Saturday, March 7, 2009

The Morrow Twins -- MB-6 and MB-565

Back in the late 60's, when I first became interested in ham radio while in junior high-school, one of my parents' friends who had been a ham (Hal Schell -- ex-K6IGQ ("Idiot Gone Quacky")) gave me an old Morrow Converter (5BRN) and IF unit (FTR) that he had used mobile once-upon-a-time.

A few years later, while in high school, I traded a BC-652 receiver (that Hal had also given me) for a Morrow MB-560 transmitter with another high-school ham (Sandy, WB6FHG). The Morrow set made a cute, incredibly compact pair (compared to my station at the time, which was a Hammarlund HQ-129X and Heathkit TX-1 Apache with SB-10 Sideband adapter ), but I rarely had the receiver on the air and never the transmitter -- didn't have a power supply.

That was more than 30 years ago -- in the intervening years those original Morrow pieces went their separate ways (I no longer recall where), but I continued to maintain a fondness for them.

A couple of years ago another friend offered me a handsome receiver and transmitter pair consisting of the Morrow MB-6 Receiver and the Morrow MB-565 Transmitter (see photo below). Although the knob layout is similar to earlier models, such as the MB-5 and the MB-560, if you're familiar with Morrow radios you'll immediately spot a few significant differences: the knobs a plastic, rather than metal, the dial is a drum, rather than a slide-rule, and the meter faces have a black background, rather than the usual yellow background.

OK, so the knobs are plastic, but to be honest, this is better than the metal knobs -- whenever I've come across metal knobs on a Morrow the knobs have always been absolutely filthy: grungy and oxidized. The plastic knobs, although looking a bit cheap, do clean up easiy and are, in my opinion, a nice improvement.

Here are some pix of a Morrow MBR-5 Receiver and an MB-560 Transmitter (that I sold on Ebay some time ago) for comparison purposes:

I have to admit, I do like the slide-rule dial of these earlier radios better than the drum, but I really dislike the metal knobs. If you click on the picture (to enlarge it), you might get an idea of what the knob oxidation looks like (it's on the sides of some of the transmitter's knobs).

Here's what the MBR-5 looks like inside. The MB-6 is similar. Pretty nice construction, eh?

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To power my MB-6 and MB-565, I modified an old Galaxy power supply that I had lying around to supply the appropriate voltages for the two radios. I also made a little external box to switch the Transmitter's B+ on and off with PTT.

I've had this pair on the air -- usually on the local (Northern California) AM net on Saturday mornings (which is why there's a crystal for 3870 KHz installed in the transmitter). To get a bit more power out, I use a linear by running the MB-565 output through an external RF power attenuator before feeding it to my AL-811 linear. The attenuator cuts the Morrow's output of 25 watts down to a level (about 10 watts) that gives me about 100 watts carrier output from the AL-811. This is pushing the three 811A tubes in the linear a bit harder than they should be pushed (they're only rated at 45 watts plate dissipation CCS, 65 watts ICAS, and the linear's total plate dissipation is about 420 watts (1.6KV * 260 mA), which is about 140 watts per tube), but it seems to work fine, and the tubes only have a very dull-red glow when I'm doing this.


KD8JXE said...

Jeff, I built a power supply for my MB-6, its my favorite receiver, so much radio in a small box. Nice website, Thanks, John

Dale Parfitt said...

Hi Jeff,
I also have the 565/6 Twins:

I use them with a D-104 and get wonderful reports. I find the RX to be very stable with nice audio recovery. In my opinion, these are the Cadillac of early mobile rigs.

Dale W4OP

Dale W4OP said...

I too have the morrow Twins and really enjoy them:

With a D104 mic, I get very complimentary on-air reports.

Stephan Domich said...

How much can I sale a morrow mb-6 for

Jeff said...

Hi Stephan. Unfortunately, I do not know their price. I suggest watching eBay. They show up there from time to time.