Hallicrafters SX-88 Receiver Test Results

[W1VD]

Receiver: Hallicrafters SX-88

Band	MDS	Blocking DR	Two-tone DR
		(20 kHz)	(20 kHz)
80 meters	-141 dBm	106 dB	81 dB
40 meters	-141 dBm	104 dB	80 dB
20 meters	-140 dBm	99 dB	78 dB

AM audio S/N: 50 dB

AM Audio Frequency Response: in dB, referenced to 1 kHz measurement    

100 Hz	200 Hz	400 Hz	600 Hz	800 Hz	1 kHz	2 kHz	3 kHz	4 kHz	5 kHz	6 kHz
0	0	0	0	0	0	0	0	-2	-6	-10

AM Audio Distortion:

Mod	100 Hz	200 Hz	400 Hz	600 Hz	800 Hz	1 kHz	2 kHz
30%	1.8%	1.1%	0.9%	0.9%	0.9%	0.9%	1.2%
50%	2.8%	1.6%	1.1%	1.1%	1.1%	1.1%	1.2%
70%	4.0%	2.2%	1.5%	1.5%	1.8%	2.7%	3.4%
90%	5.1%	3.2%	3.1%	3.9%	4.5%	5.2%	5.3%
100%	6.5%	5.3%	5.4%	5.9%	6.0%	6.1%	7.3%

10 Meter AM sensitivity: 0.3 uV for 10 dB S+N/N (1000 Hz tone, 30% modulation)

Notes: Testing performed using 500 kHz IF filter position with the tone control set for a flat audio response 20 Hz - 20 kHz. As with other BA receivers tested, the SX-88 has excess gain requiring that the rf gain control be backed off from the fully advanced position. MDS improves about 3 dB when using the 250 Hz bandwidth position. A 10 Meter AM sensitivity measurement has been included ... as requested by Carl.

A more in depth review of the SX-88 can be found at:

http://www.w1vd.com/HallicraftersSX-88.html

Info on the measurement setups and test results on other receivers can be found at:

http://www.w1vd.com/BAreceivertest.html

[ke7trp]

Very nice receiver Jay. Thanks for taking the time to test the SX88.  There was alot of discussion about its performance.  They are answered now!

C

[Todd, KA1KAQ]

Excellent work, Jay. Your thorough review of the receiver should answer any questions and settle a lot of old debates over performance. It's actually better in some areas than I expected, others not so much.

Interesting to see how closely some of the figures track with the earlier SX-28.

[WA1GFZ]

I wonder if high levels of modulation pump the AGC.
Might be interesting to run the audio distortion test with the agc in manual position set below saturation to see if it is the detector or AGC related.

[KM1H]

Excellent Jay and I hope you continue testing 10M and maybe revisit some of the ones already done. When 10-15 are hot there is quite a bit of AM on them.

Carl

[K5UJ]

Jay thanks for the work here.  hpe to catch u on 40 m. some more.  Your BA measurements are the only workbench analysis I know of for vintage receivers that are easily available.  I hope you keep getting more receivers and checking them out/report the results.

 

[W9RAN]

Nicely done as always, Jay.   I also had to remove one of the 50 kc IF coils to repair it, so I admire your willingness to examine one, knowing they're made of unobtainium.   The IF transformers certainly are a distinguishing performance element in the SX-88.    I can also attest to the overhaul of the dual gearboxes as being "particularly time consuming", as you so tactfully put it - but so nice when they're working right.

Incidentally, mine is a pre-production handbuilt unit that is substantially the same as the production model, with the exception of having one extra tube (a buffer for the external IF output) and four crystals instead of two on the 2nd Converter unit, which provide reverse-side injection on Band 2 - obviously dropped on the production run.   There are also scribe marks on the chassis and one "oops" where a tube socket hole was "moved" - that I think are kind of neat one-of-a-kind features.

Just to clarify - am I correct in that all your performance measurements were made after restoration, including replacement of the capacitors in the IF filter?

Thanks for bringing facts and data to what is otherwise an "opinion-fight" :-)

73, Bob W9RAN

[W1DAN]

Hi Jay:

Your full report was an excellent read, and shows the extensive time and detail you dedicated to this project. I always wanted to know why the SX88 is deemed to be special to collectors.

The reports on your website are an excellent resource for us all. It was good to meet you at the Lonely Guys lunch.

Thank you!!

73,
Dan

[W1VD]

Thanks for all the comments.

Bob ... yes measurements were made after the restoration including the caps in the IF filters. Interesting on pre-production unit - that certainly makes it a one of a kind. Those 'pre-prod' units don't surface very often (anymore) so you're lucky to have it.

This weekend I started looking at an NC-400 that I've had for a few years as a possible next 'victim' for restoration and measurement. Don't know much about the receiver yet ... maybe Carl will chime in.   

 

[W3GMS]

Jay,

Great job as usual!  I know it takes some time, especially when you have to restore the receiver prior to taking all the measurements.  Your process should produce the results that the receiver would exhibit when it was new which adds extra significance when comparing the various receivers that you have evaluated. 

Hopefully we will see you at Nearfest....Martha and I will be attending. 

Joe, GMS

[WA1KBQ]

Thanks Jay for reporting the test results of your latest efforts and for sharing the interesting story of this truly magnificent receiver you have rebuilt and restored for yourself. Your report might inspire others to start looking for one to restore now that the performance potential has been verified. It's also a nice bonus to have something of substantial value afterwards considering the level of effort and hours of work required to achieve those results. Very well done!!

Regards, Greg

[WA1KBQ]

Thanks for all the comments.

Bob ... yes measurements were made after the restoration including the caps in the IF filters. Interesting on pre-production unit - that certainly makes it a one of a kind. Those 'pre-prod' units don't surface very often (anymore) so you're lucky to have it.

This weekend I started looking at an NC-400 that I've had for a few years as a possible next 'victim' for restoration and measurement. Don't know much about the receiver yet ... maybe Carl will chime in.  

 

The NC-400 is another one which can jump to the center of a debate in a hurry with proponents on one side and detractors on the other. It will be interesting to see how MDS and DR of this one fares under your scrutiny with two made for television 6BZ6 RF stages and the popular twin mixers and your opinion of the two separate IF channels and the method of achieving offsets for SB-1 and SB-2 otherwise known as upper and lower.

Regards, Greg

[KM1H]

Jay, the NC-400 certainly is a strange beast.

The first run used socket rivets for ground lugs and no tooth washers and were a nightmare of instability and intermittents. I drilled out about 200 rivets myself and others did even more.
Ive no idea how many unmodified ones remain.

The 6BZ6 does well in the NC-300 and 303 in conjunction with the 6BA7 and it might be worthwhile to try a 6BY6 in place of the 6BE6. I can send you a NIB one if you want.
OTOH the 75A4 with a 6DC6/6BA7 is a dog by comparison.

The NC-400 has a very strange and different way of controlling RF gain and Id be real interested in what you find especially comparing to the HRO-60 which runs the 2nd RF at just about unity gain which is different than the 50, 50-1, and 183D. The 400 I bought has made it from El Paso to Chicago area so far and should be here in July. I didnt want to ship it as the OT owner wasnt up to a serious packing job and the various package stores are even worse down in Manana country

[WQ9E]

Well Carl,

I can tell you where at least one of the unmodified frequency jumping NC-400 receivers lives   Mine is OK through 20 meters but 15 meters and up is not good.

Do you know if the National expected most customers to use an external oscillator with the NC-400.  With the built in "calibrate tune" circuit for peaking the front end with crystal control or external control it seems possible which would have reduced the concern about stability of the internal oscillator.  This may be the perfect receiver for use with one of the little DDS vfo units.

I expected the NC-400 to be a "super NC-183D" and it is an interesting receiver.  Once I run out of other projects maybe I will pull out the drill, screws, nuts, and star washers-but not for quite awhile.

[WA1KBQ]

It would have been nice if National had gone with the NC-300/ 303's 80KC second IF in the NC-400 instead of opting for 455 to accommodate the mechanical filter option.

Greg

[KM1H]

The NC-300/303 filters are very good as is but the components are all 5-10%. Going to a match of 1% or less in all 3 stages makes a big improvement, especially with the paper caps that were in the CW BW position. I also match the filter resistors.

With a small handful of 5% carbon film resistors, silver mica and polyester film (Mylar) caps its real fast & easy to come up with well under 1% tolerance. Now if there was only an easy way to add passband tuning it would be a real "Dream Receiver"