[CW] Mackay 3010B tube receiver

Tue Sep 17 00:50:24 EDT 2019

Hi DR

A boooootiful day here & the new book is finished: with the printer now for quotes on quantities. Nothing from Bob Interbitzen or anyone else from the ARRL so my plan is to get the ISBN done & all the info from printer -before heading to the Post Office to glean the bad news on international postage rates for a single copy (ARRL can purchase one to review) plus for batches of 10, 25 & 50 copies to the States.

At the same time, I will commence local advertising/promotion with a view to operating on the pre-paid order system so I don’t have to outlay big chunks of dollars & be at everyone’s mercy!! 😊

I had a tech+ham colleague trawl through it with me yesterday & he was very impressed. We both had a chuckle at the Stateside lingo & spelling thereof….so different to ours.

Here is a shot of the new cover.

David…if the Mackay is still for sale, what price & how much would freight be to Adelaide postcode 5041 please?

Cheers OM, de Me

From: cw-bounces at mailman.qth.net <cw-bounces at mailman.qth.net> On Behalf Of D.J.J. Ring, Jr.
Sent: Monday, 16 September 2019 10:43 AM
To: CW Reflector <cw at mailman.qth.net>
Subject: [CW] Mackay 3010B tube receiver

I have a Mackay 3010B that Quincy Electronics gave to me in hopes of selling it.

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

Mackay 3010B 

Front end attenuator OFF: 

Band 

MDS 

Blocking

Two-tone D.R.

(20 kHz) 

(20 kHz) 

80 meters 

-146 dBm 

  93 dB 

68 dB

40 meters 

-141 dBm 

  96 dB 

67 dB

20 meters 

-140 dBm 

102 dB 

68 dB

Front end attenuator ON 1st position: 

Band 

MDS 

Blocking

Two-tone D.R.

(20 kHz) 

(20 kHz) 

80 meters 

-135 dBm 

  94 dB 

66 dB

40 meters 

-128 dBm 

  98 dB 

69 dB

20 meters 

-126 dBm 

103 dB 

69 dB

AM Audio S/N: 43 dB 

AM Audio Frequency Response: 

100 Hz 

200 Hz 

400 Hz 

600 Hz 

800 Hz 

1 kHz 

2 kHz 

3 kHz 

4 kHz 

5 kHz 

6 kHz 

-4 dB 

+1 dB 

0 dB 

+2dB 

+2 dB 

0 dB 

-2 dB 

-10 dB 

-24 dB 

-40 dB 

- 

AM Audio Distortion: 

Mod% 

100 Hz 

200 Hz 

400 Hz 

600 Hz 

800 Hz 

1 kHz 

2 kHz 

30% 

13% 

8.9% 

7.1% 

6.3% 

5.6% 

4.5% 

4.0% 

50% 

13% 

7.9% 

6.3% 

6.3% 

6.3% 

6.3% 

7.9% 

70% 

20% 

13% 

11% 

10% 

7.1% 

6.3% 

7.1% 

90% 

32% 

22% 

16% 

14% 

11% 

7.9% 

7.9% 

100% 

40% 

25% 

18% 

16% 

13% 

8.9% 

8.9% 

Notes: This receiver is pretty uncommon so a few comments are in order. With 0 dB front end attenuation and maximum i-f gain this receiver has extraordinary gain and sensitivity - especially at the lower frequencies. Designed mainly as a shipboard receiver it is likely this receiver would have performed well on 500 kHz with the ships antenna fully encrusted in ice and laying on the deck! Words can not adequately describe the unbridled gain of this receiver - you'll just have to try one for yourself. 

The receiver is extremely well built on a cast aluminum foundation in which individual stages occupy their own compartments. DC and bias voltages enter through feedthrough capacitors and signal openings from compartment to compartment are kept as small as possible. One wishes all receivers were built this way! 

Unfortunately, the blocking and two-tone dynamic range numbers tested disappointingly low - even with the i-f gain of the receiver cut way way back. Considerable time was spent to insure that the receiver was functioning, as best as one can tell, to factory specifications. All voltages were correct, as was LO injection levels when compared with the figures given in the manual. The rf circuitry used is somewhat unconventional. The receiver covers from 70 kHz to 30 MHz and uses up conversion to a first i-f of 38 MHz. The main signal path includes a manually switched front end attenuator, manually switched front end bandpass filters that feeds a single stage 7788 tube rf amplifier. Signal from the plate of the rf amplifier passes through a 14 section 30 Mhz low pass filter. This is applied to a 6C4 cathode follower that feeds the first mixer - a quad of 1N82A 'VHF' diodes in a balanced design. The signal is amplified and filtered by two tuned circuits, a single 6688 amplifier tube and two more tuned circuits. A 6BL8 triode section forms another cathode follower which feeds the grid of the 6BL8 pentode section as the 2nd mixer with an output at 5.94 MHz. A somewhat unusual arrangement has the LO injection in series with the rf signal to the grid. The plate of the 2nd mixer passes through a 6 kHz wide crystal lattice filter. From there it's on to the third mixer - a 6BE6 converter stage - for the final i-f of 455 kHz. Here, the signal encounters the Collins mechanical filters for either SSB or CW. No additional filter is used here for AM - just the 6 kHz filter in the previous i-f. The remainder of the circuitry is pretty straightforward. One nice feature of this receiver is that it does have a product detector. 

This receiver was on loan so it was only possible to observe its performance - not modify the receiver to try to improve it. In order to locate the source of the poor dynamic range a high impedance probe / spectrum analyzer setup was used to 'sniff' IMD stage by stage. The culprit turned out to be the 6BL8 second mixer stage. With simple tests and limited time I was unable to determine the exact cause of the poor IMD performance but would suspect the 6BL8 biasing, or more likely the crystal filter in the plate circuit or the VFO amplifier which has it's output in series with the rf signal. Even if the IMD could be improved in the second mixer, next in line is the third mixer - a 6BE6 converter - generally a dynamic range 'show stopper' in receivers where it's used. This would be one fun receiver to modify for truly high performance! 

The AM distortion numbers show the somewhat typical increase at lower audio frequencies - most often caused by the low audio frequencies riding on the AGC line. Also there is the usual increase in audio distortion as the modulation percentage increases. This is due to the detector's inability to cleanly demodulate the higher amplitude levels although this receiver does pretty well. 

It probably works but there is no schematic and there is no power plug.  The power plug it appears is like a vacuum tube octal plug.  It has no outer cabinet, it's rackmount.

Obviously there are other connections there as well.

I'd have to crate it - either in wood or cardboard.

Then mail it - it's heavy.

You have to either pick it up in Marshfield, MA or have me pack it and post it.

Cardboard is cheaper but I know a carpenter who can make a box as long as the box keeps the package under 70 pounds, it's good to go.

Inside the crate will be anti-vibration materials.

You're paying for all of this if you want me to post it.

Or you can pick it up where I live.  Free no extra cost..

Make a reasonable donation $100 or more and agree to pay the shipping cost and it's yours.

73

DR

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