Friday, October 16, 2020

Micro Mountaineer 40m Xtal locked CW transceiver review

I've just completed a build of a kit I haven't seen before. The Micro Mountaineer is a crystal locked 40m CW transceiver that is a step up from the widespread Pixie kits that you see on Ebay.


I purchased mine for AU$20 from AliExpress here. It came with crystals for 7023kHz (it uses one as an oscillator and the other as a bandpass filter).

The printed instructions appear to have been machine translated. Presumably from English to Chinese and then back again. Documentation is therefore a bit strange but understandable.

The circuit is credited to W7ZOI (he mentions it here) and K7TAU. The design is an NE602 mixer and LM386 audio stage. Receiver is based on the Neophyte design.

The original description and circuit is in the wayback machine here.

My kit arrived with a tiny surface mount LM386 and a little carrier board but happily I have full sized chips in the junk box so I used one of those.

There's no keyer circuit so this would be easy to use with Feld Hellschreiber mode - a great trick for those of us who have failed to learn morse but like the simplicity of these CW rigs.

The waveform doesn't look great. (This is via a 10x probe). Getting about 1W into 50 ohms.

I enjoyed building the kit and it was good practice before I take on the uSDX when the board arrives. All parts were supplied and even some extra passive components were added. It's a pity the supplied LM386 was surface mount but the carrier board would work - I guess it's a sign of the times that full sized through-hole components are getting harder to find.

After several months, the TinySA arrived. Initial impression is good.

6 comments:

John AE5X said...

Credit should go to W7ZOI, not ZOL. More info about this design can be found on his website.

Peter Marks said...

Thanks John, updated. Of course! I should have realised that. Unfortunately his page about it is no longer up. I will try to find it in the internet archive and link to it.

Bill said...

Just finished a build , very low power output , did you ground the crystals ? What voltage are you running it on ??

Peter Marks said...

Bill, it would have been 13.8V

High Ground said...

The rig is a little disappointing on TX: output power is less than 0.3W and drops down while keying. This is because Q6 has the emitter directly connected to ground, with no limiting resistor (47-100 ohm) parallel to a 100nF capacitor (see all other schematics). So, Q6 heats up quickly. I replaced it with 2n2222 and it was worse. I also replaced Q5 with BD139 and I got 0.5W with 12V. No better. Now, I need to review the PCB to cut the Q6 emitter to ground connection and insert the limiting resistor and the bypass capacitor.
Did you have some better results than mine?
73 de YO9JAZ

kq6up said...

Can you email me the schematic please? I built the Chinese version of this kit. I think it is nearly identical. They even include the same trim pot for frequency adjustment that is in your kit by mistake because they moved W1 to the front panel with a larger pot. It includes a case. The receiver and side tone is the best that I have used of this type of radio. I found a mod here to make it work better: http://ve7sl.blogspot.com/2015/05/49er-fake-transistors.html