ITT Mackay 3010C

[sndtubes]

I just picked up an ITT Mackay 3010C Mod 2 at Dayton this year.  It works and it seems to work pretty well.  Obviously will need some TLC, though.  I was curious if any of you have any experience with this RX?  I find 2 major drawbacks.  One is there is considerable backlash in the dial mechanism.  I still need work on lubing it, so maybe that will get better. 

The other thing I've noticed is that this RX suffers from terrible IMD and images.  It has ultra high gain IF & RF stages, but even backing off the IF Gain and switching in the attenuator doesn't always get rid of the images?   There is also an "antenna filter" which is filters out the big broadcast signals from the AM bdcst band which helps, but not totally.  So for you guys that have played with this RX, is this normal for it?  Or do you think there is a problem or just maybe alignment?  It's a delightful receiver in many other ways, though.  If anyone has any thoughts on this unusual receiver, I'd be interested in hearing them.  73, Mike WB0SND

[W1VD]

Backlash on the unit I tested wasn't bad - the cogged belt looked like new. Disappointing dynamic range performance.

http://www.w1vd.com/Mackay%203010B.html

[sndtubes]

Great info!  Thanks.  I searched on 3010C instead of 3010B, so I didn't get a hit on your receiver test page.  I've looked at others you've done and they are very informative. 

I was afraid of what your page said which pretty much confirmed what I observed.  So long as there aren't any images within the passband, it is very pleasant RX to listen to and with the 500 Hz 75A4 mech. filter, the CW performance is very good.  I've gotta stop comparing everything with my sherwood R4c!

Not sure if I'm gonna keep this one......  It really is pretty cool despite it's shortcomings. 

I think I can improve the backlash by working with the very stiff dial drive mech.  It was much worse, but I've used some light oil in a few places which improved it greatly. 

[w3jn]

I suspect you have a bad diode or two in the balanced mixer.   Replace with good RF Schottky diodes.

[vincent]

 Reading this topic on the Mackay Marine 3010C receiver brought me to mind some memories. In 1975 I had the opportunity to demonstrate to two radio amateurs’ friends (Tony and Lucio) that designing and building a receiver with very good sensitivity is not so difficult but that it’s much more complicated to build one with a good sensitivity and excellent behavior in strong signals. They said that receivers must have at least one RF amplifier stage to have good sensitivity. The receiver indicted was the Squires-Sanders SS-1R/701. The challenge and bet was that:
“I will be able to hear with my SS-1R/701, with just a piece of wire as an antenna,
the same stations that you can hear with your receiver with an external antenna!” This was not an easy task! The day of the “demonstration” was coming so I built in a hurry an RF amplifier with the best (very low noise) tube available, the 7788/E810F. The circuit was copied from that of the 3010C with some slight modifications and adaptations (no low pass filter, 6C4 cathode follower with an output impedance closer to 50 ohms, no AGC, etc.) to combine it to the SS-1R. The receiver for comparison was a brand new Collins 75S3C, a 3 elements rotatable Yagi antenna (installed in the roof) was connected to it. The owner of these equipments was Lucio and its “shack” was located in a ground floor flat. The “antenna” connected to the SS-1R/7788+6C4 combination was a piece of wire (1meter long) coupled to the hot side of the RF filter coil of the RF amplifier. To make a long story short; not only the SS-1R/701 combo was able to receive the same stations as the 75S3C but they could be heard better, much better! My friends were stupefied (me too!). An explanation seems to be that the RF amplifier was acting as an active antenna or as a high Z  “sniffing” probe with a very low noise and high gain (thanks to the 7788). The SS-1R/701, “seeing” a wideband 50 ohms termination (thanks to the 6C4 cathode follower) at its antenna input, was performing like a charm! Another explanation may be that the 75S3C was “compressed” by the signals level coming from the 3 elements antenna, but this was not apparent because also in the not crowded bands the results were the same. I won the bet.

[w3jn]

Beautiful construction for a "rush" job, Vincent!

The thing about the SS-1 is it apparently really wants a 50 ohm ant impedance for its BP filters and image traps.

[vincent]

Thanks John. As you said the SS-1R must "see" a 50 ohms source, that's its main problem or requirement.