5KC Audio

[Steve - WB3HUZ]

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.

[KM1H]

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

[k4kyv]

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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[ka3zlr]

[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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[/quote]



 ya vol mein fuhrer we need'nt Micro anything from the Rechtsberater.

Neine...



73

[Steve - WB3HUZ]

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.

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. 
/quote]

[Steve - WB3HUZ]

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.

[WB4AIO]

...it seems 5KC isn't/wasn't "most" of the receivers. Heck, my all American 5 Packard Bell is 8 KC at least.

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

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



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.

[Steve - WB3HUZ]

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

The R-388 (51J-3 and 51J-4) receivers were better than either the R-390 or R-390A for AM because they had the standard 6kc xtal filters instead.

I'll take a tunable IF band pass or xtal filter band pass over those crappy mechanical filters any day of the week.

[k4kyv]

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.

[Steve - WB3HUZ]

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.

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.

[Steve - WB3HUZ]

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.

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



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.

[KM1H]

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).

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

[k4kyv]

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.

[Steve - WB3HUZ]

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

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

What, you wanted more specifics

I could have said IF's and stuff, but I guess you would rather find fault in what I said, right?

The R-388 works better with the selectivity switch set to "0" if you want the best fidelity, which the receiver does have. With the selectivity set to "1" it still works pretty well and is far better than the R-390 in the crappy 4kc mechanical filter position. Look at the 40db and 60db points in the curve in what I posted.

So the answer is both, tunable and xtal positions...

[Steve - WB3HUZ]

With the advent of SS technology, most receivers and transceivers do as much frequency conversion as possible before mixing.

Don, how is this frequency conversion done without mixing.

Multiple active stages before the main filter is worse with solid state receivers than with tube types.

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

The best receiver would be single conversion, with no rf stage, feeding directly into the i.f. filter.

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

The

[KF1Z]

The best receiver would be single conversion, with no rf stage, feeding directly into the i.f. filter.

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

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.

[ka3zlr]

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

73  

Jack.

[Steve - WB3HUZ]

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

The best receiver would be single conversion, with no rf stage, feeding directly into the i.f. filter.

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

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.

[Steve - WB3HUZ]

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.

[ka3zlr]

Modern solid state RXs blow away nearly all old tube RXs.

That is only true on the higher HF bands and above. There is one tradeoff though; transistor RF front ends easily saturate and are prone to severe overload.

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

[k4kyv]

With the advent of SS technology, most receivers and transceivers do as much frequency conversion as possible before mixing.

Don, how is this frequency conversion done without mixing.

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.

Multiple active stages before the main filter is worse with solid state receivers than with tube types.

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

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.

[ke7trp]

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

[ka3zlr]

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.

[Steve - WB3HUZ]

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.

Have you actually looked at the Sherwood page?

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

I have no idea as to what "Sherwood page" even is and I really don't care and I never said the dynamic range in solid state receivers changes with frequency. Where did I say that?

To quote myself I said "That is only true on the higher HF bands and above."

SS receivers have better sensitivity than tube receivers on the higher HF bands and that's always been sort of a given. Designing a tube receiver with better sensitivity on the higher bands can be accomplished and I plan to do just that when I sit down to build the HRO diversity rcvr, but I will use a Nuvistor as the first RF stage on both sides. And, it still doesn’t erase the fact the SS receivers are prone to saturation and overload.

Anyway, I’m going to drop out now for a while before you guys get this topic locked up too

73’s

Brian

[Steve - WB3HUZ]

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.  

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