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Reviews For: Mizuho DC-7D

Category: QRP Radios (5 watts or less)

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Review Summary For : Mizuho DC-7D
Reviews: 2MSRP:
Description:
40m CW transceiver - 1 W output, mid '70s vintage
Product is in production
More Info: http://www.qsl.net/ku4qd/mizuho
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0022.5
KU4QD Rating: 2003-03-29
Interesting rig, but not nearly as good as Mizuho's later rigs Time Owned: 0 to 3 months.
I've been playing with my DC-7D for a couple of months now. These rigs were offered both as kits and wired and tested way back when in the mid '70s. They are "portable" rigs, 40m CW only, about the size of a Heathkit HW-7 or HW-8. They're even green, but they're olive green as opposed to Heathkit's brighter color. Mine runs on a single 9V battery, and they can also be used with an external 12V source. Mine came without a manual, but I was able to order one (in Japanese) from Mizuho all these years later. At least the schematics are usable! Power consumption is rated at 120mA on receive or 550mA when transmitting for 1W output, so the rig is not quite as stingy as later Mizuho rigs, but the battery still lasts for a good while.

I think there are actually many similarities between the HW-7 and the DC-7D, most notably the direct conversion receiver and the annoying hum when running the rig on an external power source. My solution is to run the rig on battery power 100% of the time. Receiver sensitivity is rated at onlu 1uV, which isn't very good. In practice I can certainly copy and work many stations. Receiver audio is fairly weak, and I find I turn the volume up all the way most of the time to be able to copy stations comfortably.

I haven't noticed any front end overload which the previous reviewer complained about. I suspect thet fact that I am in the U.S. and that we don't have SW broadcast stations below 7.3 MHz in this country also helps. For those of us in North America I suspect this rig will be quite acceptable in that regard.

The built in single paddle keyer is a nice touch. It takes some getting used to but it can be used effectively.

Overall, I agree that this is more of an oddity than a serious CW QRP rig. The model that replaced the DC-7D, the DC-7X, is far superior. OTOH, you can make some contacts and can have fun with a vintage DC-7D that's nearly 30 years old.
VR2XMQ Rating: 2002-07-31
This was a kit Time Owned: more than 12 months.
As a kit, if you can read the Japanese then you have no problems. I built mine using the schematics only and circuit diagram. The QRP 40M radio runs on small pen cells. I had no problems with alignment using simple signal generator and simple test equipment.

Plug the antenna in and the RX part immediately worked but as this is a simple single conversion unit, it did ehibit problems with overload from the strong Sw broadcast stations near 7 MHz. TX was tested and found to be on the chirrpy side.

Hey, remember, this was just a weekend project and a kit. Nice novelty to place in the shack but can't really take it seriously.

Steve Sebastian Beesley - VR2XMQ