Can you get high quality sound from an AM tuner?

[John]

Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?

 

[David Nicholls]

John wrote:

Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?

Depends on the tuner and the station. Back before we switched down to
9kHz spacing, local ABC RN (2CN in CBR) was very respectable using an
AWA AM3, or on the Pik Synchrodyne circuit published in Electronics
Aust. in 1975. As a gerneal rule, AM/FM tuners have crap AM stages.

AWA AM3's turn up from time to time on Ebay (au).

There's a HiFi AM group on Yahoo groups:
http://groups.yahoo.com/group/hifi-am/

DN

 

[David Nicholls]

9kHz spacing, local ABC RN (2CN in CBR) was very respectable

Make that 2CY.

DN

 

[Patrick Turner]

David Nicholls wrote:

John wrote:
Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?




Depends on the tuner and the station. Back before we switched down to
9kHz spacing, local ABC RN (2CN in CBR) was very respectable using an
AWA AM3, or on the Pik Synchrodyne circuit published in Electronics
Aust. in 1975. As a gerneal rule, AM/FM tuners have crap AM stages.

AWA AM3's turn up from time to time on Ebay (au).

There's a HiFi AM group on Yahoo groups:
http://groups.yahoo.com/group/hifi-am/

DN

Many AM tuners give only 2 kHz of audio bandwidth.
Yup, 2 kHz. Its usally because of the RF and IF bandwidth in the set which is also
only 4 kHz, hence the audio bw is limited to 2 kHz.
Tubed tuners gave slightly more on average, about 3 khz, and with
speakers used on old radios with a rising response above 400Hz the AF bw was perhaps
6 kHz.
But tubed tuners with an RF amp input stage will usually also have poor AF bw.
They gave "mellow" sound, ie, distorted with 5%+ of mainly 2H and perhaps 2.5kHz of
audio bw.


But I have two tubed AM tuners good for 9kHz due to careful over coupling in the
IF transformers and these sound very nice indeed compared to much solid state crap,
or the typical older tube radio.
The older sets were tailored to be selective allowing socially isolated ppl in the
bush
to enjoy stations far away despite the crakles and noises.
Very few AM radios or dedicated tuners were made for good reception
of local stations to suit hi-fi afficionardos in the major cities.

By the time ppl woke up to hi-fi in a big way, FM radio was with us.
People didn't need the cricket scores or horse racing to be announced in hi-fi,
and for many years live music broadcasts from Sydney Town Hall was via AM from 2FC,
and ppl enjoyed it although much programme was missing, ie, all above about 5 kHz.


Some old AM tubed radios can have the first IF altered to include a tertiary
winding of about 8 turns wound over the primary of IFT No1,
and then placed in series with the secondary winding and able to be switched in or
out.
Thus you tune using the narrow 5kHz bw if there is that much, then when tuned you
switch to
extend the bw of the IFT, and avoid the imprecise tuning with the tertiary
switched in.

6BE6 F converter, 6BA6 intermediate F amp, and a pair of cathode followers using
12AU7
plus silicon diodes will make a nice linear detector, and the sound will be very
clean.

Patrick Turner.

 

[Phil Allison]

"John"

Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

** Care to pose a question that is not utterly meaningless ??

Lest you be thought a troll.



............ Phil

 

[Trevor Wilson]

"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...

Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

**Except for interference, there is no technical reasons why AM cannot equal
or surpass the performance of FM. Many years ago, I built what is known as a
TRF (Tuned Radio Frequency) AM tuner. TRF radios suffer from a number of
problems, compared to the more usual Superheterodyne tuners. TRFs are more
complex to build, more complex to adjust and generally a PITA. They do,
however, offer excellent sound quality. I recall calling up the local radio
station to advise them that one of their turntables had a worn stylus. The
difference between turntables was easy to pick on my old TRF. There is a
'gotcha' however. AM radio stations have restricted their transmission
bandwidth, such that high fidelity reproduction is pretty much impossible
nowadays.


--
Trevor Wilson
www.rageaudio.com.au

 

[Eric]

Second time lucky

part of the reason (apart from bandwidth) is a diode is used to take the
sound off the IF for a sound detector,
a diode is a non-linear device and that is were you get the problems like
distortion


for better quality AM take a closer look at "am stereo" receiver even if
"your" radio station does not boardcast in "am stereo" the mono sound
will sound a lot better than a radio receiver made with just a (crappie)
diode for the sound detector.

for more on "am stereo" plug it into google and do a bit of reading.

take my word for it I have made a "am stereo" using the Harris system, it
will never sound as good as FM (well we know that already) bit it sound
heaps better than a standard AM radio. From EA magazine many years ago, I
believe Dick Smith had the kit, also Silicon Chip, (or was the Australian
electronics magazine before that ETI) come to think of it, it was ETI just a
little bit before SC time.


John <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM tuner
of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

 

[Sir Nigel Puke-Fuui]

On Fri, 02 Dec 2005 21:43:48 +1030, John <sittinginthepool@internode.on.net> wrote:

Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?

Build yourself a crystal set. (Seriously). Due to the small number of components

there is little to limit the audio bandwidth. The downside is that you must have a
strong incoming signal and will probably need an outdoor antenna. Take the audio
from where the headphones would normally connect.

This works. You will be pleasantly surprised.

 

[Patrick Turner]

Eric wrote:

Second time lucky

part of the reason (apart from bandwidth) is a diode is used to take the
sound off the IF for a sound detector,
a diode is a non-linear device and that is were you get the problems like
distortion

Diode plus RC circuits can produce negligible distortion if the voltage being
detected is
high, and the diode is forward biased.
Perhaps you know nothing about making such circuits, and making them
as linear as need be.

for better quality AM take a closer look at "am stereo" receiver even if
"your" radio station does not boardcast in "am stereo" the mono sound
will sound a lot better than a radio receiver made with just a (crappie)
diode for the sound detector.

Stereo AM can have the same distortion as mono AM if the detector
and the rest of the set is poor quality.

for more on "am stereo" plug it into google and do a bit of reading.

take my word for it I have made a "am stereo" using the Harris system, it
will never sound as good as FM (well we know that already) bit it sound
heaps better than a standard AM radio. From EA magazine many years ago, I
believe Dick Smith had the kit, also Silicon Chip, (or was the Australian
electronics magazine before that ETI) come to think of it, it was ETI just a
little bit before SC time.

No such kits are available now, and a DIYer has to think about all aspects of AM
detection himself
now if he wants to build anything.

But there is little AM programme worth real hi-fi tuners except
the ABC amd print hadicapped stations.
Commercials playing music play mostly MP3 and processed music to
allow poor radios to get slightly better reception.

Patrick Turner.

John <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM tuner
of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

 

[Patrick Turner]

Trevor Wilson wrote:

"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

**Except for interference, there is no technical reasons why AM cannot equal
or surpass the performance of FM. Many years ago, I built what is known as a
TRF (Tuned Radio Frequency) AM tuner.

The audio bandwidth of any AM tuner is 1/2 the RF bandwidth of the tuned
circuits,
so that if you have a 1MHz tuned circuit with a Q of 100, then the RF bw =
10kHz,
and the Af that can be recovered is -3dB at 5 kHz.

Any transmitted AM wave actually consists of the carrier tone at say 1,053 kHz,
and the
upper and lower sideband produced by the modulation, so if there is a
5 kHz tone used to modulate the amplitude of a 1,053 kHz carrier,
then in fact there are frequencies of 1,048 kHz and 1,058 kHz present as well as
the carrier of
1,053 kHz.
A tuned circuit which has a bw which is -3dB at +/- 5 kHz will attenuate the two
sidebands
by 3dB in the above case, and if the af modulation F was 10kHz, the attenuation
of the sidebands and hence the af modulation is a lot more, maybe 12dB.

With several cascaded tubned circuits, the sideband attentuation slope is quite
steep,
and the af bw will roll off quite steeply, and no amount of treble boost from a
tone control
can compensate for the losses caused by the poor RF or IF bw.
Such low RF or IF bw is good for long distance listening, but who would bother,
since noise and dull programme content defeats anyone interested in DX.

In a TRF set the problem is that you may well need 3 or 4 tuned circuits
all cascaded, and tunable and which track each other, which thus prevents
wide RF bw, maybe 2 kHz if you are lucky if the Q of each of the circuits is
above 50.

TRF radios suffer from a number of
problems, compared to the more usual Superheterodyne tuners. TRFs are more
complex to build, more complex to adjust and generally a PITA.

The reasons are listed above.
Also the skirt selectivity is poor so that stations only 50hHz away may
only be -50dB, and audible when tuned to a weak local.

They do,
however, offer excellent sound quality. I recall calling up the local radio
station to advise them that one of their turntables had a worn stylus. The
difference between turntables was easy to pick on my old TRF. There is a
'gotcha' however. AM radio stations have restricted their transmission
bandwidth, such that high fidelity reproduction is pretty much impossible
nowadays.

Most stations that are able to transmit 9kHz, will do so, and this usually
sounds very heathy
for speach and most music.
Its far better than 2.5kHz.

There is no reason why a superhet with an IF channel cannot sound equally
good and measure well compared to any TRF you may like to build.
The af bandwidth can be arranged to be 10kHz by juggling the IF
coil distances and using a tertiary on IFT no1, which was done on many
japanese imported tubed am/fm recievers.

Such a set has usally got a total of 5 tuned circuits, one RF and 4 IF,
with the 4 IF having two each and critically coupled to get a wide IF pass band
to thus get
wide band af despite the LC circuits having a high Q if measured separately.
Nobody could ever achieve the skirt selectivity that you can get with such a
superhet
with a TRF.
-60dB is easily possible at 45kHz away from a wanted station.

There were several kits produced in the past for solid state tuners which could
make
10kHz af bw and at low thd but one cannot obtain the special parts,
so if anyone wants to build a decent AM tuner tomorrow, they must learn all
about
superhets and IT tranny construction and DIY a tuner or
revise an old tube set, and hope the plate voltages don't kill them in the
attempt.

And setting up variable ľ tubes to work properly without distorting much and
setting up
a distortion free diode detector is an art and the product of a keen mind
indeed.

So in a nutshell, good AM is not available to the ordinary punter unless you buy

something special already made.

And indeed it can sound very well.

Patrick Turner.

--
Trevor Wilson
www.rageaudio.com.au

 

[Patrick Turner]

Sir Nigel Puke-Fuui wrote:

On Fri, 02 Dec 2005 21:43:48 +1030, John <sittinginthepool@internode.on.net> wrote:
Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?

Build yourself a crystal set. (Seriously). Due to the small number of components
there is little to limit the audio bandwidth. The downside is that you must have a
strong incoming signal and will probably need an outdoor antenna. Take the audio
from where the headphones would normally connect.

This works. You will be pleasantly surprised.

I will NOT be pleasantly surprised.

To get 10kHz of audio bw, the RF bw of the crystal set LC
must be 20kHz, so the Q will have to be only 50, and sure the fidelity
of a wanted station will be ok but all the other stations will be anle to be heard in
the background.

Crystal sets are only good for kids to learn basics.

And the distortion from the low signals at low currents into diodes isn't too good
either.

Patrick Turner.

 

[Eric]

sorry I can not give you the magazine PCB number, but Dick Smith PCB number
is/was ZA1699 the PCB measures about 110mm * 145mm it has 3 IC's to it part
from the regulator HCF4016, UAF774 but the heart of the decoder was a
MC13020 (I am sure it was a Electronics Australia project.)

I purchased the blank PCB from a sale when Dick Smith had there head office
in Newmarket, corner of Khyber pass Road & Park Road it must be about 15
years ago (about 1990) give or take a few years

I converted a old AM receiver, latter on I went to buy a AM-FM (Hi-fi
looking type) tuner to add on to my stereo, switching the amplifier input
from my new AM-FM tuner to my old converted AM receiver there was a
noticeable difference in sound quality.


Patrick Turner <info@turneraudio.com.au> wrote in message
news:4390FD9A.BF3EB3F0@turneraudio.com.au...


Eric wrote:

Second time lucky

part of the reason (apart from bandwidth) is a diode is used to take the
sound off the IF for a sound detector,
a diode is a non-linear device and that is were you get the problems like
distortion

Diode plus RC circuits can produce negligible distortion if the voltage
being
detected is
high, and the diode is forward biased.
Perhaps you know nothing about making such circuits, and making them
as linear as need be.

for better quality AM take a closer look at "am stereo" receiver even if
"your" radio station does not boardcast in "am stereo" the mono sound
will sound a lot better than a radio receiver made with just a (crappie)
diode for the sound detector.

Stereo AM can have the same distortion as mono AM if the detector
and the rest of the set is poor quality.

for more on "am stereo" plug it into google and do a bit of reading.

take my word for it I have made a "am stereo" using the Harris system,
it
will never sound as good as FM (well we know that already) bit it sound
heaps better than a standard AM radio. From EA magazine many years ago, I
believe Dick Smith had the kit, also Silicon Chip, (or was the Australian
electronics magazine before that ETI) come to think of it, it was ETI just
a
little bit before SC time.

No such kits are available now, and a DIYer has to think about all aspects
of AM
detection himself
now if he wants to build anything.

But there is little AM programme worth real hi-fi tuners except
the ABC amd print hadicapped stations.
Commercials playing music play mostly MP3 and processed music to
allow poor radios to get slightly better reception.

Patrick Turner.

John <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM
tuner
of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?

 

[John]

Sir Nigel Puke-Fuui wrote:

On Fri, 02 Dec 2005 21:43:48 +1030, John <sittinginthepool@internode.on.net> wrote:
Can you get high quality or "better then average" sound out of the AM tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going through
an amplifier and such?

Build yourself a crystal set. (Seriously). Due to the small number of components
there is little to limit the audio bandwidth. The downside is that you must have a
strong incoming signal and will probably need an outdoor antenna. Take the audio
from where the headphones would normally connect.

This works. You will be pleasantly surprised.

Well that wa rather comical..........

My original question was serious as a topic of interest. I
have a Realistic branded AM/FM tuner fed through an
Akai amplifier and 2 speakers. I'm reasonably happy with
the performance and was asking out of interest if AM can
be improved.......

But thankyou for the comical response Sir Nigel

 

[Bob Parker]

I remember that technique- also known as a synchronous receiver in
which the local oscillator is on the same frequency and in phase with
the carrier. So instead of the mixer stage producing an intermediate
frequency, the output is the original audio.
Many years ago I experimented with a very simple version of that
idea, and I was surprised by the quality of the audio.
Unfortunately the difficulties of tuning this kind of circuit and
keeping the LO in phase with the carrier so it doesn't lose lock and
cause a horrendous audio squeal seem to have been what stopped it from
ever being popular.

Bob


On Sat, 3 Dec 2005 17:49:59 +0800, "Alan Rutlidge"
<don't_spam_me_rutlidge@iinet.net.au> wrote:

"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?


I can recall an Electronics Australia project called the Homodyne Tuner (now
that will get Phil all fired up). Built one of these tuners (circa 1973 ?)
as a kit. Sounded quite a bit better than many commercial AM tuners of the
day. The only thing I hated about it was the method of tuning. It used
variable inductance coils (similar to those used in car radios of the era)
which IMHO was a bit cumbersome. Demodulation was based around a Motorola
IC and sensitivity was adequate.

The only drawback was the due to it's wide bandwidth and low selectivity,
listening at nights occasionally resulted in some distant station crosstalk
and interference. Other than that, the sound was very respectable for a
70's kit job.

Cheers,
Alan

 

[David Nicholls]

Alan Rutlidge wrote:

"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...

Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?



I can recall an Electronics Australia project called the Homodyne Tuner (now
that will get Phil all fired up). Built one of these tuners (circa 1973 ?)
as a kit. Sounded quite a bit better than many commercial AM tuners of the
day. The only thing I hated about it was the method of tuning. It used
variable inductance coils (similar to those used in car radios of the era)
which IMHO was a bit cumbersome. Demodulation was based around a Motorola
IC and sensitivity was adequate.

The only drawback was the due to it's wide bandwidth and low selectivity,
listening at nights occasionally resulted in some distant station crosstalk
and interference. Other than that, the sound was very respectable for a
70's kit job.

Cheers,
Alan

That was the Philip Pik synchrodyne circuit. It wasn't your typical kit
circuit (a lot more skill required to build and tune, and you had to
source all the parts yourself), but I agree with your point about the
slug tuning. The demodulation didn't involve a standard "demodulator"
chip but a couple of CMOS chips (4016 quad switch, 4013 dual D flip
flop) and some comparators and op-amps. The original papers are are
available on the hifi-am Yahoo group in the files section. EA June 1975
and Proc. IREE, Sept 1975.

As for sound, it avoided the bandwidth problem PT referred to (bandwidth
determined by the audio bandwidth, with a TRF front end with 60kHz
bandwidth) and sounded very close to FM (although mono) in quality,
provided you listened to local ABC. The AWA AM3 was sold in the US as
the McKay Dymek AM3, but it wasn't a patch on the Pik circuit for audio
quality.

DN

 

[Patrick Turner]

Alan Rutlidge wrote:

"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?


I can recall an Electronics Australia project called the Homodyne Tuner (now
that will get Phil all fired up). Built one of these tuners (circa 1973 ?)
as a kit. Sounded quite a bit better than many commercial AM tuners of the
day. The only thing I hated about it was the method of tuning. It used
variable inductance coils (similar to those used in car radios of the era)
which IMHO was a bit cumbersome. Demodulation was based around a Motorola
IC and sensitivity was adequate.

The only drawback was the due to it's wide bandwidth and low selectivity,
listening at nights occasionally resulted in some distant station crosstalk
and interference. Other than that, the sound was very respectable for a
70's kit job.

Cheers,
Alan

The problem with homodynes and synchrodynes is that their
selectivity depends on the profile of the audio filter following the
synchronous detector.

Stations which are 9kHz apart in Oz can interfere with each other because
sidebands of the modulation of one station can stretch out into the
bandwidth of another station, so you can get whistly monkey chatter
that a 9kHz notch filter cannot remove.
There needs to be good selectivity in the RF amp first stage but with no
attenuation of the modulation sidebands; this means a TRF input stage
with special tuning, and boy is thatv difficult to get right if you have never
built such a thing; a complete pita.

A superhet using tubes and IF trannies is a lot more fun although hard work to
build; the high IF voltage of about 10Vrms at 455khz is easily attainable
with a pentode and thus a maximum of 5Vrms of audio signal at 100% modulation
can be obtained
and there is negligible thd generated in the diode detector buffered by a
cathode follower.

But also a wide band ceramic IF filter could be used with solid state to get
the ideal passband of 20kHz at 445kHz but with very steep roll off each side of
the pass band.

There are other methods using 2 IF amp stages and having the IF at 2.5MHz,
so that its easier to get 20kHz bw after 6 tuned circuits in 3 IF transformers.
Winding the IFTs is easier as F goes higher, but again its a lotta effort and
pain
to teach oneself how to do it.

Its probably easier to digitise the antenna signal and use a PC to
count out the AM station you want.

The simplest tube set I have uses 6BE6 input mixer after a ferrite rod antenna,
6BA6 vari ľ pentode IF amp at 455kHz, then a 1/2 12AU7 cathode follower buffer
to drive the diode
plus CR peak detector, followed by another 1/2 12AU7 cathode follower to
prevent loading the first RC filter so that you get very low thd in the diode
detector.

I get about 4Vrms average signal level and very clean from the set.
The 6BA6 runs with about -5 to -8 V of avc voltage which
makes the the amplification of the IF envelope fairly linear, just a bit of 2H.

I have also used an RF amp in another set which accepts all the avc,
so that the IF pentode is a 6BX6 sharp cut off pentode which is more linear
than the vari ľ tube, and that sounds even better.

Audio bw can be increased by altering the distance between the
two IF windings on IFT No 1.

Unfortunately most IFTs you find in old valve sets have very high Q so that only

10kHz of IF bw is possible per IFT, so that after two such stages bw falls to
only
7kHz, thus giving 3.5kHz of audio.

But in some setys I have cut the former of the IF coils in the centre and
placed a cardboard tube sleeve over them to allow the coils to be slid slightly
closer to further flatten the response of the IFT.
Placing 100k across each IFT coil also reduces the Q somewhat and
broadens the bw but as some cost to IF amp gain.

Fiddling around with all these things are terribly prone to
oscillations at 455kHz which make the station tuning whistly
across all or part of the band.

Every old radio set you may find has had the layout carefully considered
and trialed and tweaked to get rid of stray parasitic oscillations, so if you
get an old set
to play with expect major amounts of time to get it working better.

Patrick Turner.

 

[Patrick Turner]

Bob Parker wrote:

I remember that technique- also known as a synchronous receiver in
which the local oscillator is on the same frequency and in phase with
the carrier. So instead of the mixer stage producing an intermediate
frequency, the output is the original audio.
Many years ago I experimented with a very simple version of that
idea, and I was surprised by the quality of the audio.
Unfortunately the difficulties of tuning this kind of circuit and
keeping the LO in phase with the carrier so it doesn't lose lock and
cause a horrendous audio squeal seem to have been what stopped it from
ever being popular.

Synchrodynes were never produced commercially for the general
public in tube days.

It was possible to get good performance but it cost twice as much
and a superhet was far superior in general ease of use and construction.

Chip based synchrodynes are supposed to be OK but I have never
owned one or seen one.

Patrick Turner.

Bob

On Sat, 3 Dec 2005 17:49:59 +0800, "Alan Rutlidge"
don't_spam_me_rutlidge@iinet.net.au> wrote:


"John" <sittinginthepool@internode.on.net> wrote in message
news:43902C6C.DA8E0EB2@internode.on.net...
Can you get high quality or "better then average" sound out of the AM
tuner of
a hifi system.. Typically speaking something like an AM/FM tuner going
through
an amplifier and such?


I can recall an Electronics Australia project called the Homodyne Tuner (now
that will get Phil all fired up). Built one of these tuners (circa 1973 ?)
as a kit. Sounded quite a bit better than many commercial AM tuners of the
day. The only thing I hated about it was the method of tuning. It used
variable inductance coils (similar to those used in car radios of the era)
which IMHO was a bit cumbersome. Demodulation was based around a Motorola
IC and sensitivity was adequate.

The only drawback was the due to it's wide bandwidth and low selectivity,
listening at nights occasionally resulted in some distant station crosstalk
and interference. Other than that, the sound was very respectable for a
70's kit job.

Cheers,
Alan

 

[Bob]

If you are handy with electronics, take a look at my page
http://pw2.netcom.com/~wa2ise/radios/feedback.html#solidstate
local AM can sound quite good. In the USA most stations do broadcast
10KHz of audio, occupying 20KHz of RF spectrum. Sure, AM stations here
are spaced 10KHz apart, but not in the same market.