ESE's Receiver Thread

[N1ESE]

Over on the AM Reflector, I've been talking about some things I am looking for in a receiver and I'm a bit taken a back by some of the replies I've been getting when I talk about wanting clean and very good, room filling, audio fidelity.  Here's a sample of some quotes from a few people:
 
"Good audio? These old rx are far from hifi. The average 6V6 etc audio out stage has 25+% distortion by design. Maybe loud rumbling is all what the so-called AM experts are talking about? ;-) Good luck on finding the holy grail...."

"Good audio is not achievable with these old rigs, you want loud audio just put a big speaker on your rice box"

An OM offered me an HQ-170A for $400, when I mentioned I wasn't interested and listed Slab Bacon's and Johnny's reasons why it has poor audio, he replies "What kind of name is Slab Bacon?  The HQ-170 is a perfect receiver for AM, he doesn't know what he's talking about in his mis-leading guide".
 
Another one that just came in as I'm typing this - "If all you want is AM reception, all you need is a cheap HQ-100 with a couple quick mods done to improve the audio slightly.  Don't waste your money on a big rig for fidelity that doesn't exist"

When I talk about wanting a 8 to 12 kc wide receiver and will be sweeping the rig to make sure it is clean and covers 20-10,000 Hz, I get told I am just wasting my money and time.

What the hell?  I thought good quality audio was paramount for most AM'ers, is it truly a much smaller niche of the AM community?

- JT

[ka3zlr]

Welcome Back OM,...Now..., First Rule Slow Down...,think about what you just said there, you talked to how many different people and got how many different answers, Comparative shopping is a good thing but Comparative working Knowledge is different animal.

As much as what is said is not as important as what it is you want to achieve, Not every Amateur interested in Yaam is on a Fidelity Bandwagon, Not to say that it isn't a goal as much as purity of sig generated is paramount first in keeping with the regs.

You found the right place, what Johhny and Slab offer is from years of Working Knowledge and are a great asset to the cause along with the regulars on here, you will find that not all Sigs on the air are Tall ships, you will make adjustments along the way.

The Holy Grail is a ruse it's the achievement gained from using the knowledge in building your station and achieving Your Goal...it's what JT wants that's important...Ask many questions OM your at the right place...

[w3jn]

Jack's absolutely right... there is no "holy grail". 

My receiver article is caveated very clearly that it is very much colored by my own prejudices.

If you want 20-15000 hz audio response, your only option really is to tap off the detector diode and run it into a hifi amp.    This will make any one of the tall ships - INR, VJB, the guys running class E, etc., sound fabulous on a nice full quieting signal if there's no QRM.  However that situation is the exception rather than the rule.  You're gonna need to, at times, reduce the bandwidth to cut QRM, deal with static crashes, etc.

Let us also consider the fact that a diode detector isn't low-distortion, particularly where the modulation of the transmitting station goes much over 100%.  Indeed, as it approaches 100% in the negative direction you can clearly see a sine wave being distorted if you look at the detector output on a scope.  Moreover, multipath selective fading and ionospheric conditions will add distortion.

But why build in distortion at the receiver?  I don't see the point of that, which appears to be acceptable to many on the AM reflector, at all.  Why take a somewhat distorted signal and add MORE distortion to it??

As I said in my article, the best value for a receiver you'll use on 160 and/or 75 (and even 40) is a SP-110/SP-200/SP-400/BC-779/BC1004 SuperPro.  Continuously variable bandwidth and a pair of 6F6s in the audio output combined with a well-designed detector circuit makes for great audio and some battle-mode capability.  They're inexpensive, fairly easy to fix, and built like tanks.  Of course the tradeoffs are no product detector, a bigassed heavy separate power supply, drift on the upper bands, and the rear panel is a UL inspector's nightmare 

Didn't you have, and then got rid of, an NC-183?  That would have been a very good receiver indeed.

[Jim, W5JO]

Keep in mind that almost all receivers were built for communications, not fidelity.  Fidelity on AM is a function of distortion, bandwidth and noise, both internal and external.  True high fidelity can only be found on FM where you can capture the receiver and the bandwidth is near 100 KC.  You won't find that on AM in the ham bands.

On AM you will find wide bandwidth on old BC console radios where they have 10 Kc to broadcast wider signals.  Today stations are being urged to restrict their bandwidth to 5 Kc, so there you are.

If you want true high fidelity, then you are going to be modifying something to lower the distortion, filter the DC better, and listen to a lot of noise and interference with wider bandwidth.  Best look for something that is easy to work on and spend a lot of time doing it.

[N1ESE]

Didn't you have, and then got rid of, an NC-183?  That would have been a very good receiver indeed.

Yup, I sure did.  For some reason, that NC-183 and I didn't get along very well, and I'm not entirely sure, why but there was definitely no bond between the two of us.  It was very much an impulse buy as it was my first AM receiver purchase and I kind of jumped in blind.  I probably had much higher expectations and, when they weren't immediately met, I gave up on the radio way too quick.  There was a steep learning curve there for me and I think I was impatient rushing things a bit too much.  Using the rig during the daytime was great - my favorite boys to listen to during the day, KF1Z, W1IA, WA1HnyLR, et al., all sounded beautiful in the stock speaker although I could never get the audio as loud as I wanted.  However, come night time, I couldn't tune anyone in at all.  I even experimented with the addition of an outboard Q-multiplier and still had very little luck.  However, I know a bit more now and not rushing into making any quick decisions like I did before.  This is why I am asking seemingly stupid questions frequently. 
 
- JT

[steve_qix]

JN hit it right on the head !!!!

There are MANY receivers out there which will work as good front-ends.  Once things hit the detector and AGC, the heavy distortion sets in on virtually all receivers.  But, ALL IS NOT LOST  

Simply add a simple high fidelity AM detector after the last IF of the receiver.  Here's a link to a low distortion detector and AGC system: http://www.classeradio.com/detector.pdf.
Unless the receiver has a very well built, push-pull audio system (rare rare rare), use an external high fidelity amplifier and speaker system.  Done.  You've got a high fidelity receiver.  

You could bang your head against the wall trying to get a single ended 6V6 audio stage to sound good, and you can make it sound BETTER, but it will never equal a real, external audio system.

Now, here's something interesting.  I am listening on a really good receiver; low distortion detector, good amplification, big speaker, etc. etc. etc. and even the average sounding stations sound MUCH better on this hi-fi receiver than they do on a "normal" receiver.  So, no matter what - if you want to listen to AM, even the folks with less than stellar audio will sound much more pleasing without the added (and often harsh) distortion of the stock receiver.

Regards,

Steve

[The Slab Bacon]

Others have said, and I also reiterate: THERE IS NO HOLY GRAIL OF RECEIVERS!!!!!!! good for "battle conditions" operation, and good "battle conditions" receivers are not
At least not in vintage receivers. Receivers that are good Hi-Fi are usually not very very Hi-Fi!! This is due to the nature of the circuit design needed for the desired type of operation.

ALL RECEIVERS ARE A COMPROMISE!! the trick is to find the one that best suits YOUR NEEDS!! That is why many of us have several receivers to suit the available operating conditions. Receivers can be more addicting than heroin if one is not careful.

As far as the guy that was trying to stick it to you for $400 for a 170, tell him to go
f@#$& his self! He was just trying to take advantage of you. I have seen 180's go for that kind of money, but not 170s. they typically bring half of that or less.

                                                                       The Slab Bacon

                                                  

[The Slab Bacon]

Didn't you have, and then got rid of, an NC-183?  That would have been a very good receiver indeed.

Yup, I sure did.  For some reason, that NC-183 and I didn't get along very well, and I'm not entirely sure, why but there was definitely no bond between the two of us.  It was very much an impulse buy as it was my first AM receiver purchase and I kind of jumped in blind.  I probably had much higher expectations and, when they weren't immediately met, I gave up on the radio way too quick.  There was a steep learning curve there for me and I think I was impatient rushing things a bit too much.  Using the rig during the daytime was great - my favorite boys to listen to during the day, KF1Z, W1IA, WA1HnyLR, et al., all sounded beautiful in the stock speaker although I could never get the audio as loud as I wanted.  However, come night time, I couldn't tune anyone in at all.  I even experimented with the addition of an outboard Q-multiplier and still had very little luck.  However, I know a bit more now and not rushing into making any quick decisions like I did before.  This is why I am asking seemingly stupid questions frequently. 
 
- JT

Your's has "issues"!! Mine will blow you out of the room!!

[N1ESE]

Steve, Frank, et al., thanks I do realize there is no holy grail.  It's just a difficult matter for someone like me who can't go out and buy a multitude of receivers to experiment with.  I guess what it comes down to, for me, is finding a receiver that can handle night time conditions on 75M and 40M AM that is relatively easy to work on and easy to add a product detector to so I can feed it into a stereo system.  75M and 40M are the only bands I am an interested in right now. 
 
- JT

[W2XR]

JN hit it right on the head !!!!

There are MANY receivers out there which will work as good front-ends.  Once things hit the detector and AGC, the heavy distortion sets in on virtually all receivers.  But, ALL IS NOT LOST  

Simply add a simple high fidelity AM detector after the last IF of the receiver.  Here's a link to a low distortion detector and AGC system: http://www.classeradio.com/detector.pdf.
Unless the receiver has a very well built, push-pull audio system (rare rare rare), use an external high fidelity amplifier and speaker system.  Done.  You've got a high fidelity receiver.  

You could bang your head against the wall trying to get a single ended 6V6 audio stage to sound good, and you can make it sound BETTER, but it will never equal a real, external audio system.

Now, here's something interesting.  I am listening on a really good receiver; low distortion detector, good amplification, big speaker, etc. etc. etc. and even the average sounding stations sound MUCH better on this hi-fi receiver than they do on a "normal" receiver.  So, no matter what - if you want to listen to AM, even the folks with less than stellar audio will sound much more pleasing without the added (and often harsh) distortion of the stock receiver.

Regards,

Steve

Steve,

Thanks for the interesting schematic and application notes.

Have you considered offering a board for this circuit that we can stuff ourselves?? I would really like to try this detector with my R-390A and SP-600.

I currently feed the detector output of both receivers to an external push-pull 15 watt triode audio amplifier, driving a 15" duplex speaker in a bass reflex speaker enclosure. This combination really makes for true room-filling audio, and when the transmission quality is superb, it makes listening a real pleasure.

I agree with the other comments about trying to improve the (example) single-ended 6V6GT audio stages employed in some of the more common receivers utilized within the AM community; this is usually a big dead-end. Better to use a quality outboard amplifier.

73,

Bruce

[flintstone mop]

I think this is why B'cast Analog AM cannot compete with FM radio. There is no way you are going to get the response you're looking for from any AM broadcast or Ham radio station. Unless you live about 5 miles from an AM B'cast that has been engineered for super audio. NO IBOC. There are still some excellent sounding AM B'cast stations. Short Wave stations are limited to 5khz audio too. 
With the FCC stepping in and the NRSC and now IBOC (narrowing the audio bandwidth) you'll never hear what AM WAS capable of from a well engineered station.
Amateur radio is limited also. We aren't transmitting music, so a good audio response for voice would be 80-7kcs. Some Ham transmitters crumble (and splatter) when you have to force thru anything above 5khz.
I think Steve and a couple others said to get to the detector and modify that, and you will have arrived.
I hope you are not feeling that I'm flaming you, it's just not feasible to get to audio-phile quality using AM.
Get a hold of a nice old floor model radio and you might be surprised of the room shaking audio from one of those!!!


Fred

[N1ESE]

I hope you are not feeling that I'm flaming you, it's just not feasible to get to audio-phile quality using AM.

Nope, don't feel that way at all.  I am new to all this and trying to learn as best I can so I really appreciate ALL comments, even some of the overly negative ones I've been getting by email.     Maybe my big problem is I am over-analyzing and reading too much into articles such as K1JJ's "Five Hurdles" and others that stress the importance of receiver audio output  performance.

- JT

[N1ESE]

JT, 20-10khz good audio is asking a bit much from the old rcvrs.

Well, again, I was merely referring to what I read in an article here on AM fone.  It was written by K1JJ so I figured it could be taken as gospel.

- JT

[N1ESE]

K1JJ wrote this and this is what I was looking to achieve:
 
1) I feel the first thing any AMer (worth his salt)should do is set up a decent, ~8-12kc wide-band receiver. It's MANDATORY to pick off the audio from the detector and drive an external >20watt hi-fi amplifier with big, good speakers....four speakers mounted on the four ceiling /wall corners. Audio sweep the complete RX system from antenna to 8 ohm audio output to be sure it is clean and really goes 20-10,000 hz. Those I.F.'s can fool you sometimes.

- JT

[Pete, WA2CWA]

I use earphones. Nobody else in the house, or the neighbors, want to hear amateur radio transmissions. Sort of reminds me of the "boom-box" era or the driver that has 600 watts feeding his 15 inch woofers mounted in his Pinto, driving down an adjacent street playing rap music.

[N1ESE]

For use with the SoftRock IF rcvr, you really don't need a top quality boat anchor rcvr, just one with good tuned front end characteristics and 455-500khz output already on the back panel of the chassis to save you the trouble of trying to tap off the IF signal.

Ya know, we've kinda come full circle on some of this.  You mentioned I do this in my HQ-170 thread.  The HQ-170A does indeed have an IF jack right on the back of it.  Wonder if I can get the guy to come down on price.  Hmm.
 
- JT

[WA3VJB]

JT,

You are on the right path trying to discover and acquire a receiver that suits you.  But yes, you have to figure out some criteria for yourself, and not use someone else's yardstick. Let me elaborate with some index points for your consideration.

-- Operating conditions. Try to envision the percentage of operating time for three categories of conditions: 1. uncongested 2. average 3. congested.  Will you tolerate reception where so many AMers are on that they are spaced 5Kc apart?  Then maybe the HQ170 will suit you, because its selectivity will help you pull the stations apart. For me, 80 percent of my operating time is during uncongested-to-average conditions. Other people don't care. If it's AM, they're in there, and that's cool too.

-- Prospective stations. The AM community strongly populates 160, 75 and 40 and our operators comprise a group that is the most distinct, identifiable voice activity routinely heard on these bands.  The audio quality of our stations varies greatly, with 40 meters offering the least likely chance to hear a "Tall Ship." By region, most AM activity is in the East. When 10 meters comes back, it will offer one of the best uncongested bands for LONG distance AM, so plan ahead.

-- Receive environment.  Headphones?  A decent stereo-type amp with loudspeakers?  Or a 5-in cube speaker on the desk?  I usually run headphones, a very good pair, and I keep the volume down to avoid ear fatigue from static crashes or other spikes.  If I'm just listening, I run the receiver output through the "house audio" system, which is a stereo and hi-fi speakers.

These factors can help steer you toward ONE receiver that will satisfy MOST of the time.  I could not stand a receiver with "space shuttle audio," since it would run counter to what I value the most.  I also have a realistic sense of the level of fidelity we can reasonably hope to find among radio hobbyists on the shortwave bands, and there are receivers out there that match that level of fidelity quite well.

Keep asking questions, it's the best way to insight.

[WA3VJB]

Oboy oboy.

Roll tape. I'd love to hear Frank's expanded discussion.

That's an archival quality lecture.

Better yet, why not do it on the air ? 

Haven't you got a plastic radio of some kind that you can listen through?  A little "world band" radio would do ya with Frank's typical signal.

[N1ESE]

Paul, to answer your points -
 
-- Operating conditions.  I am disabled and unable to work so I am home all the time and always want 75M tuned in here in the shack whether I am operating or not.  All my activity for the next two years will be on 75M and 40M.

-- Receive environment.  Room filling sound.. not LOUD but just really good sound that fills the room and makes you feel like the ops are in the room with you.  I've felt this way in some shacks before.

Any of this make sense?
 
- JT

[WA3VJB]

Sure it does.

75 meters, you are in the hot zone, you have a set of ears that need massaging.

For the money you've set aside, I'd go with John's recommendation of an SP-400, and run the output into a high powered mono amplifier so you can cleanly deliver the bass response at moderate volume.

Go getcha a decent speaker at Best Buy, you know, a ported Polkaudio or maybe a Yamaha NS-5. There's one for $35 at:

http://danalexanderaudio.com/clearance.html

I know this guy. Old California hippie, very cool to deal with. Just buy the good one.

OH, and among Super Pro -- I got to use W3NP's SP-210X at one or two AM Festival Stations, W3F, and that variable bandwidth was the coolest thing since the SDR.

[steve_qix]

All I can say, is don't limit yourself      There are a number of stations who can transmit a response from a few cycles to 10kHz, with distortion figures of less than 1%.  It takes little extra effort on the receive side to be able to hear this stuff.  Sure, you need a good detector / agc - no big deal - a few hours work.  A good hi-fi audio amp?  Flea market item: $25.00.  Good headphones?  This may cost a bit more      Speakers?  It depends on how good the flea markets are in your area.  I've picked up some pretty good speakers (like AR-3s) for $20.00.  You won't get 10Hz out of those, but you will from a *good* pair of headphones.  Those AR speakers are probably good to 40 or so Hz - still not bad!

Sure, it's voice but what the heck.  It's like someone who owns a Porche.  Can you drive it at 160mph?  No.  So why own it?  Why not !!!  At least we hams CAN transmit 30 cycle sounds and lower ("P" pops, rumbles, furnaces, thumps, etc. etc.) so why not be able to hear it when it's there!!!

Go for it, the results definitely will astound you and you don't have to spend a lot of money doing it.  I am the world's cheapest ham, but there's not one in the main audio chain - including the receiver - that's not full fidelity (that means from a few cycles per sec, to above my hearing range, with low distortion).

Regards,

Steve

[N1ESE]

I am the world's cheapest ham, but there's not one in the main audio chain - including the receiver - that's not full fidelity (that means a few cycles to above my hearing range, with low distortion).

Yeah!!  If I can't listen to WA1HnyLR belch in full fidelity, with feeeling, then I don't wanna turn on the rig.   
 
- JT

[flintstone mop]

ooohhh good one JT.
Hi-Fi belching
Fred

[N1ESE]

Hmm, K1ETP is selling an SX-101A - Slab says he likes this rig a lot (once he did a couple audio mods).
 
- JT

[N3DRB The Derb]

101A is built like  battleship and has the weight to prove it. underrpriced too, the "collectors" don't really like em too much.