EQUIPMENT: Re: MFJ-1026 Formal Review

[Dan Henderson <dandan2@xxxxxxxxx>]

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Mark:

You did a great job on this review.  Congratulations!!

Dan Henderson

At 05:17 PM 8/21/97 -0500, you wrote:
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>	A recently-released product has been getting quite a bit of 
>attention in radio-related E-mails, Internet bulletin boards, Web 
>pages, magazines, and personal correspondence.  The device is the 
>MFJ-1026, described as a "Deluxe Noise Cancelling Signal Enhancer" 
>by its manufacturer MFJ Enterprises, Inc. (see company address 
>information at the end of the article).  DXers will recognize
>the MFJ-1026 as a "phasing unit".  The list price is US $ 139.95; 
>outlets such as R & L Electronics of Ohio are selling it at prices 
>as low as $ 115.  It offers the ability to null interference, 
>whether from electrical noise sources or actual transmitters.  
>This is accomplished by creating a 180 degree phase shift between 
>two antennas that are presenting equal-amplitude "pest" signals 
>that cover desired DX.  There is a similar model, MFJ-1025, which
>does not have the built-in whip / preamplifier option.  The '1025
>sells for about $ 20 less.  
>
>	A little bit of phasing unit history is in order here.
>Phasing units have been around for a long time, but most of these 
>have been homebrew models built by a few dedicated DXers.  In the 
>1960's, I built some hit-or-miss L-C-R tuners / combiners to use 
>at my Menotomy Rocks Park antenna farm and by the early '70s I had 
>one of Gordon Nelson's boxes up and running ahead of my R-390A.
>Master Trans-Atlantic DXer Bill Bailey was also using a Nelson-
>built box at the time.  160-m hams such as Victor Misek were also
>experimenting with phasing circuits for steerable nulls.  Producing 
>a null in the opposite direction of a peak turned out to be a big 
>advantage over loops, especially in hearing European stations here 
>in the Boston area with the New York City (and other) "pests" off 
>the back of the beam.  In the early '80s, moving onward from the 
>L-C-R units, Gerry Thomas took a bold step into broadband phasing 
>with his delay-line-based Phase One.  His research led to my DL-1, 
>DL-2, and DCP-2 models.  In the U.K., Graham Maynard became well 
>known for the units he built.  As the 1990's opened, there was 
>still very little in the way of commercially-available hardware 
>despite the fact that many of the serious international DXers 
>were using the homebrew units both at home and on Beverage 
>DXpeditions to hear exotic stations that could not have been 
>logged any other way.  A device called the S.E.M. QRM Eliminator 
>had minimal promotion and little market penetration.  It used a 
>tapped delay-line in a circuit similar to Gerry Thomas's Phase One.  
>By 1993 (I think), the JPS ANC-4 model came onto the scene.  In a 
>trend that has followed all of the commercial units, advertising
>pointed out that elimination of local electrical noise was the 
>primary use.  One channel of the ANC-4, therefore, was a very-high-
>gain stage driven by a short "noise gathering" whip.  This arrangement
>didn't seem particularly well suited to the DXer's more common 
>objective of using two similar fairly-low-noise good-gain outdoor 
>antennas to phase in order to remove co-channel (or adjacent channel) 
>interfering STATIONS rather than NOISE.  Noise was often easily 
>discarded by using noise-reducing balun transformers with "quiet 
>grounds".  This idea - promoted by Dallas Lankford, Nick Hall-Patch, 
>and others - can get electrical noise out of the equation even ahead 
>of the phaser, leaving it with the considerably more interesting job 
>of removing dominant stations.  A few DXers got ANC-4's, but the unit 
>was prone to overload on its so-called "noise" channel and nulls 
>seemed to be hit-or-miss because of sometimes-inadequate level-
>balancing and phase-adjusting range.  Demand for homebrew units 
>continued unabated as Al Merriman and I can testify.
>
>	In 1997, the MFJ-1026 has made a big "splash" because it 
>is likely the first widely-available commercially-produced antenna 
>phasing unit that can be made to work for medium-wave DXers.  I say 
>"can be made to work" because some modifications must be made to the 
>stock version unit available at the time of this writing.  
>
>	The "long and the short of it" is that the brochure advertising
>the unit claims performance "down to VLF", customarily taken to be 
>10 kHz or so, when several E-mail communications with MFJ personnel 
>indicated that the unit comes equipped with high-pass input filtering 
>designed to attenuate frequencies below the 160-m ham band.  Indeed 
>the lower one goes below 1.8 MHz with the stock unit, the worse the 
>insertion loss gets.  Measurements taken here indicate losses of 8 dB 
>at 1600 kHz, 16 dB at 1000 kHz, and 27 dB at 530 kHz.  By the time 
>you get down to the 153 - 279 kHz European longwave broadcast band, 
>the thing has so much loss (over 35 dB) that it might as well be a 
>dummy load.  
>
>	Aside from the insertion loss, inadequate phase shifting
>range on lower frequencies was encountered in some situations.
>Oscilloscope testing showed approximate phase shift ranges as
>follow: 200 kHz = 65 deg., 400 kHz = 94 deg., 600 kHz = 113 deg.,
>800 kHz = 125 deg., 1100 kHz = 150 deg., 1500 kHz = 156 deg., and
>2000 kHz = 169 deg.  With the SW3 Phase Normal / Invert switch of 
>the MFJ-1026, dependable nulls could be produced if the R16 phase 
>range control gave 180 degrees of adjustment.  It turns out that 
>if you can easily swap the two inputs, a phase shift adjustment 
>range of as little as 90 degrees will produce nulls.  
>
>	Fortunately the modifications that have to be made to
>give the MFJ-1026 competent performance from 300 to 1800 kHz are 
>quite simple.  The MFJ-1026 schematic is shown on page 12 of the 
>instruction manual supplied with the unit.  The circuit board is
>well marked with the component designators.
>	
>	Modification 1 will increase sensitivity below 2 MHz:
>
>* Remove L3, L4, R26 (main input channel); L5, L6, R27 (auxiliary 
>input channel)
>* Change C8 and C16 from 680 pF to .01 uF 
>
>	Modification 2 (swap switch) will ensure adequate phase 
>shifting range above 300 kHz (these instructions may differ from 
>prior E-mail postings):
>
>* A double-pole / double-throw (DPDT) "swap switch" (Radio Shack
>275-614, or equivalent) is added in available space near the upper 
>right hand corner of front panel.
>* Separate the middle pin (wiper arm) of each antenna gain pot
>from the circuit board: these are R20 (Auxiliary Antenna Gain)
>and R9 (Main Antenna Gain).  
>* Install a wire from the R20 middle pin to swap switch section #1
>arm.
>* Install a wire from the R9 middle pin to swap switch section #2
>arm.
>* Install a short wire from swap switch section #1 "normal" contact
>to swap switch section #2 "swapped" contact.
>* Install a short wire from swap switch section #2 "normal" contact
>to swap switch section #1 "swapped" contact.
>* Locate the Q5 and Q8 transistors.  Each of these transistors has 
>one side having two leads (these are the drain and source leads).  
>The other side of each transistor has a single lead (the gate lead).
>Solder pads are located on plated-through holes immediately adjacent 
>to the Q5 and Q8 gate leads.  These pads will be wired to the swap 
>switch in the next two steps.
>* Install a short wire from swap switch section #1 "normal" contact
>to the plated-through hole solder pad that connects through the
>circuit trace to the Q8 gate lead.  Alternately, instead of going 
>to that point, you could wire to the circuit board pad which had 
>previously been wired to the now-cut R20 arm pin.
>* Install a short wire from swap switch section #2 "normal" contact
>to the plated-through hole solder pad that connects through the
>circuit trace to the Q5 gate lead.  Alternately, instead of going 
>to that point, you could wire to the circuit board pad which had 
>previously been wired to the now-cut R9 arm pin.
>  
>	With the DPDT switch set to "normal", the switch completes the 
>previously-wired paths: R20 arm to Q8 gate; R9 arm to Q5 gate.  In its 
>"swapped" position, the R20 arm gets connected to the Q5 gate and the
>R9 arm gets connected to the Q8 gate.  
>
>	A couple of minutes spent studying the schematic and board 
>layout should make it obvious how to install these modifications.  
>An additional modification suggested by Al Merriman is to remove  
>the existing two Antenna Gain knobs and the one Phase Control 
>knob and substitute larger knobs, such as Radio Shack part number
>274-416 (diameter = 1" = 2.54 cm).
>
>	So now you've got the modifications installed and it's time
>to put the unit into use.  If you're using two relatively short
>antennas, these should be run out at a right angle to each other
>to prevent collateral nulling of both desired DX stations and
>"pests".  With two wires at a right angle, the best null / peak 
>axis will be along the bisector (the line that divides the angle 
>in half).  Longer antennas (over 150 m / 500 ft.) can be run closer 
>to parallel and still produce good nulls, especially if there is
>some separation (1/8 wavelength or so) between them or if they
>are of somewhat different lengths or if one is terminated and 
>the other is not.  E-mail correspondence with Tom Rauch (W8JI) 
>brought up another interesting possibility.  If two similar small
>active broadband antennas (e.g. MFJ-1024 whips) are separated by 
>1/16 to 1/4 wavelength, good nulling performance can be expected.  
>The line drawn between the two antennas would describe the best 
>peak / null axis of cardioid patterns to be produced.  One-sixteenth 
>wavelength at 500 kHz (or 1/4 wavelength at 2000 kHz) turns out to 
>be 600/16 = 37.5 m = 123 ft.  Using two broadband active whips 
>(with coaxial feedlines of about 19 m each) wouldn't be a difficult 
>experiment to try.  The Robbins Road DXpedition site in Plymouth, 
>MA would be ideal because the road has no power lines along it 
>and its orientation is on an approximate 70 deg. / 250 deg. bearing 
>axis (degrees clockwise from due north).  One whip 19 m along the 
>road ahead of the car could be phased against the other one 19 m 
>behind it.  This should be quite effective for nulling out 
>NY/NJ/PA/OH domestics (at about 250 deg.) to clean up Europeans 
>coming in on bearings of about 70 deg.  Tom Rauch also mentioned 
>using broadband loops instead of broadband whips, but I haven't 
>had much experience with untuned loops that have both high 
>sensitivity (low noise floor) and good strong-signal handling 
>characteristics (minimal intermodulation products).  Two broadband 
>loops could be spaced 1/16 to 1/4 wavelength and oriented the same
>way, or they could be located closer to each other and pointed at 
>a right angle to each other as in the old "goniometers".  Also, a 
>co-located active whip / broadband loop could be used for loop-
>sense cardioid array (LSCA) operation (a la Ron Schatz). 
>
>	The MFJ-1026 can be operated with a ham transceiver as it
>has built-in transmit / receive (T/R) switching on its main antenna
>input.  I suspect that the reviews of the unit in amateur magazines
>such as QST and CQ will cover this aspect of operation.
>
>	The auxiliary channel input can be from the built-in whip
>antenna (that goes through an internal preamplifier) if the front 
>panel Pre-Amp switch is set to ON.  Otherwise, whatever antenna 
>you've connected to the rear panel auxiliary antenna jack will
>be fed to the Auxiliary Antenna Gain pot.  I have phased the whip 
>against Main antenna inputs ranging from tuned loops to untuned 
>random wires.  The internal whip on a modified MFJ-1026 has 
>reasonably good sensitivity, especially above 800 kHz.  Even at 
>530 kHz, the internal whip was able to discern Turks & Caicos at 
>threshold level (about S2 to S3) on groundwave from a receiving site 
>in Harwich, MA on Cape Cod.  This is on par with the sensitivity of 
>the Quantum and Kiwa loops.  For comparison, an outdoor sloper to 
>the top of a 20 m pitch pine tree at the Harwich site gives a Drake 
>R8A S-meter reading of about S6 on Turks & Caicos - 530 groundwave.
>
>	There are four potentiometers (pots) on the front panel of 
>the MFJ-1026 and there are four switches (five when you consider 
>the user-added Swap Switch).  The potentiometers are T/R delay (R3),
>Auxiliary Antenna Gain (R20), Phase (R16), and Main Antenna Gain
>(R19).   Switches (besides the Swap Switch) are Power On / Off (SW1),
>Pre-Amp On / Off (SW4), Freq. High / Low (SW2), and Phase Normal /
>Invert (SW3).
>
>	The T/R Delay control is only of concern if you will be
>transmitting as well as receiving.  The Power On / Off switch sends
>the Main antenna straight through to the receiver if set to OFF.
>The Freq. High / Low switch is usually set LOW for frequencies
>from 300 kHz to 7 MHz, either LOW or HIGH for 7 to 12 MHz, and 
>HIGH for 12 to 30 MHz.
>
>	The instructions in the MFJ-1026 manual are clear and will 
>get the first-time user into the nulling "game" without much trouble.
>This is an easy-to-use unit compared to the L-C-R and delay-line
>phasers which preceeded it.  I would summarize operation as follows:  
>
>* Set the (SW2) Frequency switch to LOW for medium-wave use.  Set
>the Auxiliary Gain (R20) fully clockwise and the Main Gain (R9) 
>fully counterclockwise (anticlockwise) and take note of the strength 
>of the station to be nulled.  
>* Then set the Auxiliary Gain fully counterclockwise and the Main 
>Gain fully clockwise and take note of the strength of the station 
>to be nulled.  
>* If the reading was lower with Main Gain fully clockwise, temporarily 
>set it counterclockwise and set Auxiliary Gain to get the reading that 
>you had with maximum Main Gain.  Then put Main Gain back to fully
>clockwise.
>* On the other hand, if the S-meter reading had been lower with
>Auxiliary Gain fully clockwise (rather than with Main Gain that way),
>set Auxiliary Gain fully counterclockwise and set the Main Gain
>to get the reading you had with maximum Auxiliary Gain.  Then put
>the Auxiliary Gain back to fully clockwise.
>* Rotate the Phase control (R16) to look for a null.  If the null 
>isn't obvious, or if it tends to be at either end of the Phase 
>control's range, try the opposite position of the Phase Normal / 
>Invert switch (SW3) and rotate the Phase control again to search 
>for a null.
>* If a satisfactory null still hasn't been achieved, try the opposite 
>position of the added Swap Switch and repeat the previous step.
>* Once the correct combination of Phase control, Normal / Invert,
>and Swap Switch position has been arrived-at, make small interactive
>adjustments of the non-fully-clockwise Gain control and the Phase
>control until the deepest possible null has been acquired. 
>Subdominant signals, if present, should be evident.
>
>	If the active circuits in the MFJ-1026 get overloaded by 
>strong local stations, use moderate-Q tuned inputs such as loops or 
>L-C tuned whips/wires - or, in cases of untuned wire inputs, just 
>use less gain (as selected by the two 250-ohm Gain pots).  
>
>	"Real life DXing" MFJ-1026 field tests were done on Saturday, 
>26 JUL (local) from the Robbins Road - Holmes Field beach-DXpedition 
>site located off Route 3A in Plymouth, MA (approx. GC= 70.68 W / 
>41.98 N).  I used the Drake R8A receiver.  Both the R8A and the 
>MFJ-1026 were powered from the car battery.  Two 90 ft. / 27 m 
>wires lying on the ground were used.  This (admittedly less-than-
>ideal) set-up had been used with delay-line and other phasing unit
>designs previously, so I had a feel for what to expect.  The "main" 
>antenna for the MFJ-1026 ran on a slight downslope along the side 
>of Robbins Road straight towards the sea at a bearing of about 
>70 degrees.  The "auxiliary" wire ran out at a right angle into an 
>open field of grass at an approximate 160 degree bearing.  I was 
>on site at about 7 p.m. local / 2300 UTC.  This is about an hour 
>before sunset.  I felt that one of the big challenges would be to 
>null WPLM-1390, located less than 2 miles / 3 km from the site.  
>Luckily, its very large signal did less overloading damage than 
>WRKO-680 does back at home near the Shawsheen River marsh.  
>Nulling WPLM a good 50 dB was easy !  It wasn't too long before 
>evidence of co-channel skip stations from ME, NY, and VT started 
>bubbling in behind the nulled WPLM audio.  Better yet was rather 
>good audio from Netherlands on 1395 heard somewhat later !  The 
>stations that the MFJ-1026 had the most trouble nulling were those 
>with high-angle skip, especially if some groundwave was blended in.  
>The stations on the top end of the dial, such as WNRB-1510, were 
>particularly troublesome in this regard.  Null control settings 
>required constant adjustment, especially in the period from an 
>hour before sunset to an hour after.  The best sustained null 
>depth I could manage on stations such as WNRB, WDCD, and WQEW was 
>about 15 dB (although momentarily-deeper nulls popped in and out).  
>Shortwave DXers will probably experience similarly "jumpy" results 
>above 2 MHz.  Pure "groundwavers" like WPLM and longer-skip / lower-
>frequency stations such as WLW-700 nulled more deeply and for greater 
>time intervals between required control re-adjustments.  These 
>results are consistent with those found for any previous-used 
>phasing scheme, whether delay-line, tuned L-C, or other.  
>
>	As the evening progressed, the MFJ-1026 / phased wires set-up 
>proved its value as numerous Trans-Atlantic stations were logged.  
>Some of these came in fine on the 70-degree "Euro-wire" without the 
>need for phasing, but, in a number of instances, phasing the two 
>wires made the difference between a slop-plagued DX signal and 
>crystal clarity.  The two Croatia stations (1125 and 1134) come 
>to mind.  WBBR-1130 New York has a VERY strong signal at night here 
>in eastern Massachusetts.  Indeed, outside the immediate groundwave 
>zones of locals, it's one of the five strongest stations night after 
>night.  When I was tuned to 1134, Croatia was running a good S9+20, 
>but it was still trashed by WBBR slop at times - even on the "Euro-wire".  
>With a few quick twists of the controls on the MFJ-1026, WBBR was 
>reduced by better than 20 dB and Croatia-1134 roared in with absolutely 
>beautiful audio.  On peaks, it was stronger than what was left of WBBR.  
>Not only did the phasing accomplish a nice clean-up on 1134, but also 
>the much-weaker Croatian on 1125 was brought into the clear with just 
>a bit of co-channel flak from Spain.  Prior to phasing, it didn't 
>have a ghost of a chance against the barrage of WBBR slop.  
>
>	Earlier on 26 JUL, I had done a few daytime DX tests of the 
>MFJ-1026 from Harwich, MA on Cape Cod.  The first battery of tests 
>involved feeding a Quantum Loop into the MFJ-1026 "main" input and 
>using the 1026's built-in broadband active whip as the "auxiliary".  
>With the loop at normal (i.e. high) Q, audio null depths only reached 
>about 20 dB (versus better than 40 dB for carrier).  This is 
>consistent with previous nulling scenarios where a high-Q tuned 
>source is phased against a broadband one.  You get what sounds like 
>a double-sideband suppressed carrier signal.  If the desired DX is 
>more than 20 dB below the dominant, you probably won't hear it even 
>during stable midday conditions.  Q-spoiling the Quantum Loop (15K 
>resistor shunting the L-C tank) increases nullability of "pests" 
>maybe to 30 dB, but the loop's usable sensitivity is compromised.  
>At night, this is probably a non-issue (except in aurora), but 
>during the day you need every bit of signal you can squeeze out 
>of the small loop.  
>
>	A second battery of tests at Harwich used two wires at a 
>right angle (similar to the set-up employed at Plymouth).  Daytime 
>nulls were smooth ("like butter" some would say).  WGAN-560 was 
>easily dumped to reveal WHYN, near-equal WPRO and CFCY on 630 could 
>each be brought up alone, much the same on 740 with WJIB and WGSM, 
>WJTO on 730 was nulled a good 30 dB to pull out WACE over CKAC, 
>strong WCLZ-900 was phased under the co-channel CKDH/WMVU mix, 
>WZNN-930 easily surrendered to CFBC, and so forth.  Nulling with 
>two wires was decidedly better than any loop-versus-whip or loop-
>versus-wire scheme.
>
>	Once the MFJ-1026 is modified, it makes a very competent phasing
>unit that will undoubtedly bring the technology into the hands of many 
>DXers who have not previously experienced its value in bringing new 
>stations out of "the mud".
>
> 
>Miscellaneous information:
>	Power requirements: 12 volts DC at 150 mA
>	Size: about 21 cm wide X 6.5 cm high X 15 cm deep
>
>
>Appendix: MFJ Ordering Information 
>Webpage: http://www.mfjenterprises.com/mfj/order.html
>TECHNICAL INFORMATION: (601) 323-0549 or "jshurden@xxxxxxxxxxxxxxxxxx"
>
>MAIL ORDERS: MFJ Enterprises, Inc.
>	     P.O.Box 494
>	     Mississippi State, MS 39762, USA
>
>TOLL-FREE (DOMESTIC): 1-800-647-1800 
>
>SHIPPING INFORMATION: MFJ Enterprises, Inc.
>		      300 Industrial Park Rd.
>		      Starkville, MS 39759 USA
>
>CREDIT CARDS: Visa, MasterCard, American Express, or Discover
>
>FOREIGN ORDERS: U.S. funds only
>
>