NC-200 Receiver

[Jim/WA2MER]

I'm looking for opinions on the NC-200, preferably from people who have used or owned one.  I may have a chance to pick one up and I'm wondering if it's a suitable receiver for AM.  I have other receivers that I can use for battle conditions, but the NC-200 looks like it might be an interesting addition to the stable.  Is it worth having? How does it stack up against the Hammarlund HQ-129-X, which I also have and would provide a good frame of reference for me?  It's not mint by any means, but it's reportedly a good performer.  What might I expect to pay for a good working example with its matching speaker?  I've found precious little information on the web, so here I am asking for input.  I can easily compare specs and features, but I really need to "ask the man who owns one."

Thanx & 73,,
Jim

[KM1H]

As Ive mentioned on here and elsewhere the NC-200 and NC-240D are sleepers that are better than most others of their era. I own both.

With the sliding coil carriage they have good sensitivity even on 10M and blow the HQ-120X and 129X away in that area. The Hammys have slightly better skirt selectivity due to the 3 IF stages but the Nationals have higher Q transformers which makes it almost a wash. All can benefit with one of those Kiwa ceramic filters in the IF.

Hammys drift, those particular Nationals dont after a short warm up which is due to the massivness of that coil assembly and variable cap.

The Nationals have PP 6V6 audio and an excellent noise limiter. The crystal filter is on a par with the HQ's.

Both are very easy to recap and replace resistors.

The Nationals do not have an antenna trimmer which means a balun or tuner for coax fed antennas. The Nationals have slightly better image rejection on 10-15M but neither brand is very good. A tuneable preselector such as a modified DB-22A works wonders as well as perking up deaf Hammy's.

And yes I own all the 455kc single IF Hammys and the 129X has been a lifetime favorite going back to 1957. It was deaf on 10-15M and drifted and it was only 4 years old but I improved the sensitivity and lived with the drift which was tolerable on 20 which is as high as I went with SSB a few years later. It and its brothers are also one of the best medium priced BCB DXers made thanks to that spectacular dial readout.

Carl

[k4kyv]

I totally agree.  I have used the NC-240D and NC-101XA. Like the NC-200 they have the famous National coil catacomb assembly.  Much more positive bandswitching function than with a flimsy wafer switch, and each individual  coil is thoroughly shielded in its own compartment, with its own set of dedicated trimmer capacitors. These receivers are mechanically solid, and tend not to jump frequency when bumped.

Expect to let these receivers warm up for an hour or so before they settle down, but once everything inside reaches thermal equilibrium, their stability is almost (but not quite) as good as that of the Collins PTO. The precision, accuracy and workmanship of the dial and tuning mechanism are unsurpassed by competing receivers of the same era.

Hammarlund receivers, including the SP-600, tend to be unstable even after they have thoroughly warmed up, due to inherent design deficiencies of the tuning capacitor assembly. They are fine for AM reception using normal AM selectivity bandwidth with the stock envelope detector, but from my own experience, they suck when used for CW or slopbucket reception. Another thing about the Super Pro series that sucks is that certain components in the RF and mixer stages are all but inaccessible for replacement, and these compartments contain some tubular by-pass capacitors that are notoriously prone to failure.

[WQ9E]

I will add the third vote in favor of the NC-200.   I have a NC-240D and it is a very enjoyable receiver.  I gave it a careful alignment when I restored it 6 years ago and the switch selected band spread ranges have remained well calibrated.  Restoration is very simple.  

I have several of the family members (NC-100X, NC-101X, NC-240D, a Wells Gardner RAO-7 which is basically a NC-100A with a second RF stage, and one of the RC variants of the NC-100) and all are good performers.  The NC-101X holds the distinction of probably being the only ham band only receiver with push/pull audio output.

The moving coil catacomb is a nice design but I think it was too expensive to continue to continue to occupy its place in the line as fitting below the high end HRO and the NC-173/183 series would have had much lower materials and construction cost.  My Pierson KP-81 is also a moving coil catacomb receiver but it was only produced for about a year ending production in 1947 and the NC-240-D ended production in 1949.   Is anyone aware of any moving coil catacomb receivers post 1949?

[Todd, KA1KAQ]

I'll throw in as well for the 200. Hands down it's a great set and more radio than the entry level HQ-129X.

Like Rodger, the later 240D is the one I have now, and as Don says - the band switching is very solid. Not sure that it makes any difference over a tight wafer switch, since it's not a control you fiddle with a lot. But it does work well and has a high coolness factor.

Tuning has a nice feel, too. The flywheel adds that high-end stereo tuner-feel to it, and the larger dial is much easier on the eyes. The 129 and others aside from the SP-600 used a friction pinch wheel drive which works just fine, but feels like mud. The worst part of the Hammars, in my view.

And of course - the shove/yank audio output is awesome. Much nicer than the 129.

As far as Hammars go overall, I must be the luckiest guy in the world. None of mine drift any worse than the Nationals I have here (NC-81X, RAO-7, NC-240D, HRO-5C). Proper maintenance and warm up time is the key, of course, and Hammarlund makes this clear in their manuals. One thing that also gets overlooked a lot is line voltage. I bought into the old wives tale about all Hammars being drifty too, until I swapped the tap on the SP-600 power transformer. It settled right down to the point of being more stable than my older HRO. Then again - I seldom use any of the old receiver for SSB listening. It just doesn't interest me.

And to what Don said on Super Pros having issues for getting to components, that's only true of the SP-600 turret design. Earlier SPs are a piece of cake to work on, though some caps are hidden inside IF cans. Very open and easy to access, same as the 129.

However, Carl will confirm that working on the NC-200, 240, or any of the sliding coil models is anything but easy, and at least as annoying as the SP-600. The coil drawer is indeed a work of art and of high quality. But cleaning and possibly repairing those contacts properly along with removing the coil drawer are details that often get overlooked. It's somewhat involved, and if you mess it up, you run the risk of damaging the contacts.

As with any of this old gear, there's no free lunch when it comes to performance vs maintenance/repair/restoration. But if I were me, I wouldn't hesitate to grab the NC-200 even if it's not perfect and needs some work. It's a better performer and much more enjoyable set overall.

[k4kyv]

Years ago I read an article about repairing the NC-240D.  The writer warned against removing the coil catacomb unless absolutely necessary, saying that re-installing it into the receiver without damaging anything is a little like putting ketchup back into the bottle.

National also made a small, relatively inexpensive member of this receiver line, the NC-80X (general coverage) and the NC-81X (ham band only).  It had a nice slide rule dial, but the same precision construction and weighted tuning knob. It had no rf stage, and a high frequency i.f., somewhere near the top of the AM broadcast band.  Problem was, the image rejection (the reason for the high i.f.) was poor, and the selectivity depended entirely on a phasing type crystal filter, which performed very poorly for AM. People have told me that once you get it working right, it makes a good receiver, but I never could get mine to perform worth a crap.

I recently gave mine to Dewitt, N4QNX, who needed a parts unit, and now he thinks he can put together one good complete receiver out of mine and his, each of which is missing parts, has random wear and damage, and has suffered numerous Hammy Hambone modifications.

One thing I discovered about the entire series is that the coil units that fit into the catacomb units are interchangeable, and even some of the coils themselves will work in other models of the series without modification.  The stationary contact assembly that the catacomb passes over as it moves and that the selected set of coils locks onto, is identical in all the receivers.  I ended up pulling one of those out of my 81X to replace a damaged one in my 101XA.

[Jim/WA2MER]

Guys, thanx for the responses.  All were helpful and gave me what I was looking for. Like I indicated in my original post, I already own a '129-X that I like for what it is, and I intend to keep it.  The comparisons between the HQ and the NC were solicited in order to provide me with a useful benchmark, not to choose one radio over the other.

The radio is the 75th Anniversary model and has the matching speaker.  From the photos it appears to be in decent physical shape, though not mint (whatever the term "mint" may mean to you), and it works well.  I'll get to see it this weekend.  I was asking for guidance on price because it belongs to a friend, and I want to be sure that he asks a fair price and doesn't undercut himself because a friend wants it.  He's gone to a fair amount of trouble getting the radio, testing it, cleaning it up and troubleshooting a continuing problem with the S-meter. I want the exercise to be worth his while.  Assuming of course that he doesn't fall in love with it himself!

73,
Jim

[KM1H]

However, Carl will confirm that working on the NC-200, 240, or any of the sliding coil models is anything but easy, and at least as annoying as the SP-600. The coil drawer is indeed a work of art and of high quality. But cleaning and possibly repairing those contacts properly along with removing the coil drawer are details that often get overlooked. It's somewhat involved, and if you mess it up, you run the risk of damaging the contacts.

I sorta disagree Todd. While removing the carriage is not for the timid or feeble minded its only necessary if one (or more) of the mating contacts which are mounted to the chassis below the variable cap are broken. Ive done many over 45 or so years and even built a spreader bar tool. However IF any of those sets today have broken contacts then put it aside as a parts set as replacements are almost unobtanium.

All the coils should be removed (2 screws and pull straight out) for contact cleaning (ONLY with the carriage moved to an extreme end so none of the coils are engaged) and the fixed contacts checked and also very carefully cleaned. I use Q-Tips and a diluted TarnX and insert just like the coils. A typical radio will take 30-40 Q-tips before Im satisfied. The final passes are with dry ones to remove any residue.

Replacing caps and resistors couldnt be easier, nothing is hidden. Move the carriage to the RF/IF side to expose the PS and audio first and replace all caps and then you can feel reasonably safe to turn on and set a baseline for the rest of the work. Neither transformer responds well to shorted or leaky caps . The rest of the work is on the other side of the chassis. Be sure to keep everything close to the chassis otherwise the carriage will hit them.

[WQ9E]

The only time I had to remove the catacomb was in my NC-101X to replace the bushings that fit the rear rail.  I don't recall it being that difficult but I remember reading the same Bill Orr "ketchup in the bottle" article as Don which did make me a little nervous about the removal and installation.

One of the funnier repair stories I read was from someone who recapped one half of a NC-100X and then went to slide the catacomb to the other side to finish the work and realized some of the new caps stuck up high enough to hit the catacomb. 

I would much rather work on a NC-240-D than align a set of HRO coils that have been monkeyed with since removing and installing coils as you adjust the inductance is a very tedious process.

[Todd, KA1KAQ]

I sorta disagree Todd. While removing the carriage is not for the timid or feeble minded its only necessary if one (or more) of the mating contacts which are mounted to the chassis below the variable cap are broken. Ive done many over 45 or so years and even built a spreader bar tool. However IF any of those sets today have broken contacts then put it aside as a parts set as replacements are almost unobtanium.

Which is more or less what I was saying, just not as technically or clearly, apparently. 

All the coils should be removed (2 screws and pull straight out) for contact cleaning (ONLY with the carriage moved to an extreme end so none of the coils are engaged) and the fixed contacts checked and also very carefully cleaned. I use Q-Tips and a diluted TarnX and insert just like the coils. A typical radio will take 30-40 Q-tips before Im satisfied. The final passes are with dry ones to remove any residue.

Which is on par with the tedious/annoying work on a SP-600. They're not terribly difficult either, just similarly-involved. The rest, as you say, is pretty simple and straightforward so long as you test the coil tray for travel before buttoning it up, to be sure there are no dingleberries.

National also made a small, relatively inexpensive member of this receiver line, the NC-80X (general coverage) and the NC-81X (ham band only).  It had a nice slide rule dial, but the same precision construction and weighted tuning knob.

Eh....not so much. The 81X here is certainly not as well-made as the 100/101 of the same period. I'd place it between the Sky Buddy & SX-23 for construction quality, though it's a better receiver than the Sky Buddy.

They didn't come with a weighted knob, so someone must have changed yours out or added the skirt. They did have the same knob, but the knobs are brown on mine and the few I've seen. Not many of them kicking around out there.

I would much rather work on a NC-240-D than align a set of HRO coils that have been monkeyed with since removing and installing coils as you adjust the inductance is a very tedious process.

As much of a pain as the coil tray is, I think I'd agree with that! The process for properly aligning HRO coils leaves a lot to be desired. But then, so does prying them out to change bands. Or bandspread. Or numerous other things. But when they're working right, all is forgiven.

[KM1H]

Im another with a NC-81X. While is no powerhouse its OK for monitoring 160AM when Im upstairs. Just a random wire about 60' long and maybe 15' high does well. There is some bleedthru on 1560kc at night when the din is strong but Ive been too lazy to cobble up a QRP preselector.

Carl

[k4kyv]

The weakest link in the HRO is that when you change bands and put a cold coil in the warm receiver, there is a warm-up drift all over again until the new coil comes to temperature with the rest of the set.  I used to reduce that problem by setting the unused-coil box on  top of the receiver cabinet, or when I would be working 160 I would set the 80m coil on top and vice versa.

You don't have to remove the coils to adjust the alignment trimmers. I used a 1/4" nut driver with a long spindle.  It doesn't have to be insulated, but I seem to remember that some of the trimmer heads have HV on them (maybe that was the i.f. adjustment). I just wrapped masking tape round the spindle of the nut driver.The trimmer screws are accessible behind the front panel, through holes in the  chassis, between the panel and the tuning capacitor.  I don't recall for sure, but I seem to remember there is a hole in the rear of the oscillator coil shield that allows access to the coil adjustment while the coil is plugged in.  The lower frequency coils have a rotatable brass disc for trimming the inductance, and the higher frequency coils have a half-turn of wire that can be bent to add to or subtract from the rest of the coil.

I remember what a PITA it is to change from general  coverage to bandspread on the Original coils.  You have to take out little flat-head screws on each coil and shift them over to the other hole.  Inevitably, you drop at least one and it vanishes off the face of the earth upon contact with the table or floor.  The later models changed over to a sort of two-position lever switch for this function.

[KM1H]

I remember what a PITA it is to change from general  coverage to bandspread on the Original coils.  You have to take out little flat-head screws on each coil and shift them over to the other hole.  Inevitably, you drop at least one and it vanishes off the face of the earth upon contact with the table or floor.  The later models changed over to a sort of two-position lever switch for this function.

Which is why I have 2 sets of HF coils for my 1935 HRO. A set of thick panel JR coils were cheap.

[Todd, KA1KAQ]

Yeah, there's some voltage in there alright. I got bit on my first attempt to peak on of the coils using some tips from Larry, NE1S. Decided I'd wait and do it another time when I knew the rig a little better. The early Super Pros are lying in wait to pounce as well. The last shock I got was from one of them.

The sliding coil approach was certainly a step in the right direction utility-wise, though it seems they were more lossy? Carl?

[KM1H]

A whole lot LESS lossy Todd. Those sets had one RF stage and were as hot as the switched ones with 2 stages. And as I said earlier they blow many sets away even on 10M.

[Todd, KA1KAQ]

I meant between the HRO yank out approach vs 240 sliding tray. Had an old timer explain to me that the HROs were superior in that department, but damned if I can recall exactly why.

[KM1H]

Its no different than the catacombs Todd. A very short low inductance path to the tuning caps results in much less loss and reduction in Q. All the extra RF amp in HRO's do is improve image ratio on the higher bands; 58's for example aint exactly high performance and 2 just adds twice the noise. Put a FET preamp ahead of it and reduce the 58 gains and its a pretty hot 10M radio

[Jim/WA2MER]

All the coils should be removed (2 screws and pull straight out) for contact cleaning (ONLY with the carriage moved to an extreme end so none of the coils are engaged) and the fixed contacts checked and also very carefully cleaned. I use Q-Tips and a diluted TarnX and insert just like the coils. A typical radio will take 30-40 Q-tips before Im satisfied. The final passes are with dry ones to remove any residue.

Carl, thanx for the tips and the photos you posted with regard to cleaning the sliding coil contacts.  It'll save me lots of head scratching.  Gonna pick it up tomorrow.

73,
Jim

[KM1H]

Jim, have fun with it and ask away if you have any questions.

Here is a before shot of the "RF" side of the chassis and a typical Q-Tip collection after a catacomb overhaul. The amount of crud that accumulates is amazing and really affects performance.