I've always enjoyed receiving programming direct esp FM classical music stereo programming. However, in San Diego, there aren't a lot of choices. Basically there is one (1) station that broadcasts analog monaural* classical music; XLNC1 from Tecate Mexico. Since it's about 40 miles, a well tuned yagi should do the job when put up at 30 ft or so.
However, if you have a modern FM tuner, then you discover that there are two (2) other FM stations that feature classical music. They are KPBS FM-2 and KUSC FM-1. Both of these stations use the newer HD format and KUSC uses both "analog" and HD format. So things are looking up!
I purchased a yagi from MCM Electronics [MCM was sold to "Newark Electronics"]made by Stellar Labs called
"Four Element Directional Outdoor FM Antenna" for $20. Hard to go wrong at that price!Check it out here. It features four (4) elements on a 66" boom. The driven element is a folded dipole with a built-in matching x former, 300 to 75 ohms. Info states 7db gain with 15 db F/B ratio.
I wrote a review of the Stellar Labs antenna and it's posted here. I believe it's a great antenna that works as is but can be easily modified to other configurations as you will see here.
The small yagi below the Stellar Labs 6el yagi is my Radio Shack Corner Reflector antenna used for OTA reception. Check out the section at the bottom of the page here for the detailed design and how-to-modifiy details.
What I especially like about the SL 4el yagi is the driven element built-in matching network. It matches 300 feed impedance
to 75 ohm via a internal xformer attached to the feed point of the driven element. It's sealed to prevent water entry
which means that it will last a long time in So Cal weather. Most antennas require an external balun as an add-on which
raises concerns about the balun's quality plus how well it will weather in So Cal. Recommend that you use ferrite chokes at the feed point as shown in the picture. There are three (3) snap-on ferrite chokes to ensure that there is minimal, if any, outside shield current to modify/change the yagi's pattern. The impedance of the three (3) chokes is apx 930 ohms at 100Mhz.
Good selection of snap-on ferrite chokes is available at Palomar Engineers here. Their "FSB31-1/4" is reasonably priced @ $2.75 each and have 310 ohms impedance @ 100Mhz for a single turn.
I used Antenna Optimzer [AO] to analyze the yagi and then optimize it for XLNC1 @ 104.9Mhz. The 'stock' design showed poor performance
above 95Mhz to the top of the band at 108Mhz. Check the design section below for details. The "beam" heading from my house is 121 degs and the picture shows the modified yagi pointing in that direction. Unfortunately, Mount Miguel is directly in front of XLNC1's broadcast tower so it's partially "shaded" at my house. Usually that means if you swing the yagi around, you MIGHT find a spot where the signal bounces off a tall bldg or another hill/mountain. I didn't do that. The signal is adequate when beamed directly at Tecate, MX.
The pictures shows the yagi-pair mounted in-use.Many years ago, I had a 10.5 ft Radex dish that was mounted on the top of the 14 ft pole. I kept the pole when the dish was sold so other antennas could be mounted on it. It has proved its worth over the years. The top antenna is close to 30 ft over ground.
The left picture shows the XLNC redesigned FM yagi mounted on 15 ft steel pole along with the modified Radio Shack UHF corner-reflector underneath at apx 2.5 ft below. I use it to receive all UHF/VHF OTA signals. Check out the Yagi Design section at the bottom of this page for details.
This first picture on the right shows the XLNC yagi-pair from the front of my home beamed toward Tecate, MX (121degs). The last picture shows the KUSC 6el yagi-pair beamed at KUSC xmitter (335 degs). Pretty unobtrusive IMO but I'm very biased!
* June 2016: XLNC suddenly stopped broadcasting in STEREO, going to MONO operation. About 2 weeks after continued MONO broadcasting I called the USA number and talked to a station representative who said ". . . I wasn't aware that we are not broadcasting in STEREO". They took my email address and said that I'd receive an reply from the station "techs". Nothing was received. About 1 month later, I inquired again via their web site's direct contact form but again no reply. About 3 weeks ago the music programming went silent (full carrier but no "modulation" for apx 5 hours) until somebody realized that there was no programming. It went down for apx 1 hour to return to STEREO broadcasting. About 24 hours later, STEREO ceased and replaced with MONO operation. Today, XLNC1 is still in MONO. (3/1/18) The station closed its doors and stopped broadcasting.
Sony STR-DN1010 Receiver/Amplifier 
My home audio system consists mainly of "one" component, a Sony STR-DN1010 7.1-Channel A/V Receiver. The details can be seen
here.
The info states that you can "enjoy 3D images while hearing sound closer to the way it was captured, plus improve image quality of non-HD video sources to HD using one convenient cable. Offering plenty of connectivity options for your expanding lifestyle, this A/V receiver features 4 HDMI inputs, 3 component inputs and is SIRIUS Satellite Radio-ready. You can also share your music in multiple rooms with wireless 2nd zone technology". I do enjoy its overall performance but when my "FM-quest" started, I thought (wrongfully) that the FM tuner in the STR-DN1010 would perform OK! I was very wrong . . . but it took some time to find out. Listening to the FM analog stereo @ 104.9 Mhz showed distortion, poor channel separation and overall "noises". At one point it appeared that it was signal overload, so adding some attenuation should improve the overall performance. After adding 40db in line to the 75 ohm input connector, the sound would, at times, be almost "perfect"! The reason was that it would drop stereo reception and switch to "monaural" operation. Then conditions would change and the received FM audio quality would again be extremely poor. Changing the attenuation to 20db, the receiver noise would increase indicating some kind of rcvr desense. I started to realize that it basically was mass produced FM tuner with IF selectivity problems. To test this theory, move off the main frequency on either side of center frequency. If the IF selectivity is adequate, the channel should go away. For example, 104.9 was changed to 104.8 but the channel was clear, now in MONO. Even at 200khz away, the channel was still somewhat audible . . . and that shouldn't be. In other words, the FM tuner in the STR - DN1010 is crap! There are some interesting sites that discuss the various tuner problems with references to knowledgeable sites to fix/improve the tuner's performance. Check out "The Tuner Information Center" here. Take the time to read the complete discussion and you'll be much more knowledgeable about FM tuners. I'm sure that my STR-DN1010 FM tuner could use a gang filter section to improve the awful IF selectivity. That's a task for another day. |
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Sony XDR-F1HD FM Tuner 
So how about a "new" tuner?? While FM tuner shopping, I read about the Sony XDR FM tuner that can receive analog AM and FM,
as well as digital AM and FM stations that have adapted HD Radio technology. So maybe I can still find one?? Many have abandoned AM and FM in favor of Internet and satellite radio but the sound quality doesn't compare to clean FM signal. [I've recently made some spectrum analysis plots of KUSC FM HD1, KPBS HD1 and HD2. The spectrum is full to beyond 15Khz, so my initial observation wasn't correct!] However, getting a clean OTA signal can be problematic. FM is too often plagued with static, noise, and distortion and that's where the XDR-F1HD HD Radio is so impressive. If you have a good directional yagi, it's mostly immune to those forms of interference. The Sony tuner pulls in hard-to-receive stations better than any high-end tuner that experts have ever used. Some audiophiles believe the XDR-F1HD may be the best tuner available, regardless of cost, and many agree. I've always wanted a Sony XDR-F1HD tuner but today, it is hard to find. But after some searching, I found one that was in stock condition, so I bought it. At the same time, after reading the fame of this tuner, I consulted K6STI's site here for information on the Sony XDR tuner. He has tested it in detail although some of it doesn't check-out with my findings. You should read the info contained there and follow the recommendations except for the treble rolloff 'cap' mod. 
Another prominent Sony XDR tech is Dave known as "XDRguy". His site
here details the many aspects of his repair and upgrade of the Sony XDR tuner.The left picture shows a completed, upgraded Sony XDR tuner with a custom audio preamp (lower noise/less loss), upgraded power supply with new caps, two (2) added cooling fans, Memory Backup mod, FA/HD switch w/ LED and gold plated L + R output connectors. Unit is also realigned for improved S/N ratio ensuring great reception for a low level RF input signal. I especially like his bench setup including a Sony XDR Tuner and Sangean HDT-1X. The HP8903 Audio Analyzer and the Panasonic VP-8191A FM Signal generator are key instruments to properly align and test a Sony XDR tuner.
My Sony XDR Arrives . . After unboxing it, visually inspecting it (appeared to be perfect!), I connected the 75 ohm coax as well as the L - R audio output cable to the STR DN1010 amplifier. After setting the clock and other housekeeping task, a "SCAN" was performed. To say that the sound quality is amazing is an huge understatement! The sound (even with its deficiencies) is absolutely amazing! And the channel separation places you in the center of the concert hall. The sound field settings on the STR DN1010 are quite good and turn the line-level L - R tuner output into room filling stereo sound. Needless to say I spent a lot of time listening and tuning for FM stations, both analog and digital.
This tuner has been around since 2009 and it was an instant hit back then. Click here to read a 2009 article on the tuner. |
One of the best So Cal FM stations is KUSC @ 91.5Mhz from Los Angeles. During a "SCAN", I found that it was received
at my house with typically "one" bar (out of three) indicating that I MAY be able to get a decent signal with my yagi turned
towards Los Angeles! Today, I beamed the antenna toward KUSC xmitter site [34 12 48 N; 118 03 44 W] to see the signal level possible. Maybe three (3) bars is in my future??
The beam heading from my house [32 49 6 N; 117 10 27 W] to KUSC is 332 degs. The distance and heading can be calculated from a program here. It calculates that my house to the KUSC transmitter is 109 miles.
Looking at the chart it clearly shows, I'm in the far-fringe area. The good news is the station employs 39KW and the antenna is at 2923 ft and finally, the Tx site is 5541 ft above sea-level! Click here for KUSC FM transmitter data.
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The radio horizon extends beyond the visible horizon in conditions of normal atmospheric refraction and sometimes it is substantially increased (or decreased) depending by propogation conditions. The distance of the radio horizon is given approximately by the equation Rh = (17 x H)1/2 where Rh is the distance in kilometers and H is the height in meters of the antenna above the surface. For KUSC, their Rh = 106.2miles. For me, it's 28.1 miles. The total is 134.3 miles. Of course, this assumes no "obstructions" in the path. Physically, the distance from their Tx and my Rx is 109miles. So it's somewhat easy to see why their signal is 'readable' in San Diego, CA. |
[Email from KB7NIE - tried to reply to email address but it was denied!]
Question about your Stellar Labs Yagi setup for broadcast FM reception: Have you compared reception using vertical vs
horizontal polarization? Broadcast FM transmitters are vertically polarized, while your
receive antenna is horizontal. I didn't see mention of one versus the other in your website. Thanks! 73,Henry
Not sure where you got the idea that commercial FM stations broadcast with vertical polarization only. Certainly not b/c the tower is "vertical" does it mean that its signal is vertically polarized. Some low power college and non-commerical FM stations broadcast with vertical only patterns but these are typically located at colleges, such as San Diego Community College that owns/runs KSDS @ 88.3Mhz. They broadcast a vertical signal at height of 520 ft above sea level w/ the antenna's height of 170ft. 
If you examine the FCC license info for commercial FM stations, you will see that they require the same (identical) ERP
for both horizontal and vertical polarizations for commercial stations. As stated above, some "college"
stations broadcast more power vertically than horizontally - to aid mobiles. [That is controversial - read the link
below] but most "large" FM stations use circular polarized [CP] antennas. They are lossy and expensive but they are
regurlarly used to satisfy the FCC license requirement for commercal stations. Shown in the left picture is from ERI; 1180
series CP FM broadcast antenna capable of 140KW power broadcasting an omnidirectional signal! In the right picture: PCP FM
Broadcast Antenna- 4 bay w/ 3dB gain broadcasting a directional signal.Click the link here to read a 'treatise' on the use of CP vs VP. Towards the end of the article, the author states: "Once CP is at the same ERP as VP, you should have some improved reception to vehicles that may be experiencing multi-path distortion. In urban areas with an increased possibility of reflections, you may notice CP has less momentary signal fluctuations as you drive through these reflections. They are typically very brief, lasting a fraction of a second and do not cause the listener to change channels. In these cases CP may provide a signal that is a bit more consistent but not with increased range or distance." So the author concludes that CP actually performs better than VP independent of all REQUIREMENTS (FCC, legal, etc). CP, despite its high cost, actually provides a better signal to all users including those in vehicles. |
The left side picture shows that the orientation of the SL 4el yagi is NOT 335 degs!! The reason is obvious when you look at
the pattern. It's tuned for XLNC @ 104.9Mhz, so its F/G and F/B ratio @ 91.5Mhz is "awful"! The F/G is 4.8db and F/B = 8db
so it has more gain off the back side than the front! So when re-designed for KUSC @ 91.5Mhz, it should give me reliable year
round reception. See the yagi section below for the KUSC results. [Unfortunately the HD) blinks/goes off and
the 3 bar level becomes as low as 1 bar!]
As an aside, the received FM audio produced by the Sony XDR tuner is outstanding after the ckt mods (described below) are made. There are differences in audio quality the three (3) FM stations. Ranking the three (3) stations . . .
KUSC - - - #1 by a small margin using HD1 - no compression*, great clarity and high presence!
KPBS - - - #2 almost equal to #1 using HD2 - lower presence and some compression* due to HD2 bw restrictions.
XLNC - - - #3 lowest of the three; only analog monaural FM. High THD at times and low S/N ratio; can hear noise about -50db down **
* = obviously, some recordings MUST be compressed.
** = Mar 1, 2018, they will cease FM OTA broadcasting and use Internet only.
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Memory Backup Mod As fine as the unit is, there is no memory backup ckts in the Sony XDR tuner, BION. You'd think that it would have been a major design function. But it wasn't. So the user looses all stored parameters (clock, LCD display and all memory presets) are wiped clean when main power (120Vac) is lost. Another serious deficiency that must be fixed. 
There are two (2) main ways to provide memory backup; use a "large" cap such as a 1.5 Farad or a battery. Of the two, I prefer the
battery method since it can potentially last at least 2-3 years or more! So I chose the battery method.I have a LIR 2450 3.6V LiOn button battery with leads, so it's the natural choice. Also using the battery method, you don't have to remove the main PCB, all mods can be made from the top side. The LIR 2450 specs are here. Max current draw is 120ma so there's a lot of headroom. In charging the battery, you need to limit the charge voltage to 4.2V max. Charging from a 4.7V ckt, could present problems for the battery over a long time. After making measurements with the Sony tuner operating, the voltage can NOT exceed 4.2V b/c of the D912 forward voltage drop. But the voltage comes very close, so I studied the ckt awhile and the fix was obvious. Resistor Method The measured D912 forward voltage drop is only 0.6V (4.7 - 4.1 = 0.6V) so that means there is very little current flowing through it. The solution is obvious . . cause more current flow through D912 in order to raise the FV drop to 0.7V or 0.8V by adding a resistor to ground. That will lower the max charging voltage to 4.1V. Perfect! 
Rephrasing the above; currently, the FV drop through D912 is apx 0.6V making the terminal charging voltage of 4.1V. Adding the
resistor (Rbc = 27K) causes the FV drop to increase to 0.74 reducing the terminal charge voltage to 4.0V. You can
increase Rbc value but more current is 'wasted' (in the OFF state, the battery must supply this current) further lowering the
available charging voltage. Note that D914 is not effected b/c the current flow to the Memory is low (90ua) so it's FV drop is still 0.6V. The right side chart shows what happens by using a Spice transient analysis where the 4.7V regulator is turned on for 20sec and then off for 60sec to 100sec total. The analysis shows the battery at 4.0V which is close to the max voltage point, 4.02V before draining some charge forcing the battery to recharge. Using Spice, a resistor of apx 27K ohms will cause enough extra current to flow that raises the D912 FV drop to 0.74 volts. The added resistor (Rbc) does the job and ensures that there will never be excess voltage applied to the Li-ion backup battery. 
What happens is this; as the battery slowly charges, it reaches a point where the battery's charge voltage
equals the available charging voltage. At that point the ckt reaches equilibrium; ie, the battery charging current is
"zero". So now the battery will start to slowly discharge. As that happens, the battery voltage drops to a point where now it
can be charged. The equilibrium point is apx 4.025 Volts of battery charge voltage. The chart on the right shows the a plot of Li-ion battery (B1) voltage plotted against the charging current (TPi2). At 4.02V, the charging current is barely positive (10ua). At 4.03V, the battery charging current is negative meaning that the battery is reached its max terminal voltage and is now discharging. Thus the battery can't charge above 4.02V. Neat solution IMO. 
Without the 27k Rbc resistor, my measurements showed 4.19V @ D912 cathode, tuner ON. With the tuner OFF, this results
in apx 35ua current draw with battery = 4.17V. At that current discharge rate it will provide memory backup for a very
long time! With the Rbc (27K) resistor added, the values change as shown in the above Spice chart. The picture shows the details with the cooling fan removed for clarity. Solder at the points shown; JW20 for "ground" and D912 cathode for the 220 ohm resistor going to the LIR 2450 "+" side. The Rbc resistor is soldered to the junction of D912 cathode as shown. This is a very simple and straightforward method which I believe is the best method. So far, I've tested the backup system for three (3) months with no memory loss. Even the clock time setting is preserved. Zener Diode Method Another way to accomplish the 4.0V "clamp" action on the Li-ion battery is to use a zener diode. With todays technology, almost all voltage variations are available. One such zener from NXP Semiconductors is their 4.1V zener with 2% tolerance. With that tight tolerance, it's possible to use it b/c UPPER limit = 4.11V, the LOWER = 4.02V. Mouser PN: 771-NZX4V3A-133. Perfect for this application. 
There isn't a Spice model for the NXP zener diode so I used a 3.9V, 5% zener's characteristics to get the same UPPPER voltage limit of
"4.1V". Using that zener in the Spice analysis shows the Li-ion battery at 4.08V, just before zener action at 4.1V. Inspection shows
the same action as in the "resistor" version except there is more current flow b/c of the low zener impedance of 100 ohms. During my tests, the Li-ion battery started at 4.17V at the time that the zener was installed. The battery steadily discharged at apx 35ma as the terminal voltage steadily decreased to 4.08V. This zener has a 100 ohm zener impedance which is consistent with the observed current flow. So this concept works nicely but it's a bit "tougher" on the battery. Also not EVERY zener has the desirable characteristics of the NXP zener. However, this shows the versatility that can be employed in arriving at a solution. |
Today was a good example of the need for Forced Analog [FA] reception. As the weather got bad and started to rain, reception
from KUSC @ 91.5Mhz degraded so that the HD) icon was stable for 2 minutes, then would start to flash. When that happens the
Sony XDR tuner switches from digital to analog and there are definitely artifacts while switching back and forth!
Pic by Bob Meister, WA1MIK
To say it's not pleasant listening is an understatement. So time for the FA Mod. Many have written about it and perform the required PWB cut, switch addition and wiring interconnection. If you are not proficient at making cuts to 5mil traces that are 2mils apart, then maybe somebody who is should do it for you.
I've indicated where I made the cut to the PWB b/c it's closest to pin 23 and the easiest spot to make a cut w/o having an
"accident" and cutting some adjacent trace.Solder two wires as shown and bring them up to the top side of the main board by snaking them up one of the many holes on the board. I drilled a 1/4" hole on the back panel as shown in the picture to mount the switch. It is orientated up for "HD" and down for "FA".
If you have a DPDT switch, then some have added a blue LED so that the user can see if it's in the FA (or HD mode, your choice) mode. That's all there is to it!
Treble Audio Rolloff Discussion
Testing has reported that the Sony XDR FM Tuner experiences treble rolloff from the PreAmp Ckt and is anywhere from -1.5 to
-2.5dB @ 15Khz. The chart shows a typical test of a Sony XDR tuner showing -2.3dB loss at 15Khz. Every Sony tuner is somewhat different but measurements show that they all seem to fall into this defined attenuation range. Before actually digging into this problem, I simply removed the four (4) caps no matter what treble loss they contributed. In hindsight, I'm not sure I heard that amount of treble rolloff on my Sony tuner. Tuners with circuit failures certainly would exhibit more treble rolloff than a 'good' one. I employed a K6STI chart that showed the treble rolloff of his Sony XDR tuner of -2.3dB @ 15Khz. After receiving a email from him, I decided to use my own charts. Up to this time, I hadn't really "checked" my Sony tuner for its loss . . . just assumed that mine would be the same or less. I did NOT verify the results myself. There's a lesson here, don't you think?? 5Spice preamp ckt simulation showed -0.56db @ 15Khz and -0.89db @ 20Khz. Since Spice is never wrong *, the remaining rolloff is due to the DSP Tuner module. In other words, the Preamp contributes -0.6dB @ 15Khz and the DSP Tuner + preamp totals to -2.2db rolloff. 
XDRguy's site shows a "Pete Millett" unmodified Sony XDR rolloff measurement. The sweep results of the PreAmp ckt
show -1.5dB @ 15Khz attenuation. So there are some differences evident and we still are
not certain "why" there are differences. He also has reported 0.5dB rolloff variations @ 15Khz with different Sony XDR tuners
that he has tested. XDRguy measurement of the Sony XDR Treble Rolloff [from "RF In" to "L+R output"] shows -2.3dB loss @ 15Khz and claims that it's from the PreAmp ckt, not the DSP Tuner module portion of the Sony XDR. The chart at the beginning of this section is taken from that data. However, I believe that the loss is not all from the Preamp ckt itself. * Certainly the results are only as good as the model. If it's incomplete, so are the results! When the correct transistor model [see the THD Analysis section below] was located and incorporated into the simulations, the results dramtically changed. Now DC bias levels, THD and input drive levels to produces clipping could be accurately determined. Also, I suspected that the characterization of DSP Tuner's output impedance wasn't correct. After some simulations, the correct value was found and has been used in ALL simulations. The simulation results now shadow [see the Frequency Response [FR] & Total Harmonic Distortion [THD] section below] real world performance. What's causing the difference So what is causing the difference?? Doing many Spice simulations, I found that 3300pf causes greater than 2dB loss @ 15Khz. The Sony XDR ckt board is two sided with traces on the bottom side and "wire-jumpers" used to connect crossover points. They can add 3-4pf / jumper if the trace connection is over "ground". But it would take a lot of jumpers to make 3300pf! Not a feasible answer to the problem. Another idea was a "missing" component (a component that is on the board but doesn't appear in the PDF schematic) but none was found. Another explanation was the values of C12 and C22 are larger than stated. One clue to this idea, is that removing C12 and C22, the attenuation drops to fractions of a "db". If that is true, that would throw out two arguments; it could be layout sensitive and there's a "hidden" component. However, the theory was not supported when measurements of the removed caps, C21, C22, C11 and C21 show values close to nominal. One final argument concerns the output impedance of the DSP Tuner Unit. Finding the impedance that delivers half-power into the PreAmp ckt (as the DSP Tuner's "load") will give the required value for the source resistance (Rs) used in Spice simulations. Since the DSP Tuner is DC biased (1.7V) at output pin 27 for LEFT channel, a DC blocking cap (C19 = 1uf) and series resistance (R9 = 470) is required to prevent short-circuit failures in the DSP Tuner IC. Using Spice, the output impedance [Z] shows to be apx 1200 ohms. And this value gives a good fit to measured results, so all schematics have been modified to use this value. All Spice simulations were re-run. This new value has changed some of the component values required for "Treble Rolloff - 2nd Method" and "K6JRF PreAmp Ckt Mod - 3rd Method". In general, all steady state AC frequency measurements have changed along with the recommended cap values. This relatively high impedance plus the four caps [C11, C21, C12, C22] contribute to the rolloff at higher frequencies. 
The latest 5Spice analysis shows different results, more in line with bench measurements. In order to be complete, I've
added the MUTE ckt into the schematic so that the "total" ckt can be analyzed.XDRguy asked about R302 (47) and C302 (470uf) ckt components. The R-C ckt forms a low pass filter which decouples the 8.5V power-line from other ckts using this voltage. The attenuation at 10Khz is apx -100dB! This RC ckt feeds power to the PreAmp LEFT and RIGHT channel so the power consumed in the opposite channel (RIGHT) must be included. The Rrchn resistor represents the DC current drawn by the RIGHT channel preamp, apx 3.25ma. In previous analysis I hadn't included both the LPF and Rrchn. Since both effect the operating DC BIAS for the LEFT channel, these ckt components s/b included. Tnx Dave! The new DC bias values are shown in blue next to the ckt node. Note that there's no change to the "AC" steady state analysis. Results show -2.14dB @ 15Khz with nominal values for all circuit components. So, in summary, the observed PreAmp ckt treble loss has variation from different authors ranging from -1.5dB to -2.5db. Until I actually make some measurements myself, I still believe that the DSP Tuner Module plus the PreAmp ckt cause the observed attenuation at 15Khz but, to date, measurements by others don't confirm the idea. But, bottom line, we now have a realistic circuit simulation model for an unmodified Sony XDR FM Tuner's PreAmp Ckt.
Mod #2 and #3 do not use NFB and BR. The preamp runs w/o feedback and could be overloaded producing high THD audio. Note: Mod #1 is mandatory in preparation of NFB + BR use. 2- Add one cap to neutralize the treble rolloff - this will correct the treble rolloff w/o removing any caps. Signal THD is is OK at low-to-medium signal levels. Not as good as method #1. 3- Replace the four (4) chip caps with new values - this will give a balanced low and high freq rolloff and attenuate ultrasonic noise. Preamp audio THD is low (0.01% @ 10Khz for LOW signal levels) but can/will be overloaded on high signal levels. Chip Cap Removal - 1st Method 
I have a IC and chip-part de-soldering tool, so I chose to remove the four caps. The PCB layout picture shows that the four caps are located inside the BLUE rectangle. With the proper tool it is relatively easy to unsolder each cap. The key is 'take-your-time' . . . and all will be well. After removing the filter caps (C11, C12, C21, C22) the Spice analysis shows a flat output response to 20Khz. However, the ultrasonic noise that was previously attenuated will now be present. You can't hear it but it's still there. The cap removal (C11, C21, C12, C22) method has this drawback. In summary, for the PreAmp Ckt itself, the -2.5dB treble rolloff can be reduced to a low level by removing the four capacitors and the overall THD lowered by adding a NFB resistor. |
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Tuner Treble Rolloff Spice Analysis - 2nd Method 
I decided to check the results using 5Spice using the Service Manual [SM] schematic. When captured into
5Spice the Spice compatible appears as shown on the left. This is the (LEFT)
channel only but both are identical. The load impedance is 47K || 330pf. All reference designators are as labeled in the
SM.The Audio Mute Ckt was modeled and found to NOT effect the frequency response of the Preamp Ckt so it was omitted. A standard "AC" steady state frequency analysis was run with the recommended cap, 0.01uf, (labeled "Cext" in schematic) and the results are shown in the right chart. 
There is apx 0.3dB rise @ 10Khz (BLK line) with the 0.01uf cap that has turned a -2.14 treble droop
into a small, 0.3dB treble boost! For older ears that might be welcome but it starts to rise at apx 5Khz so it will sound
"shrill". If you want a flatter response, as shown on the RED line, you should use
8200pf [0.0082uf] cap. Mouser is a great source for quality parts are decent prices. They have a Vishay Disc Ceramic cap, 8200pf, 50V rating for $0.26 each. Cap size is 3.8mm wide by 3.8mm thick and will fit under the ckt board. Direct link to 82000pf Ceramic Cap here. As to where to attach the caps, consult the PWB picture above showing where to solder the added caps. K6JRF PreAmp Ckt Mod for "Flat" Response - 3rd Method If you want a balanced freq response, the following changes result in balanced LOW and HIGH frequency response from the Sony XDR Audio PreAmp ckt. 
The schematic shows the LEFT PreAmp channel response @ TPv4, in the RED for "before" and
"after" ckt value changes. This chart spans frequencies from 20hz to 20Khz showing the family of curves
generated with different values for C12 and C22. Stock value of 22000pf gives the most attenuation whereas 470pf gives
the least loss. Replacing the two caps with 470pf gives a balanced low and high frequency rolloff = -0.2dB from 20hz to 20Khz. This is the recommended value. The advantage of this method is the ultrasonic noise spectrum coming from the DSP Tuner module is attenuated. Note you can't hear it (unless you have dog ears!) but that's what the filter network (R101 + C12 and R6 + C22) does. Completely removing C12 and C22 defeats that purpose. Don't forget the RIGHT channel PreAmp. Make the same changes for C11 and C21. That's all that is needed! "T" Pad Attenuator 
For my setup, the stock Sony XDR tuner's output is a bit too hot for both of my satellite and OTA rcvr's recovered audio, so I added
a 3.25db attenuator to make it more compatible with the overall system sound level. Used two (2) RCA unbalanced
attenuator "carcass" to mount the three (3) resistors as shown.With the use of NFB modifications to the internal SonyXDR preamp, I no longer need to use the 3.25dB attenuator. The preamp output level is compatible with my satellite and OTA equipment output levels. |
The 5Spice analysis shows that I was partially correct! At low signal levels (0.25Vpk), the preamp's THD performance is quite good but
due to the limited operating headroom, THD rises with higher signal levels. The results are shown in the chart.
For me, I want the absolute lowest THD possible with the SonyXDR preamp. To that end, making the NFB resistor,
Rnfb = 20K gives the lowest THD even for input signals (from the TU1 DSP unit) greater than 1.0Vpk. In fact the
preamp won't clip with the DSP Tuner's output level = 1.5Vpk! The chart shows the response at various signal levels.
The previous chart has been updated to show the THD values for the SonyXDR internal preamp and the K6JRF external preamp using the LT1632
opamp. The THD in general is three/four-orders-of-magnitude lower than the internal SonyXDR preamp. It clearly shows the difference
between a multi-transistor IC amplifier vs one gain stage amplifier (Q102) + emitter follower output (Q103). Impressive indeed! 
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This section has ten (10) separate design sub-sections plus a "BALUN" section ; - Regal Balun Test Data - click here - 1st - 4el yagi for KUSC @ 91.5Mhz - click here - 2nd - [6/22/20] 4el yagi for WUCF @ 89.9Mhz - click here - 3nd - [6/22/20] 4el yagi for KVCR @ 79Mhz - click here - 4th - [6/22/20] 4el yagi for CFMI @ 101.1Mhz - click here - 5th - [6/22/20] 4el yagi for KBCE @ 102.3Mhz - click here - 6th - 5el short boom yagi for KUSC @ 91.5Mhz - click here - 7th - 6el long boom yagi for KUSC @ 91.5Mhz - click here - 8th - 6el long boom yagi for FM Low-Band @ 89.1Mhz - click here - 9th - 6el long boom yagi for FM - KUSC @ 91.5Mhz - click here - 10th - 6el long boom yagi for FM Mid-Band @ 98.0Mhz - click here - 11th - [8/7/20] 7el long boom yagi for KUSC @ 91.5Mhz - click here - 12th - [5/16/19] Stellar Labs Folded Dipole - click here - 13th - Radio Shack UHF yagi for OTA HDTV - click here Note that all of the yagis detailed in the following sections are "slot" antennas and have been optimized for Forward Gain (F/G) and Feed Impedance at the stated design frequency. The 300 ohm feed impedance has been maintained by using a variation of the OWA methodology; ie move the 1st Dir close to the driven element to maintain a high feed (300 ohm) impedance. The yagis Front-to-Back (F/B) ratio and operating bandwidth has not be optimized for full FM band operation. |
"Regal" T-75 Balun Test
I recommend the use of these baluns if you can find them. I've used them with some of my designs and they seem to work nicely, are
well constructed for outdoor use and have decent SWR characteristics across the FM band (88 to 108Mhz). The picture shows a simple test setup using my RigExpert AA-170 set to 75 ohms. The SWR sweep on the AA-170 screen shows 1.2:1 SWR across the band. The resistor combo totals to 296 ohms. |
The left chart shows the SWR sweep across the FM band. It's very stable showing apx 1.2:1 SWR from the bottom to top of the band.
The right chart shows the Impedance sweep; apx 61 ohms with almost 0 ohms reactance. Can't ask much more than that. |
Using my RigExpert AA-170, I swept the full range of the instrument, 1Mhz to 170Mhz to quantize the performance of the Regal T75 Balun.
As expected, it has amazing bandwidth with the SWR dropping as the frequency increased. At the top end, 155Mhz, the SWR is 1.10:1
. . and dropping!These are avialable are various sites . . here |
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You do not need these for use with the Stellar Lab 4el Yagi since the balun is built in. |
KUSC 4el Yagi
Using Antenna Optimizer (AO), the as-delivered stock yagi was optimized for KUSC @ 91.5Mhz. The difference between
stock SL yagi @ 91.5Mhz vs optimized yagi is shown below;Desc--- Stock----KUSC-Opt F/G --- 7.5db ---- 9.3db F/B --- 8.3db ---- 9.5db SWR --- 2.43 ----- 1.03 The yagi was put up about 3 months ago and it did not have enough gain to reliably get KUSC during the "drop-out/fade" events. The FM station's distance is 109 miles from my house so it's understandable. It was replaced by the 5el, then the 6el yagi (described in the subsequent sections). 
The summary report files can be downloaded and run in AO should you have the program.The "stock" AO design file modeled @ 98Mhz is here The "optimized" [KUSC @ 91.5Mhz] AO design file is here The sketch shows the layout of the elements as well as the length of each half-element. Be careful to be accurate with the dimensions shown to have the finished product work as indicated! Download both files and rename the 'stock' file to "FMSL-STK.ANT" and "FMSL4ELO.ANT" to run with your version of AO. |
Joe, W0WD wants to receive WUCF FM @ 89.9Mhz in Orlando, FL apx 48miles from Cape Canaveral, FL. Using AO, all elements were
optimized and the results are: F/G --- 7.5db ---- 9.6db F/B --- 8.3db ---- 6.8db SWR --- 2.43 ---- 1.05 |
The picture and sketch show how to buld the antenna. Note that you will need 2 60" sections of 3/8" dia alum tubing to use
for Dir1 and Dir2. The elements sent with the stock SL 4el yagi are too short to be used. The FM station broadcasts 360W horizontally and 5.6KW vertically . . so you may have to rotate the yagi vertically depending on how far away you are from the transmitter. More station info: here. |
Bruce, KI6BPL wants to receive KVCR DT Ch5 @ 79 Mhz in Ramona, CA apx 68 miles from San Bernardino, CA. Using AO, all
elements were optimized and the results are: F/G --- 7.5db ---- 9.7dB F/B --- 8.3db ---- 8.2dB SWR --- 2.43 ---- 1.08 |
The picture and sketch show how to build the antenna. Note that you will need 3 - 72" sections of 3/8" dia alum tubing to
use for the Refl, Dir1 and Dir2. The elements sent with the stock SL 4el yagi are too short to be used. The TV station broadcasts both horizontal and vertical signals at 25.8 kW so you should be able to mount the antenna in either mode to receive the station. More station info: here. |
Jeroen, K7JBT wants to receive CFMI FM @ 101.1Mhz in Seattle, WA apx 115 miles from Vancouver, BC. Using AO, all
elements were optimized and the results are: F/G --- 7.5db ---- 9.34dB F/B --- 8.3db ---- 12.32dB SWR --- 2.43 ---- 1.10 |
The picture and sketch show how to build the antenna. Note that you will need 2 - 60" (or 4 pieces - 30" length) sections
of 3/8" dia alum tubing to use for the Dir1 and Dir2. The REFL can be cut-down from the existing
reflector element. The director elements sent with the stock SL 4el yagi are too short to be used. The FM station broadcasts with 100KW ERP from an antenna @ 2135ft above sea level. Since the station is 115 miles away, you should mount the antenna as high as possible to give the maximum radio horizon possible. More station info: here |
Chris wants to receive KBCE FM @ 102.3Mhz in Marksville, LA apx 45 miles from Boyce, LA. Using AO, all
elements were optimized and the results are: F/G --- 7.5db ---- 9.10dB F/B --- 8.3db ---- 10.28dB SWR --- 2.43 ---- 1.03 |
The picture and sketch show how to build the antenna. Note that you will need 2 - 60" (or 4 pieces - 30" length) sections
of 3/8" dia alum tubing to use for the Dir1 and Dir2. The REFL can be cut-down from the existing
reflector element. The director elements sent with the stock SL 4el yagi are too short to be used. The FM station broadcasts with 21KW ERP from an antenna @ 289ft above sea level. Since the station is 45 miles away, you should mount the antenna as high as possible to give the maximum radio horizon possible. More station info: here |
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KBCE 4el Yagi Results The antenna was constructed from a Stellar Labs (SL) 4el yagi with the Dir1 and Dir2 replaced with longer elements per AO design requirements shown above. It was put up at 30+ft on a push-mast, feed with RG6 coax and three (3) coax chokes as shown in the pictures. 
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KUSC 5el Yagi For KUSC @ 91.5Mhz, the yagi should have at least 9.5db F/G (109 miles) so that dictates a 5 or 6el beam. Preliminary design show that 9.4db is attainable on the same boom (66") with 5els. This AO design shows good "specs" for the short boom. Desc--- Stock----KUSC-Opt F/G --- 7.4db ---- 9.4db F/B ---13.8db ---- 9.4db SWR --- 1.6 ------ 1.07 Download the design file here and rename it to "FLSL5ELO.ANT" to run in AO. 
The antenna was constructed today and the plots show good gain (9.4dB) w/ 9db F/B ratio. The right side chart shows the
dimension half-length pluse element spacing needed to obtain the F/G on a short boom. And that means, it doesn't have a lot
of operating bandwidth b/c it was designed for receiving KUSC @ 91.5Mhz. It is NOT a broad-band antenna. The 'guts' consist of a stock Stellar Labs 4el yagi with a 66" boom length and an extra element. The construction of this yagi is different; the boom is 0.709" [18mm] square, the elements are not tapered, are 0.392" in dia. The folded dipole driven element extends above (1.8") and below (1.5") the boom center. Never have seen that consturction before but it looks fine. Attached to the feed element is a waterproof 4:1 balun [300 to 75 ohm] transformer. There is no need for an external balun. Overall it's very strong but light, apx 1.5 lbs, perfect for So Cal. KUSC 5el Yagi Results To say it worked as designed, is an understatement. Today's weather is cold (60F) and it has been lightly raining, so there's absolutely no inversion. After boresighting the yagi to KUSC (322 degs), the Sony XDR showed three bars plus HD) signal . . solid! But as the weather worsened, the HD) icon start to 'blink' meaning that the HD portion of the overall signal was too weak to use the Sony internal HD decoder. It would come and go indicating that more F/G is needed. This yagi would be good for the middle area, apx 50 miles max from KUSC. The pics below compare the XLNC-4el (1st) with the KUSC-5el (2nd) and KUSC-6el (3rd) and lastly, the KUSC-7el.
The 4el and 5el antennas have similar F/G, the difference being apx less than 0.5dB. So after looking at the performance of both antennas, either the 4el or 5el are suitable for use up to 50- 60miles depending on the signal strength of the FM station. KUSC employs 39KW while some use as little as 5KW. |
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KUSC 6el Long Boom Yagi During some of the recent weather conditions (heavy rain and cold), the HD) is 'blinking (weak) and the analog signal dropped to "2" bars! Albeit a short time, it did drop. Since I have two (2) Stellar Labs 4el yagis, there is enough material to make a long boom 6el yagi. This design will be optimized for F/G as was the previous 5el yagi but on a long boom for significantly more F/G. Using AO, the design parameters are below. Being 109 miles from the KUSC xmitter site, I could use as much F/G as I can get. To that end, here's my latest design; 6 els on a 8' - 9" boom. Desc--- Stock---- KUSC-5el---- KUSC-6el F/G --- 7.4db ---- 9.4db ------- 11.0db F/B ---13.8db --- 9.4db ------- 11.3 SWR --- 1.6 ----- 1.03 ---------- 1.06 As before, download the design file here and rename it to "FLSL6ELO.ANT" to run in AO. 
The construction of the Stellar Labs yagi is a home-brewers delight; it is light but extremely strong. Every element is a
solid, one piece tube unlike other yagis where the element is rolled aluminum sheet so the tube has a "slit". It's very easy
to extend the boom using an "insert". The "seam" will be sealed so no moisture can penetrate.Each yagi's boom is 66" long. Apx 41" will be cut from one yagi to make the required length, 105" + 2" inches for boom end. I plan on joining the two booms with a some sort of a square dowel insert. It needs to be apx 0.640" L x 0.640" W to extend the boom length to 8'-9" (105" + 2"). You will also need 3/8" aluminum tubing to make new elements since the SL stock elements are too short. The "picture" gives you an idea of what it will look like when complete. |
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The left chart shows the AO design parameters in the azimuth view. Great F/G with little F/B ratio. F/B ratio is not important
where I am; all other FM stations are beamed from Mount Soledad and that puts their signal into the "side" of the antenna where
there's 30db or more side null. |
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KUSC 6el Yagi Photos
The yagi was built and here's some pics showing the construction. Most HAMs save aluminum as if it was gold. So I had a
good selection of aluminum tubing for this project. The main need was for an "square-insert" in order to join the
the two boom halves. Home Depot has a 5/8" x 5/8" x 36" square dowel
here for $2.41.
I picked through the stock and found one that measured 0.635" L x 0.635" W x 36" L. I used the complete piece and the boom was razor straight. [4/14/19] However, about 2 years later, the director end started to show some sag. So I used an aluminum 1/2" angle to remove the sag. Home Depot has different versions; this one is 1/2" x 36" long for $1.98, shown here This morning I took down the 5el short boom yagi and installed the 6el long boom yagi. When I connected the coax to the Sony XDR, there were 3-bars and FLASHING HD) symbol . . . same as before! With the no-inversion weather we are experiencing, this is normal for a lower gain antenna. But this yagi is supposed to have enough gain and it's the main reason why it was designed and built.
My sadness turned to happiness after boresighting the yagi. The HD) was SOLID! 10 hrs later and it's still solid.One main reason for the difference in beamwidth [BW] of the stock yagi, 67 degs vs 46 degs for the 6el yagi. The KUSC beam heading is 332 degs per their location map above and the best HD) reception was found at 332 degs! To say I'm pleased is an understatement. The yagi was supposed to give the extra gain that was needed but sometimes "Murphy's Law" sets in! I can state that if you want a LONG RANGE yagi, the 6el design is for you. 109 miles with 3bars and HD) solid! 
Bryne, N7BB wrote to me about constructing the 6el yagi to get KMHD near Portand, OR. He bought two (2)
stock SL yagis and made the 6el. It's mounted at 22ft above ground. The FM station is 111 miles away, runs 7.9KW from a
1400 ft elevation antenna. Here's two pictures of the completed antenna. Great job! Download the design file for KMHD here and rename it to "N7BB6ELO.ANT" to run in AO. Total boom length = 8ft 11" Another version - SL 6el Short-Boom for FM Mid Band operation: F/G = 9.8db, F/B = 24.2dB on 6ft - 9inch boom length. This yagi is designed for F/B ratio for mid-band (98Mhz) operation. Download the design file here and rename it to "N7BB6ELZ.ANT" to run in AO. |
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Ernie, W7DUH wrote to me about constructing the 6el yagi to get KIPO @ 89.3Mhz in Honolulu,HI, a distance of
2564 miles! ERP is 38.5KW. He bought two (2) stock SL yagis and made the 6el using a single piece 3/4" boom. It's
mounted on a rotator at 25ft above ground. Unfortunately, he built the 6el KUSC yagi @ 91.5Mhz not the one designed for
89.3Mhz. Here's two pictures of the completed antenna.He wrote: "Thought I'd give you some followup on your 6 element antenna design for KUSC. I am very impressed, it went from the antenna craft FM6 to the new antenna S9 to S9+39db on an SDRPlay! I'm also using a Sony XDR-S3HD. Did all the mods you listed and went together without a hitch. Good tip you mentioned regarding using a clothe-tape measure attached to the boom. Helped keep things very accurate. Overall it made for a sturdy antenna. Thanks for sharing your expertise. Glad I could help you but sorry that the 89.3Mhz design was "lost" so it wasn't built! |
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with your comments |
