wrote:

As a demod filter? I would image a low order active filter to clean
things up. Remember, this is the audio band, not RF. I've seen some
write ups on 455khz IFs being done with active filters.

Kiwa sells an active filter for 455Khz
http://www.kiwa.com/kiwa455.html

Note the AR7030 has "tone controls", so certainly it has an active
filter past the demod. The problem with building LCR filters in the
audio band is they are bulky, not to mention often inaccurate. With
active filters, you have more flexibility over component values.

Drake uses an LC filter in the IF. They "Get away" with it becuase of
the
lower IF they use. R390s, original not the R390A, and the R392 use
several staged of LC filters and have excellent skirts.

The Kiwa filter you refference is not a "active filter", but a ceramic
filter
with amplification. To me active filter means opamp or norton amp
with feedback to control pass/reject charactoristics. The premium Kiwa
unit is nearly as good as a crystal or mechanical filter and MUCH
easier
to connect. I installed one in a friends R2000 and was impressed by
the quality and how well it worked.

A big advantage of passive LC filters is they are much less "fussy"
then active filters. I like not having to mess with power and proper
bypassing.
And if you are willing to wind your own torroids, it is pretty easy to
get the
L very close to what you want. The C can be built with standard value
caps in parallel.


The Tone-Tilt filter I used in all 3 of our R2000s is active because it
would be
VERY difficult to use LC filters effectively.

Terry

wrote:
wrote:

As a demod filter? I would image a low order active filter to clean
things up. Remember, this is the audio band, not RF. I've seen some
write ups on 455khz IFs being done with active filters.

Kiwa sells an active filter for 455Khz
http://www.kiwa.com/kiwa455.html

Note the AR7030 has "tone controls", so certainly it has an active
filter past the demod. The problem with building LCR filters in the
audio band is they are bulky, not to mention often inaccurate. With
active filters, you have more flexibility over component values.

Drake uses an LC filter in the IF. They "Get away" with it becuase of
the
lower IF they use. R390s, original not the R390A, and the R392 use
several staged of LC filters and have excellent skirts.

Except we are not talking about IF filters .The "fading" filter is at
the end of the chain, i.e. past the demod.


The Kiwa filter you refference is not a "active filter", but a ceramic
filter
with amplification. To me active filter means opamp or norton amp
with feedback to control pass/reject charactoristics. The premium Kiwa
unit is nearly as good as a crystal or mechanical filter and MUCH
easier
to connect. I installed one in a friends R2000 and was impressed by
the quality and how well it worked.

A big advantage of passive LC filters is they are much less "fussy"
then active filters. I like not having to mess with power and proper
bypassing.
And if you are willing to wind your own torroids, it is pretty easy to
get the
L very close to what you want. The C can be built with standard value
caps in parallel.

Except this is at audio frequencies, where the component sizes are much
larger. Again, this is not at IF frequencies.




The Tone-Tilt filter I used in all 3 of our R2000s is active because it
would be
VERY difficult to use LC filters effectively.

Terry

wrote:
As a demod filter? I would image a low order active filter to clean
things up. Remember, this is the audio band, not RF. I've seen some
write ups on 455khz IFs being done with active filters.

Kiwa sells an active filter for 455Khz
http://www.kiwa.com/kiwa455.html

Note the AR7030 has "tone controls", so certainly it has an active
filter past the demod. The problem with building LCR filters in the
audio band is they are bulky, not to mention often inaccurate. With
active filters, you have more flexibility over component values.

For an example of what I consider to be a very usefull filter, please
look at:
http://members.tripod.com/roymal/ReverbTone.htm

With minor component value chages, it is easy to get more or less
cut/booast and/or frequency range.

Please note that I had nothing to do with this page, I found it
usefull.

Terry

wrote:

Dallas Lankford has done some serious research on the cause and cure
of/for
the distortion caussed by ionospheric "hops".

Interesting! In the RTTY world, this is known as selective fading.
Usually an o'scope is used as a tuning indicator, one set of deflection
plates being connected to the "mark" signal and the other set of
deflection plates being connected to the "space" signal, giving the
classic "cross" display (looks like a 'plus' sign on the screen).

The mark and space signal generally used to be 850 Hz apart, commercial
press stuff 425 Hz apart and most of the stuff today using a 170 Hz shift.

During disturbed ionospheric conditions, you would see this selective
fading come into play; i.e., either the mark or space would fade to
nothing while the other signal was solid--even though they were only 170
Hertz apart.

"Carter, k8vt" wrote:

wrote:

Dallas Lankford has done some serious research on the cause and cure
of/for
the distortion caussed by ionospheric "hops".

Interesting! In the RTTY world, this is known as selective fading.

Gee! In the SWL'ing world, this is known as selective fading.

Who woulda thunk it.

It's multipath distortion.

dxAce
Michigan
USA

Well, it works.

I have been playing with the ELPAF since last autumn; first on my
R-390A, which, despite having done the AF Deck mod, does have its
quirks with regard to audio quality. The ELPAF cleaned up audio
admirably. Mostly doing MW DX then. Then, this summer together with a
modified IC-703 mostly on SW. It practically eliminates the distortion
caused by fades, as well as high-frequency hiss and noise giving an
audibly better signal to noise ratio. The trade-off is of course a
more limited audio response. Personally I can live with that - I never
use bandwidths wider than 6-7 kHz anyway. My ELPAF has a bypass switch
so it is easy to compare audio quality.

I used to have an SE-3 as well, and enjoyed the excellent audio it
produced. The ELPAF does little less with regard to audio recovery. I
am thinking about doing an A-B comparison between the two later on.

BM

Sorry for being such a RX newbie here. I guess I shoulda stayed awake
more during signals class. My expertise is very large switching and
resonant power supplies and transmitters.

So the multipath distortion causes fading of the carrier only?? This
makes some sense to me. A small set of the lower sideband frequencies
would also cause phase cancellation, but since the audio spectrum is
moving around so fast no one notices. I think I'm on the right track
here. So use another carrier slaved to the received carrier and you
get better reception during fade. Even if it wanders a few cycles
during fade you probably don't hear anyway. I guess that is how a sync
detector works.

I Imagine it would be a chore to build a sync detector from the ground
up, but I would also think it must have already been put into an ic
chip, no???

I like the link R2000swl posted to AmWindow for the precision full-wave
rectifier. I think I'll stick it on a pc board and give it a try. If
anybody wants a board let me know. They are very inexpensive.

bm, or anyone else, if you have good link to ELPAF or alternative RX
circuits then maybe I could throw that down on same board if not too
much room.

Details of board size at www.expresspcb.com I do the small one double
side and no silkscreen 3 boiards 60bucks.

You can contact me off board at

73
Bob
N9NEO





bm wrote:
Well, it works.

I have been playing with the ELPAF since last autumn; first on my
R-390A, which, despite having done the AF Deck mod, does have its
quirks with regard to audio quality. The ELPAF cleaned up audio
admirably. Mostly doing MW DX then. Then, this summer together with a
modified IC-703 mostly on SW. It practically eliminates the distortion
caused by fades, as well as high-frequency hiss and noise giving an
audibly better signal to noise ratio. The trade-off is of course a
more limited audio response. Personally I can live with that - I never
use bandwidths wider than 6-7 kHz anyway. My ELPAF has a bypass switch
so it is easy to compare audio quality.

I used to have an SE-3 as well, and enjoyed the excellent audio it
produced. The ELPAF does little less with regard to audio recovery. I
am thinking about doing an A-B comparison between the two later on.

BM

Back to the Future movie is on Radio tv.See if your radio has a Flux
Capacitor.According to the doc,that's what makes time travel possible.
Calling Art Bell,calling George Noory.I found the secret to time travel.
cuhulin

On 30 Jul 2006 09:28:29 -0700, "N9NEO"
wrote:

Sorry for being such a RX newbie here. I guess I shoulda stayed awake
more during signals class. My expertise is very large switching and
resonant power supplies and transmitters.

So the multipath distortion causes fading of the carrier only?? This
makes some sense to me. A small set of the lower sideband frequencies
would also cause phase cancellation, but since the audio spectrum is
moving around so fast no one notices. I think I'm on the right track
here. So use another carrier slaved to the received carrier and you
get better reception during fade. Even if it wanders a few cycles
during fade you probably don't hear anyway. I guess that is how a sync
detector works.

I Imagine it would be a chore to build a sync detector from the ground
up, but I would also think it must have already been put into an ic
chip, no???

I like the link R2000swl posted to AmWindow for the precision full-wave
rectifier. I think I'll stick it on a pc board and give it a try. If
anybody wants a board let me know. They are very inexpensive.

bm, or anyone else, if you have good link to ELPAF or alternative RX
circuits then maybe I could throw that down on same board if not too
much room.

Details of board size at www.expresspcb.com I do the small one double
side and no silkscreen 3 boiards 60bucks.

You can contact me off board at

73
Bob
N9NEO


http://users.adelphia.net/~alexmm/Prod_det/detector.htm

On 30 Jul 2006 09:28:29 -0700, "N9NEO"
wrote:

http://home.att.net/~wa1sov/technical/sync_det.html