MFJ Cub

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Last edited 01/04/2003

The MFJ Cub

Introduction

A while back MFJ introduced a new range of transceivers called the Cub. The Cub is available for bands from 80 through to 15 metres and is a CW monoband transceiver with a superhet receiver and a transmitter output of between 1 and 2 Watts. It is available either as a partially-built kit or built and ready to go.

Cub1.jpg (74880 bytes)

What is  Partially Built Kit?

Much of the circuitry for the Cub uses surface mount components. These are tiny and very fiddly to solder in place so MFJ supplies the Cub board with all that work done. All that is left to do is to solder in place some inductors and capacitors.

cub4.jpg (69984 bytes)

The inside story.

How would it be for Novices?

I wondered how appropriate the Cub might be as an entry-level radio for the newcomer to amateur radio. Certainly the construction was easy and no-one should find it at all difficult to build the Cub, even as a first real project. The alignment is rather a different matter though. The alignment is quite critical and newcomers would probably find it a more rewarding to do it with someone who has more experience in construction and might be able to impart a tip or two at the same time. Actually, as the whole kit only takes a short while to construct, it would make a great club project. Two or three evening meetings would see these rigs built and on the air. Mine took 150 minutes from starting to the first QSO (I would not recommend racing through the process though!). One point to note is that the alignment requires a special hexagonal tool to adjust the tuning cores that is not supplied as part of the kit. These cores are very fragile and the temptation to adjust them with other than the correct tool must be resisted. In my opinion, MFJ should have supplied the tool as part of the kit. I was lucky as I already had one. The mechanical part of the construction is also very easy, the circuit board slides into the box and that’s about all there is to it.

Operating the Cub

I set my Cub up to cover the Novice section of 15 metres. It covers just over 50 KHz, so it easily manages to cover the whole novice section. I had no problem in making QSOs. I didn’t have an aerial for 15 metres so just used my 80 metre dipole. Even with this rather poor set-up, I was easily able to work all around Europe. There is less activity in the novice section than lower down in the band but nevertheless I never had an operating session where I didn’t manage to make a contact. There was most activity at the weekends and reports varied from 559 to 599. I was amazed at how well this simple radio works. The filters are excellent and the automatic gain control (AGC) is better than any other QRP radio I have ever built. The whole circuit seems well thought out. It would make a good radio for taking out and about on walking trips and the like. Adventure Radio, which is operating radio as part of an outdoor adventure trip, is well established in the USA and is gathering support here. The Cub would be ideal for this application as being so small it could easily be carried in a backpack together with a battery, key, dipole and headphones. There have been some comments on the internet suggesting that the Cub drifts (the frequency alters slowly over a period of time). While mine does drift slightly at switch-on it soon stabilizes and after a minute or so, it stops drifting. There is an in-depth technical review of the Cub at the Adventure Radio Society web site.

The only grumble I have is the quality of the paint work on the case. It is poor and tends to flake off. A pretty minor grumble!

Worth the Money?

So, is it worth the money? Yes, I think that it is well worth it. I’m told that many people are buying them ready-built. This seems a pity as they are effectively paying someone 25 per hour to build the kit and missing out on part of the fun of getting to grips with some "real" amateur radio.

Thanks

I would like to thank Jeff Stanton of Waters and Stanton for providing the Cub kit for me to review. Jeff has kindly donated my completed kit to be offered as a prize for a competition in RSGB's RadCom magazine later this year.

Alan, G0TPH has just bought an 80 metre Cub so I hope that I will get some comments from him soon.

cub3.jpg (92928 bytes)

It's a tiny rig!

cub5.jpg (62380 bytes)

Those three crystals are the filter. How does it work so well?

Comments Received - Thanks!

-----Original Message-----
From: G0TPH@aol.com <G0TPH@aol.com>
To: GQRP@onelist.com <GQRP@onelist.com>; g3cwi@tesco.net <g3cwi@tesco.net>
Date: 20 October 2000 19:55
Subject: Carrier Offset Adjustment on the MFJ Cub.
>Hello all,
>
>I thought this idea might be worth sharing, as maybe it can be used elsewhere 
>too...
>
>I've just completed my MFJ Cub, and because I'm a bit tone deaf, failed to 
>get the Carrier Offset set to 600Hz (or anything like).
>
>This has to be done by "ear" and is fairly important as it gives the 
>relationship between transmitted and received signal.
>
>I then hit on the idea of feeding the Cub audio into my PC sound card whilst 
>it was running some RTTY software called MMTTY. One of the features of this 
>software is its tuning aid which is an audio frequency spectrum display.
>
>All I had to do was set the MMTTY display marker to 600 Hz, and then tune the 
>Cub's Carrier Offset until the displayed signal matched the marker. 600Hz 
>spot on, first time!
>
>MMTTY is freeware, and available from...
>
> http://www.geocities.com/mmtty_rtty/
>
>and apart from being an audio tuning aid, is also a very good RTTY program!
>
>73,
>
>Al, G0TPH
>G-QRP 7642.

 

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