Hum Bug Fixed

Noise at left speaker terminal (1V scale)

My kitchen system has had an increasingly awful "hum" (mostly 60 Hz AC line frequency and harmonics) for the last 3 years or so.  I finally had to do something about this, ironically, on Christmas Day 2024.

I used to pay very close attention to ground loops and other hum causing issues in the kitchen audio system ever since it first started coming together around 2005.  It's always been a very complicated system including VCR, digital video recorder, multiple monitors, inside and outside antennas, Tivo, big network switch, computer with loads of peripherals, etc.  I took great care when adding each new device to ensure a ground loop was not being added, and if it was, I found some way to eliminate it.

But what happened around 2022 is that the DEQ 2496 that was handling my subwoofer EQ, and which I was also using as an RTA to verify that the hum at 60 Hz was near zero (typically -110dB), summarily died after about 10 years of use as they have tended to do.

I then struggled to get the subwoofer working just as it had been before, but using the EQ built into my HTR receiver (a Yamaha HTR-5790).  But unlike the Behringer, the receiver lacked the balanced outputs to drive the small chifi preamp which gives me a subwoofer level control.  So my carefully constructed grounding scheme, reliant on a balanced connection in the middle, was no more.

And lots more stuff happened too, I just wasn't keeping track of things anymore because I didn't have a handy RTA to keep checking that things met the same hum free standard.  So I didn't much bother, and as might have been predicted, it just kept getting worse and worse as I added new features and/or devices.

Then last week I discovered to my horror that I had been connecting the Hafler 9300 power amp to the preamp output of the HTR-5790 using a 2000's vintage 12 foot Radio Shack standard interconnect.  Betting that was a problem, I ordered a new 13 foot Blue Jeans LC-2.  These are RCA terminated flexible coaxial cables with the best shield coverage you can get, along with the lowest capacitance, and they are as robust as it gets.

But as I've been rather busy with parties and preparations prior to Christmas Day, I didn't get around to installing the cables which had arrived last Friday until after my big Christmas Day dinner (a buffet with friends).

I wanted to make sure I had good before and after measurements, so I got out my Meguro MN-455B noise meter, which is a very useful thing to have (and I needed to have a real electronic "noise" meter since the 1970's, there has been hardly any other way to get "A" weighted electronic noise measurements, but I only got this wonderful Meguro in the 2000's on ebay).

Because the Revel M20 speakers have widely spaced connectors, I couldn't just plug in my coax-to-double-banana adapter into the 5 way binding posts.  I had to rig up an extended connection for the minus terminal using two more double bananas and a short wire.

When it was all together, I was shocked to discover, that with the Yamaha actually turned off, but the Hafler on, I was getting 0.88V "A" weighted hum and noise at the speaker terminals.  No wonder it was beginning to get annoying.  It made no difference whether I had the Yamaha powered on or off.

I removed the input connections to the Hafler, and the audible hum vanished.  I could not hear anything from the normal listening position, and there was just a trace of hum at the speakers themselves.  But the A weighted noise level had only gone down to 0.4V.  That was because the Hafler 9300 has a fairly high 47k ohm input impedance, and a 500 kHz bandwidth, and the "A" weighting isn't even defined above 20kHz (but is often just extrapolated, not brick-wall filtered at 20kHz because it's inaudible).  I'm not exactly sure what the Meguro meter does on the "JIS A" setting.

But open inputs, a high input impedance, and high bandwidth ensures there's going to be a lot of high frequency noise, even if there weren't much anyway.  That's what I think is going on...the hum went away but the HF noise was even greater because of the now open inputs.

I could have measured with shorted inputs, as John Curl himself told me I must do in a message after I complained about the noise level in my HCA-1000A varying with input level position.  But I didn't bother this time, because I know the amplifier is near perfect anyway.  I didn't need to test the amplifier hum, what I wanted to do is find a way to have it hooked up without hum.

So I rolled out the new 13 foot cables, only to discover that 13 feet was actually way more than needed.  It left me with an extra 3 feet curled up on top of the amplifier (until I found a better idea).  What this revealed was that the original 12 foot cable, and I pulled it out to be sure it was a 12 foot cable, was twisted around so much stuff that it was only barely long enough, even though it should have had 3 feet to spare.

Even with the excess cable piled on top of the amplifier, but plugged into it, the audible hum was gone and the noise level was now 0.19V.

New cable with excess piled on amp, first time

But finding the Blue Jeans cable was too long left me in a quandry.  Do I send the cable back, and get one made to the correct length?  I wondered if Blue Jeans had cut the cable too long, so I removed it.  Only to discover that they had just barely cut the cable by an inch or so longer than the 13 feet, not including the jacks.  Radio Shack cables barely meet the advertised length WITH the jacks.  Now it was clear how much the Radio Shack cable had been wrapped around lots of stuff, probably mostly AC line cords on the floor.

I still couldn't make up my mind, so I reconnected the LC-2 cables just to have something working.  But now the hum level had gone up, to 0.6V.

WTF!!!

I quickly discovered that even with the best-in-class shielding of the LC-2, it makes a hell of a difference how the cable is laid with respect to AC line cords and other stuff.  Particularly bad, it seems, is the back panel of the UPS that powers most of my system.  If I run the cable next to that back panel, and it tends to fall that way if I am not careful to avoid it, hum goes way up.

Hum came back when cables ran this way

Rather than experimenting with each possible variation, I decided to just do-it-right from the start, by arranging the cable to be as as far away from everything, and especially AC power cords and the UPS, as possible.  I used my AV stapler to staple the LC-2 cables to the wall (the staples are just barely big enough, and a lot of them failed to attach properly and had to be removed, but it seems to be holding now) way above everything, then over to the table leg where they are held on with velcro ties, then down to the amplifier.

This got me to my lowest measured level, but not actually much better than my lucky first hookup, at 0.18V.

Noise after re-routing new cables

It sounds hum and noise free even ear to speaker.

I used to ignore hum and noise.  I started taking it seriously around 2002 when I found my incredibly well built 1978 Pioneer Series 20 D23 4 way electronic crossover had developed a ripple-hum (around 120 or 180 Hz).  That was what ultimately led to my using digital crossovers, and finally DSP based crossovers.

The kitchen Hum had become very irritating when there was no music playing.  But I never noticed it when music was playing, and even with it present I still felt I could make very fine audio judgements.

Pioneer TX-9500 II

Pioneer TX-9500 MkII (top)

I bought this Pioneer about 8 years ago, and it finally went up into my Kitchen audio system today.

It's a fine sounding tuner, in the 3rd upper rank at least.  It's considerably more musical sounding than the Kenwood 600T and all the other silver Kenwoods from the 1970's.  Everything sounds sweet and lively.  Noise seems separated from the musical image (sadly, the Kenwood 600T does not do this).  But the noise is not as low as with the 600T.  The 600T is at least as sensitive and selective, if not slightly moreso.

I'm ranking it sonically just below the Kenwood L-1000T, and then the Pioneer F-26, in the 3rd rank of tuners which includes the Sony 730ES, Sansui D-99AMX, Yamaha TX-1000, and Marantz 20B.  The Pioneer is better sounding than a lower set includes the all the 70's Kenwoods (600T, KT917, KT7500, KT8300) I have listened to and the Onkyo 9090 MkII.  And then, most strangely of all, not sounding as good as the others mentioned, at the bottom sonically of all the super tuners I have, the McIntosh MR78.  (MR78 is plain ok sounding, but many tuners like the Pioneer TX-9500 MkII have a wider bandwidth and even lower distortion detector and MPX that give more lifelike detail without more brightness--with the MR78 already has plenty of but it doesn't help the apparent relatively dead and boring sound.)

Compared with the Pioneer TX-9500 MkII, the Kenwood 600T sounds cold, sterile, flat, uninvolving, much too bright and steely (unless high filter activated), but also slightly quieter.  In short, the noise and some of the life have been sucked out of the music with the 600T, but not with the 9500 MkII.

But I should continue to refrain that the 600T is a fine sounding tuner anyway.  If you had never heard anything else, you'd think it was fine.  Low noise and distortion, high performance.  But then fire up the 9500 MkII, and everything comes alive in a way you wouldn't have thought possible.  

(MR 78 is like the 600T in these regards, but differently.  If all you ever listened to was MR 78, you'd think it was fine.  But while the 600T adds a certain fuzziness to the sound because it has a resolution-losing but very wideband detector, the MR 78 adds a slight hardness to the sound because it's just trying too hard with a not-quite-wide-enough-wideband detector.) 

The Pioneer Signal Strength meter actually tells you nothing about the signal strength.  But it's a pretty good measure of signal quality, sort of like the inverse of "Multipath".  When you get to the top of the meter, no matter how strong the signal actually is, you're getting sound about as good as it gets.  Most stations vary from 4.5 to 5.  It's even more difficult than most to use as a precise tuning meter, so a scope hookup is recommended.

The TX-9500 MkII uses a very linear and wideband FM detector proprietary to Pioneer (P.L.B.) that works on the principle of being a phase compensated delay line.  This may have been Pioneer's all time best detectors, also used in the F-26 and F-28, all made in the late 1970's, which was a golden age for Japanese hifi because of the exchange rate.  Later, in the 1980's, the Pioneer F-91,2,3 series in the 1980's got progressively worse in terms of noise and distortion, something David Rich lamented in a classic Audio Critic tuner review in 1990 (while admitting that he himself had an F-93 because on some very weak channel he liked, the fake stereo it did was the best sound he could get).

In the wide mode, there are no ceramic filters in the IF path, only tuned filters (I used to think that was crucial) and a SAW (Surface Acoustic Wave filter, computer designed whizbang technology which became available in the late 1970's).  Ceramic filters are inherently noisy and "acoustic," so having all or mostly tuned filters could provide a "purer" sound.  But tuners using all or mostly tuned filters include MR 78, Marantz 10B and 20B, Sumo Charlie*, Kenwood 600T and KT917 in wide mode, and all classic tube tuners, a mixed bag sonically, and many ceramic-filtered tuners sound fine.

(*Inspired by the Marantz 10B, James Bongiorno used all tuned filters in the Charlie, except just one wide tuned ceramic, because, as he once told me when I asked him about this, "You need something to kill the crap way out there."  Well that's similar to Pioneer using one SAW in the TX-9500 II wide mode, except that a SAW is more sophisticated than a wide ceramic.)

The Pioneer front end is basically the best design you can do with a 5 ganged air capacitor, and more gangs are sometimes wasted in other super tuner models.  Being based on ganged air capacitors (turned by the tuning knob) rather than varactors has advantages in front end dynamic range, which is why many classic tuners are so good without being anywhere near as "sophisticated" as later tuners.

FNIRSi 2C53T scope

The FNIRSi portable scope, model 2C53T, is just the thing for viewing FM tuning for those tuners which have scope outputs.  It costs around $100.  A two-channel model is required for this application, not one of the even cheaper ones.

The screen is tiny compared to my Rigol, and it lacks the dynamic measurements.  But it's small, cheap, and doesn't have a fan.

As small as the screen is, you are going to see more than you see on some (but not all) tuners that have scopes.  Notably the Sequerra Model One had a bigger scope, and with a super cool RF spectrum analyzer option.  The scope is about the same size as on a Marantz 10B, and larger than on a 20B.

It's good for tuning each station in precisely, as well as viewing multipath and other issues.

It has rechargeable batteries, but it works while you are charging (unless, they warn you, that you try to make measurements on the same computer motherboard which is supplying the power--in that case get another USB power supply or you can create a short).

The manual is so tiny as to be unreadable (download the online version).  Even then it's not very useful, and the device is as counter-intuitive as heck.  It took me 2 days to figure out how to use it as an X-Y scope for FM tuners.  Not that selecting X-Y was hard...that was the easiest part--it's at the top of the menu when you press the Menu button.

I made the mistake of starting up the unit without looking at the screen, and ended up selecting the Chinese characters.  Then just about anything was impossible.  Indecipherable messages could appear while the unit simply locked up.  Finally it seemed to resolve, but it took a long time.  (Apparently it was some kind of Calibration, and pressing other buttons as I did frantically only makes it take longer.)

"Calibrating"

But the key discovery was that you get to Settings not through the menu, but through the startup screen (where you can select Scope, Multimeter, Generator, or Settings).  Then, at the top of Settings, you can set (or re-set) the languages.  At the bottom of Settings you can do a full reset, which I did several times before I figured this thing out.

Then you have the issue of setting the sensitivity of Channel 1, Channel 2, the "H" parameter (bandwidth) and persistence.

It took me the longest time to figure this out:  Use the "Move" button to change from Channel 1 to Channel 2.  Then use the "Select" button to select what things you want to update (see the manual: one thing updates the sensitivity, another the offset).  Then use the up/down or left/right keys to actually do the update (each Select mode assigns different things to the up/down and left/right keys).

Update on Kenwood 600T

I'm finally about to remove the Kenwood 600T from my kitchen audio system, where the tuner is by the side of my chair and so I do the most "tuning" of different stations.  I had only moved the 600T into the kitchen to test my antennas, but ended up keeping it there for 5 years because I never got around to testing the antennas before that.  It sounds fairly decent (never have hopes THAT high for FM anymore anyway) when the Mode is switched to Filter.  That rolls off the highs just enough to remove the high frequency brightness and glare that is sadly characteristic of Kenwood tuners until they got into analog multiplier MPX circuits, as with the most famous L-02T, and the later lesser known but still stellar unit I have, the L-1000T.

I had sold my KT 917 in the 1980's way too cheap because I never liked that sound.  Much later I hoped the 600T would be sonically nicer but it wasn't.  They are somewhat similar in concept and build but differ in circuit details with the  KT-917 being much more famous.  I think the KT 917 also had a filter position, as well as a separate blend control, but I didn't pay attention to those things then.

Anyway, I don't think either tuner has the there-ness as many other high end tuners because the primitive Pulse Count Detector used by both 600T and KT-917 is fundamentally inadequate, something Kenwood themselves were aware of and fixed the problem in the L-02T and later high end tuners, with their PLL Detector, aka "linear" detector.  This should not be confused with PLL multiplex, which was already a common feature in the late 1970's.  Basically all tuners with chip MPX have PLL multiplex, and that is not even such a big deal as getting the detector right.  Before the PLL detectors, which had a slow roll out in the most high end models of the 1980's, most tuners used old fashioned methods such as ratio and quadrature detectors, which have known non-linearities.

Anyway, the slight lack of ultimate transparency in the Pulse Count Detector is of little consequence in practice, since few take FM broadcasting seriously enough to utilize the full potential of the carrier.  Later similar pulse counting detectors were made with much higher resolution (such as the Accuphase tuners of the 1990's and beyond).  Interesting that Accuphase itself was created by former Kenwood engineers in the mid 1970's, and their original tuners which competed with the top Kenwood Pulse Count Detector models used conventional detectors.  It's almost as if they left because they felt it wasn't any good, and they wanted to prove it.

But we'll see how I feel after I switch in some other tuners, notably a Pioneer which was one of their "greats" from the late 1970's, like the Pioneer ST-9500 MkII.  I think it has a commonly used quadrature detector, well perfected by that point.  I know when I used the Kenwood L-1000T there was always an incredible transparency which no other tuner I'd tried possessed, it will be interesting to see how the 9500 MkII compares to it.

Anyway, I'd long denigrated the DX'ing of both the KT-917 and 600T.  I've described the 3 position IF bandwidth switch (which as labeled as Narrow, Normal, and Wide) as "Wide, Wider, and Widest."

But now I can say with absolute certainly that while the Narrow on the 600T is nothing at all like the Super Narrow on the McIntosh MR 78, it still has some use.  I've found several stations, typically low power stations not that far away, that can simply not be tuned in until you select the Narrow IF band.  (The narrow band lets the tuner be more selective, by blocking stuff on either side better.  It doesn't help with capture issues, however, for which Wide may work better.)

Stations are still listenable nearly down to 10dBf (on the meter) which is pretty amazing.

An attached scope is the best way to adjust tuning and/or antenna.  The multipath meter is nearly useless.  The signal strength meter can be used in tuning only if you very carefully dial in the very highest peak.  Around the peak for quite aways it changes very little so you have to look for very tiny deflections of the meter.  That correlates exactly with the picture on the scope, as expected the now quite out-of-alignment center tune meter does not, though it seems like on every tuner I've ever used, aging has caused the correct tune position to be at the far right of the central mark in the center tune meter.  This is usually just before the stereo light goes out for having tuned too much higher.

My two FM Antennas Compared

 

I have two outdoor FM antennas that were installed by electricians 8 years ago.*  One is normally connected to the Living Room FM tuner and the other is normally connected to my kitchen FM tuner.  For almost 20 years I've kept the Living Room tuner set to 88.3 KPAC for background music listening, and I use the kitchen tuner (conveniently next to my kitchen chair) for searching for and tuning in other stations, especially 90.1 KSYM and 91.7 KRTU, two college radio stations.

(*This was a very expensive project because of the grounding requirements.  Each antenna has its own grounding rod, and all grounding rods are connected to the main house grounding rod by a thick wire that runs 3 feet underground across the back yard.)

Five years ago I decided I wanted to measure and compare the two antennas on the same tuner.  So for this purpose I moved my classic Kenwood 600T FM tuner to the kitchen.  I was going to use the 600T's marvelous 10dB calibrated signal strength meters, multipath meter, and scope outputs with a scope to compare my two FM antennas.  Otherwise, the 600T is not my favorite sounding tuner.  I planned to do the test in a few days and then replace the 600T with one of my other tuners that sounds better.

But after setting it up in the kitchen, I discovered the 600T sounds fairly good if the MPX Filter position on the Mode control is selected.  (Otherwise it sounds bright and tinny.)   And because of that and other things, you know how it goes, I never got around to doing the tests until now (last week).

One antenna is the famous Magnum Dynalab ST-2.  Another is the less well known Godar FM DXR 1000.  They are both whip antennas not because that is the best but because that is the easiest to install, since they can simply be screwed to the side of the house and not atop a mast.  I've long dreamed of having an antenna mast but it would be a very complicated outdoor project, too complicated for me so far.  Whip antennas also have an advantage in that they are omnidirectional and never need to be rotated.  This can also be a disadvantage if you want to block some strong unwanted signal.

(Most of the differences here probably have little to do with the whip antennas themselves, which should have fairly comparable performance in the FM band, but in the differing heights of the antennas as installed, and the fact that one of them--the Godar--is now bent.  Strangely, however, the bent antenna actually worked better on some stations in this test.)

I have the ST-2 is mounted as near as it could get to the peak of the roof, as high as I can go just mounting the antenna to the side of the house.  I couldn't mount it right at the peak because it would interfere with my locked attic door.

The Godar is mounted about 4 feet away, and situated about two feet lower because of the roof slope.  The Godar is tuned to what I determined to be best by SWR in the low FM band, probably 88.3.  The ST-2 has similar fixed tuning, best at the low FM band (which is where all my stations of interest are anyway).

Sadly tree branches messed with the Godar last year, and is bent to an angle less than half way up.  So how well is the Godar still working anyway, I wanted to know.  Do I need to buy a new antenna?

The Godar antenna, because it has greater RF bandwidth* than the ST-2 is also used for my Uniden SDS200 scanner--whose importance I'm beginning to question now that police bands here are 100% encrypted, which Scanners can't legally break even if they could do it technically.  Supposedly I can still get fire and EMS communications though I need to update the programming in my scanner for the newest systems, which changed about 2 years after I bought my scanner.

*I long figured the Godar has greater specified RF bandwidth, up to 800 Mhz because of having a lower inductance choke.  However it might also be because of the thicker whip made out of aluminum rather than steel, and because you can make the antenna much shorter.  I have it extended to nearly the maximum length so maybe I am not getting the top RF bandwidth after all, but it did work OK with my scanner at frequencies around 850 Mhz when the scanner was still programmed correctly for local services.

So in between the Godar and the living room FM tuner there is a splitter, which reduces the signal sent to the FM tuner by 3dB.  I tried an FM/TV splitter, which could theoretically have zero reduction in the FM band, but decided that it curiously caused non-linearities in the FM band which were even worse than a splitter (or so it seemed).  So I went back to a plain vanilla nice quality 1000 Mhz bandwidth splitter.  The signal then passes through permanently wired RG-6 panels in kitchen and living room to reach my living room tuner, a Pioneer F-26, one of the best FM tuners ever (like many of the other FM tuners I have collected) and from the late 1970's.

I was motivated to do the test now both because of the Godar antenna being bent and because I really really want to start playing my other tuners, including the Pioneer ST-9500 MkII that I finally got down from the top shelf in my climate controlled storage building a few months ago.  A friend believes that to be one of the best tuners ever, possibly even better than the F-26.

It just happens that I haven't been listening to KRTU much on the kitchen tuner recently, but I continue listening to 2 hours of weekly space music on KSYM.

Now finally testing the Godar on the 600T playing KSYM, I was shocked to find that the signal level was 13 dB lower, and not inconsequentially (26dB vs 39dB).  But over time I became aware that it was actually sounding better.  This became more and more clear as listening went on for a few hours.

At first I was thinking the noisier sound with the ST-2 was because of some kind of distortion, possibly caused by ground loop isolator.  Over the years, I'd used a number of ground loop isolators with the kitchen tuner because otherwise I'd get a serious hum on the kitchen audio system.  Some of those isolators seemed to cause notable distortion.  But it appears that I've removed all the isolators, and now I simply run the ST-2 signal through the RF surge suppressor built into a Monster brand AV power strip.  This also ensures it is firmly grounded to the kitchen audio system ground (or vice versa).  For a moment I was thinking of bypassing the Monster surge protection.  But it would be a big hassle because of where that power strip is located.

So what else could be causing this problem that makes the ST-2 sound worse on KSYM, I thought to myself, despite having much higher signal strength.  The Multipath meter hardly ever even moves, so it didn't look like it would be "multipath."

It was necessary to hook up the scope to find out.  And it turns out the scope is far more revealing of "multipath" distortion than the multipath meter.  In fact, the 600T multipath meter is basically useless.  You need a scope to see what is actually going on.  

Mitch Cotter, who had done a study on FM tuners for Consumers Union, convinced Saul Marantz of this, and the result was the legendary Marantz 10B tuner, inroduced in 1962 with a built-in scope, and many successors with built-in scopes made by Marantz and other companies.  After the Marantz 10B was introduced, most top tuners from other companies, even if they didn't include an actual scope, have generally included scope output jacks that could be connected to scopes.  McIntosh top tuners had the scope outputs and McIntosh themselves made a purpose built scope for consumers, whose last incarnation was the Maximum Performance Indicator MPI-4 (leave it to McIntosh to give it such a fancy name).  Kenwood made various scopes primarily for amateur radio (I have one, it's too big and clunky to mess with much, and doesn't show a good picture except for Kenwood FM tuners) but also a few for consumer audio purposes.

I've normally used an aging and increasingly dysfunctional Tektronix CRT scope for this purpose, but this time, for the first time ever for me, I used my relatively easily moved and situated Rigol DS1102E digital oscilloscope.  I had never figured out how to use this as an X-Y vectorscope which is what is needed for seeing FM multipath.  It turns out that this is an X-Y option in the Horizontal menu for this.  

KSYM using Godar DXR 1000

Hooked up to the Godar antenna, the scope shows a notable V pattern.  The thickness of the V is no more than 2 screen divisions.   That "thickness" is what indicates the degree of "multipath" distortion (which technically means unwanted in-band signals which can be caused by many things including multipath, adjacent stations, and other in-band stations).

KSYM using Magnum Dynalab ST-2 antenna

Hooked up to the ST-2 antenna, the pattern might best be described as "blob" but more importantly the middle doesn't condense down to just one screen division.  You see a smattering of dots going nearly up to the top of the screen.  It's not much of the total pattern, but it's enough to make the FM demodulation much noisier.  The multipath meter wasn't showing the total spread, just some kind of average which loses these details.

I believe what the V pattern is indicating is the presence of an on-band but weaker signal, which is being rejected by the FM tuners "capture" characteristic, which gives the upper hand to a slightly stronger signal at all modulation levels.  This is specified in an FM tuners Capture Ratio which is very good for the 600T tuner, 0.8dB in wide mode, which is almost a miracle except that a few tuners, like the legendary Sansui TU-X1 do even better.

(And tellingly, the Wide FM band selection always sounds better on KSYM, even though there are alternate strong channels on both sides.  This alone suggests the interference is in-band.  And there are several in-band candidate stations possibly causing this in-band interference, including one at 100 miles away at a higher elevation--KTXI)

What seems to be happening for the ST-2 is that since it rises higher, it's picking up more of the offending in-band interference signals, which are coming from farther away.  So it's not so much the channel I want that's getting stronger, as shown by the signal strength meter, it's the other channel I don't want that's getting stronger even faster, and just enough to start overwhelming FM capture at the fringes, enough to add some very annoying noise.

I can just as well listen to KSYM on the living room system with the F-26/Godar for space music as background music from now on, and take advantage of the superior sound of KSYM on the Godar.  In the kitchen, where I'm usually sitting in front of computer screens, the sound can be too in-your-face for background music purposes, especially during the announcements.

And it turns out that the Godar is also working better on KPAC as well, the station I usually use it for too.

On KPAC the Godar measures about 10dB weaker (only 3dB probably caused by the splitter, 7dB caused by the lower height antenna) but the multipath trace is about half the thickness of the ST-2.  Despite the lower signal strength, the sound is just a bit cleaner with the Godar antenna, as suggested by the mulitpath traces on scope.

KPAC using Godar DXR 1000

KPAC using Magnum Dynalab ST-2

Both antennas have the V outline similar to the Godar antenna on KSYM.  I think this is another capture situation with the higher antenna picking up more of an interfering station.  However, not as bad, it doesn't have random dots reaching to the top of the screen.  The main strong signal (at about 60dB on the better sounding Godar as compared with 72dB on the ST-2) is sufficient to suppress the interfering stations much better, even though it's 10dB weaker.  So the overall situation is similar to KSYM on the Godar antenna, just somewhat less so.  The meter says it's worse but the scope and actual results are that it is better.  But the sound and visible multipath on the scope are very good with either antenna, it's hard to tell the difference.

I see it may actually help for KSYM and KPAC that the Godar antenna is now bent, since this might add some directivity, suppressing other directions.  Fortuitously, it's bent in the direction of the transmitters of KSYM and KPAC.  The bend would tend to block stations coming from the sides FWIW.  Since it's working so well I don't need or want to touch it.  Perhaps a brand new antenna would be higher and therefore worse just like the ST-2.  If the Godar finally breaks off I'll probably have to replace it then.

So it appears that both the signal strength and the "multipath" meters are useless in situations like this, and probably many others.  You simply need to have a scope to get a feel of what's going on.

The best FM antenna is a big multielement antenna on a rotor on a mast, which has long been my dream, but I've hardly been able to contemplate setting it up, and basically nobody does that kind of thing for hire (at any price a mortal can afford, anyway).  I called "antenna installers" and all they wanted to do was tack up a small VHF antenna for digital TV to the side of the house, just as I have done with the whip antennas.  (I have two such brand new unused antennas in my junkpile, a legendary APS-10, and a classic Radio Shack FM-6.  How to put em up has always been the problem, as well as the grounding stuff I got sorted out for my whips.)

I also dug up a quick RF disconnect for one of my antenna cables and if I install another one on the other cable, I can swap antenna cables as needed (if I want to listen to KSYM on the kitchen tuner, for example).

KRTU still measures and sounds better on the ST-2, and by no small margin.  It has 10dB more signal strength AND less "mulitpath" visible on the scope.  Even less than on KPAC with the Godar.  It's obviously best to listen to KRTU on the kitchen tuner with the ST-2, which is what I always do.

KRTU on Godar DXR 1000

Despite having less apparent in-band interference, the multipath display for KRTU on the ST-2 still shows the V shape--and perhaps even finer than the stronger KPAC.  So I tuned around the dial a bit, and it appears all the stronger stations show that "V" characteristic, even with signals as high as 75dB.  So it appears that the V shape is just what the 600T tends to show on its scope outputs, given the way it's designed to produced the scope outputs.  That actually varies a bit from one tuner to another.  I would have expected the ideal display to be a flat line.  But "idealness" for the 600T appears to be how thick the trace of the V is, or if you can't even see the V at all because it's so blurry.  It's also great for tuning as the tiniest off-tuning results in a detectable tilt one way or the other at the bottom, which is flat right at the center.  The meters are more difficult to read or interpret.  For precise fine tuning, the center tune meter is fairly useless as it's correctly tuned at the far right of the inner bubble (a through tuner alignment would fix this).  The signal strength meter is not biased like that, but around the center tuning position there are only very small changes.