National NC-173 Tube Ham Shortwave Receiver Crystal Calibrator D-Lab Gadget

A much needed accessory for the National NC-173, 183 receiver and many others. I have always realized this need, but time always got in the way of producing the solution. Well, here it is, the XCU-1M, one megahertz crystal calibrator. Similar in design to the famous XCU-300 used in the NC-300 & 303. This module simply plugs into the rear octal socket, a few wire changes and your off and running. You will install a new power switch on the front panel where the phono input jack was. No drilling required. I found a vintage switch that goes right in the existing hole. This is a great addition to these old analog receivers. I also have a model the mounts vertical into the National NC-183D. Will post the video link. D-Lab is keeping these vintage receivers alive!

[@kornami8678]

My dad had a NC-173. I loved listening to it. later I sold it. I regret it every day.

[@kornami8678]

My dad had a NC-173 and he told me when you try to tune in SSBers, you do everything you did like turn the AF gain all the way up and use the RF gain to adjust the audio. Another thing he said to do, which I did not see you do, was you should switch the AVC to MVC, since you are try to listen to a signal audio but no carrier.

[@harrilumme1875]

The accessory socket was (is) used in NC-183 for the Select-O-Ject tunable audio filter or the narrow band FM detector. Both these use octal socket pin 5 for audio. Therefore, it would be safer to use pin 3, which is usually connected to the AVC line. Unless it is needed for some custom accessory, it can be disconnected and the pin reused for the calibrator signal. On the other hand, the accessory socket is inside the enclosure in NC-183. It can easily be extended to the back wall as in Terry's NC-173. This way the pin assignments are not so critical if the internal socket pins are left stock.

[@d-labelectronics]

Just finished construction of the 183 calibrator module. I used pin 3 for the signal output. Thanks for the suggestion.

[@preiter20]

Very cool that you can design tools that make a hobby that much more enjoyable. I am struggling with the basics (trying to restore a AA5 Detrola radio) but determined to get it done.

[@rciancia]

Terry, this is so cool. I can only imagine if you were a design engineer in the 40's/50's when these were made.. you'd be a millionaire !!! Nice work

[@TheRadioShop]

Great project for these old rigs Terry.

[@d-labelectronics]

Yes Sir, need to keep them running!

[@LitesLAB]

That looks great Terry! Love that it’s a tube module :)

[@hank1519]

Great job, Terry!

[@jdmccorful]

Nice upgrade.

[@bruceclaxton5721]

Excellent Idea. There are so many of us out there that have a Collins 75A-2, but lack the crystal calibrator for that radio. Did you ever think of making one available for the Collins radios? Bruce KO4UHL

[@ordinaryaverageguy76]

What parts are hard to get for your modules? I may be able to help get some cheap from a local supplier going out of business soon.

[@d-labelectronics]

The ceramic 7 pin tube socket/Johnson air variable cap/1 Mhz crystal (HC51)

[@ordinaryaverageguy76]

I can help with some of those, though not in large quantities. Couple questions: Would other than ceramic sockets suffice? What are the specs on the cap & might APC-like types suffice? Crystals I think I can glom a handful of 1MHz with wire leads.

[@ordinaryaverageguy76]

I have about a dozen of the crystals. Let me know about the other parts (see my earlier question).

[@dhpbear2]

I assume the calibrator emits 1 Mhz and all it harmonics at 1MHz intervals?

[@drdave337]

Great video. How about a video showing your antenna setup? 😀

[@glenwoofit]

Can you not use a 1Mhz crystal oscillator module?

[@asagady2552]

So the 1 MH calibrator also generates harmonics at every 1 MH increment? How high a frequency do the harmonics go at a practically useful harmonic wave applitude?

[@ozloon2000]

would it work on my national ncx5 it has a socket 8 pin octal marked calibrator also you can use one like this with a short antenna in the shack you can turn on or off gives 1mhz or 100kc mark for all your radios vk2mu

[@billyrey9679]

U dah Man!

[@wklinger79]

What about the nc300, 303? There is a switch and a n accessory port for a calibrator already.

[@ordinaryaverageguy76]

Those sets had an optional calibrator & an octal socket inside the cabinet to accept it. There's schematics & pics of them around, and it would be easy enough to make one.

[@willrobbinson1]

prob the 1mhz xtal is hard to get?? anyway at least u used a 6ba6 or 6au6 or sim not those 3 leg silly things ! great job terry wish i had nc173 but do have nc51

[@d-labelectronics]

I have parts on hand to construct 2 more complete modules, Yes, the 1MHZ Xtal is hard to locate