#80: MFJ Cub 40m QRP CW Transceiver circuit walk-thru and review, plus bandsweep, ham radio MFJ-9340 

i guess I'm pretty randomly asking but does anybody know a good place to stream newly released tv shows online ?

@Elon Damon Flixportal

@Terrell Kristopher Thanks, I signed up and it seems like a nice service =) I appreciate it!

@Elon Damon Happy to help xD

I'm glad you liked it. Hopefully, the fact that each of my videos are numbered, it'll be easy for you to keep track of the ones you've seen and the ones you haven't.

***** For someone, like me, that can't seem to stay focused when reading a book your videos are invaluable. The pace that you speak at allowed me follow right along with you and take notes on my schematic (bigger version than the manual) at the same time. Receive is roughly aligned. Once I find my dummy load I'll align the transmit side. Thanks again. PS- they are easy to keep track of but I just found this site and the dilemma is what to watch first and when to stop for things like sleeping :o)

***** hello. i talked to rick k1bqt the designer of the cub and he gave me some suggestions to A) add and "s" meter and B) convert one to 10 meters. i'll share the email with you. 73 paul kb1iai Hi Paul- Technically, you could add a "S" meter by tapping into and amplifying the control voltage in the AGC loop. That voltage is available at the gate of Q3. You'd need to use a high-impedance op amp (TLO-80 or the like) to avoid loading down the AGC circuit. Probably more trouble than it's worth. As for the 10-meter conversion, you'd need to set the IF up in the 22-MHz range to use the stock VFO which operates in the 5-6 MHz range (22+6=28). Getting sharp selectivity using crystals that high up in frequency would likely prove difficult. Alternatively, you could convert the VFO to a VXO circuit (crystal oscillator circuit that can be "pulled" over several kHz with a capacitor or variable inductor). This modification would probably be your best bet. Simply moving the existing VFO up to 16 MHz would also work, but it would probably drift like crazy. Hope that helps. Glad you're having fun with the Cubs! 73 Rick K1BQT On Tue 07/21/15 10:09 AM , huzinasr1@aol.com wrote: hello mr littlefield, im kb1iai, paul. i have a couple of questions about the mfj cub you designed. 1) can an "s" meter be added to it?? 2)can it be converted to 10 meters?? i have just bought the 20 meter kit and im waiting for it to arrive. i already have a 40 meter one. i was considering buying another one for 10 meters. this is so i can take the three of them, a battery and solar panel and an end-fed par antenna for field work. .it will all fit in my pelican briefcase. tnx for your time. 73 paul kb1iai

Very interesting, thank you for sharing. Alan

you are welcome. now im not an engineer in any way shape or form, but i can read schematics, and i build most of my own gear. i have found a compact op-amp that mounts in an 8 pin sip socket for 7 dollars on ebay and my new 9320 should be here this afternoon. i have a couple os "s" meters i scraped out of junk c/bs. another person suggested that i tap the emitter of q1 and tie the op-amp there so as not to drag own the agc circuit. i have just finished a "son of zero beat" kit and a cw touch key(no moving parts) and a brand new norcal keyer that i found in my storage bin. im just wondering now if i can squeeze it all into the mfj case or not. if you have any ideas id be open for suggestions. 73 paul kb1iai

If band conditions are good, and the receiver is very sensitive, you can receive with very poor antennas.

Sorry - the unit is no longer in my possession, so I can't carry out these additional measurements.

@@w2aew No problems, I wasn't asking for a quantified response, just making a comment on the design. Thanks for your excellent video walk thru.

Resistors can go either way, they are not polarized. The diodes and some of the capacitors are polarized, and will be clearly marked in the parts placement.

Not absolutely necessary, but it is helpful.

I've never studied or used the TenTec, so I really can't give you a qualified answer. I can say that I liked the 9340. There are a fair amount of reviews on eham that you might want to read to help in your decision process.

It should, provided its output can emulate a simple switch closure to key the rig.

I do have one on the alignment of a Drake 2B receiver...

I supposed you could count the turns on the toroids and map that to the inductor specs for each version.

My email address is good on qrz.com.

Yes you can, it is the MFJ-9340W www.mfjenterprises.com/Product.php?productid=MFJ-9340W

Can a tech class use this??

As a receiver, yes. But a Tech cannot transmit on HF (40m in this case). You need a General Class (in the US) as a minimum. I believe there is a 10m version which a Tech can use.

Im pretty sure a us tech can use cw

Yes, but this was in my basement with just a very short wire antenna, also on the basement, next to a pile of equipment that was on.