Sony STRDH590 antenna

Try using it as a 75 Ohm input.

??? 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?

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 :-)

an antenna input, but then say there's a length of wire (no doubt, a dipole antenna).

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 b e simple to remove the single wire and run some miniature 75 ohm coax to th e tuner module, then to an F connector without drilling holes in the chassi s or case. The higher signal strength will overcome any slight mismatch.

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

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! :)

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

--
  Jasen.

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.

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.

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.

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

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.

Horizontal Polarization, while Mobile use Vertical Polarization. Stations s tarted switching from Horizontal to Circular Polarization so they could be heard in vehicles. AM broadcast is typically Vertical Polarization, but I e ngineer at at an AM BCB site with a center tapped dipole cut for 980 KHz.

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 bett er than a whip, and in extreme cases a Yagi will provide extra gain while r educing overload from other transmitters.

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.

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

essive RF, and producing Intermod.

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 m y life, both broadcast and deep Space Telemetry. Television also uses AGC i n 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 P NP RF transistors in the signal path. That isn't a problem other than havin g to buy the 1000 at a time. Luckily, that company went bankrupt. I service d hundreds of designs and all used AGC for RF and IF.

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

Our IF center frequency was 70MHz, and the maximum bandwidth, so it was sam pled 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 com pany into retiring so he could buy our company. It used a convention RF fro nt end prior to the IF filtering, and another set to process the recover vi deo so that just about any desired combination of IF Bandwidth and Video co uld be programmed into the unit by RS232/Rs245, GPIB or over a Ethernet con nection.

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

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

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 snipped-for-privacy@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

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.

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.

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.

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.

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

he

You only want limiting in the final IF amp, not every stage.

d

excessive RF, and producing Intermod.

a

p.I have worked with this most of my life, both broadcast and deep Space Te lemetry.

IF and RF stages.

at used all PNP RF transistors in the signal path. That isn't a problem oth er than having to buy the 1000 at a time. Luckily, that company went bankru pt. I serviced hundreds of designs and all used AGC for RF and IF.

You've never built a Telemetry system that had to follow a satellite fro m the ground, until it was in space, where there wasn't enough land to prov ide decent physical seperation. One of our turnkey systems for the ESA was more than 40 dB too hot for the LNA. The only solution was a mechanical shu tter that opened, as the signal level dropped. Guess how that was controlle d. We didn't have to do that to the portable earth station, since it was pa rked about 20 miles away. These systems were for a contract of just under a half million dollars, not some stereo system. Our company was consider the top in the industry at that time.