What's your favorite boatanchor?

Discussion in '"Boat Anchor" & Classic Equipment' started by AI3V, Feb 25, 2010.

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  1. WA1KBQ

    WA1KBQ Ham Member QRZ Page

    I have restored four SX-88s so far and currently have a fifth receiver apart and in-process. While I will agree with you that the SX-88 might not be the best receiver ever produced they are actually pretty good and featured fairly advanced technology for their time which Hallicrafters never duplicated in their later offerings. The SX-88 was the only Hallicrafters receiver ever produced with Litz wound 50 KC IF transformers. In addition the IF transformer windings were placed inside ferrite sleeves and had threaded adjustable ferrite cores which yielded a "Q" of over 180. All subsequent 50KC IF transformers used in other later models including SX-100, 101 and 115, etc., were wound with single wire and had ferrite adjusters suspended from threaded brass rods. We all know what happens when you insert a brass rod into a coil.

    Actually there is no best receiver when you get on the high end as compromises become necessary depending upon what the engineers were attempting to accomplish with it. The SX-88 had no peer in its day and can still more than hold its own especially in today's crowded band conditions.

    Below are links to pictures from the latest restoration job. Notice the receiver was extensively disassembled in order to gain access to hidden caps and resistors in the RF stages and second converter deck. An SX-88 cannot perform at its original design level unless all stages are made to work properly again.

    A Brief Picture History of #444 Restoration

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3178.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3198.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/444-007.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/444-021.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/444-008.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/446-022.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-009.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-010.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-011.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-012.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-026.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-022.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-023.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-024.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/444-025.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3075.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3076.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3085.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3091.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3099.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3183.jpg

    http://i104.photobucket.com/albums/m191/wa1kbq/SX 88 - 444/IMG_3182.jpg
     
  2. W1GUH

    W1GUH Ham Member QRZ Page

    'KBQ:

    That's some very interesting information about the evolution of Hallicrafters receivers. Makes me wish I could have been a fly on the wall when those decisions were being hammered out. Citing the example you described, the IF transformers, I wonder how going away from the Litz wound transformers with the ferrite cores affected the performance of the final end product? I'm sure there were a lot more of those decisions over the year. Is this information in Chuck Dachis' book? Or is it stuff you picked up in your years of restoration?

    Thanks for the great post!
     
  3. WA1KBQ

    WA1KBQ Ham Member QRZ Page

    Hallicrafters SX-88 Review; QST Magazine, June 1954
    Excerpts

    Sooner or later some wit is going to come up with the facetious remark that, "That new SX-88 is sure a lot of receiver—it's 20 inches wide and 18 1/4 inches deep." And while it's true that 18 1/4 inches is deep for a receiver and may occasionally pose a problem in finding operating-table space, there's quite a bit more to the story.

    This Hallicrafters receiver has already been advertised extensively, so some of the data you find here may be old hat. Bear with us, however—some of it hasn't been in the ads.

    The SX-88 is a double-conversion two-dial receiver that covers 0.535 to 33 Mc. in six ranges. The bandswitch also operates masks in back of the dials so that only portions of the scales, corresponding to the range in use, are back-illuminated at any time. To facilitate setting up on any amateur band, a 100-kc. crystal-oscillator "Calibrator" is included—when changing to a new ham band you throw the bandswitch, turn the "Calibrator" on, set the bandspread scale to some even 100 kc. within the ham band and set the bandset dial to a dot at the high-frequency end of the band. At this point you will be within easy reach of the 100-kc. marker signal so you rock the bandset dial, zero on the marker signal, and lock the bandset dial. The bandspread dial then reads directly in frequency, and you can, of course, check it every 100 kc. with the calibrator signal. The calibration marks on the bandspread dial are every 10 kc. on the bands up to and including 14 Mc. (they're every 20 kc. at 21 Mc. and every 50 at 28 Mc.), so it can be read easily to about 3 kc. (except on 21 and 28 Mc.) and closer if one is a good judge of distance.

    [​IMG]

    Figure 1. Block diagram of the SX-88 receiver. Only one
    r.f. stage is used in the broadcast range—all other ranges
    use the two r.f. stages. The first i.f. is normally 2.075 Mc.
    Band 2 includes this frequency, however, so on Band 2
    the first i.f. is made 1.550 Mc. The 4H4 current regulator
    is in the heater circuit of the 6U8 1st mixer, for maximum
    stability under varying line-voltage conditions.


    The receiver has a lot of selectivity (as we'll elaborate on later), and there might be times during c.w. operation with high selectivity when a 3-kc. approximation of frequency wouldn't be good enough to allow one to return from some other part of the band to a signal he had been stalking previously. (As, for example, in a DX contest when you're trotting back and forth between several pile-ups.) For such cases, there are arbitrary markings on both the scale and the tuning knob that give a 0-2400 scale for logging and reset.

    This receiver has no "selectivity" control and no crystal filter—it has a "Bandwidth" switch. This switch has six positions (not counting a seventh marked "Phono" for feeding a record player through the audio amplifier), and those positions are marked ".250," ".500," "1.25," "2.50," "5" and "10." These figures represent in kilocycles the 6-db.-down bandwidths of the 50-kc. second i.f. (the first i.f. is 2075 kc., except on one range), and the corresponding 60-db.-down bandwidths are .850, 1.50, 3.75, 7.5, 15 and 21 kc. If you dig back through old copies of QST, you will find that this degree of selectivity exceeds almost anything that has been described by home constructors, with only a few exceptions in the case of "super-selective" c.w. receivers. It certainly is better than anything that has been described in the way of graduated selectivity, because it goes all the way from a nominal 250-cycle bandwidth to one of 10 kc.

    The two sharpest positions give the kind of selectivity that the "super-selective" c.w. gang has been plugging for the past few years: no audio image at all on "the other side" of zero beat. On 'phone, the 5-kc. setting is used when there is no QRM, the 2.5-kc. bandwidth is right for s.s.b. reception of a.m. or s.s.b. signals, and the 1.25-kc. bandwidth is useful for tough QRM on a.m. or s.s.b. The b.f.o. should be used for exalted-carrier reception of a.m. signals at the 1.25-kc. bandwidth, although two operators reported that it isn't absolutely necessary—we rate them as "old pros" at copying 'phone and not necessarily typical.


    The I.F. Amplifier
    As an "old skirt-selectivity man," the writer was particularly interested in the 50-kc. i.f. amplifier, and we'll take a little time here to tell you how the SX-88 gets its wide range of bandwidths. The heart of it is, of course, the tuned circuits that are used. These are special coils tuned by a ferrite slug and surrounded by a ferrite sleeve. The special design gives a coil with a Q of 175 to 185 at 50 kc., as compared with the Q of 100 of the coils used in the S-76. An interesting sidelight is that it was found impossible to obtain a Q of higher than 130 until a metal screw was removed from the ferrite core and a means was found for threading the glass-hard and glass-brittle ferrite.

    Any skirt-selectivity man can build a sharp i.f. amplifier if someone hands him a bunch of Q = 180 coils, but the SX-88 i.f. has the various bandwidths mentioned earlier. This poses quite a problem, because the frequency must not be changed radically by the bandwidth-variation method, and the gain must be held substantially constant. This was accomplished by the Hallicrafters engineer in the general way shown in Fig. 2A.

    [​IMG]
    Figure 2. (A) Basic circuit of the variable-bandwidth i.f.
    used in the SX-88. The coupling is increased as C is
    made smaller, and the Q of L2C2 is reduced as R is
    increased. The stage gain is held constant with changes
    in bandwidth by tapping the grid and plate up or down
    on the coils. (B) The effect of varying C and R in (A) is
    that the passband "grows" out to a higher frequency,
    as illustrated here.



    This simplified diagram shows a variable condenser ganged with a variable resistor—in the actual receiver these are step-switched, of course. It can be seen that the smaller the capacity of C, the tighter will be the coupling between the two tuned circuits, L1C1, and L2C2. Furthermore, the larger the value of R is made, the lower becomes the Q of the grid tuned circuit, L2C2. By proper proportioning of the various values of C and B (at different switch positions), the wide range, in bandwidth variation is obtained. One of the three 50-kc. i.f. stages has taps on the coils, as represented in Fig. 2A by the leads to S1, and this enables the gain of the i.f. amplifier to be held relatively constant over the entire range.

    The midband frequency of this i.f. system does not remain constant—the low-frequency edge remains substantially constant. This is illustrated in Fig. 2B, and it is something the operator must remember if he is to understand fully the performance of the receiver as the bandwidth is changed. Here three conditions ("sharpest," "medium" and "broadest") are shown—the effect is as though the bandwidth "grows" to the higher frequency. It is pointed out here to explain what will undoubtedly puzzle some operators when they switch bandwidths and find that sometimes the carrier drops out and sometimes it doesn't. Obviously, it will depend on whether one has the carrier centered at around 50 kc. or on the high-frequency side of the i.f passband.
     
    Last edited: Aug 25, 2010
  4. WB5WSV

    WB5WSV Ham Member QRZ Page

    Favorite Boatanchor

    I have a TS-520, a TS-820S, both of which I bought in non-working condition and repaired as well as a total of 6 BC-348's in various stages of restoration. But my favorite boatanchor is my first piece of ham gear, my National NC-155, purchased used from AES in 1974. It's beautiful, rugged, and does a great job.

    And I have a new favorite that ranks right up there with the 155, an NC-190. I purchased it on ebay and had to install a new volume control, replace some tubes, and do alignment. On the AM broadcast band it is just awesome and on the higher bands WWV comes right in on 15 MHZ, if anything even better than on my TS-820S.

    The next step wil be to replace the electrolytic filter cap in the 155 - for the third time.

    And the NC-190 makes such a nice companion to my NC-155. It looks like National designed them to sit next to each other.


    Robert
    WB5WSV
     
  5. WA9CWX

    WA9CWX Ham Member QRZ Page

    I will just repeat myself, in terms of operating rigs, my favorite boat anchor is my Drake 'B' line, I also have a working station that includes a beautiful Home Brew 6AG7/807 rig, and a restored to original condition HQ129X. That is always a nice trip down memory lane, but the convenience of operating it is no were near the Drake...:D

    Frank
     
  6. KJ4OLL

    KJ4OLL Ham Member QRZ Page

    I have a new "favorite" boatanchor receiver!
    The R-390 audio sounds better to my old ears than the R-390A.

    [​IMG]
     
  7. ND4JS

    ND4JS Ham Member QRZ Page

    My Favorite BAs.

    Hammerlund 129
    Johnson Viking II
    Heathkit DX-100
    Hallicrafter sx110

    I now have a National nc300 not in picture.

    [​IMG]
     
  8. KE7NUB

    KE7NUB Ham Member QRZ Page

    I like the 5100B B&W alot.Injecting line audio to it with the Behringer rack. Very well layed out transmitter.Mine has had many mods over the years. My little Ranger sounds like music.I have made a few changes since this picture was taken.[​IMG]
     
  9. WD0GOF

    WD0GOF Ham Member QRZ Page

    NEW FAVORITE BOATANCHOR?!?!

    Of course it's one I don't have. I would love to get my hands on a Hallicrafters HT-45, known as the "Loudenboomer". But alass a working one is too rich for me. Even a tech unit with no final commands more $$$$$ than I have to spend.
     
  10. KB1OKL

    KB1OKL Ham Member QRZ Page

    I have several favorites, R-390A's with a DX-100 for hamming and an SP-600 for broadcast band DXing which I'm listening to right now, I have something on 693, probably BBC it's mostly below WOR's IBOC. I Also love the old National HRO's. My first good receiver was an HRO-60 I bought in 1980. I think my coolest receiver is a back wrinkle HRO-50R1 I have that is in almost mint shape.
     
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