Sony STRDH590 antenna

[David Lesher]

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[Michael Terrell]

On Wednesday, February 19, 2020 at 5:08:27 PM UTC-5, David Lesher wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....

Try using it as a 75 Ohm input.

 

[Jasen Betts]

On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.

If you have a VHF antenna you could try connecting coax directly or
via or a balun to that antenna input.

--
Jasen.

 

[mpm]

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:

On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:
RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.

If you have a VHF antenna you could try connecting coax directly or
via or a balun to that antenna input.

--
Jasen.

Mike Terrell, you want to take this one, or shall I?


David, I can't follow your post. You say the Sony receiver doesn't have an antenna input, but then say there's a length of wire (no doubt, a dipole antenna).

Where you gonna' connect it if there's no connector on the receiver.
Did I miss something?

 

On Wed, 19 Feb 2020 22:08:23 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

That is a strange design decision for a multichannel table top
receiver. Wonder why ?

At least for portable radios a proper antenna input is often not
provided, since connecting a proper outdoor antenna would heavily
overload the receiver front end

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....

 

[Michael Terrell]

On Wednesday, February 19, 2020 at 9:06:36 PM UTC-5, mpm wrote:

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:
On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:
RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.

If you have a VHF antenna you could try connecting coax directly or
via or a balun to that antenna input.

--
Jasen.

Mike Terrell, you want to take this one, or shall I?


David, I can't follow your post. You say the Sony receiver doesn't have an antenna input, but then say there's a length of wire (no doubt, a dipole antenna).

Where you gonna' connect it if there's no connector on the receiver.
Did I miss something?

Basic tuner modules are typically 75 ohm, with a balun to convert it to 300 Ohm balanced input. The external connection for 75 Ohm is one side of the 300 Ohm, to ground. You don't need a connector to test this, bit it would be simple to remove the single wire and run some miniature 75 ohm coax to the tuner module, then to an F connector without drilling holes in the chassis or case. The higher signal strength will overcome any slight mismatch.

 

[Michael Terrell]

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:

On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:
RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.

Where have you been for the last 50 years? Fixed site receivers use Horizontal Polarization, while Mobile use Vertical Polarization. Stations started switching from Horizontal to Circular Polarization so they could be heard in vehicles. AM broadcast is typically Vertical Polarization, but I engineer at at an AM BCB site with a center tapped dipole cut for 980 KHz.

 

[Michael Terrell]

On Wednesday, February 19, 2020 at 11:10:17 PM UTC-5, upsid...@downunder.com wrote:

On Wed, 19 Feb 2020 22:08:23 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

That is a strange design decision for a multichannel table top
receiver. Wonder why ?

At least for portable radios a proper antenna input is often not
provided, since connecting a proper outdoor antenna would heavily
overload the receiver front end

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....

They have a wonderful new concept called AGC, to deal with that. Analog FM radios require a strong enough signal to fully drive the limiter stage before detection, to provide a clean audio output. Try it, you might even like it!

 

On Wed, 19 Feb 2020 20:27:52 -0800 (PST), Michael Terrell
<terrell.michael.a@gmail.com> wrote:

On Wednesday, February 19, 2020 at 11:10:17 PM UTC-5, upsid...@downunder.com wrote:
On Wed, 19 Feb 2020 22:08:23 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

That is a strange design decision for a multichannel table top
receiver. Wonder why ?

At least for portable radios a proper antenna input is often not
provided, since connecting a proper outdoor antenna would heavily
overload the receiver front end

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....


They have a wonderful new concept called AGC, to deal with that.

In an AM receiver AGC is very desirable in an AM receiver, especially
with simple diode envelope detectors for best linearity, a few volt
signal is required, so the AGC will deliver just that. It also
protects he user ears when tuning from a weak station to a strong
station.

>Analog FM radios require a strong enough signal to fully drive the limiter stage before detection, to provide a clean audio output.

You must still be living in the tube era, when the IF gain cost was
very high (one or more extra tubes). These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

>Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.

 

[Jasen Betts]

On 2020-02-20, Michael Terrell <terrell.michael.a@gmail.com> wrote:

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:
On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:
RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.


Where have you been for the last 50 years? Fixed site receivers use Horizontal Polarization, while Mobile use Vertical Polarization. Stations started switching from Horizontal to Circular Polarization so they could be heard in vehicles. AM broadcast is typically Vertical Polarization, but I engineer at at an AM BCB site with a center tapped dipole cut for 980 KHz.

30 years ago I was getting better reception with a vertical antenna,
I've not made many measurements since then.


--
Jasen.

 

[Michael Terrell]

On Thursday, February 20, 2020 at 5:10:34 AM UTC-5, upsid...@downunder.com wrote:

On Wed, 19 Feb 2020 20:27:52 -0800 (PST), Michael Terrell wrote:

On Wednesday, February 19, 2020 at 11:10:17 PM UTC-5, upsid...@downunder.com wrote:
On Wed, 19 Feb 2020 22:08:23 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

That is a strange design decision for a multichannel table top
receiver. Wonder why ?

At least for portable radios a proper antenna input is often not
provided, since connecting a proper outdoor antenna would heavily
overload the receiver front end

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

I'm considering putting a turn or 2 around whatever input coil I
find to couple a folded dipole to it....


They have a wonderful new concept called AGC, to deal with that.

In an AM receiver AGC is very desirable in an AM receiver, especially
with simple diode envelope detectors for best linearity, a few volt
signal is required, so the AGC will deliver just that. It also
protects he user ears when tuning from a weak station to a strong
station.

Analog FM radios require a strong enough signal to fully drive the limiter stage before detection, to provide a clean audio output.

You must still be living in the tube era, when the IF gain cost was
very high (one or more extra tubes).

Tubes? I haven't done much with tube radios since the early '70s.

These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.

AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod. Ceramic filters? Try FIR filters that we were using 20 years ago.

 

[Michael Terrell]

On Thursday, February 20, 2020 at 5:31:00 AM UTC-5, Jasen Betts wrote:

On 2020-02-20, Michael Terrell wrote:
On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:
On 2020-02-19, David Lesher <wb8foz@panix.com> wrote:
RF: the old forgotten tech

I got friends to buy the above Sony receiver. But not mentioned
in the reviews I found was that Sony did not provide the
usual 300 ohm or 75 ohm antenna input.

Instead you get a few feet of stranded 22 gauge that you are
told to deploy horizontally. Even 5 stories up, this provides
rotten signal strength with stations more than a few miles away.

??? horizontally is nuts, FM radio is vertically polarised.


Where have you been for the last 50 years? Fixed site receivers use Horizontal Polarization, while Mobile use Vertical Polarization. Stations started switching from Horizontal to Circular Polarization so they could be heard in vehicles. AM broadcast is typically Vertical Polarization, but I engineer at at an AM BCB site with a center tapped dipole cut for 980 KHz.

30 years ago I was getting better reception with a vertical antenna,
I've not made many measurements since then.

I was a Broadcast Engineer. Most 'horizontal antennas' were nothing more than a center tapped dipole made from 300 Ofm coax.thumb tacked to a wall inside a building with a lot of metal. An outdoor FM antenna does much better than a whip, and in extreme cases a Yagi will provide extra gain while reducing overload from other transmitters.

 

On Thu, 20 Feb 2020 07:14:05 -0800 (PST), Michael Terrell
<terrell.michael.a@gmail.com> wrote:

These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.


AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod.

If you use AGC to reduce front end gain due to some strong signals in
some nearby frequency, it will also reduce the gain for a weak signal
that you want to listen, thus the weak signal may be swamped in front
end noise when a strong nearby signal is present. A sharp filter
between RF stage and mixer helps getting rid of some strong signals.
Since the filter needs to be tunable, realistically the bandwidth is
at least 1 MHz (Q=100), so it helps only in reducing strong signals a
few MHz away.

> Ceramic filters? Try FIR filters that we were using 20 years ago.

FIR ? Sounds like a digital filter. Before you can use a digital
filter, you need to use an ADC. Modern ADCs can handle only about 1
Vrms and since the ADC is quite noisy, 10-20 dB of RF gain is needed
in front of the ADC to swamp the front end noise, thus the maximum RF
amplifier input composite voltage is 100-300 mV.

If direct RF undersampling is used e.g. with about 60 MHz sampling
frequency, this requires a bandpass filter to select the correct
alias, so in this case an analog bandpass filter from 87 to 108 MHz is
required ahead of the ADC. The ADC must be capable to handle all
signals in this range and only then can digital filters reduce the
bandwidth further.

 

[Tauno Voipio]

On 20.2.20 20:18, upsidedown@downunder.com wrote:

On Thu, 20 Feb 2020 07:14:05 -0800 (PST), Michael Terrell
terrell.michael.a@gmail.com> wrote:


These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.


AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod.

If you use AGC to reduce front end gain due to some strong signals in
some nearby frequency, it will also reduce the gain for a weak signal
that you want to listen, thus the weak signal may be swamped in front
end noise when a strong nearby signal is present. A sharp filter
between RF stage and mixer helps getting rid of some strong signals.
Since the filter needs to be tunable, realistically the bandwidth is
at least 1 MHz (Q=100), so it helps only in reducing strong signals a
few MHz away.

Ceramic filters? Try FIR filters that we were using 20 years ago.

FIR ? Sounds like a digital filter. Before you can use a digital
filter, you need to use an ADC. Modern ADCs can handle only about 1
Vrms and since the ADC is quite noisy, 10-20 dB of RF gain is needed
in front of the ADC to swamp the front end noise, thus the maximum RF
amplifier input composite voltage is 100-300 mV.

If direct RF undersampling is used e.g. with about 60 MHz sampling
frequency, this requires a bandpass filter to select the correct
alias, so in this case an analog bandpass filter from 87 to 108 MHz is
required ahead of the ADC. The ADC must be capable to handle all
signals in this range and only then can digital filters reduce the
bandwidth further.

There are analog FIR filters. Google for 'SAW filter'.

--

-TV

 

[Michael Terrell]

On Thursday, February 20, 2020 at 2:33:14 PM UTC-5, Tauno Voipio wrote:

On 20.2.20 20:18, upsidedown@downunder.com wrote:
On Thu, 20 Feb 2020 07:14:05 -0800 (PST), Michael Terrell wrote:


These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.


AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod.

If you use AGC to reduce front end gain due to some strong signals in
some nearby frequency, it will also reduce the gain for a weak signal
that you want to listen, thus the weak signal may be swamped in front
end noise when a strong nearby signal is present. A sharp filter
between RF stage and mixer helps getting rid of some strong signals.
Since the filter needs to be tunable, realistically the bandwidth is
at least 1 MHz (Q=100), so it helps only in reducing strong signals a
few MHz away.

Ceramic filters? Try FIR filters that we were using 20 years ago.

FIR ? Sounds like a digital filter. Before you can use a digital
filter, you need to use an ADC. Modern ADCs can handle only about 1
Vrms and since the ADC is quite noisy, 10-20 dB of RF gain is needed
in front of the ADC to swamp the front end noise, thus the maximum RF
amplifier input composite voltage is 100-300 mV.

If direct RF undersampling is used e.g. with about 60 MHz sampling
frequency, this requires a bandpass filter to select the correct
alias, so in this case an analog bandpass filter from 87 to 108 MHz is
required ahead of the ADC. The ADC must be capable to handle all
signals in this range and only then can digital filters reduce the
bandwidth further.


There are analog FIR filters. Google for 'SAW filter'.

Sawtek used to be close to a job I had in Orlando.

 

[Michael Terrell]

On Thursday, February 20, 2020 at 1:18:35 PM UTC-5, upsid...@downunder.com wrote:

On Thu, 20 Feb 2020 07:14:05 -0800 (PST), Michael Terrell wrote:


These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.


AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod.

If you use AGC to reduce front end gain due to some strong signals in
some nearby frequency, it will also reduce the gain for a weak signal
that you want to listen, thus the weak signal may be swamped in front
end noise when a strong nearby signal is present. A sharp filter
between RF stage and mixer helps getting rid of some strong signals.
Since the filter needs to be tunable, realistically the bandwidth is
at least 1 MHz (Q=100), so it helps only in reducing strong signals a
few MHz away.

A few MHz?t could be 200KHz away, which a single FM channel in the US. Show me any FM tuner without a tuned RF stage. Some equipment might have no AGC, but that would be the $20 portable crap.I have worked with this most of my life, both broadcast and deep Space Telemetry. Television also uses AGC in the RF. All of these use the same AGC in the IF and RF stages. I serviced CATV Hetrodyne signal processors, including one crap brand that used all PNP RF transistors in the signal path. That isn't a problem other than having to buy the 1000 at a time. Luckily, that company went bankrupt. I serviced hundreds of designs and all used AGC for RF and IF.

Ceramic filters? Try FIR filters that we were using 20 years ago.

FIR ? Sounds like a digital filter. Before you can use a digital
filter,

Of course it is. You were bragging about Ceramic filters which are obsolete for high end products.

you need to use an ADC. Modern ADCs can handle only about 1
Vrms and since the ADC is quite noisy, 10-20 dB of RF gain is needed
in front of the ADC to swamp the front end noise, thus the maximum RF
amplifier input composite voltage is 100-300 mV.

If direct RF undersampling is used e.g. with about 60 MHz sampling
frequency, this requires a bandpass filter to select the correct
alias, so in this case an analog bandpass filter from 87 to 108 MHz is
required ahead of the ADC. The ADC must be capable to handle all
signals in this range and only then can digital filters reduce the
bandwidth further.

Our IF center frequency was 70MHz, and the maximum bandwidth, so it was sampled to 90MHz. It was the first dual diversity digital system on the market.. It scared the competition so much that they talked the founder of our company into retiring so he could buy our company. It used a convention RF front end prior to the IF filtering, and another set to process the recover video so that just about any desired combination of IF Bandwidth and Video could be programmed into the unit by RS232/Rs245, GPIB or over a Ethernet connection.

 

[David Lesher]

And I forgot. This is not a "table radio"...

It's a 100+w/channel 5.1 channel tuner/amplifier with 4 HDMI
inputs and 1 ARC HDMI output. It also has several line level
audio inputs and a TOS-in.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[David Lesher]

mpm <mpmillard@aol.com> writes:

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:

David, I can't follow your post. You say the Sony receiver
doesn't have an antenna input, but then say there's a length of
wire (no doubt, a dipole antenna).

Where you gonna' connect it if there's no connector on the receiver.
Did I miss something?

There is a *tiny* one-pin Molex socket on the back. You get a
wire with a mating Molex in the same bag as the remote control
AAA batteries and such.

I was relating this to the now-retired Chief Engineer of a FM
station (who I worked for in the 2-way field 45 years ago...)
and he noted that while circular polorization is long the norm,
there's a rather obscure regulation that the vertical power
shall not exceed the horizontal.


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

On Thu, 20 Feb 2020 12:19:09 -0800 (PST), Michael Terrell
<terrell.michael.a@gmail.com> wrote:

On Thursday, February 20, 2020 at 1:18:35 PM UTC-5, upsid...@downunder.com wrote:
On Thu, 20 Feb 2020 07:14:05 -0800 (PST), Michael Terrell wrote:


These days, when the IF gain is
very cheap, there is enough IF gain that the band noise or receiver
front end noise will drive the last IF into saturation. On stronger
signals, the last few IF stages will go into saturation, not just the
last. Thus, effectively, this limiting action works like "AGC"
delivering a few volt constant voltage to the FM detector.

The important thing is that all selectivity filtering must be done
prior to the first IF stage that would start to saturate on very
strong signals. This is not much of an issue with ceramic filters.
Just make sure that the RF-amplifier and mixer gain in front of the
ceramic filter has enough gain to mask the filter losses.

The situation was different in the tube era with distributed LC
bandpass IF transformers between each amplifying tube, so the final
selectivity was achieved just at the last IF stage.

Try it, you might even like it!

But why would I use AGC for the RF amplifier ? Is the mixer so weak
that it is overloaded by a strong signal amplified by the RF
amplifier? Use a stronger mixer so that full RF gain can be applied
before the mixer. A strong mixer can be a problem with low power
battery powered equipment, but using a weak mixer in a mains powered
receiver is simply incompetence.


AGC in the front end prevents overdriving the mixer in areas with excessive RF, and producing Intermod.

If you use AGC to reduce front end gain due to some strong signals in
some nearby frequency, it will also reduce the gain for a weak signal
that you want to listen, thus the weak signal may be swamped in front
end noise when a strong nearby signal is present. A sharp filter
between RF stage and mixer helps getting rid of some strong signals.
Since the filter needs to be tunable, realistically the bandwidth is
at least 1 MHz (Q=100), so it helps only in reducing strong signals a
few MHz away.


A few MHz?t could be 200KHz away, which a single FM channel in the US.

The adjacent channel filtering is done in the IF filter. A capacitance
diode tuned filter between the RF amplifier and mixer will pass 1-2
MHz to the mixer. The mixer _must_ handle any strong signals 200 kHz
away, which is then handled by the IF filter. If the RF amp/mixer
can't handle that strong signal without gain reduction, the receiver
can't be used to receive a very weak signal only 200 kHz away from a
strong signal, no mater what fancy IF filtering is used.

A gain reduction in the RF amp will degrade the noise figure and it is
no longer capable of masking the noise of subsequent stages. In a
good receiver design, the total receiver noise figure is determined by
the noise figure of the first RF stage _provided_ that the gain is
high enough to mask the noise of the following stages.

>Show me any FM tuner without a tuned RF stage.

I said nothing about omitting the RF tuned filters, but they are much
wider than the channel spacing. If some dynamic range claims are
given, look carefully at what frequency separation is used. Most
likely a few MHz is used, i.e. outside the RF filter bandwidth.

Of course, if you have a fixed tuned receiver, you could use a 1/4
wave filter with Q=500, but these are big (75 cm) and hard to tune
This would have a 200 kHz RF bandwidth.

I still maintain that applying AGC to the first RF stage is a bad idea
and a receiver design requiring it is a suspect, possibly crap design.

>Some equipment might have no AGC, but that would be the $20 portable crap.I have worked with this most of my life, both broadcast and deep Space Telemetry.

In space applications, you usually have a fixed gain LNA at the focal
point to compensate for feeder losses as well as receiver added noise
figure. In such case, reducing the indoor unit RF stage gain is not a
very bad thing.

>Television also uses AGC in the RF. All of these use the same AGC in the IF and RF stages.

Analog requires accurate AGC so that the synch pulse levels are
normalized after the diode detector. Feeding AGC into multiple stages
helps keeping the level constant. In a TV receiver, the needed IF gain
is quite low, thus only a few stages are used and you may have to use
AGC on all IF stages as well as on the RF stage.

>I serviced CATV Hetrodyne signal processors, including one crap brand that used all PNP RF transistors in the signal path. That isn't a problem other than having to buy the 1000 at a time. Luckily, that company went bankrupt. I serviced hundreds of designs and all used AGC for RF and IF.

That must have been a very old design , from the old times when
gain and selectivity distribution was not well understood .

 

[Jasen Betts]

On 2020-02-20, David Lesher <wb8foz@panix.com> wrote:

mpm <mpmillard@aol.com> writes:

On Wednesday, February 19, 2020 at 8:31:09 PM UTC-5, Jasen Betts wrote:


David, I can't follow your post. You say the Sony receiver
doesn't have an antenna input, but then say there's a length of
wire (no doubt, a dipole antenna).

Where you gonna' connect it if there's no connector on the receiver.
Did I miss something?

There is a *tiny* one-pin Molex socket on the back. You get a
wire with a mating Molex in the same bag as the remote control
AAA batteries and such.

It kind of looks like 2 pins in this photo.
https://images-na.ssl-images-amazon.com/images/I/71yharzgGgL._AC_SL1500_.jpg
(on this page)
https://www.amazon.com/Sony-STR-DH790-7-2-ch-Receiver-Vision/dp/B079YW5VQL/ref=pd_sbs_23_t_0/146-2719398-7440836?_encoding=UTF8&pd_rd_i=B079YW5VQL&pd_rd_r=bf1d57f7-a5f7-4792-80f6-46d34ff4d9b5&pd_rd_w=dtda1&pd_rd_wg=nNYpn&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=BTE46AHTCJ049ZBR9SSB&psc=1&refRID=BTE46AHTCJ049ZBR9SSB

it seems the the connector on the antenna cable has only one position
populated though which hints that the other pin may be a ground
usable for for a 50 or 75 ohm antenna, unless the socket itself has
only one pin fitted.

https://www.sony.com/electronics/support/res/manuals/4726/55cd375e0f9e7103f2b6baa747ed9072/47269061M.pdf
page 25.

--
Jasen.