The AM Forum

Brian said:
Says who?? Part 97 doesn't specify!

-Raises head above the crowd-

Are we Blocked.. [] Can we Talk Audio here..LOL...
Peeking from the Peanut Gallery. 8)

Since it all got deleted... for whatever reason...

That was my point in the first place....

The post  seemed to say that some, (really quite a few ) are breaking "the rules" by exceeding 5khz bandwidth.

No bandwidth specifications are given in the FCC rules AS THEY  PERTAIN TO AMATEUR RADIO operation.

Someone's perception of what "good operating pratice" is, is just that... a perception.. a thought... a concieveable meaning...  not a rule.

If proven otherwise, then I will install filtering etc where needed....
Since my class-e rig's filters START to roll off the audio at 7.5khz...

I had to modify this:

I couldn't have "Never" said it any better or as Eloquent Excellent...and Thank You :)

Exactly.
Having a setup that does good audio out to 10Kc is like having a stereo with 200 watts per channel. Chances are you'll never use it but it insures good operation where you normally do. HEADROOM BABY!

Even the FCC hasn't gone along with a maximum of 2.5 kc/s of audio (5 kc/s total occupied bandwidth) in the past.  Under the infamous Docket 20777, the original regulation-by-bandwidth proposal, the proposed bandwidth limit was 3.5 kc/s. And that was to accommodate slopbucket, since AM would have been precluded if that proposal had passed.

Another time when they proposed to sneak in a specific bandwidth limitation, through the "plain language" proposal of the 1980's that would have rewritten the amateur rules into the same Q-A format as they have for the CB rules, the maximum proposed occupied bandwidth (that specifically accommodated AM that time), was 7 kc/s.

Yes,

Sort of  like having an RF deck or amp, CAPABLE of 1kw+ RF outpoot... peaks to 6kw...

It's just nice to have the headroom...   8)

Not that anyone here would ever use such a thing to it's full capabilities on the air .....   :o

Headroom is the answer to this... in case of a Sneeze cough Laughter at a high note my voice has changed alot since the cancer I have a real High Pitched Laugh now That i never had my voice has changed considerably.

I have seen mention of transmitted bandwidth for amateur audio and other modes in the documents of other countries, in ITU, and in WARC information.  But I have never noted them in US documents pertaining to amateur radio.  Or have I missed them?

You Don't have to leave Brian, everyone in here enjoys
nothing More than Discussing Audio stick around man Dig in  ;D

This is where everyone in here Shines  :)

73

Jack.

To be more precise, it's not a matter of headroom, but of linear phase response within the desired bandwidth of the audio that is actually transmitted.  The UTC transformer company recommended in their old LS-series catalogue that audio iron have a flat frequency response at least one octave above and below the actual intended frequency range of the amplifier.

That means, if you wanted to transmit "communications quality" audio 300-3000~, you would need a flat response capability of at least 150-6000~. The nominal 50~ to 10,000~ response of a lot of the old broadcast iron was really optimum for more like 100~ to 5,000~ audio to modulate the carrier, which would be more typical of what AM broadcast stations throughout the 30's and 40's actually transmitted.

If the response of the amplifier is too restricted, the  result will be phase shift distortion, which can be a particularly bad problem on the low end due to waveform tilting.

Of course, AM broadcast audio has always been somewhat of a moot point, since the vast majority of receivers, then and now, aren't much better than telephone quality, particularly on the high end.  Many of the old sets that touted "hi-fi" audio, with good audio iron and speaker(s), and a push-pull final audio stage, severely restricted the high end due to a poor i.f. selectivity curve.

There are rules regarding occupied and necessary bandwidth in 47CFR 2.202. The reason most people don't see them is because they are not defined in Part 97, but in part 2. Parts 0,1, and 2 are general rules and regulations that pertain to all commision licensees. Hope this helps.

Mike,W2ZE

For the full text (subpart C), go to:

http://edocket.access.gpo.gov/cfr_2002/octqtr/pdf/47cfr2.201.pdf

and

http://edocket.access.gpo.gov/cfr_2002/octqtr/pdf/47cfr2.202.pdf

Those rules appear to define the meanings of necessary and occupied bandwidth and various modes of emission, but don't give any specific limitations that would apply to a specific service, such as broadcasting and amateur.  I would think everyone would agree that there are differences in the bandwidth standards expected with those two services, but that is not to say that amateur radio voice transmissions necessarily have to be limited to "communications quality" or telephone quality audio.

Hey Don I was reading this:

http://edocket.access.gpo.gov/cfr_2008/octqtr/pdf/47cfr2.202.pdf

an there's a statement about 0.5 percent of the total mean power..?? ???

sup with that..

Jack.

As I interpret it, it means that the occupied bandwidth is defined as the bandwidth in which 99% of the total power emitted by the transmitter lies.  The remaining 1% of total mean power lies outside that bandwidth, with half (0.5%) lying above and half below the specified range.

Cool Thanks Alot.

Jack.

Holdover from the old days when transmitter and receiver 'dispatch' audio was in vogue? Modern receivers have bandwidths that are selected independent of mode.   ::)
   

Why there's such an effort in the Receiving Dept. the melding of the old with the new :)

The warmth and Fidelity of yesterday with today's components to bring it through .

The very best that can be had is now a possibility with a minimum of effort

Man it don't get any better than that.

Till we see what the future brings.

I dont know of any "typical" set that did that except Collins A3/A4 who liked the space shuttle audio sound in their transmitters also.

Most were 8-10kc and even the high end SS HRO-500 had a 8kc position as did the true classic AM radio, the NC-300.

The ceramic filters many of us insert in 455kc IF's are 8-9kc and the cheap 4 pole Heath SB xtal version was 5kc on the nose but a nice 15kc at 50dB down giving a real nice sound on strong signals.

I particularly like the IF transformer only sound of the HRO-60 and NC-183D while some prefer the wider sound of the HRO-50, NC-183, SX-28/32, etc. or the in betweeen HRO-50-1, and early HQ's with the 3 stages of 455kc IF. The pre SP-600 Hammarlund Super Pros with the variable IF BW are nice also as the wider coupling for increased selectivity also pulls in the skirts. Not bad for only 3 stages of IF. And I know JN agrees about the performance of the NBS-1 when the going gets tough. Another surfaced at the Utica hamfest and followed a local friend home.

Carl

Out to 16 kc, in fact. 465 IF frequency though, that's gotta be why they're so great sounding.  ;D

Just a quick scan of a few receivers here(SP-10, 100, 200, NC-2-40D, SX-28A, etc etc) shows virtually all have rather broad capability. In fact, the restricted communications-quality audio only came into vogue in the 50s, mainly around the time of the arrival of SSB. Collins was all about comms, punching through and hearing under bad conditions which their gear did quite well at. Though you can easily plug a 8 or 9 kc mechanical filter into the 75A-4 and away you go. Some have even retrofit R-390A filters before the Curry filters were an option.

Along with the A-4, later rigs like the Mohawk, SX-115 and others clearly had primarily SSB in mind, not AM. Following on the restricted receiver approach came transceivers that dropped AM all together, starting with the Collins KWM and S-Line rigs. Basically they were building to what they felt the market wanted or would want. Eventually other manufacturers followed suit, and for years it was tough to buy a new transceiver that included AM.

Then a funny thing happened. The AM mode reappeared. I suspect it has zero to do with following some 'typical bandwidth' scheme and more to do with plain old marketing and demand. Business band requirements are totally different than those required for the amateur service, broadcast, etc.

But I'm preaching to the choir here. You've got pretty much all of the HiFi receivers in your stables, Carl, so you clearly understand the differences.  ;)

True for most of the American manufacturers, and a few foreign ones, from the time Collins started the trend but Yaesu, never gave up the AM mode, nor did most of the Icoms. Kenwood  only dropped AM from their hybrids, TS-520, 530, 820, and 830 although the 830M (with AM capability) was sold in foreign markets and the TS-120, 130, and 180 solid-state rigs also lacked an AM mode.

There's a "Yea Butts" there though...sure there was what they decreed as AM on their rice machines but ya might as well be channelized it's just wasn't good enough trying Appease the masses one would think, but Experimentation has led down a Better Trail and that is what this is about Experimentation where we have a license to do so this is a Good thread keep it going.

73

Peanut :)  

The early A4s had decent high frequency response, but restricted the low end with 0.01 mfd coupling caps.  Later on, they added a couple of 510 pf caps between plate and ground of a couple of the audio stages to further reduce the highs.  I think one of the reasons they restricted the lows is that the receiver has a hum problem, and limiting the low end makes it go away.  IMO, the problem is due to the fact that they use the chassis for the ground return for the tube filaments. They should have wired both sides of the filaments with real hookup wire back to the transformer, and grounded the midtap to chassis.  I had thought of rewiring mine, but gave up on the idea after looking at the  rats nest of wiring I would have to work through to make the mod.  It would be much easier to add a rectifier and filter and run all the filaments on  DC.

I removed the 510 pf caps, which improved the highs, and did what I could to get rid of the hum,  then bridged 0.1 mfd caps across the stock 0.01 mfd coupling caps (way too much trouble to remove and replace them without burning up other components and melting wire insulation with the soldering iron). That helped tremendously to get decent AM audio out of the A4.  But later, when I acquired the Sherwood sync detector, I run the audio through that to my outboard audio amp, and by-pass  the stock A4 audio altogether.  Just no comparison between the stock audio and what I have now, even considering the rough edge that the mechanical  filters add to the audio.

Ok My turn Before I got all Involved with my Newer Spectrum Analyzer an my computer Spectrum analyzer and Processing Software etc etc...One analyzer has quit on me Bummer it was present from a former RCA employee  :'(

Long story short I always Like My SX28 it ain't the best it ain't the worst it's Pre war it's older than Dirt but it looks the bestest when it's Lit up :)

That's my story an I'm keepen to it.



73 KA3ZLR.

We were talking about Amateur AM, Brian. Now your on commercial NBFM stuff.
In the context of the commercial stuff I'd hafta agree with ya. 5KC does hang out there a lot.

But your question :
Implied amateur AM receivers. With the list of THOSE receivers posted herein it seems 5KC isn't/wasn't "most" of the receivers. Heck, my all American 5 Packard Bell is 8 KC at least.

That's the fault I find with the R-390A.  They needed to have put a 6 kc filter between the 4 and 8.  The L-C filtering used with the R-390 seems slightly broader than the mechanical filters, so the 4 kc selectivity position isn't so bad for AM. I find the audio quality from the R-390 a lot better than that of the -A model.

Most of these receivers I have never even heard.  I have seen a few of them but that's about it.  But I am very pleased with the sound I get from my 75A3 with the mechanical filter out and just the IFs and a RC filter that's about 15 KHz wide and the tap on the AF pot wiper out to a p.p. 6BQ5 amp.  The A3 doesn't have the flywheel spin but I like the PTO.  As you all know, the gain with tube stages is really something!  OTOH the stock A3 with the 3 KHz mech. filter, stock audio and envelope detector would not be good in terms of audio quality.  Here's an interesting bit about Collins price back in 1954:  The 75A3 listed for $530 from most dealers.  That was around $40 to $50 more than a new SX-88.  What is wrong with that picture.

I believe if you can find the spinner knob and gear reduction mechanism, that the spinner knob can be used with the A3 and A2 as with the A4. Also with the 51J/R388 series.

The spinner knob/vernier mechanism on one of my A4s was trashed by a previous owner.  I found a replacement kit from Collins in the old Ham Trader Yellow Sheets, virgin new in the original unopened box, for $35, back in the 1980s.  I installed it in the receiver and of course it worked excellently.  To-day, that mechanism would probably fetch more $$$ than a whole 75A-4, and the owner would not dare break the seal on the original factory box lest it lose over half its value as a "collectors item".

Many professional receivers have a 16 KC bandwidth position - R390 series, any number of Racals, the RF-590, WJ 8716, etc.

The bottom line is  that we are governed by Part 97 of the rules and the Communications Act of 1934 as amended.  Where in Part 97 does it say that we are subject to limitations laid out in Part 47?  If that were the case, those same Part 47 provisions would be repeated verbatim in Part 97 or else there would be a cross-reference to it.

Another point the FCC mentioned in one of their rulemaking proceedings some years ago: "The amateur service is not a personal communications service.  It it a highly technical radio service" which  implies that, unlike CB and commercial land mobile, the standards applied to the two-way voice communications services do not apply to amateur radio voice communications.

Someone (I think it might be the guy who makes those brown plastic snap-on spreaders for OWL) sells a weighted spinner knob for the A1-A4.  I looked at it out of curiosity but it was way way too rich for my budget.  I think it was around $200.  This is nowhere near a big enough problem to warrant a $200 solution and anyway I like the stock look of the A3.  I'd rather spend $200 on parts, variacs, stuff like that.  Oh yeah, there is the thing I found:

http://www.73cnc.com/73cnc/collinsaline.html

I imagine the production cost (having the mold made and getting some injection mold business to make the parts) was pretty high so I'm not quibbling over the price; rather I have higher priorities for my cash.

Ok, I must read it wrong.
And ur right. You didn't say 5KC. You said 6KC. My bad.
But the typical AM receiver ain't 6, either!

My browser must be defective??

I don't see the opening post by someone named "Brian" anywhere... what am I missing here??
The first post I see is a follow up by WB8BIL... ::) ::)

                _-_-bear

Narrow bandwidth equals narrow mindwidth.

Rob, I have seen those weighted knobs at hamfests.  They have a good feel, but I am a  little leery.  The extra weight exerts a lot of lateral force on the shaft of the vernier mechanism, which it was not designed to handle.  Of course, if you don't already have the 4:1 gear reduction, the weighted spinner knob is useless, and I suspect finding one to-day would be about as likely finding a bag filled with $100 bills abandoned on the side of the road, and that's about what it would take to pay for one if you did find it. I was extremely lucky to find mine when I did.

Bud, as for "typical" AM  receiver selectivity, if it is of the vintage variety I would say it is about the same as "vintage" broadcast radios: about 4 kc at the -3 dB point, and more like 20 kc at the -30 dB point. I know that's about what my pre-WW2 HRO has; maybe a little tighter than a typical BC set because it has two i.f. stages at 455 kc.  The phasing type crystal filter is of limited usefulness because it has close to optimum CW selectivity, but also has broad sloping skirts.  They can be useful for "exalted" carrier AM reception, using them as sort of a synchronous detector by letting the carrier fall right on the peak, which makes the amplified carrier do a better job at demodulating the sidebands.  But you have to be careful of phase shifts to make that work.

Collins started a revolution of sorts in early 50s with the mechanical filter that offers a nearly flat passband with extremely sharp skirts. Contemporary rigs often use ceramic or crystal lattice filters to achieve the same result.  IMO, about the best i.f. selectivity around is that of the R-390 (non-A) or the R-392, which achieve selectivity approaching that of the mechanical filters, using tuned circuits with carefully controlled coupling and resistive loading. The phase shift distortion with tuned circuits is not as objectionable as that of the mechanical filters, and that's the reason the R-390A doesn't sound as good on AM as the plain 390. It's a pity they did not include a nominal 6 kc selectivity position between the 4 and 8 in both versions of the receiver.

Interestingly, the military did not go from the tuned circuit i.f. stages to mechanical filters to improve selectivity.  It was part of a cost-cutting measure.  The original R-390 was too heavy and too expensive, so they decided to lighten things up both in terms of mass and cost.

I borrowed a Super Pro with continuously variable selectivity for a short while, but was not impressed with either its selectivity or its stability.

Steve, the way I have always put it is that the (intended) bandwidth of the signal is directly proportional to the mindwidth of the operator.  :)

Indeed. If I want to listen to 2.5 kc narrow audio, I'd switch to SSB.

Part of the debate here is, "Is 5kc audio necessary?  - can it even be heard in a man's voice"?


I say, "YES it is and yes it can!"


Back a few months ago I was running my new class E rig with a sharp audio roll-off at 4kc. I thought it sounded pretty good in the monitor and was told my on-air bandwidth was a very clean ~8kc, as expected. After a week of this Chris/JBL axes me for the reason I was running restricted audio. (Chris has excellent ears for critical reports) Immediately a couple others (Tron included) in the QSO chimed in the same thing. I was surprised they even knew this by listening. I opened it up to 6kc and I heard a sigh of relief on freq. All said it sounded MUCH better.  (BTW, the rig was clean and the audio chain was clean running  6kc audio.)

These guys were using receivers that could hear the high freqs.   Six kc audio requires a 12kc position on the receiver.  One has to have the ears and the receiver to hear the extreme  highs, and room ambience that it produces.  Most stock ham receivers into a speaker will not produce these results. We must come off the detector into a good amplifer and external speakers to get a big hi-fi sound, for both extreme lows and highs. The RX I.F must also be able to handle the extreme highs and some cannot without mods.  There IS energy in a man’s voice above 4kc, no doubt. S’s and CH’s, etc become cleaner, as well as other consonant sounds.


I have proven this to myself when hearing recordings sent to me from Flex owners. I've heard myself in 3.5kc, 5.5kc and 7kc and hear the difference. The 7kc is open and airy, while the 3.5kc and lower sounds just as you'd expect – like someone put a gag cloth  across my mouth... ;D

Sure, we can use 3kc audio and get through OK, but there IS a difference in quality to a trained ear and good receiving system.

That said, I have since rolled my audio back to about 4.5 - 5kc and run it there most of the time to be a good neighbor on the bands. To me, 2.5-3kc audio is narrow, 5kc is normal and over 7kc is wide, depending upon conditions.

There are many Amers who find 3kc audio satisfactory. The mil nets, stock rig guys abound. That’s FB.  But to a trained ear using a good RX system, the differences in 5kc+ audio can be heard in a man’s speaking voice - and it is significant to some hi-fi AM enthusiasts.

T

It was from a different thread that got locked out and many posts on the subject deleted...

Hi Big Guy,

 There was a Probable Personal Bias lingering about and a Hidden intervention came upon
the Forum yesterday an excersized a personal will, but the Thread continued on in Strong
an in AM Fashion.  ;D

Well done I'm glad the discussion continued. :)

73

Jack.

Yes Sir Peanut gallery Member #8 Present an accounted for..LOL ;D

Oh an as far as any issues tossed around sometimes making good
friends takes on a sportsman like conduct little tussle here a little
tussle there a few fellas hustle an bustle that's all nothing personal
got injured on this end,  but I had fun wit the front office  ;D

Good Afternoon Everyone :)

73

I think the FCC will step in and start to control this. The single reason is the Flex radio.  Hams are now running 8 to 10 KC wide SSB with these things as there are no limits on the bandwidth. Its really upsetting SSB operators. I hear the Flex guys on AM. "I have it at 50KC now, How do I sound????" ect.. 

I am glad I have the filter in line. I have learned so much in the last few weeks. Its just idiotic to run the way I did for a year. At 25KC wide, Nobody was even listening to me past 6 to 8KC.  I ran a poll on the air and very few people ever use the 16KC of the recievers they own.  Once in a while when its full scale conditions its fun to open it up. I run 8 to 4KC on the reciever most of the time to kill the noise off.

I am at 10KC now.  Its a sharp, sharp cutoff.  I used an RDL labs Stick on NRSC filter. If you can find one, They are cheap on the ebay.  You can add this into your audio rack in minutes.

You can buy the new "Kit" but its $450. It includes the filter, and the DE and PRE emphisis modules.   Look for them used.  THey even have an AGC unit really pumps up the audio.  At $50 used on ebay.

Anyone know of any other cheap options for a filter?  I think if there where simple and cheap options, Hams might try it.  But there is so much of this the MORE then better mentality out there on the bands, Its probably a worthless thread.

Hi Clark,

Ya know for a time they were a Marvel, I thought Wow look at this Bandwidth Magic at your fingertips in DSP no less. Dig this man :D
Then reality sunk in like it always does and before I got this Small Cell Cancer I was Studying these things on the air monitoring their signals
in phone CW Digital meaning PSK31 the ones I could catch collecting making comparisons building up a Data Base an those rigs have some
splatter issues you no how once in a while ya climb up a little to close on the mic or run a little to much fire in the on CW an Not paying
attention just wana get the QSO over I have seen some not so good looking sub peaks now this could very well have been someone learning
or testing an so on  but the widening you outta watch that once on an analyzer when one of is playing essb or whatever they call it The waveforms are something to see .

But they are Type accepted. :)

73

Jack.

I doubt it. The FCC is no longer interested in the burden of regulating and micro-managing ham radio the way they were back in the 50's. I think it is more accurate to say that they would rather see us just go away so they wouldn't have to bother with us at all. Why else did they stop giving amateur exams, drop callsigns by district, logging requirements, notification requirements for portable operation, the code requirement, and abandon enforcement in all but the most egregious cases of rule violations and increasingly take a one-size-fits-all approach to rulemaking?

I disagree.  Since the woman was hired the ham related letters, fines and license revocation has gone way, way up


C

Please provide link to those notices. The link I have shows no recent activity.

http://www.fcc.gov/eb/AmateurActions/Welcome.html (http://www.fcc.gov/eb/AmateurActions/Welcome.html)

I think the bigger issue is, fewer folks on the air means less congestion = no issue. Other than the occasional horse's ass drawing attention to themselves and the few who will always press for it based on their principals, I really don't see it being an issue for us.


Which will eventually happen, through attrition. I wonder if they have some threshold for activity before they consider the service no longer viable?

Very valid point Todd. On 80/75 meters, following expansion of the U.S. phone allocation, the area between 3.6 MHz and 3.7 MHz remains a vast sea of open space. People call CQ and have nice one-on-one conversations without a single interruption or collision between phone modes. The area from 3.7 - 3.8 is somewhat more populated, but quite friendly as well. Your other thought regarding a threshold of activity is also valid as well. It seems, however, that the pressure for HF frequencies is slacking off as more services go up and beyond UHF. The very characteristics of propagation that make HF interesting to us, make it too unreliable for other services.

I have to agree with Don too. The FCC has clearly backed away from the table and is in the other room washing their hands. They're busy leasing frequencies in the GHz bands to raise revenue...

This could be a good thing because commercial interests won't be knocking themselves out to grab our HF allocations. The down side is that the FCC and national agencies in other countries may consider HF too unreliable to be worth protecting from electromagnetic pollution generated by "incidental radiators" like switching power supplies in consumer junk, digital devices, BPL, power  line interference, CFLs, touch lamps, ad nauseum.

HF's one redeeming attribute is its value as a back-up means of  long distance communication in case satellites and undersea cables are disabled either due to natural events (an unusually intense solar flare, earthquake or undersea volcanic eruption) or deliberate sabotage (EMP detonations, earth-bound jamming of the up-links, or deliberate destruction of the cables).  Unfortunately, that value will probably be ignored by the bean-counters because of the unlikelihood that the inevitable catastrophe will happen within the next month or the next six months.

There are a number of ship to shore operations still in operation around 4-18 MHz doing emails. They say they are more reliable than satellite and less expensive.

http://globewireless.com/network.php?page=hf (http://globewireless.com/network.php?page=hf)

<<<The down side is that the FCC and national agencies in other countries may consider HF too unreliable to be worth protecting from electromagnetic pollution generated by "incidental radiators" like switching power supplies in consumer junk, digital devices, BPL, power  line interference, CFLs, touch lamps, ad nauseum.>>>


I think it has become obvious that the decision has been made.  They have in fact deemed HF to be not worth protecting.

This is, in my opinion, part of the fruits of the "war on government" especially government regulatory agencies which was begun in 1980 by the Reagan Administration, and more or less continued right up through the Bush and Cheney years.  Gov't agencies such as the EPA, FCC, (and now we can add the Minerals Management Service to the list) and others were routinely regarded as a waste of money, unneeded, unnecessary, and a damper on private industry and the free market.  So, they were underfunded. 

The best government money can buy was purchased by industry lobbyists who influenced or tried to influence such agencies as the FCC and the MMS.  All you have to do is look back to the BPL deployment for an example of how the FCC kept their hands off the electric power industry, ignored competent engineering advice, and looked the other way at every turn in this sad saga of an agency perverted into ignoring its charter and becoming a BPL public relations firm instead.   If it had not been for the ARRL relentlessly calling the FCC out on its shirking of its responsibility to regulate unintentional emitters, ultimately taking them to court, we'd probably have a much more severe BPL problem.

It shouldn't have to be that way, but the results of roughly 30 years of war on the federal government's regulatory functions can't be reversed overnight.   The sad thing is a lot of hams backed these administrations.  Well.  As my former boss down in Alabama would say, "Now y'all are just going to have to sleep in the bed you made for yourselves."

The extended SSB thing has been around since at least the mid-90s. If the FCC was going to do something about it, they would have by now. Enforcement was much more active under Hollingsworth than it has been lately.

Don't worry. The ESSB thing will fade out as the ADHD follower crowd moves on to something else.

Ive never used my A4 on AM and cant comment. It was built strictly for chasing DX and contesting when I bought it in 65 and first modified it and has had a few changes over the years. It currently has cascaded 200 Hz crystal, plus 800 Hz and 2.1 KHz mechnical filters. It is better than my TS-940's on CW which have 400 Hz filters.

The 8 kc R-390A filter is really closer to 10kc at the 3dB points. I dont know if its due to aging. The 16kc is also a bit over spec in the 3 IF modules I have.

The SX42 and SX-62 series have nice audio but I wouldnt call it great due to the limited tone control. Im feeding the detector output on one of my 62A's to a mid 50's RCA console audio chassis that has that great treble/bass circuit I mentioned in another thread. The RCA ends up in PP 6V6's and a pair each of 12" and I think 5" speakers and can shake the house on FM.  On AM its limited to the 455 kc IF bandwidth. The other feeds a R-42 in the BR and the difference between the pair is pronounced, at least to my ears.

Id say that the NC-183 (not the D) and the NBS-1 variant have audio equivalent to the HRO-50 and 50-1 respectively. They are far more user friendly than the SX-42; I have one but dont particularly like using it. Once in awhile I use the HT-18, HT-9, SX-42, and R-42 on the 20M Hallicrafters net. Other times its the HT-32B, SX-115 and NCL-2000 (horrors but I dont want to get involved with the HT33A/B PL-172 tube problems). BTW, the HT-32 AM is pretty good especially thru the NCL-2000 at around 350W out.

Carl

I picked up a 9.7 kc mechanical filter at Dayton one year.  I installed it in my 75A-4, and can tell absolutely no difference between it and the 8 kc one out of an R-390 that I shoehorned into the receiver.  I suspect the filters are electrically identical with different nominal specs.  The 9.7 one was single ended, with solder terminals at the end.  I straightened out the hook-shaped terminals, since they were spaced exactly the same as the prongs on the stock A4 filters, made of the same gauge wire, and are of identical length, and the filter fit right in. The only thing, I have to carefully insert it into the socket, since the other unused pins are missing, and it is possible to insert it the wrong way.

I think enforcement was better under Hollingsworth because he had a personal stake in amateur radio.  Laura is a lawyer, and probably never gave a thought about ham radio until she was hired to her current position. Amateur radio is just one of the services she oversees.  She is not a ham, and that could be a good thing; less likely to result in a conflict of interest.  Remember, Johnny Johnston was a ham and had a personal interest in amateur radio, too.

OTOH, I recall what a stickler for the rules the FCC monitors used to be back in the late 50s. In one instance, a couple of CBers were in conversation. This was back when CBers had to take out a licence and were issued call signs. A couple of guys were in conversation, and ended their contact with legal IDs giving their call signs per the rules. Then one of the stations came back and said a final "good night" without uttering the call sign routine all over again. He got a pink slip for not properly IDing. Thing is, if he hadn't at least obeyed the spirit, if not the letter of the law with his ID, and fulfilled the basic purpose of the ID rule, how did the FCC monitor know to whom to send the citation?

In another case, a CW contester was reported to have received a citation after a station inspection, when the FCC field inspector measured his power input at 1100 watts instead of 1000.

I am all for fair, reasonable, common-sense enforcement, but I don't think we would want the FCC to micro-manage amateur radio the way they used to.
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[I am all for fair, reasonable, common-sense enforcement, but I don't think we would want the FCC to micro-manage amateur radio the way they used to.
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 ya vol mein fuhrer we need'nt Micro anything from the Rechtsberater.

Neine...



73

I use a 9.4 kc mechanical filter in my 51J-4. I haven't done side-by-side comparisons with a R-390A and the 8 kc filter but it has a very similar sound working from memory. It's nice BW since only when things are really crowded do I need to go to the 6 kc filter, but the 9 kc yields superior audio on stations with good audio. The crystal phasing filters in the 51J-4 (rest of the 51J series too) are about useless for AM - too narrow and much more difficult to find a good phasing spot than compared to the phasing filters found on many Hammarlund receivers.

6 kc what? When the crystal phasing filter is out of the circuit, the selectivity is provided by the LC IF cans. It isn't 6 kc.

The Kenwood R-1000 had a wonderful 12 kHz filter (with a gradual transition to the stopband) that sounded great on a high-quality signal, particularly when coupled with its low-distortion detector. The "6 kHz" filter also had a fairly gentle slope and pretty good sound.

I can only describe the audio, on a good speaker system (I heard it on a Cerwin-Vega D9), as "jewel-like." It's as if the presence of the clean highs and transients made the low end sound cleaner and tighter than it would have on a lesser system. The same stations heard on a Heathkit Mohawk sounded muddy.

I was able to get a similar "jewel-like" sound from my TS-440 by altering the diode logic to switch out the 455 kHz 6 kHz filter, relying on the first IF filter only. It was a dead flat 8 kHz passband and then a very gentle slope to 20 kHz or so where it fell off a cliff. Sounded beautiful when band conditions were right and was a pretty close match to the inverse of NRSC preemphasis as a bonus.

To give you an idea of what a more typical, but still quite decent modern receiver does on AM, I have been listening to an unmodified online Icom IC-718. The filter is called a 6 kHz filter, which one would think would allow only 3 kHz of audio, but it actually rolls of gradually enough to allow audible AM audio out to 5 kHz.

I recorded the output of the IC-718 during a session of the AM "What's for Dinner" net recently. Many of the participants have very high quality transmitters -- K1JJ and K3ZRF among them. The recording can be found at:

http://liberty.3950.net/What%27s%20for%20Dinner%202010-0223-510pm.mp3 (http://liberty.3950.net/What%27s%20for%20Dinner%202010-0223-510pm.mp3)

And here's the energy versus frequency plot of the first 8 minutes or so of that recording:

(http://liberty.3950.net/What%27s%20for%20Dinner.jpg)

As you can see, there is still a lot of energy from these stations and this receiver at 4 kHz and still enough energy to be significant at 5 kHz. (To confirm this, as I write I am listening to this same online receiver, and KG2IR is running sine wave checks with WB2CAU on AM, and I can clearly hear the 5kHz tones at 30% modulation.)

Digitally filtering out everything above 3 kHz on this same recording (as I did as an experiment) takes away a huge amount of its perceived quality, even though the relative amount of energy removed is small.

Well, which is it, crystal or a tunable IF? Just how is the IF tuned from the front panel?

Tunable IFs are practical only with double conversion receivers.  The first IF is tunable, but the 2nd IF is the standard fixed IF, which in the R-390 series is 455 kc.  In the 51J series it is 500 kc.  The tunable IF is tuned with the main tuning dial; that is what does the frequency tuning in the receiver.  The 1st converter is fed with a crystal controlled oscillator. You can think of a double conversion receiver with tunable IF as a simple one-band conventional superhet with a crystal controlled converter ahead of it.  The R-390 series is triple conversion on some bands.

It takes extremely good design to get good dynamic range from a triple conversion receiver.

All true, except the part about triple conversion. Dynamic range is mostly (if not completely) determined by the RF amp and/or first mixer (assuming proper gain distribution in the following stages).

Anyway, a tunable IF won't have any effect on the audio or no more/less effect than a fixed IF.

Nice recording. Extended play!

But Ralph was PW.

Playing with the upper cutoff of a wideband recoding in a DAW can be quite enlightening.

Some more of the WFD from 2008.

While that applies to the active stages the passive filters can contrbiute significant distortion of their own and that doesnt even cover the phase shift/distortion in the passband even under low signals.

Carl

In a multi-conversion receiver, the tunable i.f. has nothing to do with audio quality or the selectivity of the receiver. That's determined by the final i.f. stage, which contain the selectivity elements: fixed tuned circuits, crystal filters, mechanical filters, etc.

The purpose of the tunable i.f. is to improve stability and the precision of the tuning range.  The high frequency oscillator may be crystal controlled, so that the stability element is the variable oscillator that runs the tunable i.f.

Another purpose of multi-conversion is image rejection.

For best dynamic range, you want a minimum number of active stages between the antenna and i.f. selectivity elements. Active stages include rf amplifiers, 1st i.f. amplifiers and mixer stages. A triple conversion has three mixer stages, usually one or two rf stages and one or two i.f. stages preceding the primary selectivity stage, allowing plenty of opportunity for overloading and undesirable intermodulation.  Multiple active stages before the main filter is worse with solid state receivers than with tube types.

With the advent of SS technology, most receivers and transceivers do as much little frequency conversion as possible before mixing the stage that has the primary passband (or is it bandpass?) selectivity.  Instead of a tunable i.f., the crystal oscillator and VFO are pre-mixed to produce the desired conversion carrier to heterodyne with the rf signal in the first converter stage. In more recent designs, the conversion carrier is generated with a PLL or direct digital synthesis, instead of analogue mixer circuits.  By using a higher i.f. than the traditional 455 kc, good image rejection can be achieved with single conversion.  I believe Hallicrafters first introduced that concept in about 1966.  There was also an article in QST in the late 50's or early 60's titled "What's wrong with our receivers", that addressed the issue of the pitfalls of too many converter stages before the main i.f.

The best receiver would be single conversion, with no rf stage, feeding directly into the i.f. filter.  Such a configuration is feasible with a beam deflection tube like the 7360 as the mixer stage.  It has enough gain to feed a crystal or mechanical filter, yet has excellent dynamic range characteristics.

What is tunable? You are not being clear.  IFs and stuffs is rather nebulous.

Don, how is this frequency conversion done without mixing.



Just not true. Look at the numbers on Sherwood and other pages. Modern solid state RXs blow away nearly all old tube RXs.



This is essentially what the Soft-Rock and other SDRs are doing, except the low IF is digitized.

The

Yup, they mix down to 11kc, then digitize.

The "high-end" SDRs  don't mix, or downconvert anything...
The entire HF band is directly sampled.

LOL Hey Bob this sounds like the 75'er No RF stage..LOL it ain't so nice...

73  8)

Jack.

Good point on the direct digitzing approach. Everything rests on the quality of that ADC.

Have you actually looked at the Sherwood page? Show me a tube RX that is even close to the latest generation of solid state receivers. The only tube RX in the top 10 of narrow spaced DNR is the tricked out R4C. It's not even in the top 20 for widespaced DNR. The only other tube RX in the top 20 of either DNR category is the R-390 at about 16.

Please also explain how the dynamic range of the solid state receivers changes with frequency.

Ah Haaa "Splash" like the Cbers say LOL, overloading Splash  8)

My mistake.  I guess I was in too much of a hurry.  I meant to say they do as little frequency conversion within the signal path as possible before the selectivity filter.  I have corrected that in my original message. Conversion and mixing are the same thing.



Maybe to-day SS receivers approach or even surpass tube type receivers, but until recently at least, no SS receiver could "blow away" a well designed tube type receiver. They struggled to approach them in performance.  For many years, performance was sacrificed for the convenience of solid state.

I agree with this statement.  I added a BW SSB converter to my R390.  It "blows away" my Icom 756 pro.  Hands down.   The only area where the icom is better is when you want to narrow down on SSB to hear only one station for DX.  Otherwise, The BW/R390 far surpasses the Icoms performance.
C

I wouldn't say that, some of the old Hy-brid rigs with a li'll interest preformed rather well :)
an receive was solid state.

Since we were talking about dynamic range..... Once again, you were unclear. Almost any decent RX made in the last 40 years has more than enough sensitivity for HF use. External noise is the limiting factor not receiver sensititity.

Do you have some numbers that dispute Sherwoods?  Remember, we're talking about front-end overload and RX DR. Sherwood shows the R-390A with 81 and 79 dB for wide and close-spaced DRs. The 756 Pro III is shown with 99 and 75 dB DRs. Hardly blown away.


I only want to hear one station (no QRM or intermod) on my RX. Maybe you're different.   :D

Data?  LOL!!!!   How about using them side by side. Screw the data.  I use the one that works better :)  Modern SS rigs are made for one purpose.  To go into a pile up, hear one guy and null the rest.  Roofing filters, DSP, twin PBT, auto notch ect.. are all made for that purpose.  In this area the icom is fantastic. However, Its signal to noise ratio, its audio quality and sound cannot compare to the old BW/R390.


C

And this is where DR is important. Audio wasn't part of the discussion.

I completely agree that many old receivers will produce better sounding audio than many newer SS RXs (mostly due to wider bandwidths in the older RXs). I have several old RXs just for this reason (and they look cool too) - some dating back the 1930's. But, I've also used a ton of new SS RXs. And many sound just as good or better than the old tube radios (mostly due to better AGC and detectors).

Blanket statements like "SS RXs can't compare to tube RXs", and "tube RXs sound better than SS RXs"  are not only wrong in many specific cases, as time passes, they are wrong in the general instance too.

More info on DNR


http://familydoctor.org/online/famdocen/home/pat-advocacy/endoflife/003.html

klc

One of the worst examples of that type of receiver was the Yaesu FT-101E series, circa 1978.  The  receiver was double conversion with tunable i.f. somewhat like the 75A-4, but everything was solid state.  The receiver is sensitive enough, but it goes belly up in the presence of a nearby strong signal, even if that signal is at the other end of the band. The old Kenwood T599/R599 pair has similar problems.

Later on, Yaesu went to the FT-300 series which pre-mixed the VFO with the xtal oscillator and used single conversion, for a tremendous improvement.  Then they came out with the FT-901 series that used a PLL configuration instead of simply mixing the oscillators with heterodyne converters.

My friend across town had an FT-301 and he used to be perplexed that I could hear signals on my old pre-WW2 National HRO with the 2.5 volt tubes better than he could with his Yaesu.

My kenwood TS-520 hears quite well, but is of course very narrow, listening to one sideband of an AM signal can be useful under certain band conditions, but not really what it was designed for it's definitely optimized for CW and SSB.

 The 390A is FB running an outboard amp to good size speakers, salvaged the amp board from an old home stereo and feed the rectified IF output to it.

If only we could make a storm QRN eliminator we'd be in good shape this time of year. 
Oh yeah, such a thing exists--it is called the 1 KW carrier.  Unfortunately we're not allowed to use it.

Back to receivers now....

I use 4 KW TS-830's as IF's for 6M and up. After a few simple mods, filters, etc, they are pretty much bullet proof and that is with the additional RX gain from the transverters.  In fact they are so hot I bypassed the transverters IF amps in the DEM units as I didnt need the gain to overcome anything.

For years I had a pair of Drake C Lines with lots of mods not mentioned by Sherwood. Its been too long ago to remember the IMD performance but they were excellent under DX contest conditions and Im LOS to many of the top stations in the country. Ive learned to take Sherwoods list with a bit of skepticism as the test setups vary over the years so there is no true correlation. Plus some tests were done by others.

The NCX-3 was a 1960 design with a single high IF and there were probably others even earlier. The NCX-5 has a reputation of being extremely sensitive along with a great AGC and overload handling.

Carl

I found that my EE had little sensitivity above 20 meters and had to use a preamp to make it hear.