Pre-selectors
 

Hello all,

It is nearing Christmas time and I am preparing my wish list for the
family. Before I put one on my list I would like some of your opinions on
pre-selectors. I am mainly looking at the MFJ line. If any of you have any
of these products I would be interested in hearing how you ell about them.
With this in mind I also need to let you know that I wish to enhance my
listening abilities, *NOT* make it an overly complex task. Some of these
look as though I could spend hours fiddling and not be able to take the time
to listen.

As usual your help is always appreciated.

Regards

Tim

Tim ODonnell wrote:

Hello all,

It is nearing Christmas time and I am preparing my wish list for the
family. Before I put one on my list I would like some of your opinions on
pre-selectors. I am mainly looking at the MFJ line. If any of you have any
of these products I would be interested in hearing how you ell about them.
With this in mind I also need to let you know that I wish to enhance my
listening abilities, *NOT* make it an overly complex task. Some of these
look as though I could spend hours fiddling and not be able to take the time
to listen.

As usual your help is always appreciated.

Regards

Tim

Why do you think you need a preselector?


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Why do you think you need a preselector?


Good question..

IF you use an antenna amp, the Preselector can go in between the
pre selector & the radio.
If you have continuous overload problems, Then maybe you need one.
I do have one, ( MFJ 1046 ) have had it hooked up for years
but rarely use it except on pass-thru mode..

Dan

This may be a bit naive of me but I just want to get the best reception that
I can. I have read some of the advertisements and a few reviews of
pre-selectors and everyone said that the helped reduce noise, and aided in
better reception. Now if these are a gimmick to grab your bucks then please
enlighten me. I really thought that they were common-place in peoples
shacks? Your question makes me think otherwise.

I also use a Sony AN-LP1 antena with my portable when traveling. This is an
active loop with a pre-selector. It is better than the whip with my DX398
and sometimes by tuning the pre-selector off band I can reduce gain and
noise and get a bit better reception or audibility.

So now my question is this. Is my thinking off? I just want the best
reception that I can get. I just thought that a pre-selector might help.
Like Dan said below I really don't expect to use it all the time. Just when
it may help.

Regards

Tim

"starman" wrote in message
...

Why do you think you need a preselector?

Tim ODonnell wrote:
So now my question is this. Is my thinking off? I just want the best
reception that I can get. I just thought that a pre-selector might help.
Like Dan said below I really don't expect to use it all the time. Just when
it may help.

You can hear down to the internal noise of the receiver. If the antenna brings the
propagating noise up over that level, no further improvement in the antenna will help,
except making it directional to favor signal or disfavor noise, if noise is directional.

Modern receivers are very sensitive, but tend to succumb to overload and cross modulation
that results (hearing anything loud in lots of places instead of the one it's at).

A preselector kills off loud things that aren't where you want to listen, giving you
the ability to get a little bigger antenna to work for you, up until it exceeds the
internal noise, and then a bigger antenna doesn't help again.

So you get the possibly small improvement between hearing propagating noise and
the intermodulation limit somewhat expanded, is all. The usual experience though
is that the preselector ``reduces the signal,'' because you tend to compare it with
the big antenna without preselector and not the built-in whip.

They put a preselector on some active antennas because of the intermodulation; other
active antennas (McKay Dymek DA100E) have lots of headroom and don't need the
preselector, and so you don't have to tune it. It may still overload your receiver
though, for instance almost any portable; and then you have to add a preselector
because of the receiver. It doesn't overload an R8B.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

In article , "Al - KA5JGV"
writes:


Personally I wouldn't bother with a preselector. The slight improvement is
not worth the cost, the additional knob tweaking required, or the lost space
taken up by it. If you are having problems with overloads, save the
preselector money and invest it into a better receiver.

Al KA5JGV

- I've rarely used mine ( Except with the cheap one IF sets)
- But they look Cool As Hell

If they had a blinking light to show how the'd saved your set from overload
they'd sell a million
:)

I don't want any extra knobs to turn that's for sure. One post talked about
propagation noise over receiver noise or other noises. now we're reaching
the limits of my knowledge. I don't know what propagation noise sounds like!
So that in itself is a problem. I use an old R8 and it doesn't overload I
know what that sounds like. I was just hoping that on occasions that I could
possibly eliminate cross talk on frequecies that I cannot tune out thru the
passband. It is the same type of problems that everyone has who loves to
listen to the radio and DX. I just thought that the Preselector might be a
tool that might be used to reduce a little noise, intermod and other types
of interference. Sorry folks I don't know all the terminology I just like to
listen and tinker a little.

If anyone else has something to share on this subject I am interested to
here what they have to say.


Tim

"Al - KA5JGV" wrote in message
...
Hi Tim,
No, a preselector is not a gimmick, but as long as you use phrases such as
"might help" or "a bit better" then you have a decent picture of what to
expect from it.

Use of a preselector is most noticeable with a lower quality receiver. If
it
tends to overload or pick up stations that shouldn't be there, a
preselector
"might help". The better quality receivers already have preselectors built
into them and they are properly matched to the receiver circuitry.

Personally I wouldn't bother with a preselector. The slight improvement is
not worth the cost, the additional knob tweaking required, or the lost
space
taken up by it. If you are having problems with overloads, save the
preselector money and invest it into a better receiver.

Al KA5JGV

Preselectors are very broadband; they just knock down 80m when you're
listening to 40m, say. They're on the order of MHz.

Passband is well attacked by selectable sideband (to get to the side
away from the interference), or a brickwall audio filter in the
special case of an interfering SSB signal offset in the direction
of the SSB sideband you're listening to. Passband is order of kHz.

Heterodynes are knocked down with an audio notch.

General background hiss type noise can be gotten at with a DSP.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

ToD,

Pre-Selectors: Do They Work ?
- Sometimes Yes :o)
- - Sometimes NO ;-{

MFJ makes many Antenna Tuners and Pre-Selectors.

1. Some are for SWL "Receive Only" Use.
* MFJ-956
* MFJ-959C
* MFJ-1020C (Active Antenna & External Antenna Pre-Selector)

2. Many others are for HAMs who are using them with Transmitters.
- - - If devise has a SWR-Meter, Inductor or Delay Function then it is
a HAM type unit.
* MFJ-901B
* MFJ-904
* MFJ-1040B (Active Antenna & External Antenna Pre-Selector)
* MFJ-1048
* MFJ-949
* MFJ-901B

3. If you have 'noise' problems in your area/location; then consider a
"Passive" Pre-Selector (NO built-in Amplifier).
* MFJ-1045C
* MFJ-1026 (Noise Cancelling Antenna)

4. If you do NOT have 'noise' problems in your area/location the
consider an "Active" Pre-Selector (with a built-in Amplifier).
* MFJ-959C

TBL: When it comes to Pre-Selectors:
- Can't Hertz ;-{
- - Just Mitz Help :o)
It is better to focus on your Antenna
and Spend your Time & Money there first.


iane ~ RHF
..
..
= = = "Tim ODonnell"
= = = wrote in message .. .
Hello all,

It is nearing Christmas time and I am preparing my wish list for the
family. Before I put one on my list I would like some of your opinions on
pre-selectors. I am mainly looking at the MFJ line. If any of you have any
of these products I would be interested in hearing how you ell about them.
With this in mind I also need to let you know that I wish to enhance my
listening abilities, *NOT* make it an overly complex task. Some of these
look as though I could spend hours fiddling and not be able to take the time
to listen.

As usual your help is always appreciated.

Regards

Tim


..

"Tim ODonnell" wrote in message ...
I don't want any extra knobs to turn that's for sure. One post talked about
propagation noise over receiver noise or other noises. now we're reaching
the limits of my knowledge. I don't know what propagation noise sounds like!
So that in itself is a problem. I use an old R8 and it doesn't overload I
know what that sounds like. I was just hoping that on occasions that I could
possibly eliminate cross talk on frequecies that I cannot tune out thru the
passband. It is the same type of problems that everyone has who loves to
listen to the radio and DX. I just thought that the Preselector might be a
tool that might be used to reduce a little noise, intermod and other types
of interference. Sorry folks I don't know all the terminology I just like to
listen and tinker a little.

If anyone else has something to share on this subject I am interested to
here what they have to say.


Tim

If you set it for "unity (zero) gain", what you have is an additional
tuned RF stage that gives extra RF selectivity, and it can be a
blessing on a weak station. However, most people try to use a
preselector as an RF amplifier and cause more problems with intermod
and cross-talk than they already had.

They can be a useful tool, but they are not a cure-all.

Tim ODonnell wrote:

I don't want any extra knobs to turn that's for sure. One post talked about
propagation noise over receiver noise or other noises. now we're reaching
the limits of my knowledge. I don't know what propagation noise sounds like!
So that in itself is a problem. I use an old R8 and it doesn't overload I
know what that sounds like. I was just hoping that on occasions that I could
possibly eliminate cross talk on frequecies that I cannot tune out thru the
passband. It is the same type of problems that everyone has who loves to
listen to the radio and DX. I just thought that the Preselector might be a
tool that might be used to reduce a little noise, intermod and other types
of interference. Sorry folks I don't know all the terminology I just like to
listen and tinker a little.

If anyone else has something to share on this subject I am interested to
here what they have to say.

Tim

Now I see what you're getting at. Preselectors are generally used to
improve the dynamic range of receivers (usually portables) that suffer
from spurious signals caused by intermodulation. The R8 has very good
dynamic range so a preselector is not likely to improve it
significantly. As for improving the bandwidth (selectivity) to reduce
"cross talk", a preselector would be useless. The tuning is not sharp
enough to reject a signal only a few Khz from the desired station. If
you really want better selectivity, I suggest trading your R8 for the
R8B. The selectable sideband sync' detector of the latter does wonders
for reducing and often eliminating adjacent channel interference.


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Ron Hardin wrote in message ...
Tim ODonnell wrote:
So now my question is this. Is my thinking off? I just want the best
reception that I can get. I just thought that a pre-selector might help.
Like Dan said below I really don't expect to use it all the time. Just when
it may help.

You can hear down to the internal noise of the receiver. If the
antenna brings the propagating noise up over that level, no further
improvement in the antenna will help, except making it directional
to favor signal or disfavor noise, if noise is directional.


RH,

So What Is Your Choices: (Why? -v- Why Not?)

[ ] Continue to use a simple Random Wire Antenna
and ADD a "Pre-Selector" to make it 'better'.

[ ] First improve your old antenna and try rebuilding/replacing
it into a "Low Noise" Antenna a la John Doty.

~ RHF



Modern receivers are very sensitive, but tend to succumb to overload and cross modulation
that results (hearing anything loud in lots of places instead of the one it's at).

A preselector kills off loud things that aren't where you want to listen, giving you
the ability to get a little bigger antenna to work for you, up until it exceeds the
internal noise, and then a bigger antenna doesn't help again.

So you get the possibly small improvement between hearing propagating noise and
the intermodulation limit somewhat expanded, is all. The usual experience though
is that the preselector ``reduces the signal,'' because you tend to compare it with
the big antenna without preselector and not the built-in whip.

They put a preselector on some active antennas because of the intermodulation; other
active antennas (McKay Dymek DA100E) have lots of headroom and don't need the
preselector, and so you don't have to tune it. It may still overload your receiver
though, for instance almost any portable; and then you have to add a preselector
because of the receiver. It doesn't overload an R8B.

RHF wrote:
So What Is Your Choices: (Why? -v- Why Not?)

[ ] Continue to use a simple Random Wire Antenna
and ADD a "Pre-Selector" to make it 'better'.

[ ] First improve your old antenna and try rebuilding/replacing
it into a "Low Noise" Antenna a la John Doty.

I'd always go to a low noise antenna; I do it myself on MW chiefly by
using pairs of outdoor active antennas combined in an ANC-4; it's low
noise because it's outdoors on buried coax, and I can steer a null on
an interference source. It works on locally-generated interference (ie.
not skywave) on any frequency, but skywave only on the low end of the
MW band. But on MW weak signals aren't much of a problem compared to
competing stations.

A broadband active loop plus a co-located active whip does the same thing
without taking any real estate, combined in and ANC-4. Its nulls are a
steerable V shape from one double-null endfire to the other, ``endfire''
being in the plane of the loop (its stand-alone maximum). With two whips
instead of a whip and a loop, endfire is in the direction of separation
of the whips (give it a quarter wave if you can) and you get the same V shape.

Lots of people use passive antennas instead of active in the same arrangement.

I don't go in much for a low-noise _single_ antenna because I'm never trying to
dig out a really weak signal, just one that's weaker than competition.

If your receiver overloads (mine doesn't) you'll have to use a preselector in any
case.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

I think that I finally made my point. I am sorry that you all had to figure
out what I was saying. Its terrible when you really don't know the lingo and
really don't want to go that deep into a hobby.

I think that I will do the following. 1, Improve my existing antenna. 2, add
a second antenna in a different directind and possible a different length.
3, I will probably add a preselector to my equipment. perhaps a MFJ959C or
the MFJ1045C. Finally number 4, Learn more about the radio listening hobby
to include the terminology.

Thanks all for your help and direction.

Tim


"Richard Cranium" wrote in message
om...
If you set it for "unity (zero) gain", what you have is an additional
tuned RF stage that gives extra RF selectivity, and it can be a
blessing on a weak station. However, most people try to use a
preselector as an RF amplifier and cause more problems with intermod
and cross-talk than they already had.

They can be a useful tool, but they are not a cure-all.

Tim You're quite welcome;

It takes a while to figure out what works & what doesn't; or what doesn'r
really work but is still good to have around just in case.

Adding a Second antenna at right angles to your first one will be the least
costly
giving the best return on your efforts..

Have fun ( Thats what it's all about, really )

Dan



In article , "Tim ODonnell"
writes:


I think that I finally made my point. I am sorry that you all had to figure
out what I was saying. Its terrible when you really don't know the lingo and
really don't want to go that deep into a hobby.

I think that I will do the following. 1, Improve my existing antenna. 2, add
a second antenna in a different directind and possible a different length.
3, I will probably add a preselector to my equipment. perhaps a MFJ959C or
the MFJ1045C. Finally number 4, Learn more about the radio listening hobby
to include the terminology.

Thanks all for your help and direction.

Tim

TOD,

Sounds Like a Plan :o)

~ RHF
..
..
= = = "Tim ODonnell"
= = = wrote in message .. .

I think that I finally made my point. I am sorry that you all had to figure
out what I was saying. Its terrible when you really don't know the lingo and
really don't want to go that deep into a hobby.

I think that I will do the following.
1, Improve my existing antenna.
2, add a second antenna in a different directind
and possible a different length.
3, I will probably add a preselector to my equipment.
perhaps a MFJ959C or the MFJ1045C.
Finally number 4, Learn more about the radio
listening hobby to include the terminology.

Thanks all for your help and direction.

Tim


"Richard Cranium" wrote in message
om...
If you set it for "unity (zero) gain", what you have is an additional
tuned RF stage that gives extra RF selectivity, and it can be a
blessing on a weak station. However, most people try to use a
preselector as an RF amplifier and cause more problems with intermod
and cross-talk than they already had.

They can be a useful tool, but they are not a cure-all.


..