[AMRadio] Best AM BoatanchorReceiver or AM

Jim Wilhite w5jo at brightok.net
Sun Oct 1 19:48:04 EDT 2006

I had a NC 300 paired with my B&W 5100B for vintage SSB.  As a matter of 
fact, I use these every time I do SSB and really like them.  How many people 
can still zero a separate transmitter to a receiver and know they are on 

For me, the 117 out performs the 300 in two areas.  First the 300 is a bit 
more sensitive and secondly the S meter is more liberal.  These are two 
shortcomings I can live with in the 117.  With greater sensitivity you get 
more noise and more adjacent channel (dare I use that phrase) interference.

Even though the 300 has a crystal filter and the IF selectivity knob, I 
found it to be a bit too wide on position 2 and way too wide on position 1 
like the SP 600.  The 300 worked well following extensive tuning of all the 
knobs.  However the slope of both of the bandwidth knobs lead to some 
interference from strong signals due to the sensitivity.  The SX 117 doesn't 
have that problem.

As a tube aficionado, I am loath to put good money into equipment that has 
transistors or ICs in it.  Many of the ICs and processors for that equipment 
are proprietary and if one fails, you just throw the receiver in the trash 
after a few years.  There is nothing to salvage for other projects, unlike 
tube gear.  It is a sign of the throw away mentality of the current 
generations.  More money than brains.

I had an SP 600 one time for about a year.  Wonderful SWL type receiver and 
great sounding.  But I found it tough to tune and had the same problems you 
mentioned.  They also suffer sensitivity problems a bit on the upper bands, 
but a 6BZ6s will cure most of that.  Direct replacement parts are wonderful.

73  Jim

> Jim,
> I lover your term, 'Aflak'! Pardon me, but I am going to use it..:-)
>  That Sx-117 is a pretty neat receiver. I was just looking at the 
> specifications at the following sight:
> The IF selectivity at .5, 2.5 and 5 khz @ -6db is pretty tight for AM, and 
> I bet that is why you did pretty good on 75 yesterday with 3 AM signals 
> spaced 5 Khz apart, and a duck on either side. My Sp-600 with a 3 and 8 
> and 13 khz options just did not have the right bandwidth position for the 
> conditions. There was also an Aflak at 3918 Khz running an amplifier, and 
> was about 150 yards from my home. The SP-600 could not handle it, S-meter 
> would go down about 1/2 what it was, and undetected SSB came right through 
> the speaker - loud too. The R75 with preamp off, and attenuator off had no 
> trouble with the 3918 Aflak.
> In defense of that SP-600, later during the traders net the QRM subsided, 
> and I opened the Super Pro to 8 Khz, and turned up the audio. It was clear 
> as a bell, and the audio from those guys really came through nicely. Then 
> the signals faded, QSB, selective fading, noise, etc. came in.
> The R75 sync detector has issues, and many complaints. That said, if you 
> use the passband tuning (say +/- 2.4 khz), with AM sync ON, it locks every 
> time. With normal AM tunining mine seldom locks. The Kiwa mods take care 
> of that, and several other issues.
> Jim

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