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Old March 23rd 04, 05:19 PM
Alan Horowitz
 
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Default best architecture for a homebrewed single-station FM broadcast dx receiver?

a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?

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Old March 24th 04, 04:31 PM
Jerry Greenberg
 
Posts: n/a
Default

Building a good receiver of any kind is complex, if you really want
good specs. Very few people have been able to accomplish this at home.
Just for calibration, you will require the proper instruments and
skills.

A good FM receiver with the proper antenna will do it, as long as the
antenna can see over the horizon, and within your distance range there
are no other stations at the same frequency. There are also the
physical limitations to consider as well.

Since the range of an FM station is about 120 to 140 miles at the very
best with a good antenna, there may be allowance for other stations to
broadcast within a 150 mile radius. If there are other stations, these
may be difficult to tune out.

You would be best off with an antenna that is cut to the frequency you
want to recieve, it will have to be able to see over the horizon
enough to see the transmitter site, have the proper directivity, and
be very well impedance matched to the receiver.

All the high end FM tuners are designed to be able to use an external
antenna, using a 75 ohm coax type hookup.

Have you considered calling this station to see if they are on the
net, satellite service, or on your local cable TV service? Many of
these small stations are on the net, and broadcast streamed
programming. This way you can use your computer to listen to them. '


Jerry Greenberg

--

(Alan Horowitz) wrote in message ...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?


  #3   Report Post  
Old March 24th 04, 04:31 PM
Jerry Greenberg
 
Posts: n/a
Default

Building a good receiver of any kind is complex, if you really want
good specs. Very few people have been able to accomplish this at home.
Just for calibration, you will require the proper instruments and
skills.

A good FM receiver with the proper antenna will do it, as long as the
antenna can see over the horizon, and within your distance range there
are no other stations at the same frequency. There are also the
physical limitations to consider as well.

Since the range of an FM station is about 120 to 140 miles at the very
best with a good antenna, there may be allowance for other stations to
broadcast within a 150 mile radius. If there are other stations, these
may be difficult to tune out.

You would be best off with an antenna that is cut to the frequency you
want to recieve, it will have to be able to see over the horizon
enough to see the transmitter site, have the proper directivity, and
be very well impedance matched to the receiver.

All the high end FM tuners are designed to be able to use an external
antenna, using a 75 ohm coax type hookup.

Have you considered calling this station to see if they are on the
net, satellite service, or on your local cable TV service? Many of
these small stations are on the net, and broadcast streamed
programming. This way you can use your computer to listen to them. '


Jerry Greenberg

--

(Alan Horowitz) wrote in message ...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?


  #6   Report Post  
Old March 24th 04, 04:31 PM
xpyttl
 
Posts: n/a
Default

You need to look at your particular situation. It sounds like you are out
in the desert. Is this the case? Are there other strong FM stations
nearby? Any others close in frequency?

Sensitivity is relatively easy to come by. The "best" audiophile receivers
are more about selectivity, which sounds like it might not be an issue in
your case. There is a similar issue with antennas. Directionality is there
more to combat multipath then it is to get gain. Is the terrain flat? If
you are between a lot of buildings then nothing you do at the receiver will
make up for what you don't do at the antenna.

You are right about needing to get your antenna high, but for a single,
point to point circuit, there is such a thing as high enough. More won't
help. But less will hurt dramatically.

The other big problem is getting the signal from the antenna to the radio.
At FM frequencies, line losses are significant, as is noise pickup. If the
signal is marginal, then you need to get an amplifier at the antenna. If
what reaches the receiver is mostly noise then no amount of sensitivity at
the receiver is going to help.

At any given frequency there is only a certain amount of sensitivity that
you can use. At FM broadcast frequencies, that amount of sensitivity is
easily obtainable these days. You can probably do "better" in terms of
sensitivity by building something, but you wouldn't hear the station any
better ... in fact, probably worse by having too much of a good thing.

...

"Alan Horowitz" wrote in message
...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?




  #7   Report Post  
Old March 24th 04, 04:31 PM
xpyttl
 
Posts: n/a
Default

You need to look at your particular situation. It sounds like you are out
in the desert. Is this the case? Are there other strong FM stations
nearby? Any others close in frequency?

Sensitivity is relatively easy to come by. The "best" audiophile receivers
are more about selectivity, which sounds like it might not be an issue in
your case. There is a similar issue with antennas. Directionality is there
more to combat multipath then it is to get gain. Is the terrain flat? If
you are between a lot of buildings then nothing you do at the receiver will
make up for what you don't do at the antenna.

You are right about needing to get your antenna high, but for a single,
point to point circuit, there is such a thing as high enough. More won't
help. But less will hurt dramatically.

The other big problem is getting the signal from the antenna to the radio.
At FM frequencies, line losses are significant, as is noise pickup. If the
signal is marginal, then you need to get an amplifier at the antenna. If
what reaches the receiver is mostly noise then no amount of sensitivity at
the receiver is going to help.

At any given frequency there is only a certain amount of sensitivity that
you can use. At FM broadcast frequencies, that amount of sensitivity is
easily obtainable these days. You can probably do "better" in terms of
sensitivity by building something, but you wouldn't hear the station any
better ... in fact, probably worse by having too much of a good thing.

...

"Alan Horowitz" wrote in message
...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?




  #8   Report Post  
Old March 24th 04, 07:19 PM
Tom Bruhns
 
Posts: n/a
Default

Thought I posted a reply yesterday, but it doesn't appear to have made
it.

Before we head off into the weeds with all sorts of opinions, how
about some clarification? I'd be interested in answers to several
questions, and suspect others will add more.

o What sort of distortion levels and signal to noise ratio are you
wanting to achieve?

o What level of desired signal will you be able to deliver to the
receiver's input terminals? Will it be strong enough, and free enough
from multipath, to make the desired distortion and SNR practical?

o What levels and relative frequencies will strong potentially
interfering signals be? -- Let's hope there's nothing significant on
an adjacent channel, and nothing really big on alternate channels
(+/-400kHz).

o How skilled are you in RF and digital construction, and what tools
do you have available for design, construction and turn-on/alignment?

o Do you want the receiver to be portable and battery-powered, or can
it be relatively large and line/mains powered?

(o Why would you not just buy a good FM tuner, and perhaps just build
a preselector if alternate-channel stations were a problem?)

Cheers,
Tom


(Alan Horowitz) wrote in message ...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?


  #9   Report Post  
Old March 24th 04, 07:19 PM
Tom Bruhns
 
Posts: n/a
Default

Thought I posted a reply yesterday, but it doesn't appear to have made
it.

Before we head off into the weeds with all sorts of opinions, how
about some clarification? I'd be interested in answers to several
questions, and suspect others will add more.

o What sort of distortion levels and signal to noise ratio are you
wanting to achieve?

o What level of desired signal will you be able to deliver to the
receiver's input terminals? Will it be strong enough, and free enough
from multipath, to make the desired distortion and SNR practical?

o What levels and relative frequencies will strong potentially
interfering signals be? -- Let's hope there's nothing significant on
an adjacent channel, and nothing really big on alternate channels
(+/-400kHz).

o How skilled are you in RF and digital construction, and what tools
do you have available for design, construction and turn-on/alignment?

o Do you want the receiver to be portable and battery-powered, or can
it be relatively large and line/mains powered?

(o Why would you not just buy a good FM tuner, and perhaps just build
a preselector if alternate-channel stations were a problem?)

Cheers,
Tom


(Alan Horowitz) wrote in message ...
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many
hundreds of miles.

thus I have decided to build my own single-station hi-performance
receiver to get the one station.

I know enough to know that ideally, the bulk of the gain,
directionality, selectivity should be at the antenna itself. Or even
more to the point, tower height. At least ideally. And
hi-performance single FM channel yagi's are easily spec'd from a
number of antenna houses. So that issue is not being placed on this
table.

The rest of the gain budget is.

Let the discussions begin. For example, what approach do the known
"name" receivers (Kloss Model One, GE Super Radio) use? can a
homebrewer do better?
Which commercial house builds the best resonant chambers for the 108
Mhz frequency? Can be be done easily at home? how about the
demodulation and audio portions?


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