"Pete KE9OA" wrote in message
...
It wouldn't be quite the same. You would be clipping the sidebands, and
experience quite a bit of distortion. A 110kHz filter is about as narrow
as
you can go.
I've been meaning to come up with a tuner that would be in the class of a
McIntosh MR78 for the past couple of years, but something has always come
up. Maybe after my current project, I will do this, if there is enough
interest.

Pete

I hear that FM RX's are pretty complicated affairs. Most FM DXers it seems
just modify commercial sets. Reduce bandwidth from say 230Khz to 110 Khz. I
suppose that going this way has quite a lot of merit. Cheaper probably.

Richard wrote:
I hear that FM RX's are pretty complicated affairs. Most FM DXers it seems
just modify commercial sets. Reduce bandwidth from say 230Khz to 110 Khz. I
suppose that going this way has quite a lot of merit. Cheaper probably.

It's certainly the most bang for the buck. Really, a good FM receiver
isn't much more complicated than a good AM receiver -- but a
bare-bones-just-barely-receives-the-strongest-stations FM receiver is
quite a bit more complicated than a bare-bones-..... AM set.

Usually you can reduce the bandwidth of a FM receiver by simply removing
the monolithic ceramic filters and replacing them. I've done that on my
Technics ST-G50; at my location 30 miles outside Nashville, I have
received at least one DX station on every frequency that doesn't have a
local. (yes, that includes the frequencies adjacent to 100,000-watt
locals)

Forget what I paid for the filters - it was definitely less than $5
apiece. My tuner needed two.

=============================

Regarding going to 20KHz bandwidth...

In DX situations with heavy interference, a very narrow bandwidth might
be helpful for identifying DX stations. The programming will be mostly
unintelligible in a 20KHz bandwidth, but maybe it'll be more
intelligible than it would be against the interference from adjacent
channels in a more reasonable bandwidth.

I occasionally use the narrow filters in my TH-F6 HT to DX television
audio. Nobody would dream of listening to that audio for entertainment
but one can identify things they'd never ID on a TV set.

Don't know anyone who's tried putting a 10.7MHz IF 20KHz or similar
bandwidth filter in a FM broadcast tuner. You'd want it to be one of
multiple bandwidths, so you could select something more reasonable for
stronger signals.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Actually, they aren't much different than an AM design, except that
generally, you use quadrature detection for demodulation, and that you have
a deemphasis filter. The I.F. bandwidth is different, but pretty much
everything else is the same.

Pete

Richard wrote in message
...

"Pete KE9OA" wrote in message
...
It wouldn't be quite the same. You would be clipping the sidebands, and
experience quite a bit of distortion. A 110kHz filter is about as narrow
as
you can go.
I've been meaning to come up with a tuner that would be in the class of
a
McIntosh MR78 for the past couple of years, but something has always
come
up. Maybe after my current project, I will do this, if there is enough
interest.

Pete

I hear that FM RX's are pretty complicated affairs. Most FM DXers it seems
just modify commercial sets. Reduce bandwidth from say 230Khz to 110 Khz.
I
suppose that going this way has quite a lot of merit. Cheaper probably.

Richard wrote:
I hear that FM RX's are pretty complicated affairs. Most FM DXers it seems
just modify commercial sets. Reduce bandwidth from say 230Khz to 110 Khz. I
suppose that going this way has quite a lot of merit. Cheaper probably.

It's certainly the most bang for the buck. Really, a good FM receiver
isn't much more complicated than a good AM receiver -- but a
bare-bones-just-barely-receives-the-strongest-stations FM receiver is
quite a bit more complicated than a bare-bones-..... AM set.

Usually you can reduce the bandwidth of a FM receiver by simply removing
the monolithic ceramic filters and replacing them. I've done that on my
Technics ST-G50; at my location 30 miles outside Nashville, I have
received at least one DX station on every frequency that doesn't have a
local. (yes, that includes the frequencies adjacent to 100,000-watt
locals)

Forget what I paid for the filters - it was definitely less than $5
apiece. My tuner needed two.

=============================

Regarding going to 20KHz bandwidth...

In DX situations with heavy interference, a very narrow bandwidth might
be helpful for identifying DX stations. The programming will be mostly
unintelligible in a 20KHz bandwidth, but maybe it'll be more
intelligible than it would be against the interference from adjacent
channels in a more reasonable bandwidth.

I occasionally use the narrow filters in my TH-F6 HT to DX television
audio. Nobody would dream of listening to that audio for entertainment
but one can identify things they'd never ID on a TV set.

Don't know anyone who's tried putting a 10.7MHz IF 20KHz or similar
bandwidth filter in a FM broadcast tuner. You'd want it to be one of
multiple bandwidths, so you could select something more reasonable for
stronger signals.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Actually, they aren't much different than an AM design, except that
generally, you use quadrature detection for demodulation, and that you have
a deemphasis filter. The I.F. bandwidth is different, but pretty much
everything else is the same.

Pete

Richard wrote in message
...

"Pete KE9OA" wrote in message
...
It wouldn't be quite the same. You would be clipping the sidebands, and
experience quite a bit of distortion. A 110kHz filter is about as narrow
as
you can go.
I've been meaning to come up with a tuner that would be in the class of
a
McIntosh MR78 for the past couple of years, but something has always
come
up. Maybe after my current project, I will do this, if there is enough
interest.

Pete

I hear that FM RX's are pretty complicated affairs. Most FM DXers it seems
just modify commercial sets. Reduce bandwidth from say 230Khz to 110 Khz.
I
suppose that going this way has quite a lot of merit. Cheaper probably.