, NH USA
Drake R8B/AD Sloper
Sony SW 77
Sony 2010
Phillips/Magnavox D2935
Uniden CR2021
Knight Kit Star Roamer
tuning since 1963
Brian Denley
Clifton's software doesn't let you turn the AGC off because Ten-Ten's
receiver design doesn't allow the AGC to be turned off. This is true of
most modern SW receivers. I think one reason is that many s-meter circuits
no longer works when the AGC is turned off. Also if the AGC (AVC) is off
the RF gain must be turned way down for strong signals.
Slow AGC is not at all like AGC off: With slow AGC, the receiver takes
several seconds to react to a change in signal. A receiver with AGC off
reacts immediately! For a modern receiver, fast AGC is the closect thing to
AGC off.
--
Brian Denley
http://people.ne.mediaone.net/bdenley/index.html
"Al Klayton" <akla...@pcisys.net> wrote in message
news:t9fpgnl...@corp.supernews.com...
Bill Meacham
>
> Al:
> Clifton's software doesn't let you turn the AGC off because Ten-Ten's
> receiver design doesn't allow the AGC to be turned off. This is true of
> most modern SW receivers. I think one reason is that many s-meter circuits
> no longer works when the AGC is turned off. Also if the AGC (AVC) is off
> the RF gain must be turned way down for strong signals.
>
> Slow AGC is not at all like AGC off: With slow AGC, the receiver takes
> several seconds to react to a change in signal. A receiver with AGC off
> reacts immediately! For a modern receiver, fast AGC is the closect thing to
> AGC off.
>
> --
> Brian Denley
And that is another penny-saving shortcoming peculiar to modern
receivers based on the concept that CW is dead.
---
Bill Meacham WX4A
Al Klayton
Thanks for the info -- and yep, fast AGC is closest to no AGC. I realized
that shortly after hitting the send key on my post. Guess I needed to SLOW
down my thinking about FAST AGC!
Al
"Brian Denley" <bde...@mediaone.net> wrote in message
news:5EZl6.10938$CW1.8...@typhoon.ne.mediaone.net...
Jake Brodsky
wrote:
>Can someone discuss the advantages/disadvantages of fast vs med vs slow AGC?
>What is the strategy for deciding when to use each?
The ultimate, if you can stand it, is NO AGC. This requires two
things: First, it requires a very good receiver with excellent dynamic
range. Second, it requires an excellent audio amplifier --one with
low noise and low distortion across a wide range of signals.
The result? Yes, you will ride your hand on the AF gain knob. On the
other hand, most AGC systems serve to cover up a receiver with crummy
dynamic range and miserable audio. The signals you'll hear will have
a clean "presence" against a background of other signals or the noise
floor. Surprisingly, you won't find yourself adjusting the gain too
much. I and many others have found that you can stand quite a bit of
gain variation, provided the audio remains clean.
This has been my experience with an interesting Direct Conversion
Single Signal receiver known as the R2. It was designed by Rick
Campbell, KK7B, and first published in 1993 in QST.
That's my experience. Yours may be different.
Jake Brodsky, AB3A mailto:fru...@erols.com
"Beware of the massive impossible!"
Dave
GHFS with my R8B. Sounds like FM...very low noise.
On Mon, 26 Feb 2001 10:29:21 -0500, Jake Brodsky <fru...@erols.com>
wrote:
AC6V
pileup or very busy adjacent frequencies. If you are on a weak DX station with
slow AGC and a big W6 bombs in a kHz away - this drives your receiver to low gain
and you will lose the DX until the AGC decays. Fast or no AGC for this situation.
For no AGC - use your RF Gain control and AF gain to optimize the conditions.
For a commercial CW station (any left?), in the clear, slow AGC would be fine,
but not for contesting or DXing.
Slow AGC works fine for SSB ragchewing when the other station is strong, this
alleviates the noise rush when the other guy puts pauses in his speech.
My 2 cents worth
who?
(400Hz is ok - 100 Hz is better) and slow AGC seems best. The narrow
filter removes the other stations (and noise as well!). A weak signal
is no problem as the AGC will tend to increase the gain until the
signal level into the detector is correct. At max gain, you get the
same signal as no AGC but also have your ears protected when the
lid down the street fires up his KW...
- 73 de Glenn
AC6V wrote in message <3A9A9D64...@ix.netcom.com>...
Steve H
tuning over a strong station doesn't "hang" so long as to make it likely
you'll miss a nearby fainter station as you tune across it. Slow AGC makes
listening to a station more enjoyable as it levels out the volume variations
of the signal as it gets stronger and then fades as SW usually does. I
usually leave mine on fast except when listening to very strong signals and
regular MW am stations.
"Al Klayton" <akla...@pcisys.net> wrote in message
news:t9ecnls...@corp.supernews.com...
al
>> Can someone discuss the advantages/disadvantages of fast vs med vs
>> slow AGC?
>>
>Steve H wrote:
>Use fast agc when tuning around the band so the gain reduction triggered
>by tuning over a strong station doesn't "hang" so long as to make it
>likely you'll miss a nearby fainter station as you tune across it. Slow
>AGC makes listening to a station more enjoyable as it levels out the
>volume variations of the signal as it gets stronger and then fades as SW
>usually does. I usually leave mine on fast except when listening to
>very strong signals and regular MW am stations.
>
Good info.
The only thing I would add is 'slow' agc setup is often better for usb/lsb
trans as 'fast' sometimes distorts in usb/lsb.
AGC adjustments can also be critical re fading,especialy fast fades.Having
a radio that allows RF adjustment & the AGC to be turned off is a very
effective 'fade' tool.
Al
--
al dudley....wash dc , usa
535,r70,c3g,m1200,m7000
al olg com