Exceedingly rare Northern Radio modified SP-600

Many thanks to SWLing Post contributor, Dan Robinson, who writes:

Those of us who still use SP-600s, and those of us who once did but can’t deal with them in retirement, lust after some of the rarer versions of the radio. This is one of them, the Northern Radio modified SP-600.

Click here to view on eBay.

Wow! Many thanks for the tip, Dan!

I must say that when Dan finds these rare treasures on eBay, they usually carry a very hefty price.  In my opinion, this is a good deal for a rare SP-600. Best of all, it has a BuyItNow price, so first-come, first serve and no bidding up the amount.  The shipping price is a bargain considering this radio probably weights upwards of 80 lbs.

This SP-600 may need some electrical restoration and possible re-capping. It’s listed as: “For parts or not working.” If you’ve been looking for an SP-600 to restore, this might be worth consideration. Thanks again, Dan.

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5 thoughts on “Exceedingly rare Northern Radio modified SP-600

  1. DanH

    Diversity operation: two or more receivers and antennas used to copy CW or RTTY from one or more transmitters. Most of the Hammarlund SP-600s were models built for diversity use including the well-known JX-17, the most common SP-600. Diversity models can be used as single receivers. In this eBay example Northern Radio has modified a SP-600 J-11 for diversity use.

    SP-600 nomenclature: J means joint army/navy (JAN) mil-spec components. L means low frequency. X means crystal frequency control in addition to VFO. My SP-600 is a JX-21, which is not a diversity model. Higher model numbers do not necessarily mean later production dates. All SP-600s use the same serial number sequence regardless of model. Somewhere between serial numbers 15,000 and 17,000 (mid 1950’s) Hammarlund stopped using molded black beauty capacitors and switched to installing ceramic capacitors.

    The two-digit model numbers indicate model types. JX-1, 7, 10 and 21 were similar non-diversity receivers. SP-600s built for military contracts will have an additional tag showing the military model number(s).

    Here is a great page showing Northern Radio modified SP-600s in action with accompanying Northern Radio RTTY gear.


  2. RICK A.

    I recommend passing on this one – it is overpriced.
    It will immediately need a full recapping. In fact, it should not be powered up before recapping – there are a couple of the BBODs that if they decide to short, will take out one or both of the big chokes with them. That is a big job (42 capacitors)
    The front panel is nice, but behind the panel, it is not in great condition.


    1. Michael Black

      They made things for commercial and maybe military installations. Too expensive, and generally too exotic, to be of interest to the hobbyist. Kind of like TMC, but smaller. TMC advertised in the ham magazines, but virtually none of it was aimed at hams. I assume they advertised because it might reach people making purchase decisions, and maybe lured in employees. TMC did make the GOR-90, with bandspread calibrated for the ham bands, but I don’t think many were sold to hams.

      So in this case, Northern Radio modified an SP-600 to add switches so the oscillator and BFO could be external. The receiver is fine, but lacks the calibration and bandspread, and stability, of say the Collins receivers. This mod was only a means to an end, Northern Radio sold a unit that provided the needed oscillators, that were more stable and had a better dial. I don’t think the mod is anything else, so without the external oscillator (nowadays one could throw together some synthesizer and get the same end effect.

      I thought Hammarlund had some other model for diversity reception. But running two receivers from one oscillator is one thing needed for diversity reception. It’s hazy, but the SP-600 that I had the use of might have been one of these. Its been too long, and I’ve never seen another SP-600 close up.

      It is a good price, but shipping would be crazy.



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